home *** CD-ROM | disk | FTP | other *** search
Text File | 1991-07-05 | 157.7 KB | 3,027 lines |
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Program JPLCLOCK
-
- NASA/JPL Multimission Computer Control Center Clock
-
-
-
-
-
-
- (C) Copyright David H. Ransom, Jr., 1991
- All rights reserved.
-
-
-
-
-
-
-
- Version 9128
- July 05, 1991
-
-
-
-
-
- by David H. Ransom, Jr.
- Rancho Palos Verdes, CA
-
-
-
-
- RPV ASTRONOMY BBS
- (213) 541-7299
- (310) 541-7299 [November, 1991]
- Program JPLCLOCK Multimission Control Center Clock Page i
-
-
-
-
-
- TABLE OF CONTENTS
- -----------------
-
-
- INTRODUCTION ......................................................1
- JPLCLOCK FEATURES ............................................1
- PROGRAM DESCRIPTION ...............................................5
- JPLCLOCK HARDWARE AND SOFTWARE REQUIREMENTS .......................7
- JPLCLOCK FILES ....................................................7
- STARTING PROGRAM JPLCLOCK .........................................9
- JPLCLOCK Command Line Options ................................9
- Setting UTC Zone and Daylight Flag ...........................9
- JPLCLOCK MAIN CLOCK DISPLAY .......................................12
- JPLCLOCK MAIN MENU ................................................16
- F1 Program Information .....................................17
- F2 Set LOCATION CLOCKS .....................................18
- F3 Set EVENT/MISSION TIMERS ................................20
- Set MISSION/EVENT TIMERS ................................21
- Set SELECTED EVENTS .....................................27
- F4 Set DAYLIGHT and Defaults ...............................28
- F5 Read or Save INI Files ..................................29
- INI Files from Other Locations ..........................30
- Editing INI Files .......................................30
- F6 Self-Calibration using TIMESET ..........................32
- F7 Switch TEXT Mode ........................................34
- F8 Switch PAGE Mode ........................................34
- F9 DOS SHELL (DOS 3.3+ ONLY) ...............................34
- F10 TIME SYNCHRONIZATION ....................................35
- Configuring Program TIMESET .............................35
- Time Synchronization Menu ...............................37
- VIEW or SET Time Sync Data ..............................37
- TIMESET Time Synchronization ............................38
- DOS CLOCK CALIBRATION .............................................39
- Setting DOS Time .............................................40
- Maintaining DOS Time .........................................41
- Calibrating DOS Time .........................................43
- Manual Hardware Clock Calibration .......................45
- Manual Software Clock Calibration .......................46
- USING TEXT MODE ...................................................48
- Preparing TEXT Files .........................................49
- COMMENTS AND KNOWN PROBLEMS .......................................50
- Computer BIOS Problems .......................................50
- Monitor Type and Video Adapter Cards .........................50
- Computer Processor and Math Coprocessor ......................50
- DOS Version and the Shell Feature ............................50
- Unstable Hardware or Software Clocks .........................51
- Typical Calibration Results ..................................51
- Color Variations .............................................52
- FUTURE IMPROVEMENTS AND FEATURES ..................................53
- UTC AND TIME ZONES ................................................54
- JPLCLOCK REVISION HISTORY .........................................56
- Program JPLCLOCK Multimission Control Center Clock Page ii
-
-
-
- JPLCLOCK (NORMAL MAIN CLOCK SCREEN)
-
-
-
- ║ JPLCLOCK by David H. Ransom, Jr. Version 9126 ║ JD2448422.63779 14 JUN 1991
- ■■■■■■■■■■
- ╔[ NASA Jet Propulsion Laboratory ]══════════════╗ ┌[ Magellan ]─────────────┐
- ║ ║ │ 604 12:18:25 │
- ║ ╒═══╗ ╔═══╗ ╒╗ ╔═══╗ ╒═══╗ ╔═══╕ ║ └─────────────────────────┘
- ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║
- ║ ╔═══╝ ║ ║ ║ ╠═══╣ ╔═══╝ ╚═══╗ PDT ║ ┌[ Ulysses ]──────────────┐
- ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║ │ 251 15:31:10 │
- ║ ╚═══╛ ╚═══╝ ╘═╩═╛ ╚═══╝ ╚═══╛ ╘═══╝ ║ └─────────────────────────┘
- ║ ║
- ║ ╔═══╗ ╒═══╗ ╒╗ ╔═══╗ ╒═══╗ ╔═══╕ ║ ┌[ Galileo ]──────────────┐
- ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║ │ 616 14:18:25 │
- ║ ║ ║ ╞══╣ ║ ╠═══╣ ╔═══╝ ╚═══╗ UTC ║ └─────────────────────────┘
- ║ ║ ║ ║ ■ ║ ║ ║ ■ ║ ║ ║
- ║ ╚═══╝ ╘═══╝ ╘═╩═╛ ╚═══╝ ╚═══╛ ╘═══╝ ║ ┌[Hubble Space Telescope]─┐
- ║ ║ │ 403 14:44:33 │
- ╚════════════════════════════════════════════════╝ └─────────────────────────┘
-
- ┌[ GDX Goldstone ]────┐ ┌[ CAN Canberra ]─────┐ ┌[ Gamma Ray Observatory]─┐
- │ 165 20:18:25 PDT │ │ 166 14:18:25 │ │ 70 11:55:40 │
- └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘
-
- ┌[ JSC Houston ]──────┐ ┌[ MAX Madrid ]───────┐ ┌[ ROSAT Observatory ]────┐
- │ 165 22:18:25 CDT │ │ 166 04:18:25 CES │ │ 378 05:30:26 │
- └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘
-
-
-
- NOTE: Pages ii and iii use the IBM "line drawing" characters as they appear
- on the display screen. If your printer cannot print these characters, these
- pages may appear garbled. These line drawing characters are not used
- elsewhere in this documentation; instead, I substitute similar characters
- from the normal character set.
- Program JPLCLOCK Multimission Control Center Clock Page iii
-
-
-
- JPLCLOCK (SMALL MAIN CLOCK SCREEN)
-
-
-
- ║ JPLCLOCK by David H. Ransom, Jr. Version 9127 ║ JD2448436.59025 28 JUN 1991
- ■■■■■■■■■■
- ╔[ NASA Jet Propulsion Laboratory ]══════════════╗ ┌[ Galileo ]──────────────┐
- ║ ║ │ 522 15:09:58 │
- ║ 179 19:09:58 PDT 180 02:09:58 UTC ║ └─────────────────────────┘
- ║ ║
- ╚════════════════════════════════════════════════╝ ┌[ Magellan ]─────────────┐
- │ 780 18:09:58 │
- ┌── SELECTED EVENTS ───┐ ┌── PRIORITY EVENTS ───┐ └─────────────────────────┘
- │ │ │ │
- ┌[Hubble Space Telesc]─┐ ┌[ Test 6 ]────────────┐ ┌[ Ulysses ]──────────────┐
- │ 417 13:36:06 │ │ 0 00:24:08 │ │ 265 08:23:58 │
- └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘
- │ │ │ │
- ┌[Gamma Ray Observato]─┐ ┌[ Test 5 ]────────────┐
- │ 84 10:47:13 │ │ 0 00:24:18 │
- └──────────────────────┘ └──────────────────────┘
- └──────────────────────┘ └──────────────────────┘
- ┌[ GDX Goldstone ]────┐ ┌[ CAN Canberra ]─────┐ ┌[ Gamma Ray Observatory]─┐
- │ 179 19:09:58 MST │ │ 180 13:09:58 │ │ 84 10:47:13 │
- └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘
-
- ┌[ JSC Houston ]──────┐ ┌[ MAX Madrid ]───────┐ ┌[ ROSAT Observatory ]────┐
- │ 179 21:09:58 EST │ │ 180 03:09:58 CES │ │ 392 04:21:59 │
- └──────────────────────┘ └──────────────────────┘ └─────────────────────────┘
-
-
-
- NOTE: Pages ii and iii use the IBM "line drawing" characters as they appear
- on the display screen. If your printer cannot print these characters, these
- pages may appear garbled. These line drawing characters are not used
- elsewhere in this documentation; instead, I substitute similar characters
- from the normal character set.
- Program JPLCLOCK Multimission Control Center Clock Page 1
-
-
- INTRODUCTION
- ------------
-
- JPLCLOCK is a clock and event timer program written especially for use
- in the NASA Jet Propulsion Laboratory's Multimission Computer Control
- Center (MCCC) in Pasadena, California. JPLCLOCK provides mission
- controllers in the MCCC with current JPL time (Pacific Standard or Daylight
- Time), UTC (Coordinated Universal Time), and DSN (Deep Space Tracking
- Network) times as well as up to 60 selected mission or event timers. A text
- presentation mode allows the display of supplementary text and other
- messages when the program is used for more general applications.
- JPLCLOCK is copyrighted software; you are hereby granted a non-
- exclusive license for non-commercial or educational use only. Agencies of
- the U. S. Government are hereby also granted a non-exclusive license for
- the use of this program. Use it if you like it, discard it if you don't.
- There are no warranties of any kind. If you wish to use JPLCLOCK
- commercially, write for license information.
-
-
- JPLCLOCK FEATURES
- -----------------
-
- - JPLCLOCK can turn an "ordinary" IBM-compatible personal computer into
- a precision clock, synchronized to the National Institute of Standards
- and Technology in Boulder, Colorado or to the U.S. Naval Observatory
- in Washington, DC.
-
- - When used with the NIST or USNO Telephone Time Service, JPLCLOCK can
- maintain its displayed time to an accuracy of 0.2 seconds or better
- over extended periods of time.
-
- - JPLCLOCK automatically and continuously compensates for the drift of
- the DOS software clock.
-
- - JPLCLOCK can display your local time and Universal Coordinated Time in
- large, easy to read characters in its Main Window.
-
- - JPLCLOCK can display the local time at four additional locations
- around the world.
-
- - JPLCLOCK tracks as many as 60 different missions or events, displaying
- the Mission Elapsed Time or a countdown to Time Zero for each event.
- Mission/event times may range from -27 years to +274 years!
-
- - JPLCLOCK can display up to four special PRIORITY EVENT timers that
- automatically select events whose Time Zero is closest to the current
- time.
-
- - All features and events are set by the user so that JPLCLOCK may be
- easily configured for each installation.
-
- - JPLCLOCK can present supplementary text information on as many as 10
- successive display screens for news and public information.
-
-
- Program JPLCLOCK Multimission Control Center Clock Page 2
-
-
- JPLCLOCK Version 9126 was the first limited public release of the
- program, after a number of beta versions tested by Charles White at the
- NASA Jet Propulsion Laboratory. Thanks to Charles, a number of interesting
- features have been added to the early versions, bugs have been squashed,
- and the program has been tested in the MCCC and elsewhere. Other interested
- individuals at JPL have also evaluated the program, offered criticism and
- suggestions, and researched some of the older mission times. Mike Gardner
- in Sunnyvale has reviewed an early version of my documentation apart and
- offered his usual constructive criticism. To all of these people, my
- thanks!
- Although my initial discussions at JPL envisioned a "simple" program,
- JPLCLOCK is definitely NOT simple. The original idea was to adapt my
- program ASTROCLK to the task required in the MCCC. I have indeed borrowed
- freely from ASTROCLK (as well as from another of my programs, STSORBIT) and
- this helped get the first versions up and running relatively quickly. As
- usually happens, the project quickly grew in scope and complexity. Everyone
- involved, myself included, had new ideas or suggestions. Equally
- significant, the personal computer is hardly the ideal precision clock, yet
- JPLCLOCK is intended for the JPL MCCC where accuracy is critical. Making
- sure that JPLCLOCK will maintain the required accuracy has consumed
- considerable time and thought. It wasn't long before the source included
- thousands of lines of code and the documentation grew to over 40 pages. All
- this in the space of a couple of weeks of my "spare time"!
- Given the clock drift and accuracy problems inherent in the design of
- the typical IBM-compatible personal computer, JPLCLOCK would not have been
- practical without the various time services provided by the National
- Institute of Standards and Technology (NIST) and the U.S. Naval Observatory
- (USNO). The NIST radio stations WWV and WWVH provide an inexpensive and
- convenient means for "ordinary folks" to synchronize clocks and other
- equipment. The NIST and USNO Telephone Time Services offer a high precision
- standard time calibration source when such accuracy is required.
- Every effort has been made to assure that program JPLCLOCK performs
- its task accurately and reliably. However, while no known errors of any
- consequence remain, JPLCLOCK is still a young program and it is almost
- certain that some bugs are yet to be discovered. In addition, there is
- still much that can be done to further enhance JPLCLOCK, so new versions
- can be expected from time to time. User comments, suggestions, and bug or
- problem reports will be appreciated!
- Programs such as JPLCLOCK take many hours to develop and maintain.
- While it is not required, I would appreciate your registration of the
- program; the cost is very nominal and it will encourage me to continue
- supporting the program. The only other request I make of users is that they
- take the time to complete and return the confidential questionnaire in file
- README. The questionnaire gives users a chance to offer comments and
- suggestions, and lets me know that people use and appreciate JPLCLOCK.
- For those who are interested in our space program and who have access
- to a modem, I recommend NASA's SpaceLink Bulletin Board System in
- Huntsville, Alabama, (205) 895-0028, available twenty four hours per day.
- NASA SpaceLink, supervised by Bill Anderson of the NASA Marshall Space
- Flight Center, provides a wealth of information on NASA and its projects.
- Orbital elements for a Space Shuttle mission are usually available while a
- mission is in progress. In addition to educational materials, general
- information on NASA programs and plans, news releases, and graphics images
- from current and prior spacecraft missions such as Voyager and Magellan,
- SpaceLink also provides current news and information on missions in
- Program JPLCLOCK Multimission Control Center Clock Page 3
-
-
- progress. Mission status reports for all active missions are generated
- periodically. I regularly call SpaceLink and post files of interest on my
- own bulletin board system (BBS).
- Special thanks to Charles White of the NASA Jet Propulsion Laboratory
- for his comments and suggestions during the development and testing of this
- program, as well as a fascinating visit to the JPL Multimission Computer
- Control Center. Like many others, I consider the Jet Propulsion Laboratory
- to be a unique national resource, unequaled anywhere else in the world.
- JPLCLOCK is entirely "a labor of love", to repeat a well-worn phrase; to
- see my software operating in the MCCC where amazing projects such as
- Voyager and Magellan are controlled is sufficient reward.
- A brief biographical note: I am a retired physicist and engineer who
- spent all of his professional life in the world of electronics, data
- communications and, more recently, computers. As a young man I was actively
- involved in the early American space program as a contractor for the Jet
- Propulsion Laboratory, working on projects such as Ranger and Mariner.
- Perhaps as a consequence of these and the many other remarkable NASA
- projects directed by JPL, my respect and admiration for The Lab and its
- people practically knows no bounds. I was also involved with the Mercury,
- Gemini, and Apollo projects and my interest in space has continued to this
- day. My experience includes both hardware and software, and I designed and
- implemented software professionally for many years with considerable
- success.
- I have been writing software for IBM-compatible personal computers,
- usually oriented toward space and astronomy, for a number of years. Since
- 1987 I have also maintained the RPV ASTRONOMY BBS, a free access bulletin
- board system with an emphasis on space and astronomy. So successful has
- my latest "hobby" become that it is threatening to overwhelm my bulletin
- board system and consume all of my available time just answering the mail!
- All of my programs are free although I do encourage users to register them
- for a modest fee. If my software also serves to help spark the interest of
- young people in science and technology or can be a learning tool at any
- level, I will have more than achieved my purposes.
- Two of my programs, ASTROCLK and STSORBIT, have become widely known
- throughout United States, Canada, and Europe. ASTROCLK is an attempt to
- consolidate a multiplicity of astronomy and time related programs into a
- single useful computer tool. My desire to "keep in touch" with our Space
- Shuttle missions led to the development of STSORBIT, a simulation of the
- large wall map in Mission Control at the Johnson Space Center in Houston,
- Texas. STSORBIT eventually found its way (several times) to JPL where it is
- now often projected in the MCCC during Space Shuttle missions and for other
- Earth orbiting missions, and was the catalyst for JPLCLOCK. The initial
- versions of JPLCLOCK were written over a period of several weeks in June of
- 1991 with close coordination with JPL. Even before the program was
- "finished" (if such programs are EVER really finished!), JPLCLOCK was being
- used during a planned power outage as the primary time standard in the
- Mission Control Center. JPL is also considering use of the program outside
- the Mission Control Center to help inform Lab personnel and visitors. How
- useful it may be to others remains to be seen.
- For current space and astronomy programs and data, as well as the most
- recent version of this program, call my bulletin board system (BBS). If the
- BBS has not answered after the fourth ring, hang up, wait TWO MINUTES, then
- call back; the system has a power controller and if the system is off it
- takes that long for the computer to start up and do its housekeeping
- chores. The system now has almost 1000 users and is often busy, so be
- Program JPLCLOCK Multimission Control Center Clock Page 4
-
-
- patient.
-
-
- RPV ASTRONOMY BBS
-
- (213) 541-7299
-
-
- IMPORTANT NOTE
- --------------
-
- The area code for my BBS telephone number is scheduled
- to change in November, 1991 as the Los Angeles 213 area
- code is once again split to accommodate Southern
- California's continuing growth. The new number will be
- (310) 541-7299.
-
-
- If you do not have access to a modem, you may send US$10.00 to cover
- materials, postage and handling for a copy of the latest version on disk;
- please specify 5-1/4" 360K or 3-1/2" 720K disks.
- JPLCLOCK can be a complex program when all of its features used,
- perhaps more complex than was originally anticipated. This documentation
- attempts to completely describe the program and its operation. There may be
- errors in this documentation, but please read it BEFORE you drop me a nasty
- note or give up!
-
- David H. Ransom, Jr.
- 7130 Avenida Altisima
- Rancho Palos Verdes, CA 90274
- Program JPLCLOCK Multimission Control Center Clock Page 5
-
-
- PROGRAM DESCRIPTION
- -------------------
-
- The NASA/JPL Multimission Computer Control Center (MCCC), located at
- the Jet Propulsion Laboratory in Pasadena, California, is the "nerve
- center" where all NASA planetary missions and some Earth orbiting missions
- are controlled. Other NASA and ESA (European Space Agency) missions may
- also be supported by MCCC from time to time. The Control Center resembles
- other similar installations with consoles for each of the controllers and
- other responsible individuals directing the progress of a mission and
- coordinating the operation of the NASA Deep Space Network and other
- critical resources. Operations continue around the clock with a number of
- missions typically active. Missions active at this time include Voyager 1
- and 2, Magellan, Ulysses, and Galileo.
- Above the main floor of the Control Center and in plain view of all
- controllers and individuals in the visitors gallery are seven projection
- screens, five large and two slightly smaller. These screens display
- television or computer generated images related to missions in progress.
- For example, NASA Select Television is frequently displayed when it is
- broadcasting. JPLCLOCK is normally displayed on one of the screens as
- selected by Control Center personnel.
- JPLCLOCK displays various time information for the convenience of
- Control Center personnel. The current local time (Pacific Standard/Daylight
- Time) and Coordinated Universal Time (UTC, or GMT as it was formerly
- designated) are displayed in large characters in the program's main window.
- Below that window are four smaller windows displaying local time at the DSN
- locations or other selected installations. On the right side of the screen
- are six smaller windows which display the Mission Elapsed Time for selected
- missions in progress (green background) or Countdown Time for missions or
- events due to occur (red background). The background color switches from
- red to green when the countdown reaches zero or the event occurs. As many
- as 60 different missions or events may be monitored with these timers.
-
- IMPORTANT NOTE
- --------------
-
- Before using program JPLCLOCK in applications requiring
- high accuracy, read the section DOS TIME CALIBRATION in
- this documentation!
-
- JPLCLOCK may be operated in two modes: NORMAL and PAGE. The NORMAL
- mode displays the main window, four location time windows, and from one to
- six timer windows continuously. The PAGE mode displays the same main window
- and four location windows but sequences through up to 60 different timer
- windows using ten different timer "pages". The timer page is normally
- switched every thirty seconds; however, when any timer on a particular page
- is within one hour of of "Time Zero", the display will "freeze" on that
- timer page. As long as events which occur within several hours of one
- another are arranged on the same screen page, JPLCLOCK will automatically
- ensure that the timer for each event is displayed from one hour before to
- one hour after Time Zero.
- In addition, up to ten screen pages of supplementary text information
- or messages may be displayed in conjunction with the PAGE mode. When the
- TEXT mode is active, the program cycles through all of the active timers
- then switches and presents the text pages in sequence. This real time to
- Program JPLCLOCK Multimission Control Center Clock Page 6
-
-
- text to real time sequence repeats indefinitely unless an active timer
- reaches the plus or minus one hour period around its Time Zero, in which
- case that timer page freezes as described above.
- The default JPLCLOCK configuration is arranged for the convenience of
- the Jet Propulsion Laboratory MCCC. One or more initialization files, files
- with a file type ".INI" and containing alternate or supplementary time and
- location data, may also be included from time to time. Manual configuration
- features are included for setup at other locations. Window titles, mission
- or event names, and window times are easily configured for the desired
- location or event. Inactive location or timer windows may be removed from
- the screen. The current configuration is saved each time JPLCLOCK is run so
- that the program may be resumed at any time. While the program is running,
- all keyboard operations are timed so that inattention on the part of the
- user for more than ten to thirty seconds (depending upon the operation
- being performed) will result in automatic restarting of the program.
- JPLCLOCK is intended for a dedicated IBM-compatible computer running
- MS-DOS version 3.3 or higher. Best performance will be achieved using a 286
- or better processor equipped with a math coprocessor chip. However, the
- program should execute correctly (but perhaps with perceptible delays)
- using any IBM-compatible computer with or without a math coprocessor chip.
- For normal use, the program should started from the computer's AUTOEXEC.BAT
- file so that it is restarted in the event of a power failure.
- As of June 1991, JPLCLOCK is still a relatively new program. Although
- all known problems have been corrected, there are doubtless a few minor
- bugs yet to be discovered. User comments and suggestions are welcome.
- Future versions are anticipated at periodic intervals as new features are
- added and/or problems are corrected. Planned features include optional
- automatic synchronization with compatible external time signals.
- Program JPLCLOCK Multimission Control Center Clock Page 7
-
-
- JPLCLOCK HARDWARE AND SOFTWARE REQUIREMENTS
- -------------------------------------------
-
- JPLCLOCK is written for use on IBM-compatible computers and has only
- been tested on computers equipped with an 80286 or higher processor. Most
- of the features should operate correctly on older computers but those
- features which use the clock/calendar chip, introduced with the AT-class
- computer and subsequently retrofitted to older computers as an add-on chip
- or circuit card, may not operate correctly. Several different clock chips
- have been used on PC and XT machines which are NOT compatible with the AT
- chip and may not be compatible with program TIMESET.
- JPLCLOCK requires a modest amount of the computer's memory. The
- program has not been tested on a machine with less than 640K of main RAM.
- Although most JPLCLOCK operations are entirely memory resident, program
- startup, use of program TIMESET, and the DOS shell all require disk
- accesses. Because of the excessive time delays associated with floppy disk
- drives, a hard disk is strongly recommended. Even with a hard disk, delays
- and system software vary considerably and performance may differ from drive
- to drive.
- JPLCLOCK assumes DOS Version 3.3 or higher; MS-DOS and PC-DOS are
- considered equivalent although testing has been performed only on systems
- using MS-DOS. Limited testing has been performed using a beta version of
- DOS 5.0 with no problems encountered. The DOS shell feature of DOS,
- required for use of program TIMESET, is considered unreliable for versions
- of DOS prior to DOS 3.1. If you have not upgraded to at least DOS 3.3,
- consider doing so!
- As discussed in more detail elsewhere, the DOS software clock varies
- considerably from computer to computer and from one version of DOS to
- another. Avoid using your favorite TSR (Terminate and Stay Resident)
- programs when running JPLCLOCK. Several hours of operation with JPLCLOCK
- will establish whether or not your computer and DOS software clock are
- suitable for use with the program. If the DOS software clock varies too
- much with time or temperature it cannot be used with JPLCLOCK and there is
- no remedy in most cases except to use a different computer.
- Because JPLCLOCK is a new program (as of Version 9128), user feedback
- on both problems and successes will be appreciated! The variety and range
- of quality of hardware and software "out there" is almost unbelievable and
- it is helpful if I know which brands of hardware and software work or fail.
- Please take the time to fill out the questionnaire in file README, whether
- or not you wish to register the program.
-
-
- JPLCLOCK FILES
- --------------
-
- JPLCLOCK is normally distributed in archived format using either the
- PAK or ZIP format. The following files are usually included:
-
- JPLCLOCK.EXE Main program (required)
- JPLCLOCK.DOC Documentation (not required)
- JPLCLOCK.INI Initialization data (optional)
- JPLCLOCK.MTD Mission Timer Data (optional)
- JPLCLOCK.MSG Sample TEXT file (optional)
- JPLFONT.COM Experimental EGA font (optional)
- README Program Registration (not required)
- Program JPLCLOCK Multimission Control Center Clock Page 8
-
-
-
- Files noted as "(required)" must be in the current default directory for
- program operation. Files noted as "(optional)" do not need to be in the
- default directory when JPLCLOCK is operated but may provide additional
- features or information if present. File JPLCLOCK.MTD contains data for
- selected missions. If file JPLCLOCK.INI is not present, it will
- automatically be created the first time the program is executed.
- Additional MTD files (files with filetype ".MTD", standing for
- "Mission Timer Data") may be included from time to time with interesting or
- upcoming events pre-programmed. Other MTD files may be posted periodically
- on my bulletin board system for upcoming events.
- Registration of program JPLCLOCK is not required but certainly will be
- appreciated! See the file README for registration information. JPLCLOCK has
- required considerable effort to develop and test and your response will
- encourage me to continue enhancing and supporting the program. As an
- additional "bonus" for registration, I will send the latest version of
- JPLCLOCK to you on disk; please specify the disk size desired: 5-1/4" 360K
- or 3-1/2" 720K (supplied if no disk size specified).
- Program JPLCLOCK Multimission Control Center Clock Page 9
-
-
- STARTING PROGRAM JPLCLOCK
- -------------------------
-
- Before starting program JPLCLOCK for the first time, make sure that
- all required files are in the current drive and directory (see below).
- Delete the file JPLCLOCK.INI if it has been created by a previous version
- of JPLCLOCK or you are using the program at a different location from the
- one which prepared the file. The format of the INI file may change with
- new versions and, although the program may read prior versions of .INI
- files, it is safer to "start from scratch". The INI file also includes
- specific information related to the local time zone.
- To start program JPLCLOCK for operation in the NORMAL mode, enter the
- following command at the DOS prompt:
-
- JPLCLOCK
-
- As described in the summary of command line options below, you may add the
- "/M" command line option to the examples above to force monochrome
- operation on CGA, EGA, and VGA systems.
-
-
- JPLCLOCK Command Line Options
- -----------------------------
-
- All JPLCLOCK program features (except monochrome operation) may be
- enabled or disabled from within the program. However, to facilitate use
- with batch files, certain features may be enabled using "command line
- options", specific words preceded by the slash ("/"), used when the program
- is started from the DOS prompt. A command line consists of the program name
- followed by the desired command line option(s): "JPLCLOCK [option] ...
- [option]". The following command line options are available:
-
- ? (Special option) Displays brief help information to remind
- users of the principal command line options and then returns
- to DOS.
-
- /M Force monochrome operation. On color monitors, this usually
- forces white or light white on black background.
-
- /SMALL Enables the SMALL main clock window and the additional four
- SELECTED/PRIORITY timer windows.
-
- /PAGE Enables PAGE mode operation with up to 60 Mission/Event
- Timers displayed in "pages" of six timers each. Default is
- the non-page mode with only 6 Mission/Event Timers.
-
- /TEXT Enables TEXT (and PAGE) mode operation if file JPLCLOCK.MSG
- is found. Up to ten screen pages of prepared text may be
- sequentially displayed.
-
-
- Setting UTC Zone and Daylight Flag
- ----------------------------------
-
- JPLCLOCK must know the correct time and time zone in order to operate
- Program JPLCLOCK Multimission Control Center Clock Page 10
-
-
- accurately. The first time JPLCLOCK is executed (or any time the program
- cannot find the file JPLCLOCK.INI), the program prompts you for your UTC
- Offset and asks if you are now on Daylight or Summer time:
-
- Set UTC TIME ZONE OFFSET and DAYLIGHT FLAG
-
- JPLCLOCK must know the difference between your local time zone and
- Universal Coordinated Time (UTC), also sometimes known as Greenwich
- Mean Time (GMT). With this information, JPLCLOCK can automatically
- adjust launch times and dates for your local time zone. In addition,
- JPLCLOCK must know if you are now on STANDARD or DAYLIGHT (SUMMER)
- time.
-
- First, enter the difference between your STANDARD time zone and UTC in
- hours. Do NOT include the hour for daylight time if you are now on
- DAYLIGHT time; it will be entered separately. For most time zones in
- the United States and Canada, the entries required are:
-
- Eastern Standard Time EST -5.00
- Central Standard Time CST -6.00
- Mountain Standard Time MST -7.00
- Pacific Standard Time PST -8.00
-
- Enter UTC Offset (hours) [not set]: -8
- Enter Daylight Flag (0=OFF, 1=ON) [0]: 1
-
- The example entries shown above illustrate the required information for
- Pacific Daylight Time: "-8" for the standard time zone offset from UTC and
- "1" to signify that Daylight Time is in effect. Enter the information that
- is appropriate for your time zone. Once the UTC Offset and Daylight Flag
- information have been entered, these data are saved in file JPLCLOCK.INI
- and will not be requested again.
- Not surprisingly, JPLCLOCK relies upon the internal clock in your
- computer to maintain accurate time. However, not all computer clocks are
- created equal; some are much more accurate than others and it is difficult
- to predict that performance in advance. The computer clock was simply not
- designed as a high precision timekeeping instrument. Further, recent
- versions of DOS (3.3 and higher) can reset an otherwise relatively accurate
- hardware clock if the software clock loses time.
- Just as your quartz watch will keep time most consistently (as opposed
- to accurately) when you leave it always on your wrist, so too your computer
- clock will keep time best if it is left on continuously. Time and
- temperature changes are a quartz oscillator's worst enemy, along with a
- long term crystal aging effect. Taken together, these effects can cause
- your clock to lose or gain up to several seconds per day. For reasonably
- accurate operation, your computer clock should be synchronized against a
- time standard from time to time. See the sections DOS CLOCK CALIBRATION and
- TIME SYNCHRONIZATION for additional discussion, especially for
- installations where high precision is desired or required.
- Other factors may also affect the accuracy of the computer's clock.
- One of the most common and severe offenders is Local Area Network (LAN)
- software; while this can vary depending upon the LAN BIOS and network
- hardware being used, the networking software in many systems may completely
- or partially ignore the clock's "time ticks" during network operations.
- Another frequent offender is high speed communication (usually about 50Kb
- Program JPLCLOCK Multimission Control Center Clock Page 11
-
-
- per second or higher) via the serial communications ports, CON1 through
- COM4; in this case too, time ticks may be lost and the clock will fall
- behind. Clock problems related to networking or other software can result
- in time losses up to tens of seconds or even minutes per day! There is no
- remedy for this situation except to avoid using the software which causes
- the problem.
- Once the UTC Offset and Daylight Flag are set, JPLCLOCK continues with
- its normal startup and displays the title screen (see below). Verify that
- the current local and UTC time and date (including your local time zone
- abbreviation if you are located in the United States) are correct before
- proceeding. JPLCLOCK will start automatically in 10 seconds and the message
- on the screen will count down during the wait time. No operator action is
- required if you wish JPLCLOCK to start; you may also press ENTER twice to
- immediately start the program, bypassing the 10 second delay.
- JPLCLOCK's full name and the current version are shown on the title
- screen, followed by the current time and date. At this point the program is
- awaiting user input; if no keyboard input is detected within 10 seconds,
- the program will automatically begin operation. Press ENTER to display the
- Main Menu or ESC to quit the program and return to DOS. All other keys are
- ignored except that a timed message is displayed at the upper right of the
- screen reminding the user to press ENTER for the Main Menu.
- Program JPLCLOCK Multimission Control Center Clock Page 12
-
-
-
-
- Program JPLCLOCK
-
- NASA/JPL Multimission Computer Control Center Clock
- Version 9128
-
-
- Current time: 20:18:02 PDT 03:18:02 UTC
- Current date: 06/30/1991 07/01/1991
-
-
- JPLCLOCK will start automatically in 10 seconds
-
- OR
-
- Press ENTER for MENU, ESC to QUIT
-
-
-
- (C) Copyright David H. Ransom, Jr., 1991
- All rights reserved.
-
-
- Note both the local time and date (Pacific Daylight Time in the
- example) and UTC time and date (Coordinated Universal Time). Be sure that
- ALL time and date items are correct. If not, press ENTER to go to
- JPLCLOCK's Main Menu and then press F4 to correct the information.
-
-
- IMPORTANT NOTE
- --------------
-
- If you are using a JPLCLOCK.INI file (or any other INI
- file) prepared at some other location, your local time
- and date may not be correct. If all else fails, quit
- program JPLCLOCK, delete file JPLCLOCK.INI, and restart
- the program. JPLCLOCK will assist you in setting up the
- program for your time zone and will create a new
- JPLCLOCK.INI file for subsequent use.
-
-
- JPLCLOCK MAIN CLOCK DISPLAY
- ---------------------------
-
- The Main Clock display for JPLCLOCK is illustrated on Pages ii and iii
- above. Two screen layouts are available, selectable either by a command
- line option or by a Function Key, NORMAL or SMALL. The NORMAL screen
- provides a large window with special large characters for Local and UTC
- Times and is recommended when the program will be used on a normal monitor
- which may have to be viewed from some distance. The SMALL screen provides a
- smaller window for Local and UTC Times along with up to four additional
- timers and may be preferred when JPLCLOCK is projected on a large screen.
- The remaining windows are the same for both screen layouts. The four
- Location Clocks are below the main window, and the six Mission/Event Timers
- Program JPLCLOCK Multimission Control Center Clock Page 13
-
-
- are on the right side of the screen. The Location Clocks and the
- Mission/Event Timers are separately described in following sections. In
- addition to these data, the main clock display also includes the program
- name and version, as well as the current Julian Date (a standard method of
- day numbering used by scientists and astronomers) and local date (day-
- month-year) at the upper right corner of the display.
- The following keys are active while JPLCLOCK is running and the clocks
- and timers are displayed on the screen:
-
- ENTER Stop the main clock display and go to JPLCLOCK's Title
- Screen. Press ENTER again to go to the Main Menu. See
- the section below for a description of the available
- commands at the Main Menu.
-
- ESC Quit JPLCLOCK and return to DOS. You will be asked to
- press ESC again to confirm that you wish to quit the
- program. If not, press ENTER to resume operation.
-
- ALT-F1 Freeze the display. Updating the screen stops EXCEPT
- that Local and UTC Time will be updated above the Main
- Window and the word "FREEZE" will flash in yellow above
- the Mission Timer Windows while the freeze is in
- effect. The freeze will be automatically released in
- five minutes, or press ENTER to release the freeze
- immediately. (Actually, pressing any key except keys
- which do not generate a character, such as SHIFT, ALT,
- or CTRL, will release the freeze.)
-
- ALT-F5 Change SELECTED/PRIORITY EVENTS display. This key is
- active ONLY when the SMALL Main Window is active. The
- choices are: four SELECTED Mission Timers; two SELECTED
- Mission Timers and two PRIORITY Mission Timers; or,
- four PRIORITY Mission Timers. Press again for the next
- arrangement.
-
- ALT-F6 Switch between the LARGE Main Window and the SMALL Main
- Window. Enabling the SMALL Main Window also displays
- the four SELECTED/PRIORITY Event Timers (as currently
- selected).
-
- ALT-F7 Enable or disable the TEXT mode if the file
- JPLCLOCK.MSG is present; otherwise, this command has no
- effect. See the section USING TEXT MODE for further
- information on this mode of program operation. This
- command is the same as the F7 command on the Main Menu.
-
- ALT-F8 Enable or disable the PAGE mode. If the TEXT mode is
- enabled when the PAGE mode is disabled, the TEXT mode
- will also be disabled. This command is the same as the
- F8 command on the Main Menu.
-
- ALT-F9 EXPERIMENTAL COMMAND to enable a special screen font,
- similar to "Helvetica", for EGA and VGA monitors ONLY.
- The special font is designed primarily for EGA systems
- and may not operate correctly on VGA systems. (On one
- Program JPLCLOCK Multimission Control Center Clock Page 14
-
-
- VGA system, for example, the last few lines of the
- screen show a variety of text and graphics symbols when
- program TIMESET is executed, and these symbols remain
- on the screen when JPLCLOCK resumes operation.)
-
- ALT-F10 Immediately perform TIME SYNCHRONIZATION using the
- external program TIMESET to call either the National
- Institute of Standards and Technology (NIST) or the
- U.S. Naval Observatory (USNO). See the section TIME
- SYNCHRONIZATION for further information on this command
- and program TIMESET. This command is the same as the
- F10+F1 commands on the Main Menu.
-
- Four additional timer windows appear on the screen below the Main
- Clock window when the SMALL Main Window is selected. These are divided into
- two classes: SELECTED EVENTS and PRIORITY EVENTS. SELECTED EVENTS are just
- like regular Mission/Event Timers except that they are always displayed;
- they may be selected from the current Mission/Event Timers by pressing
- F3+F2 from the Main Menu. PRIORITY EVENTS are those events which have a
- Time Zero which is within 24 hours of the current time.
- Three different arrangements of SELECTED EVENTS and PRIORITY EVENTS
- may be selected by pressing ALT-F5 when the SMALL Main Clock is displayed.
- These two classes of events are always selected from the available 60
- Mission/Event Timers; note that the titles have been truncated because the
- window width is shorter than the normal Mission/Event Window. The default
- arrangement displays four SELECTED EVENTS:
-
- +--------------- SELECTED EVENTS ----------------+
- | |
- +[Hubble Space Telesc]-+ +[ Voyager 1 ]---------+
- #1 | 424 01:38:02 | | 5,051 01:13:54 | #3
- +----------------------- +----------------------+
- | |
- #2 +[Gamma Ray Observato]D+ +[ Voyager 2 ]---------+
- | 90 22:49:09 3 3 5,066 23:47:54 | #4
- +----------------------+ +----------------------+
- +------------------------------------------------+
-
- Pressing ALT-F5 once will change the arrangement to two SELECTED
- EVENTS and two PRIORITY EVENTS:
-
- +-- SELECTED EVENTS ---+ +-- PRIORITY EVENTS ---+
- | | | |
- #1 +[Hubble Space Telesc]D+ | | #1
- | 424 01:37:27 | | |
- +----------------------+ | |
- | | | |
- #2 +[Gamma Ray Observato]-+ | | #2
- | 90 22:48:34 | | |
- +----------------------+ | |
- +----------------------+ +----------------------+
-
- Note that only the first two SELECTED EVENTS are now displayed. In this
- example, there are no active PRIORITY EVENTS and therefore that window area
- is blank. JPLCLOCK continuously scans all 60 Mission/Event Timers to
- Program JPLCLOCK Multimission Control Center Clock Page 15
-
-
- determine if any are less than 24 hours (plus or minus) from the current
- time. Events which have not yet occurred are shown with a RED background,
- and events yet to occur are shown with a GREEN background. If any events
- are found within the 24 hour range, they are sorted in such a way that #1
- is that event now closest to Time Zero and #2 is the next closest to Time
- Zero. The ordering of PRIORITY EVENTS is set dynamically and will change as
- the time difference between the Time Zero set in the Mission/Event Timers
- changes with respect to current time.
- Pressing ALT-F5 again will change the arrangement to four PRIORITY
- EVENTS:
-
- +--------------- PRIORITY EVENTS ----------------+
- | |
- +[ Test Event ]--------+ |
- #1 | 0 01:38:02 | | #3
- +----------------------- |
- | |
- #2 | |
- | | #4
- | |
- +------------------------------------------------+
-
- As described above, the PRIORITY EVENTS are continuously scanned and
- sorted. With this display arrangement, from zero to four PRIORITY EVENTS
- may be displayed. In the example shown, the Mission/Event Timer called
- "Test Event" has been detected as within 24 hours of Time Zero (1 hour and
- 38 minutes past Time Zero in this case) and is therefore displayed.
- Program JPLCLOCK Multimission Control Center Clock Page 16
-
-
- JPLCLOCK MAIN MENU
- ------------------
-
-
- Program JPLCLOCK
-
- NASA/JPL Multimission Computer Control Center Clock
- Version 9128
-
-
- Current time: 20:18:50 PDT 03:18:50 UTC
- Current date: 06/30/1991 07/01/1991
-
-
- JPLCLOCK will start automatically in 10 seconds
-
-
-
- F1 Program Information F6 CLOCK Calibration [OFF]
- F2 Set LOCATION CLOCKS F7 Switch TEXT Mode [OFF]
- F3 Set EVENT/MISSION TIMERS F8 Switch PAGE Mode [ON]
- F4 Set DAYLIGHT and Defaults F9 DOS Shell (3.3+ ONLY!)
- F5 Read/Save INI & MTD Files F10 Time Synchronization
-
- ENTER Resume Program JPLCLOCK ESC Quit Program JPLCLOCK
-
- Enter selection:
-
- As with the title screen, JPLCLOCK is awaiting user input; if no
- keyboard input is detected within 10 seconds, the program will
- automatically resume operation. Note that the Main Menu displays the
- current status of CLOCK Calibration, TEXT Mode, and PAGE Mode. Press ENTER
- to immediately resume program operation. Press ESC to quit and return to
- DOS; the program will request that you press ESC a second time to confirm
- that you wish to return to DOS. (To resume JPLCLOCK when this message
- appears, press ENTER.) To go to one of the sub-menus, press the indicated
- Function Key. The purpose and operation of each menu item is described on
- the following pages.
- Program JPLCLOCK Multimission Control Center Clock Page 17
-
-
- F1 Program Information
- ------------------------
-
-
- Function Key F1 displays a brief description of the program and
- gives the telephone number of my bulletin board system (BBS), RPV ASTRONOMY
- BBS, in Rancho Palos Verdes, California near Los Angeles. This is a free
- access BBS which I maintain as a public service. There are nearly 1,000
- more or less regular callers, and the system is frequently busy, so please
- be patient! The BBS computer has a power controller; if the BBS has not
- answered by the fourth ring, hang up and call back in approximately two
- minutes.
-
- RPV ASTRONOMY BBS
-
- (213) 541-7299
- (310) 541-7299 [November, 1991]
-
-
- IMPORTANT NOTE
- --------------
-
- The BBS area code number will change in November, 1991
- as the telephone company again splits the Los Angeles
- 213 area code into two areas. The new number will be
- (310) 541-7299.
-
- Program JPLCLOCK was written especially for the NASA/JPL Multimission
- Computer Control Center. It provides a main window with local and UTC
- time, four location clocks usually displaying local time at the NASA
- Deep Space Network sites in Goldstone, Canberra, and Madrid, and six
- event timers used to display mission elapsed time or the time for an
- upcoming event of interest. The current version of JPLCLOCK is always
- available on my BBS.
-
- David H. Ransom, Jr.
- Program JPLCLOCK Multimission Control Center Clock Page 18
-
-
- F2 Set LOCATION CLOCKS
- ------------------------
-
- JPLCLOCK displays from one to four LOCATION CLOCKS. When the program
- is used in the JPL Mission Control Center, three of the clocks normally
- display the time for the DSN (Deep Space Network) antenna locations; the
- fourth location clock may be used for another location of interest or may
- be left blanked out. The location clocks are numbered #1 through #4 and are
- located in the lower left portion of the display screen below the main
- window in the following relative positions:
-
- | Main Window | |
- +------------------------+ +---
-
- +----------+ +----------+ +---
- | #1 | | #3 | |
- +----------+ +----------+ +---
-
- +----------+ +----------+ +---
- | #2 | | #4 | |
- +----------+ +----------+ +---
-
- Each Location Clock displays the local time at the location using the
- following format (all times in 24-hour notation, HH:MM:SS):
-
- 147 13:24:16 PDT
- --+ -+ -+ -+ --+
- | | | | |
- | | | | +--- Time Zone Abbreviation (if present)
- | | | |
- | | | +------- Local Seconds
- | | +---------- Local Minutes
- | +------------- Local Hours
- |
- +------------------ Local Day of the Year
-
- Function Key F2 allows the user to change the name and time zone
- information for the four location clocks displayed below the main window.
- If a location name is PRESENT for a given location clock, that clock will
- be displayed on the screen; if the location name is ERASED (the "Location
- Name" column for the clock is blank in the display), the clock will NOT be
- displayed on the screen. The default location clocks are shown below:
-
- Uses
- # Location Name UTC Offset DST
- -----------------------------------------
- 1 GDX Goldstone -8.00 YES
- 2 JSC Houston -6.00 YES
- 3 CAN Canberra 11.00 NO
- 4 MAX Madrid 1.00 NO
-
- Enter LOCATION # to change:
-
- JPLCLOCK will automatically resume operation if no keyboard input is
- detected within 30 seconds. Each keystroke resets the 30 second timer.
- Program JPLCLOCK Multimission Control Center Clock Page 19
-
-
- Press ENTER to cancel this function and return to the Main Menu making no
- changes. To continue, enter the number of the location clock to change and
- press ENTER. Then enter the new location name for that clock:
-
- Enter new LOCATION NAME:
-
- Press the TAB key to leave the name unchanged for this clock and skip to
- the time information. Press ENTER to erase the name and remove the clock
- from the display screen. To enter a new or corrected location name, type
- the new name and then press ENTER. JPLCLOCK will automatically capitalize
- the first letter of each word if it is lower case.
- In order to show the local time correctly for each location, JPLCLOCK
- must know the UTC Offset for the location; this is the number of hours
- which must be ADDED to UTC (Universal Coordinated Time) in order to obtain
- the local STANDARD time for the location. Do NOT include the additional
- hour if the location is on U.S. Daylight Savings Time; DO include the
- additional hour if the location is on daylight or summer time but the time
- changes do not correspond to those used in the United States. See the
- additional discussion below.
-
- Enter New UTC Offset (hours):
-
- Press the TAB key to leave the current UTC Offset value unchanged. Press
- the ESC key to cancel all changes to this location clock. Otherwise, type
- the new UTC Offset in hours (and decimal parts of an hour if necessary) and
- then press ENTER.
- JPLCLOCK will independently adjust each location clock time for U.S.
- Daylight Savings Time if the special flag in the column "Uses DST" is
- marked "YES". As a general rule, therefore, respond "YES" if the location
- is within the United States (including Alaska and Hawaii); respond "NO" if
- the location is outside the United States.
-
- Uses US Daylight (N=NO, Y=YES):
-
- IMPORTANT NOTE: When the main Daylight Flag is changed (using F4+F3
- from the Main Menu), the appropriate correction will be automatically made
- for all locations which indicate "YES" in the "Uses DST" column. Locations
- outside the United States which use daylight or summer time but which
- change at different times from the United States should indicate "NO" in
- the "Uses DST" column and must be manually adjusted for each time change.
-
- When all of these questions have been answered, the information will
- be updated on the screen and the user may either continue to another
- location clock or return to the Main Menu.
- Program JPLCLOCK Multimission Control Center Clock Page 20
-
-
- F3 Set EVENT/MISSION TIMERS
- -----------------------------
-
- One of the most important functions of JPLCLOCK is to be able to
- display Mission Elapsed Time (MET) or Countdown/Countup Time for a variety
- of missions and events. MIssion Elapsed Time usually measures the time
- since the mission was launched and is the primary time measure used for the
- Mission Timeline, the schedule of planned events and operations; this
- applies equally to short duration missions such as the Space Shuttle as
- well as to long duration missions such as Voyager and Hubble Space
- Telescope. Countdown/Countup Times may be critical events in the progress
- of a mission, such as scheduled Launch Time or Venus Orbit Insertion for
- Magellan, and controllers need to be able to judge the time remaining until
- (or time passed since) specific tasks or operations are to be (or were
- supposed to have been) performed.
- JPLCLOCK is able to independently time up to 60 different events or
- missions using six MISSION TIMER WINDOWS on the display screen and
- switching from one mission timer "page" to another to display up to ten
- pages. The mission timer windows are numbered #1 through #6 and are located
- on the right of the display screen beside the main window in the following
- relative positions:
-
- ---+ +----------------+
- | | TIMER #1 |
- M | +----------------+
- a |
- i | +----------------+
- n | | TIMER #2 |
- | +----------------+
- W |
- i | +----------------+
- n | | TIMER #3 |
- d | +----------------+
- o |
- w | +----------------+
- | | TIMER #4 |
- ---+ +----------------+
-
- ---+ +----------------+
- | | TIMER #5 |
- ---+ +----------------+
-
- ---+ +----------------+
- | | TIMER #6 |
- ---+ +----------------+
-
- Each Mission/Event Timer displays the current time value for that
- mission or event using one of the following formats (all times are shown as
- HH:MM:SS, hours:minutes:seconds):
-
- 143 13:01:47 The event occurred 143 days plus time ago.
- When applied to a mission, this format is
- measured from the time of launch and is known
- as Mission Elapsed Time (MET) and is used for
- all mission event planning.
- Program JPLCLOCK Multimission Control Center Clock Page 21
-
-
-
- -16 01:33:19 The event will occur in 16 days plus time.
-
- -0 07:44:51 * The event will occur in the time shown and a
- flashing asterisk denotes less than 24 hours.
-
- -0 00:58:29 ** The event will occur in the time shown and
- two flashing asterisks denote less than 1
- hour remains.
-
- -0 00:08:14 *** The event will occur in the time shown and
- three flashing asterisks denote less than 10
- minutes remain.
-
-
- Pressing F3 from the Main Menu displays the menu for setting the
- MISSION/EVENT TIMERS and the SELECTED EVENTS:
-
- F1 Set MISSION/EVENT TIMERS
- F2 Set SELECTED EVENTS
-
- ENTER Return to Main Menu
-
- Press the Function Key for the desired selection or press ENTER to return
- to the Main Menu.
-
- Set MISSION/EVENT TIMERS
- ------------------------
-
- Using F1, each Mission/Event Timer may be set to any desired time and
- date in the past or future over a range of approximately minus 27 years (-
- 9,999 days before the event) to approximately plus 274 years (99,999 days
- after the event) referenced to the current time. Given the time scale of
- interplanetary missions such as Voyager 1 and 2 or Pioneer 11, these time
- ranges are reasonable and necessary even though it may seem like "overkill"
- for a 5-day Space Shuttle mission. The Mission Timer Window background
- color (for color monitors) is RED if the event has not yet occurred and
- GREEN if the event has occurred. The color switch occurs when the Mission
- Timer reaches 0 days and 00:00:00 (hours:minutes:seconds).
- As a special feature to call attention to events about to occur, a
- single asterisk ("*") appears to the right of the countdown time when the
- event is less than 24 hours from occurrence; this changes to two asterisks
- at T minus one hour and to three asterisks at T minus ten minutes. The
- asterisks are removed once the scheduled event time occurs.
- When JPLCLOCK is operated in the NORMAL mode, Mission Timers #1
- through #6 are displayed continuously; the remaining 54 timers are neither
- checked nor displayed. However, when JPLCLOCK is operated in the PAGE mode,
- all 60 Mission Timers are checked and are displayed if a valid time and
- date has been entered. The Mission Timers are divided into ten pages of six
- timers each. The pages are numbered 0 through 9; Mission Timers #1 through
- #6 appear on Page 0, Mission Timers #7 through #12 appear on Page 1, and so
- forth. If any one of the timers in a given page is valid, that page will be
- displayed; if no timers in a given page are valid, that page will be
- skipped. Each page is displayed for 30 seconds and then the program cycles
- to the next valid page. With active Mission Timers in each of the ten
- Program JPLCLOCK Multimission Control Center Clock Page 22
-
-
- pages, it can require up to 5 minutes to complete a full cycle through the
- timers.
- When the PAGE mode is active and JPLCLOCK is cycling through all
- active Mission Timers, a special "bar meter" is displayed at the top right
- of the Mission Timers. This is a row of ten special square symbols, one for
- each of the ten Mission Timer pages, which indicates the status of the
- page. If there are no active Mission Timers on the page, the symbol is
- GRAY. If one or more Mission Timers on the page is in the countdown mode
- (the event has not yet occurred), the symbol is RED. If all active Mission
- Timers on the page are in the countup or Mission Elapsed Time mode, the
- symbol is GREEN. The current active page is flashing.
- With up to 60 Mission Timers active in the PAGE mode, it might be easy
- to overlook an event which is scheduled to occur in the near future. The
- flashing asterisks described above may help to avoid this situation but
- JPLCLOCK solves the problem by "freezing" the display on a page if any
- Mission Timer on that page will reach Time Zero within the next hour. The
- freeze remains in effect until all timers on that page are either more than
- one hour before Time Zero or have passed Time Zero by more than one hour.
- When the freeze is removed, normal cycling is resumed and the program
- checks for other potential freeze opportunities on each page as it is
- displayed.
-
-
- IMPORTANT NOTE
- --------------
-
- If two Mission Timers are on different pages and are
- scheduled to reach Time Zero at approximately the same
- time (within two hours), the first timer encountered
- will enable the freeze for its page and the second
- timer will not be checked! Some care must therefore be
- used in selecting events for each page in order to
- avoid this type of "freeze conflict".
-
- Not all Mission Timers on a particular page must be programmed. If the
- Event/Mission Name is blank, that Mission Timer will not be displayed and
- its position on the display screen will be blank. The user may therefore
- arrange both which page(s) will be displayed as well as what position(s)
- is(are) used to display the active timers on a given page. As noted above,
- if ALL Mission Timers on a particular page are blank, that page will be
- skipped.
- Function Key F3 provides the capabilities to enter, erase, or correct
- the Mission Timers. The first time F3 is used, Page 0 and the first six
- Mission Timers will be displayed; subsequent uses of F3 may start on a
- different page. The Page Number is shown along with the data for the
- individual Mission Timers on that page.
-
- Program JPLCLOCK Multimission Control Center Clock Page 23
-
-
- # Event/Mission Name Time(UT) Date (MDY) Julian Date
- PAGE ---------------------------------------------------------------
- 1 Magellan 15:00:00 10/18/1989 2447818.125000
- +---+ 2 Ulysses 11:47:15 10/06/1990 2448170.991146
- | | 3 Galileo 13:00:00 10/06/1989 2447806.041667
- | | 4 Hubble Space Telescope 12:33:52 05/07/1990 2448019.023519
- | | 5 Gamma Ray Observatory 15:22:45 04/05/1991 2448352.140799
- +---+ 6 ROSAT Observatory 21:47:59 06/01/1990 2448044.408322
- (Home, PgUp, PgDn, ENTER to return to Main Menu)
- Enter EVENT # to change (1-60):
-
- NOTE: The dates and times for Magellan, Ulysses, and Galileo shown above
- are dummy values entered for testing purposes. Subsequent releases of the
- program will include the actual values.
-
- The reminder enclosed in parentheses indicates the special keys that
- are active at this prompt:
-
- Home Display PAGE 0
- PgUp Go to NEXT PAGE
- PgDn Go to PRIOR PAGE
- ENTER Return to Main Menu
-
- Use PgUp or PgDn to review each of the ten Mission Timer pages or type the
- number of the desired Mission Timer followed by ENTER to edit that Mission
- Timer. When a Mission Timer has been selected, a flashing diamond will
- appear to the left of the Mission Timer number in the display and you will
- be asked to enter a new MISSION NAME. For the following example, Mission
- Timer #7 was desired and "7" was typed:
-
- # Event/Mission Name Time(UT) Date (MDY) Julian Date
- PAGE ---------------------------------------------------------------
- * 7 Voyager 1 03:59:02 10/16/1977 2443432.666000
- -+ 8 Voyager 2 19:59:31 08/01/1977 2443357.333000
- | 9
- | 10
- | 11
- --+-- 12
- (TAB to SKIP, #nn to COPY, ESC to CANCEL, ENTER to ERASE #7 data)
- Enter #7 EVENT/MISSION NAME:
-
- The asterisk shown above will actually be displayed as a flashing
- diamond to indicate the selected Mission Timer. The reminder enclosed in
- parentheses indicates the special keys that are active at this prompt:
-
- TAB SKIP the name, leaving it unchanged, and continue.
- ESC CANCEL making changes to this Mission Timer
- ENTER ERASE all data for this Mission Timer
-
- In some cases, you may wish to copy an event from one Mission Timer to
- another. If the event is simply being moved, you would then go back and
- erase the original entry; otherwise, the event will appear in multiple
- Mission Timers (which might be desired for certain important events). The
- "#nn" format may be used for this purpose by substituting the SOURCE
- MISSION TIMER NUMBER for "nn". Thus, after selecting the DESTINATION
- Program JPLCLOCK Multimission Control Center Clock Page 24
-
-
- MISSION TIMER NUMBER in the previous step, you would enter "C13" to copy
- all data from Mission Timer #13 to the selected Mission Timer.
- In other cases, you may wish to prepare a group of related Mission
- Timers relative to a single time. A sequence of operations following launch
- or satellite deploy are examples of this situation. To do this, first
- select the "base time" event and enter its information into a selected
- Mission Timer. Next, select each successive Mission Timer whose time is
- relative to the "base time" and use one of the following formats:
-
- #nn+ddd/hh:mm:ss
- #nn+hh:mm:ss
- #nn-ddd/hh:mm:ss
- #nn-hh:mm:ss
-
- where:
-
- # Specifies the COPY syntax
- nn SOURCE MISSION TIMER NUMBER, 1 to 60
- + Specifies ADD to "base time"
- - Specifies SUBTRACT from "base time"
- ddd The number of DAYS to add/subtract to "base time"
- / Separates DAYS from TIME
- hh The number of HOURS to add/subtract to "base time"
- mm The number of MINUTES to add/subtract to "base time"
- ss The number of SECONDS to add/subtract to "base time"
- : Separates hours:minutes and minutes:seconds
-
- Note that the days portion of the command, "ddd/", may be omitted if the
- value is zero; omitting the days is equivalent to a days portion of "000/".
- The number of digits shown for each portion of the command may not be
- exceeded, but leading zeroes may be omitted. Times may differ by as little
- as one second. (In fact, they may be identical if you wish.)
- As an example of relative Mission Timer programming, suppose that the
- "base time" for a sequence of events is on 7/11/1991 at 13:44:00 UTC and
- that a series of subsequent events will occur at this "base time" plus 37
- seconds, 1 minute and 30 seconds, and 3 hours and 7 minutes. The following
- commands will set up this sequence of Mission Timers:
-
- 25 Event Timer Number
- Base Event Event Name
- 7/11/91 Event Date
- 13:44 Event Time
-
- 26 First Subsequent Timer Number
- #25+00:00:37 Relative time to Mission Timer 25
-
- 27 Second Subsequent Timer Number
- #25+00:01:30 Relative time to Mission Timer 25
-
- 28 Third Subsequent Timer Number
- #25+03:00:07 Relative time to Mission Timer 25
-
- After these commands have been entered, Mission Timers 25 through 28 will
- contain the base event and the three subsequent events. Since the "copy"
- format has been used for the subsequent events, the names will be identical
- Program JPLCLOCK Multimission Control Center Clock Page 25
-
-
- in all four Mission Timers. You may then edit Mission Timers 26 through 28
- by selecting them in turn, entering a new event name, then pressing TAB in
- place of a date entry to leave that information unchanged.
- Future events are sometimes rescheduled. To accommodate this
- situation, the "#nn" command may be used to copy an event to the same
- Mission Timer with a positive or negative time adjustment. Select the
- Mission Timer number you wish to adjust, enter the "#nn" command as
- described above (including the relative time adjustment) and the change
- will be made. For example, to advance the time for Mission Timer 44 by one
- hour and thirty minutes, enter the following commands:
-
- 44 Timer Number to adjust
- #44+1:30 Advance the time by 1:30
-
- This example illustrates a "shortcut": if the seconds are zero, they may be
- omitted. Similarly, if both minutes and seconds are zero, both may be
- omitted. The hours could also have been entered with a decimal fraction and
- the minutes omitted: "#44+1.5" to achieve the same result. The optional
- days ("#44+3/1:30" to advance the time by 3 days, 1 hour, 30 minutes) could
- have been used if required.
- If you wish to enter new data for this mission timer, type the new
- name for this Mission Timer followed by ENTER. You will then be asked to
- enter the new DATE for this timer:
-
- (ESC to CANCEL)
- Enter new DATE (MM/DD/YYYY or JD/MJD):
-
- Press ESC to CANCEL making changes to this Mission Timer or type the new
- DATE followed by ENTER. Dates are normally entered using "MM/DD/YYYY"
- format where "MM" is the MONTH (month number), "DD" is the DAY, and "YYYY"
- is the YEAR. JPLCLOCK will also accept a two-digit year and add 1900 to the
- value entered; "1991" and "91" will both be accepted as "1991". JPLCLOCK
- will also accept several "JD" (Julian Date) formats by prefixing the date
- entry with one of the following:
-
- Prefix Julian Date Format Name Starting Date
- -------------------------------------------------------------------
- JD 2448424.375000 Standard Julian Date (-4713 JAN 1.5)
- MJD 48423.875000 Modified Julian Date (1858 NOV 17.0)
- DJD 33404.375000 Dublin Julian Date (1900 JAN 0.5)
- TJD 8423.875000 Truncated Julian Date (1968 MAY 23.0)
-
- All of the Julian Date formats in the example are equal to June 16, 1991,
- at 14:00 PDT. "JD" is the standard format used by astronomers and most
- scientists. The other formats have been developed to reduce the number of
- digits required to uniquely identify a specific date but have more
- restricted range if negative numbers or large numbers are to be avoided.
- NASA, for example, frequently uses the "TJD" format.
-
- NOTE: When one of the Julian Date formats is used, the time is implicit and
- the "New TIME" prompt will be skipped. Thus, an entry of "JD2448424.375" or
- "TJD8423.875" would yield the same time and date as "6/16/91" (for DATE)
- and "14:00P" (for TIME).
-
- After the new date has been entered (and provided you did not use one
- Program JPLCLOCK Multimission Control Center Clock Page 26
-
-
- of the Julian Data formats), you will be prompted for the new TIME:
-
- (ESC to CANCEL)
- Enter new TIME (UTC or Zone):
-
- Type the desired new time using the "HH:MM:SS" format followed by ENTER.
- JPLCLOCK is very flexible as to the time format. JPLCLOCK requires the 24-
- hour format. Decimal fractions for the last value entered are accepted,
- leading zeroes are NOT required, the separator may be either the colon
- (":") or the comma (","), and the entry may omit values which are zero.
- Each of the following examples will be accepted as 14:15 (2:15 PM):
-
- 14:15:00
- 14,15
- 14.25
-
- JPLCLOCK assumes that the time entered is Coordinated Universal Time (UTC)
- unless a suffix is added to indicate otherwise. The following time zone
- suffixes are supported by JPLCLOCK:
-
- U UTC Universal Coordinated Time
- A AST/ADT Atlantic Time Zone
- E EST/EDT Eastern Time Zone
- C CST/CDT Central Time Zone
- M MST/MDT Mountain Time Zone
- P PST/PDT Pacific Time Zone
- Y YST/YDT Yukon Time Zone (sometimes "Alaska")
- H HST/HDT Hawaiian Time Zone
-
- Except for UTC, JPLCLOCK will automatically adjust the entered time
- for the appropriate time zone AND for daylight savings time (if in effect).
- Thus, an entry of "14:00P" will be interpreted as Pacific Standard Time
- (PST) if the Daylight Flag is OFF, and as Pacific Daylight Time (PDT) if
- the Daylight Flag is ON. If no suffix is included or if the "U" suffix is
- added, no adjustment for the Daylight Flag will be made and the time entry
- will be accepted as UTC. By using the appropriate time zone suffix, times
- may thus be entered directly in local time for each time zone in the United
- States, Alaska, and Hawaii without making any conversions (or mistakes!).
- JPLCLOCK makes the required conversions to the time (and date, if
- necessary) and displays the resulting Mission Timer values in UTC.
- Program JPLCLOCK Multimission Control Center Clock Page 27
-
-
- Set SELECTED EVENTS
- -------------------
-
- Press F2 to set the SELECTED EVENTS. The program will display the
- currently selected SELECTED EVENTS, if any, and remind you that the
- SELECTED EVENTS are displayed ONLY when the SMALL Main Clock window is
- active. To make the SMALL Main Clock window active, press ALT-F6 when the
- Main Clock window is on the screen.
-
- SELECTED EVENTS are active with SMALL Main Window ONLY!
-
- # MT# Mission/Event Name
- ----------------------------------------
- 1 11 Hubble Space Telescope
- 2 17 Gamma Ray Observatory
- 3 23 Voyager 1
- 4 24 Voyager 2
-
- (ENTER to CLEAR, TAB to SKIP, ESC to CANCEL)
- Enter MISSION/EVENT TIMER # for Selected Event #1:
-
- In the sample display above, the column marked "#" lists the four SELECTED
- EVENT timers in order; tThe column marked "MT#" lists the Mission/Event
- Timer which is associated with the corresponding SELECTED EVENT; and, the
- column marked "Mission/Event Name" lists the name of the selected
- Mission/Event Timer.
- The information for each SELECTED EVENT is requested in turn. The
- first prompt asks for Selected Event #1. As noted, press ENTER to clear
- that event, press TAB to skip to the next event, or press ESC to cancel and
- return to the Main Menu.
- The only information that can be entered here is the Mission/Event
- Timer number which you wish to be associated with each SELECTED EVENT. The
- actual data, the event name, date, and time, must already have been entered
- into the Mission/Event Timer (F3+F1 from the Main Menu). Note also that the
- while the full Mission/Event Name is displayed on the menu as shown above,
- the actual window on the screen will truncate the name to a maximum of 19
- characters; this is because the SELECTED EVENT windows are somewhat
- narrower than the main Mission/Event Timer windows. If you wish to edit the
- name so that it will fit correctly in the SELECTED EVENT windows, you must
- edit the Mission/Event Timer entry using F3+F1 from the Main Menu (or just
- F1 from the event menu).
- Program JPLCLOCK Multimission Control Center Clock Page 28
-
-
- F4 Set DAYLIGHT and Defaults
- ------------------------------
-
- Function Key F4 allows you to switch the system from local STANDARD
- time to local DAYLIGHT time and set a number of program defaults. Pressing
- F4 from the Main Menu displays the following menu:
-
-
- Enter selection:
- F1 Switch STANDARD/DAYLIGHT Time
- F2 Set LOCAL NAME and TIME ZONE
- F3 Restore Program DEFAULT DATA
- F4 Set PAGE and TEXT Mode Delays, 15 30
- ESC Return to Main Menu
- ENTER Resume Program JPLCLOCK
-
- Enter selection:
-
- Pressing ESC will return you to the Main Menu.
- Pressing ENTER will resume operation of program JPLCLOCK.
- Pressing F1 will switch the Daylight Flag between Standard time and
- Daylight time. NOTE: This function does NOT change your computer's clock;
- you must set the correct local time BEFORE using this function!
- Pressing F2 will allow you to enter a new name for your location and
- to set its standard UTC Offset (in hours) and Daylight Flag.
- Pressing F3 will restore the "hard-coded" program default data for the
- Local Name, Location Clocks and Mission Timers.
- Pressing F4 will prompt you to enter new values for the PAGE delay and
- the TEXT delay. The current values are shown at the right. The following
- information will be displayed and you will be asked for the PAGE Delay:
-
- PAGE Delay sets the time to display each page of Mission
- Timers. TEXT delay set the time to display each text page.
-
- PAGE Delay must be between 5 and 900 seconds.
- TEXT Delay must be between 5 and 900 seconds AND an even
- multiple of PAGE Delay. The times are adjusted if necessary.
-
- Enter PAGE Delay [15] (seconds):
-
- The current PAGE Delay is shown in square brackets. Enter the desired new
- value for the PAGE Delay in seconds or press ENTER to leave the present
- value unchanged. You will then be asked for the TEXT Delay:
-
- Enter TEXT Delay [30] (seconds):
-
- The current TEXT Delay is shown in square brackets. Enter the desired new
- value for the TEXT Delay in seconds or press ENTER to leave the present
- value unchanged.
- Note the minimum and maximum values allowed for these delays, 5 and
- 900 seconds respectively. Note also that the TEXT Delay must be an even
- multiple of the PAGE Delay (for internal programming reasons). If this is
- not the case, TEXT Delay will be automatically adjusted accordingly. I
- recommend the values shown in the examples above as the minimum values for
- JPLCLOCK. Smaller values allow insufficient time for reading.
- Program JPLCLOCK Multimission Control Center Clock Page 29
-
-
- F5 Read or Save INI Files
- ---------------------------
-
- JPLCLOCK reads the file JPLCLOCK.INI each time it is started, and
- writes a new JPLCLOCK.INI file each time the program is halted. This INI
- file contains all the information about the local installation, the
- Location Clocks, and the Mission Timers. For installations where only the
- first six Mission Timers are used, this information will change only
- infrequently and additional INI files will probably not be required.
- Users may find it convenient to re-read the normal INI file,
- JPLCLOCK.INI, if they have incorrectly changed information and wish to
- restore the original information. (NOTE: Exiting program JPLCLOCK in this
- situation will cause the incorrect information to be written to file
- JPLCLOCK.INI and the original data in that file will be permanently lost!)
- As a protection against this sort of problem, it is recommended that all
- users create a standard INI file, named STANDARD.INI for example, that
- represents the normal program configuration. Function Key F1 may then be
- used from this menu to reload that normal configuration at any time.
- However, installations using JPLCLOCK in the PAGE mode may find that
- advance preparation of INI files (using another computer running JPLCLOCK)
- is very helpful in preparing for upcoming events on multiple missions. In
- order to facilitate this process, JPLCLOCK can both read and write INI
- files. This takes advantage of JPLCLOCK's internal editing capabilities
- (using Function Key F3 from the Main Menu) and may avoid errors due to
- manual editing and time/date conversions. A new set of Mission Timers can
- be prepared on the "offline computer", tested, and written to an INI file
- for use on the "online computer". Files may be exchanged either via disk or
- via local area networks. Once the new INI file has been loaded onto the
- "online computer", JPLCLOCK may be paused, the new INI file read, and
- program operation resumed. Performed in this manner, the entire updating
- process will take the "online computer" offline for a few seconds. Any
- number of INI files may be prepared in this fashion, the only requirement
- being that they have unique names.
- INI files MUST have the file type ".INI". The filename may be any
- legal file name EXCEPT "JPLCLOCK.INI". Manual editing of INI files is NOT
- recommended; however, if this is done be certain to use a simple ASCII
- editor or an editor which has a "non-document" mode. Although the format of
- the INI file uses a simple comma-delimited format, an error in the file
- structure may cause the program to operate incorrectly or to crash (halt
- with an error message). If all else fails, delete the file JPLCLOCK.INI and
- restart the program; JPLCLOCK will then use its internal default data and
- construct a new INI file.
- Pressing Function Key F5 from the Main Menu will display the following
- menu:
-
- F1 Read external INI File
- F2 Save external INI File
- ESC Return to Main Menu
- ENTER Resume program JPLCLOCK
-
- Enter selection:
-
- Press F1 to read an INI file or F2 to write an INI file. All files are
- assumed to be in the current drive and directory. For file read operations,
- the file must exist. For file write operations, if the file does not exist
- Program JPLCLOCK Multimission Control Center Clock Page 30
-
-
- it will be created and if the file does exist it will be overwritten. If
- either F1 or F2 is pressed, the following prompt will be displayed:
-
- INI files contain the setup and mission/clock data for JPLCLOCK.
- Enter the name of the INI file which you wish to read or write.
- Do NOT include a filetype; the program automatically adds '.INI'.
-
- Enter filename (without .INI):
-
- Press ESC to CANCEL the file read or write. Press ENTER to use the default
- file name JPLCLOCK.INI. Otherwise, type the filename WITHOUT the ".INI"
- filetype followed by ENTER. JPLCLOCK will automatically append ".INI" to
- the filename and then read or write the file and return to this files menu.
-
-
- INI Files from Other Locations
- ------------------------------
-
- Except when JPLCLOCK is first started, the information specific to
- your location (Location Name, UTC Offset, Daylight Flag, etc.) is NOT
- processed when you read an INI file using F5. Therefore, if you receive an
- INI file from elsewhere, you should rename it to a convenient name (which
- might remind you of the source of the data, for example) and then read it
- into JPLCLOCK using F5. Since all of the remaining information in the INI
- file is recorded using UTC, JPLCLOCK will be able to make the necessary
- time conversions for display in your time zone.
- If you wish to use missions or events from a received INI file, you
- may read it in using F5, then view (and record or capture from the screen)
- the information in each Mission Timer Page. Having recorded the
- information, you may then re-read your own JPLCLOCK.INI file (press ENTER
- when asked for the INI filename) and enter the mission or event data you
- recorded using F3 as usual. Note that the times and dates shown on each
- Mission Timer page are always Coordinated Universal Time (UTC), not your
- local time, so do not include a time zone suffix when entering the time
- recorded from another INI file!
-
-
- Editing INI Files
- -----------------
-
- Although it is not recommended for the novice computer user, the
- Mission Timer information contained in an INI file may be edited or copied
- from one file to another. Before editing INI files, make a backup copy of
- your JPLCLOCK.INI file using another name such as "BACKUP.INI". This will
- preserve your JPLCLOCK.INI file in the event you make a mistake. Use only a
- simple ASCII editor, or use a word processor program in the "non-document"
- or "ASCII" mode!
- The last 60 lines of the INI file contain the information for Mission
- Timers #1 through #60. A typical line appears as:
-
- "Mission Name",2448135.30419
-
- The words within the quotation marks ("Mission Name") are the name of the
- mission or event, followed by a comma, and the number is the Julian Date
- for the mission or event time. An unused Mission Timer is shown as:
- Program JPLCLOCK Multimission Control Center Clock Page 31
-
-
-
- "",0
-
- This is known as the "comma delimited format", used by BASIC and other
- software for file data. No error checking is performed, so observe the file
- structure and format exactly! Errors in the INI file structure, especially
- in the initial several lines, can cause JPLCLOCK to crash (exit with an
- error message); if all else fails, erase the bad file and start over with a
- fresh INI file copied from the file JPLCLOCK.INI as written by JPLCLOCK.
- By editing an INI file, events from other locations or sources may be
- "spliced" into your own INI file. For example, if you receive an INI file
- which includes a number of events of interest, use your editor to snip out
- the Mission Timer lines you want and then replace a corresponding number of
- lines in a copy of your JPLCLOCK.INI file with the new lines. I recommend
- placing the new lines at the END of the file; you may use F3 from the Main
- Menu to copy them to the desired Mission Timer once you read in the edited
- file. Do NOT edit file JPLCLOCK.INI; always make a copy with a new name and
- read it using F5. This will preserve your data in case your make an error!
- Program JPLCLOCK Multimission Control Center Clock Page 32
-
-
- F6 Self-Calibration using TIMESET
- -----------------------------------
-
- Function Key F6 enables a special self-calibration procedure which
- causes JPLCLOCK to use program TIMESET to perform a series of calibration
- measurements over a period of 7 hours. Note that TIMESET must have been
- correctly configured and tested prior to automatic use. See the procedure
- for configuring TIMESET in the section F10 TIME SYNCHRONIZATION below and
- read the TIMESET documentation.
- When the Self-Calibration procedure is initiated, JPLCLOCK immediately
- makes a call using TIMESET and resets the drift and offset parameters. The
- program then makes subsequent calls at 1, 2, and 4 hour intervals (for a
- total of four calls) to enable calculation of new parameters. When the last
- call has been completed, a reasonable calibration of the DOS clock should
- have been calculated.
- The computer must be allowed to run JPLCLOCK continuously, with the
- clocks displayed, during the procedure. However, the usual commands are
- available for use between calls PROVIDED you do not exit to DOS and the
- clocks are displayed when the time comes to make each call. Of particular
- interest after the second call (in other words, after more than one hour
- has elapsed since the procedure was started) is the calculated DOS Clock
- Drift. With the main clock display on the screen, press ENTER twice to
- obtain the Main Menu, then press F10+F1 to view the current data:
-
- DOS time: 06:45:26.17 07-05-1991
- CMOS time: 06:45:27 07-05-1991
- JPLCLOCK time: 06:45:27 PDT 13:45:27 UTC
- JPLCLOCK date: 07/05/1991 07/05/1991
-
- JPLCLOCK will start automatically in 88 seconds
-
- Current Julian Date: 2448443.073229
- Last Synchronized: 2448442.500926
- Time since Last Sync: 0.572303 days
- Current Clock Offset: 0.00 seconds
- Current DOS Drift Rate: -1.512899 seconds/day
- Current Total Adjust: -0.87 seconds
-
- Press ESC for Sync Menu, ENTER to ADJUST data:
-
- In the example above, about half a day has elapsed since the last
- synchronization was performed. As a result of that measurement, JPLCLOCK
- has calculated that the drift rate of the DOS clock is -1.512889 seconds
- per day and that the current time must be adjusted by SUBTRACTING -0.87
- seconds from the DOS clock. Above these data are four time displays showing
- the present DOS clock (the one being calibrated), the CMOS clock (the
- computer's hardware clock), and the JPLCLOCK time and date both for the
- local time zone and for UTC. The JPLCLOCK time is the time displayed in the
- Main Clock window and reflects the current calculated adjustment from the
- DOS time.
- When using self-calibration, ALWAYS press ESC after viewing these data
- to return to normal operation. If you press ENTER by mistake, press the TAB
- key to leave all items unchanged.
- JPLCLOCK generates a "temporary" automatic synchronization schedule
- during self-calibration, saving the prior schedule (if any). Thus, the
- Program JPLCLOCK Multimission Control Center Clock Page 33
-
-
- program will perform the procedure over 7 hours and then revert to the
- original automatic schedule (if automatic synchronization is ENABLED) or
- turn off automatic synchronization (if automatic synchronization is
- DISABLED). You may verify the current status of the automatic
- synchronization from the Main Menu by pressing F10+F3; this will show the
- schedule now in effect; note that the times shown in the schedule are UTC.
-
- F1 Execute TIMESET (Manual)
- F3 Set Automatic Synchronization: ENABLED
- NEXT TIME = 00:55:00 UTC
- START = 08:55:00 UTC
- INTERVAL = 04:00:00
- ESC Return to Sync Menu
- ENTER Resume Program JPLCLOCK
-
- Enter selection:
-
- In the example shown, the automatic synchronization schedule has been set
- to start at 00:55:00 UTC and repeat every four hours. Comparing this
- schedule against the current time, JPLCLOCK will next perform the
- synchronization at 08:55:00 UTC.
- Program JPLCLOCK Multimission Control Center Clock Page 34
-
-
- F7 Switch TEXT Mode
- ---------------------
-
- Function Key F7 permits you to enable or disable the TEXT mode
- provided the text file JPLCLOCK.MSG is present on the current drive and
- directory when the program is started. This command is equivalent to the
- "/TEXT" command line option. If the file JPLCLOCK.MSG has been added while
- using the DOS SHELL (F9), the text will NOT be available since the file is
- read ONLY when JPLCLOCK is started from DOS. Quit program JPLCLOCK and
- restart the program if you wish to add or edit JPLCLOCK.MSG.
-
-
- F8 Switch PAGE Mode
- ---------------------
-
- Function Key F8 permits you to enable or disable the PAGE mode. This
- command is equivalent to the "/PAGE" command line option. Disabling the
- PAGE mode will also disable the TEXT mode if it is currently enabled.
-
-
- F9 DOS Shell (DOS 3.3+ ONLY)
- ------------------------------
-
- Function Key F9 invokes the DOS SHELL, loading a second copy of
- COMMAND.COM and displaying the usual DOS prompt. Most DOS commands and
- programs are now available. To return to JPLCLOCK, type the following at
- the DOS prompt (followed by ENTER):
-
- EXIT
-
- Note that using the SHELL with versions of DOS prior to Version 3.3
- may yield unpredictable results. Because program JPLCLOCK remains in memory
- and a second copy of COMMAND.COM is also loaded into memory, the memory
- available to execute programs under the SHELL is considerably reduced. Some
- programs may fail to execute due to insufficient memory or you may receive
- an "Out of Memory" message. If this happens, check to see that all TSR
- (Terminate and Stay Resident) programs that are not required have been
- disabled. If this does not solve the problem, the program in question
- cannot be executed with the shell.
- Except for the potential memory problem, the SHELL operates exactly
- the same as normal DOS. Although JPLCLOCK is resident in memory, it is not
- active. The timer which causes execution of the program to automatically
- resume after some seconds is therefore also NOT active and the computer
- will remain in the SHELL until you type "EXIT" followed by ENTER.
- Program JPLCLOCK Multimission Control Center Clock Page 35
-
-
- TIME SYNCHRONIZATION
- --------------------
-
- As discussed at length elsewhere, the hardware and software clocks on
- the typical personal computer do not keep accurate time. In order to use
- JPLCLOCK in a critical installation such as the JPL Multimission Computer
- Control Center, additional steps must be taken to ensure the accuracy of
- the JPLCLOCK display.
-
- NOTE: Before proceeding with this section, please read the section DOS
- CLOCK CALIBRATION below. An understanding of that section and its
- procedures is essential before time synchronization is attempted.
-
- Time synchronization may be accomplished either manually (using the
- DOS TIME command outside program JPLCLOCK) or by using the program TIMESET.
- TIMESET, in turn, may be invoked either on demand or its use may be
- scheduled to occur at any desired interval. The balance of this section is
- concerned with the use of program TIMESET. TIMESET is copyrighted software
- distributed separately, and it must be registered before regular use. See
- the TIMESET documentation for details. (Additional information on TIMESET
- is also given in the section DOS CLOCK CALIBRATION, below.)
-
-
- Configuring Program TIMESET
- ---------------------------
-
- Before program TIMESET may be used with JPLCLOCK it must be configured
- for your computer system. In addition to the "regular" configuration
- described in the TIMESET documentation, an additional process is required
- here. In order for TIMESET to operate successfully with JPLCLOCK, two
- special version of the program must be prepared: one for your local
- STANDARD time and one for your local DAYLIGHT time. If you have not already
- done so, configure TIMESET by entering the following command at the DOS
- prompt:
-
- TIMESET /C
-
- The following configuration screen will be displayed for your
- approval. The information shown here is that used on one of my test
- computers.
-
- Outside phone: NULL
- Naval Observatory: 12026530351
- Inst. Stds. Technol.: 13034944774
-
- ===> Time zone: PACIFIC
- ===> Time season: STANDARD
-
- Serial port: COM1
- Dialing method: TONE
- Dialing baud rate: 2400
- Lock modem speed: NO
-
-
- User's commands: L2X4S7=45&C1&D2
- Program JPLCLOCK Multimission Control Center Clock Page 36
-
-
-
- Computer clock: DOS CLOCK-CALENDAR
-
- ===> Immediate/countdown: IMMEDIATE
- ===> Manual/automatic: AUTO NIST
- Video type: COLOR
-
- You will not need to change some of the information shown here. Verify that
- the modem information is correct. You WILL need to set your TIME ZONE to
- the correct zone and to set the TIME SEASON to STANDARD. Make sure the
- IMMEDIATE/COUNTDOWN is set to IMMEDIATE and that MANUAL/AUTOMATIC is set to
- AUTO NIST or AUTO USNO (depending upon the time service you wish to use.
- The four critical items are each marked with an arrow ("===>") in the
- sample above. Once all data are correct, press F10 to save the configured
- version.
- You will now have a program file, TIMESET.COM which represents your
- basic TIMESET configuration for STANDARD time in your time zone. It may be
- used at any time by simply entering the following command at the DOS
- prompt:
-
- TIMESET
-
- Use the DOS COPY command to save a separate STANDARD TIME version of this
- program for JPLCLOCK's use:
-
- COPY/B TIMESET.COM TIMESTD.COM
-
- Now, repeat the configuration process by entering the command "TIMESET /C"
- and leave everything the same EXCEPT change the TIME SEASON to DAYLIGHT.
- Press F10 when you have made the change to save a DAYLIGHT version of
- TIMESET. Then use the DOS COPY command to save a separate DAYLIGHT TIME
- version of this program for JPLCLOCK's use:
-
- COPY/B TIMESET.COM TIMEDAY.COM
-
- Use the DOS DIR command to be certain that you now have two specially named
- versions of TIMESET on disk:
-
- TIMESTD.COM
- TIMEDAY.COM
-
- Copy these two files to your JPLCLOCK disk and/or directory.
-
-
- IMPORTANT NOTE
- --------------
-
- Unfortunately, TIMESET cannot be instructed to select
- STANDARD TIME or DAYLIGHT TIME from the command line,
- only by changing the its configuration. JPLCLOCK
- already knows which time season is in effect and uses
- these two special versions of TIMESET as appropriate.
- If these two files are not present, JPLCLOCK's auto-
- matic time synchronization functions will NOT execute
- correctly!
- Program JPLCLOCK Multimission Control Center Clock Page 37
-
-
-
- CHECK AGAIN TO BE SURE THESE TWO FILES ARE IN YOUR
- JPLCLOCK DRIVE AND DIRECTORY:
-
- TIMESTD.COM
- TIMEDAY.COM
-
- TEST BOTH PROGRAMS CAREFULLY TO BE CERTAIN THAT EACH
- VERSION CALLS THE SELECTED TELEPHONE TIME SERVICE AND
- SETS YOUR COMPUTER CLOCK CORRECTLY AND FOR THE SELECTED
- TIME SEASON. JPLCLOCK HAS NO WAY OF DETECTING IF YOUR
- COMPUTER CLOCKS ARE SET INCORRECTLY!
-
- This completes configuration of program TIMESET for use with JPLCLOCK.
- It might be wise to make backup copies of the two special versions of the
- program so that they will be readily available if needed.
-
-
- Time Synchronization Menu
- -------------------------
-
- F1 VIEW or SET Time Sync Data
-
- F3 TIMESET Time Synchronization
-
- ESC Return to Main Menu
- ENTER Resume Program JPLCLOCK
-
- Enter selection:
-
- Select F1 to view the current time synchronization data or to manually
- execute program TIMESET. Select F3 to enable or disable automatic time
- synchronization using program TIMESET.
-
-
- VIEW or SET Time Sync Data
- --------------------------
-
- Current Julian Date: 2448430.351713
- Last Synchronized: 2448428.036412
- Time since Last Sync: 2.315301 days
- Current Clock Offset: 0.00 seconds
- Current DOS Drift Rate: -3.034839 seconds/day
- Current Total Adjust: -7.03 seconds
-
- Press ESC for Sync Menu, ENTER to ADJUST data:
-
- Press ESC to return to the Time Synchronization Menu, or press ENTER to
- adjust the Last Synchronized, Clock Offset, and/or DOS Drift Rate
- parameters. See the section DOS CLOCK CALIBRATION for additional
- information on measuring these parameters. During CALIBRATION or after the
- DOS software clock has been correctly set, do NOT manually adjust these
- data!
-
-
- Program JPLCLOCK Multimission Control Center Clock Page 38
-
-
- TIMESET Time Synchronization
- ----------------------------
-
- F1 Execute TIMESET (Manual)
- F3 Set Automatic Synchronization: ENABLED
- NEXT TIME = 20:55:00 UTC
- START = 00:55:00 UTC
- INTERVAL = 04:00:00
- ESC Return to Sync Menu
- ENTER Resume Program JPLCLOCK
-
- Enter selection:
-
- Press F1 to immediately execute program TIMESET. JPLCLOCK will select
- either program TIMESTD or TIMEDAY depending on whether it is set for
- STANDARD or DAYLIGHT time.
- Press F3 to enable, disable, or change the automatic time
- synchronization function. The sample shown above indicates that the
- automatic function is ENABLED, that it will next occur at 20:55:00 UTC, and
- that JPLCLOCK will automatically schedule time setting starting at 00:55:00
- UTC each day and at four hour intervals thereafter. Press ENTER to DISABLE
- the automatic time synchronization feature, or enter the START time and the
- TIME INTERVAL when requested.
- As a general rule and to minimize use of the NIST and USNO telephone
- time services, the longer the synchronizing interval, the better accuracy
- is obtained. This is because the DOS clock ticks occur at 55 millisecond
- intervals and in order to maintain the desired accuracy of plus or minus
- 250 milliseconds per day or better, we must make this "granularity" small
- compared to the total time used to make the measurements. Where practical,
- I recommend a normal interval of at least 8 hours and preferably 12 or
- more.
- Program JPLCLOCK Multimission Control Center Clock Page 39
-
-
- DOS CLOCK CALIBRATION
- ---------------------
-
- The primary purpose of JPLCLOCK is to display the current time and
- other related information in the JPL Multimission Computer Control Center.
- Accuracy and precision in that environment are essential. There is a
- tendency these days to accept whatever a computer says as the absolute
- truth without regard for whether or not the information is even
- "reasonable". For something as basic as time, even an experienced computer
- user often assumes that it is correct. JPLCLOCK attempts to match reality
- with that expectation.
- Given that a computer clock has been set with reasonable accuracy, the
- computer's time will indeed be sufficient for many applications; if you are
- using a word processing or spreadsheet program, knowing the time to within
- a minute or two is probably adequate. For JPLCLOCK, however, this level of
- accuracy simply will not suffice; when used in the Mission Control Center,
- the information displayed must be correct to within a second. Unless other
- steps are taken to set the clock and to maintain its accuracy, this will
- not be the case. No matter how accurately the clock on a typical personal
- computer is set, it will only be a matter of hours before the time will
- have drifted by some seconds. Measured over a number of days, the
- accumulated errors can easily amount to several minutes.
- The timekeeping operations of an IBM-compatible computer are actually
- performed by two separate and independent functions: a clock-calendar
- integrated circuit and lithium battery combination which maintains the
- current time and date in hardware; and a section of the MS-DOS or PC-DOS
- operating system software which maintains the current time and date in
- software. When computer power is off, the hardware chip continues to
- operate using its battery; when the computer is started ("booted"), the
- operating system software reads the hardware clock and sets its internal
- software clock. Absent special software, the DOS time relies entirely on
- the software clock until the next time the computer is restarted.
- Unfortunately, neither of these clocks was designed for accuracy; early
- versions of the PC did not even include the hardware/battery arrangement.
- Even the typical electric clock, which uses the power line frequency for
- its timekeeping reference, is far more accurate.
- The accuracy of the DOS time at any instant is the result of the
- accumulated errors in both clocks. The hardware clock will drift as a
- function of time, temperature, and crystal aging; the software clock will
- gain or lose time depending upon the skill with which its software was
- written and how well that software "cooperates" with the balance of the
- computer's hardware and software. Some software, especially network and
- high speed communications software, can prevent the DOS clock software from
- incrementing when it should, usually resulting in the DOS clock losing
- time. The problem was compounded with the release of DOS Version 3.3;
- beginning with that version, the DOS TIME and DATE commands adjust BOTH the
- hardware and software clocks and thereby potentially eliminate the hardware
- clock as even a modestly reliable reference. If today's personal computers
- used the power line frequency as their primary reference, and only used the
- battery powered crystal oscillator if the power line was not present, clock
- accuracy could at one stroke be improved by at least several orders of
- magnitude.
-
-
- Program JPLCLOCK Multimission Control Center Clock Page 40
-
-
- Setting DOS Time
- ----------------
-
- Bearing these considerations in mind, there are a number of approaches
- to the DOS time question. The most obvious approach, used by the vast
- majority of computer users, is to either ignore the computer clock entirely
- or to say "It's close enough". Regardless of the application, I strongly
- recommend that the DOS clock be set to the approximate time if only to
- assure that files are more or less correctly date stamped. If the accuracy
- of DOS time is important, the computer clock may be set or synchronized
- in a number of ways, some of which are described below. In this context,
- "ACCURACY" means the accuracy of the time setting operation and NOT the
- longer term accuracy of the DOS time.
-
- 1. TELEPHONE: Many local telephone companies offer a telephone time
- service, usually with a message such as "When you hear the signal
- the time will be ... (beep)". I am not aware of any commercial
- equipment which uses this signal for time setting purposes.
-
- ACCURACY: Generally plus or minus 5 seconds. With the advent of
- digital voice response equipment, the accuracy has improved in
- recent years to perhaps plus or minus 1 second.
-
- 2. COMMERCIAL RADIO: Use commercial radio hourly time signals to
- manually set the time. (My experience suggests that the CBS time
- signal is normally quite reliable.)
-
- ACCURACY: Usually within plus or minus 2 seconds, depending upon
- the source.
-
- 3. SHORTWAVE RADIO: Time signals are broadcast on shortwave radio
- stations WWV and WWVH by the National Institute of Standards and
- Technology. These time signals may be used to manually set the
- time. WWV and WWVH broadcast on several frequencies: 2.5MHz,
- 5MHz, 10MHz, 15MHz, and 20 MHz (WWV only). Reception will vary
- according to your distance from the transmitter, time of day, and
- atmospheric conditions. These time signals are very precise; the
- only major variable is the transmission time. Outside North
- America, other national radio services such as the British
- Broadcasting Company's BBC World Service offer accurate hourly
- shortwave time signals.
-
- ACCURACY: Time setting using WWV or WWVH can usually be performed
- to within about plus or minus 250 milliseconds, of which up to 25
- milliseconds is transmission time and the balance is user
- response time. With practice, plus or minus about 100
- milliseconds is practical.
-
- 4. NIST/USNO TELEPHONE TIME SERVICE: When real precision and
- accuracy are required, the computer clock may be set remotely
- using the telephone time service of either the National Institute
- of Standards and Technology (NIST, formerly the National Bureau
- of Standards or NBS) in Boulder, Colorado or Hilo, Hawaii, or the
- U.S. Naval Observatory (USNO) in Washington, D.C. This method
- requires a modem connected to a telephone line and is available
- Program JPLCLOCK Multimission Control Center Clock Page 41
-
-
- for systems using DOS version 3.3 or higher AND equipped with
- 80286 processor or higher; some 8088-equipped systems may also
- use this method depending upon the type of clock hardware
- installed and the version of DOS being used. The recommended
- method uses the program TIMESET (see below) although other
- similar commercial and shareware programs are available.
-
- ACCURACY: This is the most accurate method available for setting
- the DOS clocks. Depending upon which service is used, NIST or
- USNO, and whether or not line delay compensation ("lag") is
- employed, the DOS time can be set to within plus or minus 2
- milliseconds. However, since the "time ticks" of the DOS software
- clock occur every 55 milliseconds, or 18.2 times per second, this
- "granularity" effectively limits the accuracy of reading the DOS
- clocks. See the documentation for program TIMESET for additional
- discussion.
-
- 5. HEATH GC-1000 MOST ACCURATE CLOCK: The GC-1000 is a combination
- digital clock and scanning shortwave radio receiver which may be
- equipped with an RS-232 communications port for use with
- computers and other electronic equipment. This is the only method
- which provides more or less continuous accurate time information.
- RECOMMENDED!
-
- ACCURACY: When properly configured for your location, equipped
- with an external antenna, used with appropriate computer
- software, and when the receiver is locked to one of the WWV (or
- WWVH) time signals, the GC-1000 can provide time information and
- a standard calibration frequency to an accuracy of plus or minus
- 10 milliseconds. When signal lock is lost, the receiver scans the
- 5MHz, 10MHZ, and 15MHz broadcasts to reacquire signal and lock.
- Even after signal lock is lost, the receiver maintains an
- accuracy of plus or minus 100 milliseconds for some hours.
-
- Choose one of the methods suggested or a suitable alternative based
- upon your precision and accuracy requirements. Other methods of maintaining
- an accurate time standard, such an atomic clocks and NIST time code
- equipment, are available -- for a price. Those methods are beyond the scope
- of program JPLCLOCK and this documentation.
-
-
- Maintaining DOS Time
- --------------------
-
- Just in case you missed the point earlier, accurately setting DOS time
- is only half the battle. Even if the DOS time is set very precisely as
- discussed above, all that assures is that the time is correct to the
- required accuracy at that instant. The problem then becomes one of knowing
- how the DOS clocks change or drift with time and how to compensate for
- those changes or, alternatively, checking the DOS time frequently enough
- that any drift on the part of the DOS clocks is acceptable for the intended
- application.
- Of the two clocks in a typical personal computer, the hardware clock
- is considerably more consistent and reliable. I have checked perhaps a
- dozen PC hardware clocks in recent years, and almost all kept reasonably
- Program JPLCLOCK Multimission Control Center Clock Page 42
-
-
- good time over a period of several days; as expected, none kept "perfect"
- time. Typical drift rates ranged from about 3 seconds per day to near zero
- seconds per day, with the magnitude and direction of the drift more or less
- constant over the period of measurement. Once a hardware clock has been
- calibrated, therefore, the drift can be calculated with reasonable accuracy
- over periods of some weeks or more. For best results, the computer should
- always be left on and the ambient temperature held constant. Crystal aging
- rates suggest that calibration should be performed at least annually.
- The hardware clock is normally interrogated only when the computer is
- first started or rebooted. The correct time can therefore only be predicted
- at that moment for a calibrated hardware clock and given the last time that
- clock was synchronized with an appropriate time standard. Microsoft
- provides no standard software tools for interrogating the hardware clock at
- other times. Quite the contrary; beginning with DOS Version 3.3, using the
- DOS TIME and DATE commands to set the DOS software will also set the
- hardware clock and effectively destroy its usefulness as a calibrated time
- reference. I am at a complete loss to understand the reasoning behind this
- change in DOS; I presume that users were being "confused" by differences
- between the hardware and software clocks; instead of either explaining or
- fixing the problem, Microsoft elected to "legislate" the problem away -- a
- process any politician would recognize instantly. The only mitigating
- consideration is that any really effective solution would probably require
- hardware as well as software changes. Blame IBM, I guess.
- The software clock provides the only time information accessible to
- DOS using standard software. Since this clock is maintained entirely in
- software, with no reference to the hardware clock except at bootup, it is
- at the mercy of other software which may execute from time to time. The
- software clock increments its time using "interrupts", a technique which
- stops a software process in progress just long enough to do the required
- tasks and then resumes the interrupted process. These interrupts occur
- every 55 milliseconds. So long as none is missed, the software clock should
- keep accurate time -- if the software is written correctly and if the
- computer's crystal controlled oscillator is in turn accurate. It may be
- that neither of these conditions is true; certainly the crystal controlled
- oscillator (quite similar to the one which runs the hardware clock) was not
- designed for accuracy or stability. It's original purpose was solely to
- generate the necessary timing signals for the correct operation of the
- computer. Cost, not keeping accurate time, was the primary consideration in
- its design.
- Other software designers have contributed to the problem by writing
- software which, deliberately or inadvertently, prevents the software clock
- from being updated. Off-brand BIOS firmware can present occasional
- problems. Local Area Network (LAN) and high speed communications software
- are typical culprits in this respect. For example, a casual check of the
- clock while using Brooklyn Bridge (a computer-to-computer transfer program)
- indicated that the clock was effectively suspended when data transfers were
- in progress. In one relatively brief period, the DOS clock lost about 30
- seconds.
- As a result of all of these factors, the accuracy of the DOS software
- clock can vary wildly from one computer to the next and from one
- manufacturer to another. One inexpensive "clone" computer that I'd rather
- forget couldn't manage to keep time to better than about 30 seconds per
- HOUR! Before planning to use a particular computer as a time reference with
- programs like JPLCLOCK, check the computer hardware and software you intend
- to use very carefully.
- Program JPLCLOCK Multimission Control Center Clock Page 43
-
-
-
-
- Calibrating DOS Time
- --------------------
-
- Regardless of the method used, the DOS time must be set from time to
- time in order to maintain even reasonable accuracy. More demanding
- applications will require calibration of the hardware or software clock or
- both. The method and frequency of calibration will depend upon your
- accuracy requirements and cost. For my "normal" work, involving program
- development and word processing, I use NIST station WWV and a digital
- PLL shortwave receiver to manually set my computer clocks on a regular
- basis. From time to time I require higher accuracy; given my location in
- California, I usually use a program like TIMESET to call the NIST Telephone
- Time Service in Boulder, Colorado when precise time setting is required.
- When using a program such as JPLCLOCK where consistent accuracy is
- essential over extended periods of time, calibration of the hardware and
- software clocks may be required. I recommend program TIMESET for this
- purpose. TIMESET is a copyrighted program by Peter Petrakis which is
- distributed using the "shareware" concept. If not available on a
- convenient bulletin board system, TIMESET may be obtained by writing:
-
- Life Sciences Software
- 8925 271st N.W., Suite 112
- P.O. Box 1560
- Stanwood, WA 98292
-
- (206) 387-9788
-
- US$35.00/copy (as of April, 1991)
-
- TIMESET is an elegant and very precise method for setting the hardware
- and software clocks in your computer. Note that TIMESET sets your computer
- based upon Coordinated Universal Time (UTC) rather than UT1; the offset
- between UTC and UT1 is displayed by TIMESET but is not used. TIMESET is
- superior to any of the several other similar programs I have evaluated. You
- must have a modem and a telephone line connected to your system to use
- TIMESET. Note that the process involves making a telephone call to either
- Boulder, CO or Washington, DC and toll or long distance charges may apply!
- For additional information on configuring TIMESET for use with JPLCLOCK,
- see the section TIME SYNCHRONIZATION.
- The current version of TIMESET, Version 6.0, is not without its
- shortcomings. First, if the modem does not make connection to a telephone
- line correctly, TIMESET may hang indefinitely waiting for a response from
- the modem which will never arrive. This is the case with one of my internal
- modems that is convinced that the first call after initialization is at
- 2400 baud; since the call to NIST is being made at 1200 baud, the modem is
- definitely "confused". This problem has not been observed when using a
- standard Hayes 2400 modem. Second, TIMESET does not record the statistical
- results of its operations to a disk file. This means that calibration must
- be performed manually; normal time setting, however, operates automatically
- with no problems. Third, TIMESET does not return an "error code" to
- indicate whether or not synchronization was successfully performed. I hope
- to convince Mr. Petrakis of the need to address these relatively minor
- problems in an otherwise excellent program.
- Program JPLCLOCK Multimission Control Center Clock Page 44
-
-
- The method being used for time synchronization and adjustment will
- determine whether or not calibration of your hardware clock is required. If
- you use the Heath GC-1000 Most Accurate Clock, calibration is probably not
- required. Similarly, if you place a program like TIMESET in your
- AUTOEXEC.BAT file and synchronize your DOS clocks every time you start your
- computer, hardware calibration is not required. If, on the other hand, you
- wish to call NIST as infrequently as possible so as to minimize the
- telephone charges, hardware clock calibration is definitely recommended.
- Unless you use the Heath GC-1000 (or some other time standard) and poll it
- regularly, calibration of the software clock is always required.
- The following suggested calibration procedures assume the use of
- program TIMESET and that TIMESET has already been configured for your
- computer and for your time zone. See the TIMESET documentation for
- instructions. If you use some other program, it must provide similar
- information and you must make appropriate changes to these procedures as
- required by the software actually used.
- Program JPLCLOCK Multimission Control Center Clock Page 45
-
-
- Manual Hardware Clock Calibration
- ---------------------------------
-
- Hardware clock calibration requires a minimum of 48 hours to
- accomplish. The computer should be located in the environment in which it
- is expected to operate and should be turned on and off at the "usual"
- times. The idea is to duplicate the actual operating conditions to the
- maximum extent possible, especially temperature. The following procedure is
- suggested:
-
- 1. Operate the computer in its normal environment and according to
- its usual schedule for at least 24 hours prior to the test.
-
- 2. Set the hardware clock using TIMESET according to instructions.
- Use a screen capture program or manually record the ACTION
- SUMMARY prepared by TIMESET. The most significant information is
- shown as:
-
- Local computer time was: 06:59:41.95
- Set to: 06:59:44.01 Pacific Daylight
- Local computer date was: 06-19-1991
- Set to: 06-19-1991, Wednesday
-
- 3. Operate the computer normally for the next 24 hours. Do NOT use
- the DOS DATE and TIME commands!
-
- 4. After approximately 24 hours, repeat the time setting with
- TIMESET and record the same information as in Step 2.
-
- 5. Using the data obtained in Steps 2 and 4, calculate the hardware
- clock drift in seconds per day.
-
- 6. Operate the computer normally for the next 24 hours. Do NOT use
- the DOS DATE and TIME commands!
-
- 7. After approximately 48 hours, repeat the time setting with
- TIMESET and record the same information as in Step 2.
-
- 8. Using the data obtained in Steps 4 and 7, again calculate the
- hardware clock drift in seconds per day. Repeat as required until
- consistent results are obtained. If consistent results cannot be
- obtained, the selected computer may not be suitable for your
- intended use.
-
- NOTE: The current version of JPLCLOCK does not directly use the hardware
- clock drift in its time adjustment calculations. This capability will be
- added in a future version. Instead, JPLCLOCK accepts a "Clock Offset" value
- which represents the total hardware clock drift in seconds between the last
- time synchronization was performed and the most recent time the computer
- was booted. If the computer is always synchronized immediately prior to
- running JPLCLOCK, the hardware calibration is not required and the Clock
- Offset should be set to zero.
- Program JPLCLOCK Multimission Control Center Clock Page 46
-
-
- Manual Software Clock Calibration
- ---------------------------------
-
- Manual software clock calibration is quite similar to hardware clock
- calibration and is recommended for all installations using JPLCLOCK which
- do not plan to use the automatic synchronization and calibration features
- of the program. The recommended procedure requires 28 hours to accomplish.
- The computer should be located in the environment in which it is expected
- to operate and should be turned on and off at the "usual" times. The idea
- is to duplicate the actual operating conditions to the maximum extent
- possible, especially temperature. The following procedure is suggested:
-
- 1. Operate the computer in its normal environment and according to
- its usual schedule for at least 24 hours prior to the test.
-
- 2. Set the hardware and software clocks using TIMESET according to
- instructions. Use a screen capture program or manually record the
- ACTION SUMMARY prepared by TIMESET. The most significant
- information is shown as:
-
- Local computer time was: 06:59:41.95
- Set to: 06:59:44.01 Pacific Daylight
- Local computer date was: 06-19-1991
- Set to: 06-19-1991, Wednesday
-
- 3. Operate the computer normally for the next 4 hours. "Normal
- operation" means using the particular software, JPLCLOCK in this
- case, that is planned for the computer. Do NOT use the DOS DATE
- and TIME commands!
-
- 4. After 4 hours, repeat the time setting with TIMESET and record
- the same information as in Step 2.
-
- 5. Using the data obtained in Steps 2 and 4, calculate the software
- clock drift in seconds per day.
-
- 6. Operate the computer normally for the next 12 hours. "Normal
- operation" means using the particular software, JPLCLOCK in this
- case, that is planned for the computer. Do NOT use the DOS DATE
- and TIME commands!
-
- 7. After 12 hours, repeat the time setting with TIMESET and record
- the same information as in Step 2.
-
- 8. Using the data obtained in Step 7, again calculate the software
- clock drift in seconds per day. Repeat as required until
- consistent results are obtained. If consistent results cannot be
- obtained, the selected computer may not be suitable for your
- intended use.
-
- 9. Now enter the latest synchronization date and time (from Step 7)
- and calculated drift (from Step 8 or Step 5) in seconds per day
- into program JPLCLOCK. From the Main Menu, press F10+F1 and enter
- the data as prompted. Enter zero for Clock Offset.
-
- Program JPLCLOCK Multimission Control Center Clock Page 47
-
-
- Other time sources may be similarly used to calibrate the DOS clock.
- The final result of this calibration should be a software clock drift in
- seconds per day that should remain reasonably stable for relatively long
- periods of time. The calculated clock drift is POSITIVE if your DOS clock
- GAINS time with respect to the time source and NEGATIVE if your DOS clock
- LOSES time with respect to the time source. These data may then be entered
- into JPLCLOCK so that the program will automatically adjust the displayed
- time for the predicted drift.
- Note that the predicted drift calculations assume that JPLCLOCK is
- operating continuously. If you exit JPLCLOCK and perform operations that
- affect the DOS clock (such as disk accesses or high speed communications),
- the drift calculations will still be accurate but you will have to add a
- clock offset to compensate for the DOS clock changes. If you turn off your
- computer, you must reset your clock (to the desired accuracy) and then
- adjust the last synchronization time to correspond to the time you reset
- your computer clocks. For maximum accuracy, perform a manual time
- synchronization (F10+F3+F1 from the Main Menu) each time you reboot your
- computer; JPLCLOCK will automatically update the last synchronization time.
- Program JPLCLOCK is a "well behaved" program written and compiled
- using Microsoft's QuickBASIC Compiler, Version 4.5. No "clever tricks" are
- used to fool the system into doing something that might interfere with
- accurate timekeeping by the DOS software clock. The software clock drift
- obtained by this suggested procedure should be relatively consistent from
- day to day.
- Program JPLCLOCK Multimission Control Center Clock Page 48
-
-
- USING TEXT MODE
- ---------------
-
- In addition to its use in the Multimission Computer Control Center,
- JPL is also considering the use of JPLCLOCK as a means of displaying
- the current mission and event times in other locations at the Laboratory,
- and for display to visitors and guests. In order to explain the data, to
- provide additional commentary on missions in progress, and to provide
- other supplementary information, JPL suggested the addition of a TEXT mode
- to further enhance JPLCLOCK.
- Each time JPLCLOCK is started, it searches for a special message file
- named "JPLCLOCK.MSG" in the current drive and directory. If the file is
- found, it reads the file into memory and thereafter permits the TEXT MODE
- to be enabled. This occurs ONLY when the program is started from the DOS
- prompt; if you use the DOS SHELL (Function Key F9 from the Main Menu) to
- copy or create the special message file, JPLCLOCK will NOT recognize the
- file until the program is restarted.
- The TEXT mode has a capacity of up to 10 screen pages of text with 20
- lines per screen page. The normal distribution of the program includes a
- demonstration message file with the name JPLCLOCK.MSG. To enable TEXT mode,
- you must first enable PAGE mode. This may be done when the program is
- started from the DOS prompt:
-
- JPLCLOCK /PAGE/TEXT
-
- or by using Function Key F8 (to enable PAGE mode) and then Function Key F7
- (to enable TEXT mode) from the Main Menu. Disabling PAGE mode automatically
- disables the TEXT mode. TEXT mode cannot be enabled in the special message
- file JPLCLOCK.MSG was not found when the program was started OR if the file
- contains no text.
- When the TEXT mode is enabled, JPLCLOCK first cycles through all
- active Mission Timers (as in the usual PAGE mode), then cycles through all
- available text pages in order. The process then repeats. The sample special
- message file contains five text pages.
- When the TEXT mode is active and JPLCLOCK is cycling through all
- active Mission Timers and text pages, a special "bar meter" is displayed
- at the top left of the Mission Timer Windows. This is a row of ten special
- square symbols, one for each of the ten text pages, which indicates the
- status of the page. Each available text page is denoted by a BLUE symbol;
- the active text page symbol is flashing. Inactive text pages (pages without
- any text) are shown with a GRAY symbol.
- In addition to the prepared text in file JPLCLOCK.MSG, the display
- includes a title line with the program version number, the current Julian
- Date, and the local date in conventional notation. The second line displays
- the current UTC Time, Local Time, and the two "bar meters". The left bar
- meter gives the status of title pages, and the right meter the status of
- the Mission Timer pages. The following is the first screen page in the
- supplied sample file JPLCLOCK.MSG. Special "line drawing" characters
- actually used in the display have been replaced in this text by similar
- printing characters.
- Program JPLCLOCK Multimission Control Center Clock Page 49
-
-
- | JPLCLOCK by David H. Ransom, Jr. Version 9126 | JD2448430.26897 22 JUN 1991
- 18:27:19 UTC 11:27:19 PDT ********** **********
- ---------- NASA Jet Propulsion Laboratory -------------------------------------
-
- Welcome to JPLCLOCK!
- --------------------
-
- Written by
- David H. Ransom, Jr.
- Rancho Palos Verdes, CA
-
-
- JPLCLOCK is a real time clock and mission/event timer program written
- especially for the NASA Jet Propulsion Laboratory in Pasadena, California for
- use in the Multimission Computer Control Center (MCCC) and elsewhere in the
- Laboratory. The MCCC is the "nerve center" where all the NASA planetary
- missions such as Magellan, Ulysses, and Galileo are controlled. Other NASA and
- European Space Agency missions are also supported by the JPL MCCC either
- directly or through NASA's Deep Space Network, three large antenna systems
- located in Goldstone, California, near Madrid, Spain and near Canberra,
- Australia. The MCCC is in turn supported by the scientists and engineers at JPL
- and at the California Institute of Technology, which operates JPL for NASA.
-
-
- Preparing TEXT Files
- --------------------
-
- The sample demonstration message file JPLCLOCK.MSG may be used as a
- template to create customized text files. When preparing text files for use
- with JPLCLOCK, use an ASCII editor, or use a word processor program in the
- "non-document" or "ASCII" mode. Before editing, make a backup copy of file
- JPLCLOCK.MSG. I recommend that all text files for JPLCLOCK be created with
- the filetype ".MSG". Future versions of JPLCLOCK may include a feature to
- read additional text files and the required filetype will be ".MSG".
- The sample file contains 5 screen pages of text. Each screen page
- consists of exactly 20 lines of text, and a maximum of 10 screen pages (or
- 200 text lines) is allowed. After creating a new text file (and having made
- a backup copy of the original JPLCLOCK.MSG file!), copy the new file to
- JPLCLOCK.MSG and start program JPLCLOCK in the TEXT mode to view the
- results. My testing indicates that it takes several attempts before the
- appearance of the screen pages suit my taste.
- The TEXT mode displays text lines exactly as it finds them in file
- JPLCLOCK.MSG. As illustrated in the sample file, the "line drawing"
- characters and other special characters are displayed. (Some editors are
- unable to place these special characters in a text file. I recommend the
- shareware editor QEDIT for editing text files for JPLCLOCK.)
- Program JPLCLOCK Multimission Control Center Clock Page 50
-
-
- COMMENTS AND KNOWN PROBLEMS
- ---------------------------
-
- 1. Computer BIOS Problems
-
- Not all PC's are created equal. A program like JPLCLOCK may execute
- correctly on one machine and not on another. The most likely culprit in
- these cases is the computer's BIOS (Basic Input Output System) which is
- built into each machine (in ROM, Read Only Memory) by the manufacturer.
- Even computers with the same model number may have a different BIOS,
- depending upon when they were manufactured; different model numbers by the
- same manufacturer may perform differently. Brands which have demonstrated
- problems in this area include Tandy, Leading Edge, and Ergo.
-
- 2. Monitor Type and Video Adapter Cards
-
- Not all video adapter cards are created equal either. While most CGA
- adapters perform about the same, EGA and VGA adapters can vary
- considerably. The same card, operated in different video modes, can be a
- star or a lemon. There are too many different types of adapters to even
- attempt any generalizations. One practical note: Some VGA monochrome
- monitors "confuse" the VGA BIOS and/or the VGA adapter and require the
- command "MODE CO80" (from the DOS prompt) for proper gray-scale operation
- with JPLCLOCK.
-
- 3. Computer Processor and Math Coprocessor
-
- JPLCLOCK has been tested primarily on computers equipped with the
- 80286 or higher processor and including a math coprocessor chip. There are
- no known problems if the computer does NOT have a math coprocessor chip but
- there may be perceptible delays visible on the screen; obviously, there's
- no solution except a faster computer or the addition of a math coprocessor
- chip. No testing has been performed on 8088-class machines (the original PC
- and XT computers and their clones). Operations involving the CMOS
- clock/calendar chip will usually fail on these machines since their design
- did not include that feature; the various add-on clock chips and circuit
- cards are usually incompatible with the current clock chips. If you have
- such a computer and wish to use program TIMESET, read the TIMESET
- documentation carefully and test the program thoroughly before use with
- JPLCLOCK.
-
- 4. DOS Version and the Shell Feature
-
- The "Shell to DOS" feature, used by Function Key F9 from the Main
- Menu and when program TIMESET is executed from within JPLCLOCK, is
- generally NOT reliable for versions of DOS prior to 3.1 and the results of
- attempting to use this command with DOS Version 2.x and lower are
- unpredictable. I recommend MS-DOS/PC-DOS Version 3.3 as the best, most
- stable DOS available. The Shell feature may also fail on certain computers
- for no apparent reason, probably related to the BIOS. I have also performed
- limited testing on DOS Version 5.0 without any problems to date. (I'm still
- using a Beta Version of DOS 5.0 and will resume testing as soon as I get
- the Real Thing installed.)
-
- Program JPLCLOCK Multimission Control Center Clock Page 51
-
-
- 5. Unstable Hardware or Software Clocks
-
- Some clock circuits have been implemented in such a manner that they
- are essentially a simple tuned resistance-capacitance design which
- effectively ignores the presence of a crystal. Such circuits may drift
- wildly as a function of time, temperature and/or voltage, and make the host
- computer unsuitable for an application such as JPLCLOCK. Any decent crystal
- controlled oscillator should be able to hold to within a second per day,
- but not many PC computer clocks are that good. I've been told that tests on
- a typical PC hardware clock several years ago showed a 5% difference in
- clock frequency when operated on AC power versus the lithium battery. I
- would not have believed that big a difference was even possible with a
- crystal oscillator!
- However, what appears to be an unstable DOS clock may, in fact, be the
- fault of certain software. Network and communications software are
- notorious for turning off the interrupt system and doing other bad things
- which prevent the DOS clock from keeping accurate time. This problem
- usually shows up as a significant time loss AFTER network access or high
- speed communications. Avoid the use of these programs when running JPLCLOCK
- and eliminate any TSR (Terminate and Stay Resident) programs which may
- interfere with the clock.
- The fact that there are two clocks in the PC can cause confusion and
- apparent errors. While JPLCLOCK is running, only the DOS clock is
- interrogated and it is this clock that requires the most careful
- calibration for extended operations. However, each time a computer with a
- battery supported clock/calendar is booted, the hardware clock is used to
- initially set the DOS clock. These two clocks have independent drift
- direction and rate; thus, the time may appear to drift in one direction if
- the computer is booted frequently, and in the opposite direction if it is
- left on. Microsoft compounded the problem by "fixing" the DOS TIME command
- in Version 3.3 and up so that it sets both the hardware and software
- clocks, thereby eliminating the hardware clock as any sort of a reliable or
- stable reference!
-
- 6. Typical Calibration Results
-
- During the testing of JPLCLOCK I have used both 286 and 386 computers
- and have calibrated each of their software clocks using the NIST telephone
- time service. While the drift rates varied from computer to computer, each
- computer was able to maintain the correct time using JPLCLOCK to within 150
- milliseconds after: a) running for a minimum of 4 hours prior to attempting
- calibration; and b) using a calibration time of at least 4 hours. Since the
- DOS clock ticks occur at 55 millisecond intervals, calibration runs of less
- than four hours will yield an uncertainty which is of the same order of
- magnitude as the desired calibration accuracy.
- For applications requiring maximum accuracy, these tests indicate that
- the computer should be set using NIST each time the computer is booted and
- then resynchronized at 4 to 24 hour intervals. The stability of the DOS
- clock will determine the optimum interval. JPLCLOCK records the measured
- drift rate each time it makes a synchronization call; use F3+F3+F1 from the
- Main Menu to view the data and adjust the synchronization interval to the
- longest time which yields consistent results. Another consideration is to
- minimize the number of calls to NIST or USNO; these telephone time services
- are a precious resource and should be used as infrequently as possible
- consistent with the needs of your application (as well as your willingness
- Program JPLCLOCK Multimission Control Center Clock Page 52
-
-
- to pay the toll charges).
-
- 7. Color Variations
-
- Especially with EGA and VGA adapter cards, displayed colors may vary
- considerably from those described. The most common variation is "dim
- yellow" (used for the version number on JPLCLOCK's title screen) which
- often appears as either brown or a dim red which is all but
- indistinguishable from the "real" dim red. Other colors may also vary from
- system to system and from monitor to monitor.
- Program JPLCLOCK Multimission Control Center Clock Page 53
-
-
- FUTURE IMPROVEMENTS AND FEATURES
- --------------------------------
-
- JPLCLOCK is still a very young program and, in addition to repairing
- the inevitable bugs and problems that are bound to be found, I have a
- number of additional features that I hope to add in future releases of the
- program. Here are a few that are being considered:
-
- 1. Add better manual calibration procedures to include a brief tone so
- that users who don't choose to pay the telephone charges to NIST or
- USNO can still calibrate their systems reasonably accurately by using
- ratio stations WWV or WWVH. Casual experimentation on my part has
- indicated that I can hear differences as small as about 100
- milliseconds without much difficulty. Propagation delay from Fort
- Collins, Colorado to the Los Angeles area is only about 20 milli-
- seconds so it should be simple to calibrate the clocks to plus or
- minus 250 milliseconds in a day or so.
-
- 2. Add automatic calibration of the hardware (CMOS) clock comparable to
- that now provided for the software (DOS) clock. This is a little more
- complicated since the hardware clock can only be read to the nearest
- second.
-
- 3. Add automatic synchronization using the Heath GC-1000 Most Accurate
- Clock. When equipped with an RS-232 interface and external antenna,
- the GC-1000 can maintain an accuracy of plus or minus about 10
- milliseconds with WWV or WWVH. With software overhead, this probably
- translates into about plus or minus 50 milliseconds for the PC, the
- resolution of the DOS clock ticks.
-
- 4. Give the user the choice of displaying UTC or UT1 (required for
- navigation, for example) if synchronization is done using the NIST
- telephone time service or the Heath GC-1000 Clock (which are the only
- available services which supply the correction from UTC to UT1). The
- current correction is +0.2 seconds as of July 1, 1991.
-
- 5. For systems equipped with a CMOS clock/calendar chip (286 and higher),
- add the optional capability to use the hardware clock to adjust the
- DOS time when leaving JPLCLOCK to do disk operations, etc.
-
- 6. Add automatic correction to/from Daylight Savings Time. This will
- require automatically adjusting the DOS clock by one hour at the
- appropriate times each April and October. This is a real "must do"!
-
- 7. Improve readability of the times (especially when using the SMALL Main
- Window) by using an alternate font for EGA and VGA monitors. I'm at
- the mercy of QuickBASIC and the computer's BIOS for this feature; some
- systems accept alternate fonts from within a QuickBASIC program and
- others do not.
-
- Not all of these features may ever be added and others may find their way
- to the top of the list first. Comments and suggestions will be appreciated.
- Program JPLCLOCK Multimission Control Center Clock Page 54
-
-
- UTC AND TIME ZONES
- ------------------
-
- Coordinated Universal Time (UTC) is the world wide civil standard time
- as broadcast by national radio time services such as stations WWV and WWVH
- of the U.S. National Institute of Technology and Standards (formerly the
- National Bureau of Standards) and the BBC World Service. It is roughly the
- same as UT1, the time standard used by astronomers and scientists for
- celestial and solar system measurements. However, because the orbital time
- and rotation rate of the Earth is not constant, periodic adjustments of one
- second are required. These adjustments, called Leap Seconds, are usually
- made at the end of June and/or the end of December in order to maintain the
- difference between UTC and UT1 to within 0.9 seconds. As I discovered while
- writing my program ASTROCLK, there are many other defined time standards.
- Because of the ready availability of UTC for synchronization, JPLCLOCK
- assumes that the computer's internal clock is set to local time and that
- time has a fixed relationship to UTC.
- The original plan for time zones required each zone boundary to be
- located at the 15 degree meridians around the globe. Since that arrangement
- seldom coincided with national or political boundaries, many adjustments
- have been made over the past one hundred years for political reasons or for
- local convenience. Some time zones are approximately "nominal" while others
- are quite large; all of China, for example, uses a single national time
- zone -- at least officially.
- All civil time zones are related to UTC, usually by an integral number
- of hours (although there are several "half hour zones" and at least one
- "quarter hour zone"). Many countries, including the United States and most
- of Europe, also adjust their civil time by one hour during summer months.
- In the United States, Daylight time begins on the first Sunday in April and
- ends on the last Sunday in October. Other countries use different dates and
- those dates may change from time to time. JPLCLOCK can adjust for Daylight
- time for all time zones in the United States (including Alaska and Hawaii)
- with a single function key; other time zones must be individually set for
- standard or summer time.
- The following time zone abbreviations are used by JPLCLOCK for the
- main window and the four location clocks at the lower right of the display
- screen:
-
- UTC Coordinated Universal Time
- (formerly GMT = Greenwich Mean Time)
-
- AST Atlantic Standard Time
- ADT Atlantic Daylight Time
- EST Eastern Standard Time
- EDT Eastern Daylight Time
- CST Central Standard Time
- CDT Central Daylight Time
- MST Mountain Standard Time
- MDT Mountain Daylight Time
- PST Pacific Standard Time
- PDT Pacific Daylight Time
- YST Yukon Standard Time
- YDT Yukon Daylight Time
- HST Hawaiian Standard Time
- HDT Hawaiian Daylight Time
- Program JPLCLOCK Multimission Control Center Clock Page 55
-
-
-
- GMT Greenwich Standard Time (UK)
- BST British Summer Time (UK)
- CET * Central European Time
- CES * Central European Summer Time
-
- * denotes non-standard abbreviation
-
- Users with specific information on time zone names, abbreviations, and
- and relationship to UTC as well as official times for changing to and from
- daylight/summer time are encouraged to send me that information so that I
- may update or correct the program if necessary. The information will be
- added to subsequent versions of JPLCLOCK.
- Program JPLCLOCK Multimission Control Center Clock Page 56
-
-
- JPLCLOCK REVISION HISTORY
- -------------------------
-
- Each released version of JPLCLOCK uses a four digit revision code
- such as 9126. The first two digits indicate the year and the second two
- digits indicate the week of the year. In some cases, an additional letter
- suffix is added to distinguish changes occurring within the same week. A
- partial week at the beginning or end of the year is counted as a full week.
- Using this method, a year will typically have 53 weeks although it is
- possible to have 54 weeks in a leap year (1972 is an example). The current
- year-week revision code is shown on the Julian Date display, Display Mode
- 7, in my program ASTROCLK.
- This file records the revision history of program JPLCLOCK through all
- of the minor twists and turns that usually accompany the evolution of such
- a program. It illustrates the tortuous process of maintaining and refining
- a program as ideas and problems are reported from every quarter. These
- notes may also be helpful to users who are upgrading from one version to
- another to find out what has changed.
-
- David H. Ransom, Jr.
-
-
- 9128 7/05/91
- -----------------
- -Repaired bug that caused CALIBRATION (F6) to fail to execute subsequent
- TIMESET calls at the correct time interval after the first two. Also
- corrected a sign error in the drift calculation during self-calibration.
- -Corrected screen text for CALIBRATION (F6) to show correct calibration
- intervals of 1, 2, and 4 hours. The total time required is 7 hours.
-
- 9127 7/01/91
- -----------------
- -Added "/SMALL" command line option to display smaller Main Window with
- Local Time and UTC Time. See text for details.
- -Added ALT-F6 during clock display to switch between LARGE and SMALL Main
- Window.
- -Added four additional SELECTED and PRIORITY EVENT windows below the SMALL
- Main Window. User may select: four SELECTED EVENTS (default); two SELECTED
- EVENTS and two PRIORITY EVENTS; or, four PRIORITY EVENTS. Change using ALT-
- F5 when SMALL Main Window is active. These additional four windows are
- displayed ONLY when the SMALL Main Window is selected ("/SMALL" command
- line option or ALT-F6 when clock display is active).
- -Added "/SYNC" command line option to force immediate time synchronization
- (using program TIMESET) when JPLCLOCK is started. The time synchronization
- performed as a result of the "/SYNC" command line option is independent of
- the automatic time synchronization (F10+F3+F3).
- -Changed "/TEXT" command line option so "/PAGE" is no longer also required.
- "/TEXT" now forces PAGE mode.
- -The word "HOLD" now appears above the Mission Timer windows if the current
- page of Mission Timers is being held on the screen because one or more of
- the timers is within 1 hour of its Time Zero.
- -Changed SCREEN FREEZE (ALT-F1) to time out in 5 minutes if no key is
- pressed. Current UTC and Local time are now displayed and updated on line 2
- during the screen freeze. JPLCLOCK will no longer freeze indefinitely!
- -Changed Location Clock prompts for "Uses US Daylight Time" (F2) to "Y" for
- Program JPLCLOCK Multimission Control Center Clock Page 57
-
-
- YES and "N" for NO.
- -Corrected bug in Mission Timers: countdown time at zero days displayed "0"
- days rather than "-0" days.
- -Corrected a bug introduced at Version 9126: INI files were interpreted
- incorrectly and reset the Daylight Flag on the Location Clocks which use US
- Daylight Savings Time.
- -In most instances, pressing BACKSPACE will reset the timer in the message
- "JPLCLOCK will start automatically in NN seconds". When typing characters,
- the BACKSPACE will delete the previous character.
- -Modified large clock logic in the Main Window to write only digits that
- have changed. This improves performance with slower computers and/or slow
- video adapter cards.
- -Improved prompts for Read/Write INI & MTD files (F5) and corrected a minor
- bug when ESC was pressed to CANCEL. Added warning that disk operations may
- affect JPLCLOCK's time accuracy.
- -Added warning when exiting to DOS (F9) that disk operations may affect
- JPLCLOCK's time accuracy.
- -Fixed "?" command line help so correct time is shown and added "/TEXT"
- command line reminder.
- -Corrected references to the DOS timer rate. The timer ticks occur 18.2
- times per second or every 54.945 milliseconds. Previous text had the
- frequency given where period was indicated.
- -Various cosmetic changes.
-
- 9126 6/22/91
- -----------------
- NOTE: Program JPLCLOCK and this documentation were prepared largely from
- memory some hundreds of miles away from my usual references and other
- resources. Technical revisions and corrections can be expected in future
- releases! Comments and suggestions are welcome.
- -INITIAL PUBLIC RELEASE OF JPLCLOCK.
- -Added F10 to Main Menu for manual and automatic time synchronization and
- calibration functions. See the section TIME SYNCHRONIZATION for details.
- -Added automatic offset and drift compensation to JPLCLOCK displayed time
- based upon measured time offset and drift rate. Once the average drift rate
- of the computer's clock is known, JPLCLOCK will compensate for that drift
- and display the corrected time.
- -Added TEXT mode for the display of up to 10 screen pages of supplementary
- information or messages. A sample text file, JPLCLOCK.MSG, has been added
- to the standard distribution files. See text for details.
- -Added "bar meter" above the Main Window to provide countdown to automatic
- time synchronization. Meter appears 100 seconds before JPLCLOCK suspends
- and counts down in increments of 10 seconds.
- -Added two "bar meters" above the Mission Timer windows to display active
- Mission Timer pages and active TEXT pages. The right meter is for Mission
- Timer pages and the left for TEXT pages. Active page markers are in color
- and inactive page markers are gray.
- -Added "#nn" copy format to Mission Timer input (F3).
- -Added TAB to skip an entry and leave it unchanged in several menus.
- -Added F7 to switch TEXT mode from Main Menu.
- -Added F8 to switch PAGE mode from Main Menu.
- -Added ALT-F1 to FREEZE clock display. Press any key to resume operation.
- -Added ALT-F7 to switch TEXT mode from clock display. NOTE: PAGE mode must
- first be enabled before TEXT mode can be enabled.
- -Added ALT-F8 to switch PAGE mode from clock display. NOTE: TEXT mode will
- Program JPLCLOCK Multimission Control Center Clock Page 58
-
-
- be disabled (if enabled) when PAGE mode is disabled.
- -Added F4 on the DEFAULTS menu (F4+F4 from Main Menu) to allow the user to
- set the PAGE Delay and the TEXT Delay. See text for details.
- -Swapped Location Windows #2 and #3 to make numbering scheme conform to the
- other windows, top to bottom in a given column.
- -INI file format has changed but JPLCLOCK will correctly read Version 9125B
- INI files and subsequently write the new format. Use F5 from the Main Menu
- to convert prior files; first read the old file then write a new file using
- the same or a new filename.
- -The menu message "JPLCLOCK will start automatically in NN seconds" now
- counts down as the allowed time for keyboard input decreases.
- -Various cosmetic changes and minor bug repairs.
- -Documentation updated.
-
- 9125B 6/16/91
- -----------------
- -Added /PAGE command line option for page mode operation.
- -Number of timers now set to 60 in 10 pages.
- -Mission Timer capacity changed to allow from -9,999 days to +99,999 days
- to accommodate long duration interplanetary missions such as Voyager 1 and
- 2 and Pioneer 11 as they leave the solar system.
- -Corrected Daylight Savings Time adjustment and default values for the four
- location clocks.
- -Added Voyager 1 and 2 to default data but times and dates are only
- approximate.
- -Function keys on several menus changed or swapped.
- -Many minor and cosmetic changes.
- -Documentation updated.
-
- 9125A 6/14/91
- -----------------
- -Interim test release.
- -Documentation not updated.
-
- 9125 6/12/91
- -----------------
- -First fully functional release.
- -All configuration features now available.
- -Preliminary documentation released.
- -Mission Elapsed Time for Magellan, Galileo, and Ulysses are NOT correct.
- Dummy values have been used for testing.
-
- 9124 6/10/91
- -----------------
- -Initial BETA VERSION Release. This version was an operational
- demonstration of the program and did not include any configuration
- features.
-
-