home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
HAM Radio 1
/
HamRadio.cdr
/
satel
/
trackst2
/
traksat.doc
Wrap
Text File
|
1990-08-12
|
181KB
|
4,239 lines
╔═════════════════════════════════╗
║ ║
║ ▀▀█▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ ║
║ █ █▀█ █▀█ █ █▀█ █▀█ ▀█▀▀▀ ║
║ █ █ █ █ █ █ █ █ ║
║ █ █ █▀█ █▀█ ▀▀█ █▀█ █ ║
║ █ █ █▄█ █ █ █▄█ █▄█ █ ║
║ █ ║
║ █ ║
║ Version 2.45 ║
╚═══╦═════════════════════════╦═══╝
║ ║
║ Paul E. Traufler ║
║ 111 Emerald Dr. ║
║ Harvest, Al 35749 ║
║ (205) 726-5511 ║
║ ║
╚═════════════════════════╝
Satellite Tracking Program
12 August, 1990
TRAKSAT
(C)opyright 1990
All Rights Reserved
╔══════════════════════════════════════════════════════════════════╗
║ ║
║ TRAKSAT is free for NON-COMMERCIAL use only. ║
║ ║
╠══════════════════════════════════════════════════════════════════╣
║ ║
║ If you find TRAKSAT useful and would like to use it in a ║
║ commercial operation please call or write for more information. ║
║ ║
╚═══════════════════╗ ╔════════════════════╝
║ ║
║ Paul E. Traufler ║
║ 111 Emerald Dr. ║
║ Harvest, Al. 35749 ║
║ 205-726-5511 (work) ║
║ 205-830-8450 (home) ║
║ ║
╚═════════════════════════╝
════════════════════════════════════════════════════════════════
****************************************************************
TRAKSAT and its companion files is being distributed as
shareware. You are encouraged to share this software with others
provided that it is distributed complete with documentation and
in unmodified form and that no fee or other consideration is
charged or accepted.
****************************************************************
════════════════════════════════════════════════════════════════
TRAKSAT makes no warranty of any kind, either express or implied,
including but not limited to implied warranties of
merchantability and fitness for a particular purpose, with
respect to this software and accompanying documentation.
Paul E. Traufler, author of TRAKSAT, SHALL NOT BE LIABLE FOR ANY
DAMAGES (INCLUDING DAMAGES FOR LOSS OF BUSINESS PROFITS, BUSINESS
INTERRUPTION, LOSS OF BUSINESS INFORMATION) ARISING OUT OF THE
USE OF OR INABILITY TO USE TRAKSAT.
TRAKSAT Satellite Tracking Program Page 2
TABLE OF CONTENTS
-----------------------------------------------------------
INTRODUCTION ........................................... 4
THEORY OF SATELLITE MOTION ............................. 5
HARDWARE REQUIRED TO RUN THE PROGRAM ................... 6
RUNNING THE PROGRAM .................................... 7
ADVANCED FEATURES (MAIN MENU OPTION ZERO) .............. 8
READ SATELLITE DATA (MAIN MENU OPTION ONE) ............. 9
TRACKING STATIONS (MAIN MENU OPTION TWO) ............... 11
REAL-TIME MODE (MAIN MENU OPTION THREE) ................ 13
DELTA-TIME MODE (MAIN MENU OPTION FOUR) ................ 14
GRAPHICS (MAIN MENU OPTION FIVE) ....................... 16
SUN TERMINATOR ......................................... 18
TABULAR OUTPUT (MAIN MENU OPTION SIX) .................. 25
VISIBILITY (MAIN MENU OPTION SEVEN) .................... 29
MULTI-TRACK MODE (MAIN MENU OPTION EIGHT) .............. 31
MULTI-TRACK TABULAR OUTPUT MODE ........................ 33
QUITTING THE PROGRAM (MAIN MENU OPTION NINE) ........... 35
USER DEFINED SATELLITE PLOTTING COLOR .................. 35
ADVANCED FEATURES OPTION DESCRIPTION ................... 36
REVERSE SOLUTION (ADVANCED FEATURES MENU OPTION ZERO) .. 37
USER DEFINED/ALL SATELLITES ............................ 40
ANALYTICAL SOLUTION (LOS/OPTICAL) ...................... 41
NORAD/NASA 2-LINE SATELLITE DATA ....................... 46
WHAT ARE THE MEAN CLASSICAL ELEMENTS ................... 48
MODELS FOR PROPAGATION OF NORAD ELEMENT SETS ........... 53
THE PROPAGATION MODELS ................................. 53
COMPATIBILITY WITH NORAD ELEMENT SETS .................. 54
PROGRAM LIMITATIONS AND ASSUMPTIONS .................... 55
USER DEFINED STAR DATA ................................. 56
ACCURACY OF TRAKSAT .................................... 58
A BRIEF EDITORIAL ...................................... 60
SPECIAL THANKS ......................................... 61
QUESTIONS AND COMMENTS ................................. 62
FUTURE UPGRADES ........................................ 64
OBTAINING NORAD SATELLITE DATA SETS .................... 65
FILES REQUIRED FOR TRAKSAT ............................. 66
BIBLIOGRAPHY ........................................... 67
Trademarks used in this document
-----------------------------------------------------------------
IBM,PS/2 PC DOS are registered trademarks of International Business
Machines Corporation.
Microsoft MS, MS-DOS, QuickC, are registered trademarks of
Microsoft Corporation.
Epson FX,LQ, is a registered trademarks of Epson American Inc..
Hercules is a registered trademark of Hercules Computer Technology.
TRAKSAT Satellite Tracking Program Page 3
INTRODUCTION
Ever since college I have been interested in satellites and
tracking methods. I have often looked up into the night sky and
thought, "I know satellites are up there but can I predict when
and where to look to see one".
I have several small programs to calculate different satellite
related quantities but there was not one program available to do
all the things I felt a satellite tracking program should do.
After several years of working in the aerospace field, I decided
that I could take on such a programing task.
I started it all with a program called STS, it was geared towards
tracking the space shuttle, but used the same basic orbital
calculations.
STS, version .95, is available on several BBS around the country,
see the references at the end of this document.
For a first attempt at such a satellite tracking program I was
some-what pleased with the results. But I felt there is room for
improvement and that is where TRAKSAT steps in.
TRAKSAT is a general purpose satellite tracking program, by that
I mean any satellite that has a NORAD, NASA 2-Line element set
can be used. There are some limitations in the program along with
some assumptions, the reader is directed to the section on limits
and assumptions for further study.
The solution to the satellite motion which is used by TRAKSAT is
completely analytic and therefore requires no numerical
integration. This makes the program fast, even faster when a
coprocessor is used, since the solutions can be evaluated at
arbitrarily large, or small, time intervals.
The purpose of this program is to provide the user with a means
of propagating NORAD element sets in time to obtain tracking
information of the space object.
TRAKSAT Satellite Tracking Program Page 4
THEORY OF SATELLITE MOTION
A complete development of the theory required to predict
the position of an artificial satellite about the earth is not
presented here because this is not proper place for it. Such a
development would require a volume in itself and would be more
of a distraction than an aid to the potential user. Only enough
of the concepts required for a general understanding plus the
final results are given. References to detailed works from which
these results are derived are provided for the more than
casually interested reader.
At the end of the TRAKSAT operating instructions is a brief
overview of the fundamentals used in this program and is included
to help the reader understand the motion of an artificial
satellite about the earth.
TRAKSAT Satellite Tracking Program Page 5
HARDWARE REQUIRED TO RUN THE PROGRAM
In order to run the program the user will need the following
hardware;
IBM or compatible PC,XT,AT,PS/2,386, 640K Ram
(510K FREE RAM IS REQUIRED), Floppy or Hard Disk,
Text mode display (25x80), Hercules, CGA, EGA,
or VGA graphics (used for plotting only),
Math coprocessor is NOT required for TRAKSAT,
(IF A COPROCESSOR IS PRESENT IT WILL BE USED *),
Epson FX-80 printer or compatible (for graphic print
out only), PC DOS or MS DOS version 2.1 or above.
* It should be noted that a coprocessor will be 3 to 4 times
faster than the emulator version. If the user plans on using the
real-time tracking mode, a coprocessor will "smooth out" the time
steps to such a small delta as to appear instantaneously. At any
rate the real-time mode runs as fast as the host computer can
calculate the data and update the screen.
******************
* IMPORTANT NOTE *
******************
The user will not be able to run TRAKSAT on a 360K floppy drive,
The size of the executable and the earth map data plus a
satellite data file will simply not fit on the 360K floppy disk.
The best solution to the problem would be run TRAKSAT from a hard
disk! The prices of hard disks have come down to a point where
practically all computers have them. If the user needs a "good
reason" to buy a hard disk, perhaps TRAKSAT can convince them to
do so.
******************
* IMPORTANT NOTE *
******************
To print out the document, TRAKSAT.DOC use the DOS copy command.
The syntax to use would be "COPY TRAKSAT.DOC PRN", without the
quotation marks.
TRAKSAT Satellite Tracking Program Page 6
RUNNING THE PROGRAM
To start TRAKSAT you type "TRAKSAT", without the quotation marks,
at the DOS prompt. After a few moments the default tracking
station name will be displayed at the bottom of the screen. After
the opening screen has been displayed the TRAKSAT main menu will
appear. The main menu is the core of the program, i.e. from this
menu the user can setup satellite data, tracking station data,
and output selections.
Here is an main menu example;
╔═══════════════════════════════════════════════════════════════╗
║ Date: 3/26/1990 Time: 18:30:00 ║
╠═══════════════════════════════════════════════════════════════╣
║ ╔═════════════════════════╗ ║
║ ║ TRAKSAT ║ ║
║ ╠═════════════════════════╣ ║
║ ║ MAIN MENU ║ ║
║ ╠═════════════════════════╣ ║
║ ║ (0) Advanced Features ║ ║
║ ║ (1) Read Elements ║ ║
║ ║ (2) Tracking Stations ║ ║
║ ║ (3) Real Time Tracking ║ ║
║ ║ (4) Delta Time Mode ║ ║
║ ║ (5) Graphics ║ ║
║ ║ (6) Output Data ║ ║
║ ║ (7) LOS Visibility ║ ║
║ ║ (8) Multi-Track ║ ║
║ ║ (9) QUIT ║ ║
║ ║ Enter Option (0 - 9) ║ ║
║ ╚═════════════════════════╝ ║
║ ║
╚═══════════════════════════════════════════════════════════════╝
the date and time will be the current system values. The date
format used is mm/dd/yyyy, while the time format is hh:mm:ss,
based on a 24 hour clock, i.e. 14:00:00 is the same as 2 PM. From
this menu the input data and output data can be directed. If the
user enters other than the listed options numbers an error
message will appear at the bottom left of the screen. If the file
TRAKSAT.DEF is present the default tracking station from that
file will be displayed to remind the user of the default tracking
station. To change the default tracking station data see section;
TRACKING STATIONS, main menu option one.
******************
* IMPORTANT NOTE *
******************
All error messages are displayed for 3 SECONDS, then depending on
what the error was, program control will return to the user to
correct the problem. It is recommended that the user NOT press
any keys while the error message is being displayed, any key
presses may cause other error messages to appear.
TRAKSAT Satellite Tracking Program Page 7
ADVANCED FEATURES (MAIN MENU OPTION ZERO)
The advanced features option will control access to the "Advanced
Features" menu. The term advanced features should NOT frighten
the potential user off, as the options in this section are NOT
hard to use just that some people will never need to use them.
For a full description of these menu options see the section;
ADVANCED FEATURES MENU.
TRAKSAT Satellite Tracking Program Page 8
READ SATELLITE DATA (MAIN MENU OPTION ONE)
The main menu option 1 will call the read satellite data menu.
This program uses the NASA, or NORAD 2-line satellite element
data file format to read data into the program, (in this text the
use of NORAD refers to NASA 2-Line or NORAD satellite element
data sets). For a full explanation of the NASA 2-line satellite
element data sets see section; NASA 2-Line Satellite Data.
The read satellite data screen will appear;
╔═════════════════════════════════════════════════════════════════════╗
║ ╔═══════════════════════════════════════════════════════╗ ║
║ ║ ║ ║
║ ║ READ NASA 2-LINE SATELLITE FILE ║ ║
║ ╠═══════════════════════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ Enter Satellite Filename: [NASA668.TXT ] ║ ║
║ ║ Enter Search String: [ ] ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ╚═══════════════════════════════════════════════════════╝ ║
║ Press Esc to Exit ║
╚═════════════════════════════════════════════════════════════════════╝
the cursor will be placed at the satellite filename position. The
program will display the current satellite filename, if this
choice is acceptable for the user just press RETURN. If a
different satellite data file is desired the user will type in
the satellite data filename. To exit this option press Escape.
The next line requires the name of the satellite to track, a
maximum length of 12 characters is allowed. The program will
check if the file is present and display an error message if the
data file is NOT found.
To help the new user a NORAD satellite date file is included with
TRAKSAT, see section; Satellite Data Sets.
The search method used by the program will locate the first
occurrence of what was typed in for a search string when compared
to the satellite names, i.e. typing in "mi" could locate the
satellite named "Mir". The search is NOT upper/lower case
sensitive. If a match is found the full name is displayed and the
user is asked to accept this data or read for the next occurrence.
If the user does not know ANY satellite names they can enter a
carriage return, (Return or Enter), and ALL of the satellite names
will be displayed one at a time.
TRAKSAT Satellite Tracking Program Page 9
******************
* IMPORTANT NOTE *
******************
TRAKSAT is limited to the first 2000 satellites in any data file.
If the user has more than 2000 satellites in a data file they will
need to remove, using a text editor, satellite data sets as to
include the desired data set in the 2000 limit. This may not prove
to be a limitation for most users as most satellite data sets have
less than 150 data points.
If no match is found a error message is displayed and the user
will try another match.
If the file is found and the satellite name has been located the
screen will appear like;
╔═════════════════════════════════════════════════════════════════════╗
║ ╔═══════════════════════════════════════════════════════╗ ║
║ ║ ║ ║
║ ║ READ NASA 2-LINE SATELLITE FILE ║ ║
║ ╠═══════════════════════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ Enter Satellite Filename: [NASA668.TXT ] ║ ║
║ ║ Enter Search String: [Mir ] ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ Found MIR ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ Satellite Name [MIR ] ║ ║
║ ║ ║ ║
║ ║ Keep Reading Satellite File (y/n) [N] ║ ║
║ ╚═══════════════════════════════════════════════════════╝ ║
║ Press Esc to Exit ║
╚═════════════════════════════════════════════════════════════════════╝
the next step would be for the user to press return to stop reading
the satellite data file and return to the main menu.
The routine that reads the NASA 2-line satellite data does a check-
sum on the data to insure that the data is correct. If the check-
sum fails the user is notified with only a warning message, the
data may NOT be correct. THE USER CAN STILL USE THIS DATA BUT THE
RESULTS IT PRODUCES MAY NOT BE ACCURATE. For a full explanation
of NASA 2-line satellite element sets see section; NASA 2-Line
Satellite Elements.
TRAKSAT Satellite Tracking Program Page 10
TRACKING STATIONS (MAIN MENU OPTION TWO)
The next option, number 2, will only need to be run once, unless
a different tracking station is used, by the user. The program
defaults to using Huntsville, Al. as the tracking station, if the
user does not want to use the default option they can select a
city from the city data file. The cite data file has over 720 of
the larger U.S. cities latitude and longitudes in it.
The tracking station search works very much like the satellite
name search. The user is asked for a search string and the first
occurrence is displayed, then the next one and so on, until no
more matches are found.
If the user accepts a match some additional data is asked for by
the program. The altitude above mean sea level in meters, hours
from Greenwich, daylight savings flag (1 = daylight savings, 0 =
standard time) , and time zone name, are required for the
tracking station. (Some examples of the hours from Greenwich; EDT
= -4, CDT = -5, CST = -6). If the altitude of the tracking
station are not known the user can enter zero with out to much
loss in accuracy.
If the user can not find a match to the city data then they will
need to use a text editor to add the city data in the file
TRAKSAT.CTY or use the closest city in the file.
Below is an example for Huntsville, Al..
╔═══════════════════════════════════════════════════════════════╗
║ ╔═══════════════════════════════════════════════════════╗ ║
║ ║ READ TRACKING SITE DATA FILE ║ ║
║ ╠═══════════════════════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ Enter Search String: [Hun ] ║ ║
║ ║ ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ Found: Hun ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ Tracking Station Name [HUNTSVILLE, AL ] ║ ║
║ ║ Keep Reading Tracking Data File (y/n) [n] ║ ║
║ ║ HUNTSVILLE, AL ║ ║
║ ║ Enter Altitude Above Sea Level (M) [228.6 ] ║ ║
║ ║ Enter Hours From UT, i.e. CST = -6 [-5] ║ ║
║ ║ Enter Daylight Savings, i.e. 1 = Daylight [1] ║ ║
║ ║ Enter 3 Character Timezone Name, i.e. CST [CDT] ║ ║
║ ╚═══════════════════════════════════════════════════════╝ ║
╚═══════════════════════════════════════════════════════════════╝
the program pauses for a few seconds to allow the user to review
the data for any errors.
TRAKSAT Satellite Tracking Program Page 11
******************
* IMPORTANT NOTE *
******************
The daylight/standard time flag, (and time zone name), are NOT
used in ANY CALAULATIONS for TRAKSAT. IT IS ONLY TO REMIND THE
USER OF ANY TIME CHANGES. All of the calculations are done in UTC
times.
******************
* IMPORTANT NOTE *
******************
If the tracking station changes from the default values the file
TRAKSAT.DEF will hold the last saved tracking station data. While
running the program if a new tracking station is selected the
user will be asked if the old tracking station data should be
overwritten or not.
If the user saves the current data then the next time TRAKSAT is
run that new data will be the default else the old TRAKSAT.DEF
will be used.
A text editor can be used to change the TRAKSAT.DEF data also,
the user will need to use some caution with this method. The TWO
EXCEPTIONS are the multi-track options, see the section on its
recommended use (MAIN MENU OPTION EIGHT) and the user defined
area, see section; Analytical Solution.
After the tracking station has been chosen the main menu will
appear waiting for the next user choice.
TRAKSAT Satellite Tracking Program Page 12
REAL-TIME MODE (MAIN MENU OPTION THREE)
If the user would like to track in real-time, press 3, the program
defaults to this mode at start-up. The screen will display the
current time mode (i.e., real or delta modes) by changing the
main menu background colors on the time modes and placing an arrow
on the current option.
The real-time mode will update the screen as fast as the hardware
will allow. For an XT class machine with no coprocessor, the
update time may be 1 to 2 seconds. An AT class computer with a
coprocessor can whip along at about 0.4 seconds per update. The
powerful and fast 386 coprocessor equipped machine can sing along
at 0.1 seconds per update. The average user will not require this
great of detail but it is included for the advanced user.
******************
* IMPORTANT NOTE *
******************
The time is read from the system clock, and as such is only as
accurate as the setting of this clock. The software date and time
can be set before running TRAKSAT to insure the correct time.
Refer to your DOS manuals to use the time and date functions.
A brief note about tracking satellites.
The accuracy of the data is the most important part of the
prediction process. NORAD does track some 8000+ objects in orbit
around the earth, and maintains a data base of the objects. The
earth modeling and perturbations are the most important factors
in satellite tracking. This program uses the NORAD element sets
mainly because they are available and have reasonably good
accuracy.
If the user would like to "see" a satellite in the night sky the
precision of 1 or 2 seconds is not important, several minutes may
not even be that important. This is not to say that the average
person can not locate the satellite, it is going to pass over
some site sooner or later, its the time of the passing that is of
importance.
It could be said that if you tell me where to look for the
satellite and tell me about when I should be looking for it the
chances are it will be spotted. The sky is a big place and it
would be almost impossible to locate a satellite without any help
from programs such as TRAKSAT.
TRAKSAT Satellite Tracking Program Page 13
DELTA-TIME MODE (MAIN MENU OPTION FOUR)
If the user would like to track a satellite from say todays date
to some future date, the delta time mode is the choice to use.
The basic idea is track from some starting date to some stopping
date. At any rate the user will see the screen below with the
delta time mode screen;
╔══════════════════════════════════════════════════════════╗
║ ║
║ ║
║ ╔═══════════════════════════════════════════════╗ ║
║ ║ DELTA TIME MODE ║ ║
║ ╟───────────────────────────────────────────────╢ ║
║ ║ STARTING DATE AND TIME (UT) ║ ║
║ ║ ║ ║
║ ║ YEAR [1990] ║ ║
║ ║ MONTH [ ] ║ ║
║ ║ DAY [ ] ║ ║
║ ║ HOUR [ ] ║ ║
║ ║ MINUTE [ ] ║ ║
║ ║ SECOND [ ] ║ ║
║ ║ TIME STEP (MIN) [ ] ║ ║
║ ║ ║ ║
║ ║ Press Esc to QUIT ║ ║
║ ╚═══════════════════════════════════════════════╝ ║
║ ║
║ ║
╚══════════════════════════════════════════════════════════╝
the user will need to "fill in the blanks". The program will
display "defaults" which the user will press return to accept. If
the default is not correct the user will be required to enter in
a new default. At the start of this section the default date and
time are the current local date and zero hours UTC, however, if
the user changes the data the next time this section is called
the "new" default data will be used. At any time during the
delta mode data entry the user presses the Esc key the program
will stop the data entry and the Main Menu will appear.
It is noted that the maximum length, that is from the starting
date to some future time, of the simulation is 99 days 99 hours
59 minutes 59 seconds.
An example is included for the user to "get the idea" on entering
the starting date information. This example starts on 26
december, 1989 at 0 hours UTC, and uses a 1 minute time step. The
user can enter smaller or larger time steps depending on the
requirements of the user.
TRAKSAT Satellite Tracking Program Page 14
╔══════════════════════════════════════════════════════════╗
║ ║
║ ╔═══════════════════════════════════════════════╗ ║
║ ║ DELTA TIME MODE ║ ║
║ ╟───────────────────────────────────────────────╢ ║
║ ║ STARTING DATE AND TIME (UT) ║ ║
║ ║ ║ ║
║ ║ YEAR [1989] ║ ║
║ ║ MONTH [12] ║ ║
║ ║ DAY [26] ║ ║
║ ║ HOUR [00] ║ ║
║ ║ MINUTE [00] ║ ║
║ ║ SECOND [00] ║ ║
║ ║ TIME STEP (MIN) [1.0 ] ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ╚═══════════════════════════════════════════════╝ ║
║ ║
╚══════════════════════════════════════════════════════════╝
An approach most people use is to pick a 2-3 minute time step and
check the output for any passes near the tracking station for
that day. Then return back to the delta time mode and use a
smaller time step to obtain a better estimate of the satellite
visibility. Another method is to use the analytical solution
option, see the section on Advanced Features for more
information.
The next step for the user is the length of time for the
propagation. The format is days, hours, minutes, and seconds.
Below is an example for 0 days, 12 hours, 30 minutes, 0 seconds;
╔══════════════════════════════════════════════════════════╗
║ ║
║ ╔═══════════════════════════════════════════════╗ ║
║ ║ DELTA TIME MODE ║ ║
║ ╟───────────────────────────────────────────────╢ ║
║ ║ LENGTH OF PROPAGATION ║ ║
║ ║ ║ ║
║ ║ DAY [00] ║ ║
║ ║ HOUR [12] ║ ║
║ ║ MINUTE [30] ║ ║
║ ║ SECOND [00] ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ╚═══════════════════════════════════════════════╝ ║
║ ║
╚══════════════════════════════════════════════════════════╝
after the length of propagation is entered the program will
return to the main menu.
TRAKSAT Satellite Tracking Program Page 15
GRAPHICS (MAIN MENU OPTION FIVE)
Option number five, from the main menu, controls the graphics
output. If the user selects the graphics output a new menu will
be displayed with several options for the user to choose from.
A graphics menu screen will appear such as;
╔══════════════════════════════════════════════════╗
║ ║
║ ╔═════════════════════════════╗ ║
║ ║ TRAKSAT ║ ║
║ ╠═════════════════════════════╣ ║
║ ║ GRAPHICS MENU ║ ║
║ ╠═════════════════════════════╣ ║
║ ║ ║ ║
║ ║ (1) Ground Tracks ║ ║
║ ║ (2) Star Background ║ ║
║ ║ (3) 3D Projections ║ ║
║ ║ (4) Return To Main Menu ║ ║
║ ║ Enter Option (1 - 4) ║ ║
║ ╚═════════════════════════════╝ ║
║ ║
╚══════════════════════════════════════════════════╝
The options available from this menu control the graphics output.
The user has the choice of satellite ground tracks or star
background plots. If the user selects option 1 from the graphics
menu a satellite ground track will be produced, while a option 2
will display a star background. The star background option will
display visible stars from a database of 58 navigational stars,
the Sun, the planets, and the moon.
The term "star background" will be used in this document to mean
the 58 navigational stars, the Sun, the planets (not including
the earth), and the moon.
******************
* IMPORTANT NOTE *
******************
The star data is internal to TRAKSAT, i.e., there are no
provisions for the user to MODIFY THE INTERNAL STAR DATA at this
time. Star positions are for Epoch J2000.0, from USNO Floppy
Almanac 1988, Version 2.11.88, file STAR1.CAT. HOWEVER THE USER
CAN SUPPLY ADDITIONAL STAR DATA TO THE PROGRAM, see the section
on USER DEFINED STAR DATA.
The star background is a view looking from the tracking site
towards the stars. This plot will be useful for producing a "star
map" to take outside with you to compare the night sky with the
satellite path.
The option to print out this "star map" is included in TRAKSAT,
as of version 1.80 and up. The user will require a Epson FX-80
or compatible printer to use this feature. Again this will prove
valuable to the user in determining where and when to look to
"see" the satellite, this option will work for LOS or Optical
TRAKSAT Satellite Tracking Program Page 16
visibility modes. To print out a screen copy the user will only
have to press a "P" or "p". After the output is printed the
program will continue with the plot. The user can interrupt the
printer process by pressing any key, the printer output will stop
and the program will continue.
******************
* IMPORTANT NOTE *
******************
The printer MUST be connected to parallel printer port number 1,
LPT1. To stop the printer output the user can press any key. A
Epson FX-80 or graphics compatible printer must be used for any
output. The print out routines have been tested on several
different Epson compatible printers without any problems. Some
laser printers can emulate the Epson printers and will produce
good results also.
THE DEFAULT NUMBER OF PRINTER PINS (9 OR 24) IS READ FROM THE
FILE TRAKSAT.DEF. The user can change the "Printer Pins = 9" to
"Printer Pins = 24" as required for the printer being used.
******************
* IMPORTANT NOTE *
******************
If the user selects any graphic output the program will test for
a graphics adapter and based on the type of graphics hardware
will select the "highest" graphics mode supported. An example
would be;
VGA mode 640x480 pixels,
EGA mode 640x350 pixels,
CGA mode 640x200 pixels,
HGC mode 720x348 pixels (Monochrome).
******************
* SPECIAL NOTE *
******************
The Hercules graphics mode requires running the driver
MSHERC.COM, this is the driver supplied with several Microsoft
programing languages, before using the TRAKSAT program. Type
"MSHERC" and then "TRAKSAT" to start the program. (A TRUE
Hercules card works with TRAKSAT, some clone cards may NOT.)
I can not test this mode as I do not have any 100% Hercules
graphic cards. Dave Ransom (author of ASTRO CLOCK and good
friend) has tested TRAKSAT on a TRUE Hercules card and had NO
MAJOR PROBLEMS. A few problems with the screen cursor but NOT
serious. (TRAKSAT version 2.20 has corrected the cursor
problems.) Many thanks to Dave for his testing!
Do not use a Microsoft mouse AND the Hercules graphics cards
together, according to Microsoft, as this may cause some
"problems". Any mouse drivers that are installed should be
removed before running TRAKSAT with a Hercules card also.
If the hardware does NOT support graphics an error message will
TRAKSAT Satellite Tracking Program Page 17
be displayed and the program will return to the main menu. All of
the text modes will still be available to the user however.
******************
* IMPORTANT NOTE *
******************
****************************************************************
If the user has a computer that is not 100% compatible or the
graphic card is not 100% VGA compatible the program can be forced
to use the EGA mode. To use this method invoke the program with
"TRAKSAT\EGA", without the quotes. This will set the display to
EGA modes only and MAY eliminate any graphic problems
encountered. NO OTHER GRAPHIC MODES CAN BE SET THIS WAY.
****************************************************************
(GRAPHICS MENU OPTION 1)
If the ground track option is entered (1) the program proceeds to
draw a Mercator projection map of the world. The upper left
corner is at latitude 90 degrees and longitude -180 degrees,
while the lower right corner is latitude -90 degrees and
longitude 180 degrees. The grid spacing is 30 degrees for both
the latitude and the longitude. A "+" will be plotted for the
tracking station coordinates, the coordinates from TRAKSAT.DEF or
the currently loaded data.
The plotting process may take a minute or two on a slow XT type
computer, something under 2 seconds on the particular computer I
use.
The user will be asked about displaying the sun terminator. The
sun terminator is not dependent on the satellite but rather the
tracking station. The terminator is plotted based on a zero sun
elevation angle. (That is to say the terminator is the line where
the sun is "just" below the local horizon.) The terminator is
accurate to about 10-15 minutes of actual. The effects of the
local horizon and atmospheric refraction can "shift" the
terminator a few minutes anyway so great accuracy may not be
achieved. The sun is plotted as an "+" in the center of the
terminator. This will tell the user on what side of the
terminator the tracking station is on. (Daylight or darkness.)
The sun terminator will be "refreshed" every 4 minutes in either
the real or delta time modes. The refresh may take several
seconds on the slower machines. (About 20 seconds.)
******************
* IMPORTANT NOTE *
******************
THE SUN TERMINATOR PLOTTING PROCESS MAY TAKE A MINUTE OR SO ON A
SLOW XT TYPE COMPUTER, something under 1 second on the particular
computer I use.
The ground track plot is the only option that will display the
sun terminator.
The file EARTH.DAT contains the world map data, some 8200 points
in all. This file is compressed to save space and reduce the
reading time. (TRAKSAT version 2.10 and up has improved the
TRAKSAT Satellite Tracking Program Page 18
compression ratio (45%), older versions of the program can NOT be
used with this new data file, nor can TRAKSAT use the older data
file.)
If the EARTH.DAT file is not found an error message will be
displayed and the program will return to the main menu again.
After the world map is displayed the simulation begins. The
starting position for the satellite is marked as a yellow filled
(if that is the user defined color) circle, this was added to
help locate the starting position. The screen will plot the
orbital ground trace of the chosen satellite along with other
valuable data. The top line will have the UTC date and time,
while the second line will have the local date and time
displayed. The lower lines will have the tracking data displayed.
An example of the output screen would be;
-----------------------▌ TRAKSAT Version 1.80 ▐--------------------
| |
| UTC 21:37:26.1 Date 12/26/1989 Satellite Name: MIR |
| Local 15:37:26.1 Date 12/26/1989 Tracking Station: HUNTSVILLE,AL |
| |
| (The version number may be different in this display.) |
| (no world map drawn in this example) |
| |
| Lat 45.1635° Azimuth 309.1281° Range 7115.4 Km |
| Long -175.3926° Elevation -30.1331° Rev # 22120 NOT Visible |
| |
-----------------------------------------------------------------------
The Lat and Long are the satellite latitude and longitude. The
Azimuth and Elevation are as seen from the tracking station,
while the Range is the distance from the satellite to the
tracking station.
The azimuth is always between 0 and 360 degrees with north being
0, east 90 south 180 and so on. The elevation will be always be
between -90 and +90 degrees. If the elevation is less than zero
the satellite is below the horizon as seen from the tracking
station.
The Rev # is based on the input data starting revolution number
plus the number of revs per day times the days past the epoch
date, i.e. the formula;
rev = rev_epoch + (mean motion(rev/day) * (epoch date - date).
The epoch refers to the NORAD satellite data set, see section;
NORAD/NASA 2-Line Satellite Data, for a full explanation of the
input data.
The last item displayed is based on if the satellite is visible
from the tracking station. See main menu option seven for a
complete description of the methods used by TRAKSAT to test for
visibility.
TRAKSAT Satellite Tracking Program Page 19
******************
* IMPORTANT NOTE *
******************
To stop the display the user can press any key and the screen
will "freeze". The user will need to press any key again to
continue the simulation. If the user presses Esc, escape key, the
simulation will stop and the user will be returned to the main
menu.
******************
* IMPORTANT NOTE *
******************
The ground track will continue until the user stops the
simulation by pressing Escape (Esc). After 8-9 ground tracks have
been plotted the screen will be "very busy", the user can re-draw
the screen by pressing Esc, than pressing main menu option five
and one again. The world map will be drawn again along with the
new orbital ground tracks. This will cut down on the screen
"clutter".
The user can print out the screen output with the ground track
option. To print the output of the screen press "P" or "p",
without the quotation marks. The print out may take a minute or
so depending on the type of printer being used. The print out
will start with the upper right side of the screen.
TRAKSAT Satellite Tracking Program Page 20
(GRAPHICS MENU OPTION 2)
If the graphics menu option 2 has been chosen the program will
ask the user for some additional data. The user can display the
visible star names if so desired. (Only the internal star data
names will be displayed, not the user defined star data.) The
user will choose what direction to look, i.e., North, East,
South, or West. The field of view of the star background is 180
degrees in azimuth and 0 through 90 degrees in elevation. If the
user selects North the visible range of the azimuth will be 270
degrees (west) to 90 degrees (east). If the user selects East the
visible range of the azimuth will be 0 degrees (north) to 180
degrees (south) with 90 degrees being the center of the screen
(due east). The option South will display from 90 degrees (east)
to 270 degrees (west). The option for West will display from 180
degrees to 360 degrees with 270 degrees (west) being the center
of the screen (due west).
An example could be to see a satellite rise out of the west the
user would select W, that will display from due south through
west to the north. The screen will appear such as;
╔══════════════════════════════════════════════════╗
║ ╔═════════════════════════════╗ ║
║ ║ TRAKSAT ║ ║
║ ╠═════════════════════════════╣ ║
║ ║ GRAPHICS MENU ║ ║
║ ╠═════════════════════════════╣ ║
║ ║ ║ ║
║ ║ (1) Ground Tracks ║ ║
║ ║ (2) Star Background ║ ║
║ ║ (3) 3D Projections ║ ║
║ ║ (4) Return To Main Menu ║ ║
║ ║ Enter Option (1 - 4) ║ ║
║ ╚═════════════════════════════╝ ║
║ ╔══════════════════════════════════╗ ║
║ ║ Display Star Names (y/n)? [Y] ║ ║
║ ║ ║ ║
║ ║ User Star Database (y/n)? [N] ║ ║
║ ║ ║ ║
║ ║ Looking N,E,S,W (N,E,S,W) [W] ║ ║
║ ╚══════════════════════════════════╝ ║
╚══════════════════════════════════════════════════╝
By default TRAKSAT will display the star names, including the
planets and the moon, not use a user defined star database, and
look west. The user will only need to change these options by
typing in the correct response.
If the user selects the option to include a user defined star
database the program will ask for the file name. If the file is
not found the program will continue and display the internal star
database only. The FIRST 1500 stars will be read from the user
defined file and then the program will continue. The user will
have the responsibility to check the user defined star data for
duplicates of the TRAKSAT internal star data. (See the section on
TRAKSAT Satellite Tracking Program Page 21
PROGRAM LIMITATIONS AND ASSUMPTIONS for a list of the internal
stars used in TRAKSAT.)
*****************************************************************
** REMEMBER TO USE EPOCH J2000 FOR ANY USER DEFINED STAR DATA. **
*****************************************************************
An example of a star background would be;
UTC 14: 2:12.2 Date 3/26/1990 Az 211.3715° Rev# 23519
Local 8: 2:12.2 Date 3/26/1990 El -43.8641° Vis NOT Visible
----------------------------------------------------------------
| Satellite: Mir TRAKSAT 1.85 |
| |
75- |
| |
| O Moon |
60- |
| |
| EXAMPLE |
45- (NO PLOT SHOWN) |
| (This is only an example, the |
| DATA displayed is NOT correct) |
| |
| |
30- o Venus |
| |
| |
15- . Alpharatz |
| |
| west |
----------------------------------------------------------------
210 240 270 300 330
the side axis is the elevation while the bottom axis is the
azimuth. (Observer coordinates are the only output type at this
time). In this example star names were displayed and the option
to look west was selected. The "sky track" of the satellite will
also be plotted on the screen. The top two lines will display the
local and UTC time and dates, azimuth, elevation, rev, and if the
satellite is visible (based on the setting of option 7 LOS or
Optical). The star map background will remain black even if the
sun has risen. (The version number may be different in this display.)
******************
* IMPORTANT NOTE *
******************
If the delta time mode is selected time steps are marked on
the screen and labeled for the user. It is recommended that the
delta time mode be used for star backgrounds so a "time tag" can
be placed on the screen. The real time mode will not place "time
tags" on the screen. This approach was used to help reduce screen
clutter, i.e., to many time tags. This method was chosen because
few people have laptop computers "out in the field" to use for
viewing aids. A printed "sky map" generated before the nights
viewing will be of much greater use to most people.
TRAKSAT Satellite Tracking Program Page 22
******************
* IMPORTANT NOTE *
******************
It is noted that the star background will be refreshed EVERY 15
MINUTES, in either delta or real time modes. It is therefore wise
to select a starting time about 15 minutes PRIOR to the time of
interest and run the program in the delta mode until PAST the
time of interest. An example of this would be;
Time of interest 11:30:00 UTC,
Starting time 11:23:00 UTC,
Time span 00:14:00.
This will provide the user with the "sky map" from 11:23 to 11:37
UTC and avoid the screen refresh.
******************
* IMPORTANT NOTE *
******************
To stop the display the user can press any key and the screen
will "freeze". The user will need to press any key again to
continue the simulation. If the user presses ESC, escape key, the
simulation will stop and the user will be returned to the main
menu.
(GRAPHICS MENU OPTION 3)
If the user presses option 3 from the graphics menu a 3-D
orthographic projection of the earth and the satellite will be
drawn. The perspective will be centered on the tracking station
coordinates with the altitude above the earth being set by the
semi-major axis of the satellite to view. A small "X" will mark
the tracking station coordinates. The grid lines are drawn 10
degrees apart with the orthographic projections.
The 3-D graphic will plot the "orbital trace" above the planet,
i.e., not the ground trace, WHILE HOLDING THE EARTH STILL. The
earth will be non-rotating with the satellite going around it.
The close earth satellites (1000 Km altitude and less) will
produce a good quality plot while near geosync satellites will
display the earth as a small hard to see "ball". The highly
eccentric orbits (ecc. > .3) will not display the complete
orbital trace due to some limitations of the methods used in
TRAKSAT. This should not pose much of a concern to most users.
****************************************************************
THE 3-D PROJECTION WILL BE SLOW ON XT TYPE COMPUTERS WITHOUT A
COPROCESSOR SO IF THE USER DOES NOT WANT TO WAIT FOR THE COMPLETE
EARTH TO PLOT OUT PRESS ANY KEY AND THE EARTH LAND MASS PLOT WILL
STOP AND THE SATELLITE VIEW WILL START. (Only the grid lines will
be displayed.)
****************************************************************
The screen can be stopped and started the same way as any other
graphic modes, i.e., any key to freeze and Esc to stop.
TRAKSAT Satellite Tracking Program Page 23
At this time the altitude above the earth is not a user changed
option. If the user would like a polar (either north or south)
projection select Main Menu option 2 and select either the north,
south or even the equator tracking station coordinates.
******************
* IMPORTANT NOTE *
******************
It is recommended that the user edit the TRAKSAT.CTY file and
change the first three tracking station coordinates to his or her
LOCAL LONGITUDE. The user will answer the questions about
tracking station altitude and time zone information based on the
local conditions.
Below is an example of the TRAKSAT.CTY file with the first three
"extra" tracking stations included. The format of the tracking
station is;
City Name Long. (deg) Lat. (deg).
'North Pole ',-86.5867,90.0
'Equator ',-86.5867,.0
'South Pole ',-86.5867,-90.0
'Rancho Palos Verdes CA ',-118.403334,33.767501
'Calaveras County, CA ',-120.566667,38.15
'Washington (USNO), DC ',-77.06575,38.920556
'Auburn, AL ',-85.4833,32.6067
'Birmingham, AL ',-86.81,33.5169
'Gadsden, AL ',-86.0114,34.0158
'Huntsville, AL ',-86.5867,34.7317
The TRAKSAT.CTY file can hold a maximum of 1000 tracking stations
in it. (The file included with TRAKSAT has 723 "cities" in it).
TRAKSAT Satellite Tracking Program Page 24
TABULAR OUTPUT (MAIN MENU OPTION SIX)
TRAKSAT can also produce a tabular output of the satellite
tracking data, the output is in a text mode not graphics. If the
user picks main menu option six, the program will display another
menu asking if the output is to go to a file or the screen.
I chose NOT to include the option for a printer mainly because of
all the different printers and the problems that go along with
different hardware. However, the file option output can be edited
and printed out by the user if so desired.
At any rate, the screen will look like;
╔══════════════════════════════════════════════════════╗
║ ║
║ ╔═════════════════════════════════════╗ ║
║ ║ OUTPUT DATA TO SCREEN/FILE ║ ║
║ ╟─────────────────────────────────────╢ ║
║ ║ ║ ║
║ ║ S = Output to Screen ║ ║
║ ║ F = Output to File ║ ║
║ ║ ║ ║
║ ║ Choice (S,F) [S] ║ ║
║ ║ ║ ║
║ ║ A = All Passes ║ ║
║ ║ V = Visible Passes ║ ║
║ ║ ║ ║
║ ║ Choice (A,V) [A] ║ ║
║ ║ ║ ║
║ ╠═════════════════════════════════════╣ ║
║ ║ Ra & Dec (J2000 Epoch) ║ ║
║ ╠═════════════════════════════════════╣ ║
║ ║ Do you want to display the ║ ║
║ ║ Ra & Dec coordinates (Y/N)? [Y] ║ ║
║ ╚═════════════════════════════════════╝ ║
╚══════════════════════════════════════════════════════╝
the user has to enter S or F. If the user presses any other keys
than the S or F the program will default to using the screen for
the output.
If the user presses the S key the program will display a header
with some of the tracking station data and the units of the data.
Below is an example of the screen output without the Ra & Dec;
Tracking Station: HUNTSVILLE, AL Satellite: Mir
Date Time (UTC) Azim Elev Range Lat Long Rev
V
HR:MN:Sec Deg Deg Km Deg Deg
Thr 25Jan90 01:27:5.550 268.7678 -43.87 9384.23883 -1.65793 -176.815 22575
Thr 25Jan90 01:27:5.600 268.7689 -43.87 9384.00198 -1.65535 -176.813 22575
Thr 25Jan90 01:27:5.660 268.7702 -43.87 9383.72069 -1.65229 -176.811 22575
Thr 25Jan90 01:27:5.710 268.7712 -43.87 9383.48382 -1.64971 -176.809 22575
this example was run using the real-time mode and the default
tracking station, Huntsville, Al..
In this case the LONG is the satellites longitude, positive (+)
TRAKSAT Satellite Tracking Program Page 25
means EAST longitude while negative (-) means WEST longitude.
The column "V" is the visibility flag, i.e., if the satellite is
visible the flag is set to "Y" else it is blank.
The other output quantities are the same as in main menu option
five.
If the user had chosen to include the Ra & Dec the output would be
like;
Tracking Station: HUNTSVILLE, AL Satellite: Mir
Date Time (UTC) Azim Elev Range Ra Dec Alt
V
HR:MN:Sec Deg Deg Km HH:MM:SS DD:MM:SS Km
Thr 25Jan90 01:27:15.38 268.9799 -43.57 9337.76175 21:58:19 -01:05:53 388
Thr 25Jan90 01:27:15.44 268.9811 -43.56 9337.47902 21:58:20 -01:05:42 388
Thr 25Jan90 01:27:15.55 268.9835 -43.56 9336.95618 21:58:21 -01:05:22 388
the user will notice that the latitude and longitude have been
replaced by the Ra & Dec.
******************
* IMPORTANT NOTE *
******************
The Ra & Dec are based on the J2000 epoch, 1,1.5,2000 UTC date,
and are NOT user selectable, perhaps in the next version of
TRAKSAT. The J2000 epoch is the "current" epoch on most star
charts.
The user will notice that the header is stationary just the data
is scrolling. This option is useful for a quick view of tracking
data, since no graphics are used.
If the user was in delta-time mode the step between outputs would
be the delta time step value set in main menu option four.
******************
* IMPORTANT NOTE *
******************
To stop the display the user can press any key and the screen
will "freeze". The user will need to press any key again to
continue the simulation. Pressing ESC will return the user to the
main menu.
The other option, F, will place the tracking data output into a
file. The file name will consist of the first 8 characters of the
satellite name with the extension ".PRT" added to the end. The
name of the output file will be displayed for the user.
An example could be the satellite Mir, the filename for output
would be "Mir.PRT".
******************
* IMPORTANT NOTE *
******************
The program will produce the file xxxxxxx.PRT, the x being the
current satellite name, if one is not found, but will OVERWRITE
TRAKSAT Satellite Tracking Program Page 26
an old one if found. The user will have the responsibility to re-
name the file after completing a run if they would like to save
the output.
The output in the file is very similar to the screen output
option. Below is an example of the file output mode;
TRAKSAT Version 1.90
Tracking Station: HUNTSVILLE, AL
[ Line Of Sight (LOS) Visibility ]
Satellite: Mir
Satellite Data Set:
1 16609U 86 17 A 90 91.75081924 .00058269 00000-0 66933-3 0 5052
2 16609 51.6174 355.6250 0013230 341.6181 18.4560 15.61365027236165
Date Time (UTC) Azim Elev Range Lat Long Rev V
HR:MN:SEC Deg Deg Km Deg Deg
Thr 25Jan90 01:26:42.04 268.26 -44.61 9494.42 -2.86 -177.67 22575
Thr 25Jan90 01:26:42.21 268.26 -44.60 9493.63 -2.86 -177.66 22575
Thr 25Jan90 01:26:42.32 268.27 -44.60 9493.12 -2.85 -177.66 22575
Thr 25Jan90 01:26:42.43 268.27 -44.60 9492.60 -2.84 -177.65 22575
again this example used the real-time mode. This output is a
standard 80 columns, for printers or the 25x80 text screen. In
this example a line of sight (LOS) mode was chosen. If the
visibility mode was optical the header, the line under the
tracking station name, would display; [ Optical visibility ].
If the file mode and the real-time mode are chosen the screen
will display the number of records that have been written to
file. The program DOES check the remaining disk space and stops
the program if the record space exceeds available disk space. The
data prior to exceeding the disk space is written and an error
message is displayed, no data will be lost.
It is recommended that the real-time mode NOT be used for file
output, mainly because of the large files that could be produced.
If the file mode and delta-time mode are chosen the screen will
display the same record count as above, but also the total number
of records to calculate. This method produces the smallest file
size the user requires.
The total number of records to calculate would be;
total_records = (stop_time - start_time)/delta_time.
The size of the file is approximately 81 bytes per record,
therefore 1440 records, one day at one minute intervals, will
produce a file size of about 116K. (ALL TIME STEPS DISPLAYED).
TRAKSAT Satellite Tracking Program Page 27
******************
* IMPORTANT NOTE *
******************
To stop the display the user can press any key and the screen
will "freeze". The user will need to press any key again to
continue the simulation. Pressing ESC will return the user to the
main menu.
The option has been added to TRAKSAT version 1.5, and up, to
display only the visible passes, based on the setting of the flag
for main menu option 7, or ALL passes. The program will default
to ALL if a return is pressed.
The output, in the tabular modes, can display Ra & Dec of the
satellite also. The coordinate used is based on J2000 epoch, this
was chosen to be used with "current" star charts. The default is
to include Ra & Dec in the output.
Remember the default is to include the Ra & Dec in the output,
but by answering No to the question about Ra & Dec, that will
place the satellite latitude and longitude in the output file.
TRAKSAT Satellite Tracking Program Page 28
VISIBILITY (MAIN MENU OPTION SEVEN)
There are two different methods used by TRAKSAT to determine
visibility. The first method is simply when the elevation is
greater than zero degrees the satellite will be visible to the
tracking station. This method is called line of sight (LOS) in
the program. This method would be suitable for monitoring
satellite radio transmissions, interesting RF signals no doubt.
It should be noted that at most tracking sites zero degrees
elevation is not visible due to ground based obstructions, i.e.
trees buildings, and other such objects. A rule of thumb is if
you hold out your arm straight and stick out your thumb
horizontal to the ground so it appears to touch the horizon the
upper edge of your thumb is about two degrees elevation, while
your closed fist is about ten degrees elevation.
The second method, optical visibility, requires the satellite to
be above zero degrees elevation also, however the satellite must
be sun-lit while the tracking station is in darkness. This
method would be used for viewing satellites with the aid of say
binoculars. It is of interest to note that some satellites are
NOT visible even if the elevation angle is above the horizon,
because they are in the earth's shadow. It is difficult to
observe a satellite "coming out" of the earth's shadow, it is
easier to see the entrance into the shadow.
If the lighting conditions are favorable a "bright" satellite can
be seen with the naked eye also. The best time for these
favorable lighting conditions usually occur an hour before sun
rise or an hour after sun set, as seen at the tracking site. The
best type of satellite is low, about 250 - 400 kilometer
altitude, ones for naked eye observations. (Mir, Hubble, Shuttle
are a good examples.)
******************
* IMPORTANT NOTE *
******************
TRAKSAT version 1.60 and above use NAUTICAL twilight, i.e. the
sun is greater than or equal to -12 degrees BELOW the local
horizon, to determine the lighting conditions. The user can not
change the type of twilight used in TRAKSAT, i.e., civil,
nautical, or astrodynamic.
The type of visibility is set from the main menu, the default is
to use the LOS method. If the user would like to change the
visibility method, select main menu option number seven. The
main menu will always print the type of visibility test that
will be performed by the program. This menu option is a toggle
function, i.e. selecting option 7 changes from one method to the
other.
******************
* IMPORTANT NOTE *
******************
With either method the visual magnitude is NOT calculated. Such
a calculation would require knowledge about the emissivity of the
TRAKSAT Satellite Tracking Program Page 29
satellite, and atmospheric conditions, neither of which is readily
available to the user.
TRAKSAT Satellite Tracking Program Page 30
MULTI-TRACKING (MAIN MENU OPTION EIGHT)
TRAKSAT version 1.7 and above have the capability to track
several satellites at the same time. The main menu option number
eight will bring up another menu, this menu is used for the
multi-track option. The multi-track menu will appear asking the
user to select ground track or tabular output modes. After that
selection the program will ask for a real time or delta time
mode.
Below is an example of the multi-track options menu.
╔═════════════════════════════════════════════════════════════╗
║ ╔════════════════════════════════════╗ ║
║ ║ TRAKSAT ║ ║
║ ╠════════════════════════════════════╣ ║
║ ║ MULTI-TRACK MENU ║ ║
║ ╠════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ (1) Ground Tracks ║ ║
║ ║ (2) Tabular Output ║ ║
║ ║ (3) Return To Main Menu ║ ║
║ ║ ║ ║
║ ║ Enter Option (1 - 3) ║ ║
║ ╟────────────────────────────────────╢ ║
║ ║ Satellites To Track ║ ║
║ ║ File: NASA668.TXT ║ ║
║ ║ Satellite #1 [MIR ] ║ ║
║ ║ Satellite #2 [SALYUT 7 ] ║ ║
║ ║ Satellite #3 [IRAS ] ║ ║
║ ║ Satellite #4 [SEASAT 1 ] ║ ║
║ ║ Satellite #5 [EGP ] ║ ║
║ ║ Satellite #6 [NOAA 9 ] ║ ║
║ ║ ║ ║
║ ╚════════════════════════════════════╝ ║
╚═════════════════════════════════════════════════════════════╝
The satellite data file is displayed, this can be changed from
the main menu option number one, along with the default satellite
names. The user can return to the main menu by pressing option
number three.
If the satellite data file name is NOT correct then return to the
main menu, press 3, and run option number one. Enter the correct
file name and any search string, this search string will not be
used in the multi-track modes. If the data file is found return
to the main menu and run option eight again, this time the
correct file will be read. The default file name used for both
the single and multi-tracking modes is stored in TRAKSAT.DEF,
and can be edited and changed. It is not the best way to change
the default data but can be used.
The program will read the default data at startup and if any
changes are made DURING A RUN before the program terminates the
user will be asked to save this new data or keep the old data.
TRAKSAT Satellite Tracking Program Page 31
******************
* IMPORTANT NOTE *
******************
The user can ONLY change the satellite names by editing the
TRAKSAT.DEF file and changing the default names. The format for
the satellite names is as follows;
COLUMN
1 - through - 16 CAN BE ANYTHING,
COLUMN 16 STARTS THE SATELLITE NAME,
THE NEXT 12 CHARACTERS USED ARE THE
NAMES OF THE SATELLITES TO TRACK.
Below is an example, this is the data
included in the TRAKSAT.DEF file.
Satellite # 1: MIR
Satellite # 2: SALYUT 7
Satellite # 3: IRAS
Satellite # 4: SEASAT 1
Satellite # 5: EGP
Satellite # 6: NOAA 9
It is recommended that the FULL name of the satellite be used,
the search routine will use the first match found and not look
for any other matches. If the name of a satellite is not found
the output will display a NO DATA, i.e., no data for the
requested satellite has been loaded.
Six satellites MAXIMUM can be tracked, if the TRAKSAT.DEF has
fewer than TWO the program will issue a error and return to the
main menu. (Use the single tracking mode.)
The user has the option of either ground tracks or a tabular
output. If either option, ground tracks or tabular, is chosen
then program will ask the user to use real time or the delta time
modes next.
If the ground track option is chosen the program will proceed to
plot the tracks on the world map. The plots are very similar to
the main menu option five, except that for every satellite a
different colored line is drawn. The order of the colors are;
1st satellite = yellow
2nd satellite = cyan
3rd satellite = green
4th satellite = lite red
5th satellite = lite magenta
6th satellite = lite green.
(The colors can NOT be changed by the user)
******************
* IMPORTANT NOTE *
******************
Users with monochrome monitors will have trouble identifying the
ground tracks in the multi-track mode as no difference in the
colors will be seen. As of TRAKSAT version 1.90 and above a
number (1 - 6) along with the "starting circle" is plotted to
help identify the satellite on the monochrome screen.
TRAKSAT Satellite Tracking Program Page 32
Below is an example of the multi-track ground tracks. It is noted
that no actual graphics plot is included due to the limits of
storing graphics and text together.
-------------------▌ TRAKSAT Version 1.80 ▐------------------
| UTC 17:17:36.3 Date 2/20/1990 Satellite Name: MULTI-TRACKING |
| Local 11:17:36.3 Date 2/20/1990 Tracking Station: HUNTSVILLE, AL|
| |
| (The version number may be different in this display.) |
| (no world map drawn in this example) |
| |
| Mir Salyut 7 IRAS SeaSat 1 EGP NOAA 9|
|Azi 32.079 227.66 274.10 220.47 4.9673 2.2960|
|Ele 14.499 -60.75 -50.48 -57.27 33.954 -15.43|
----------------------------------------------------------------------
The output will display the ground tracks, the azimuth as seen
from the tracking station, and the elevation. The elevation is
the angle above or below the tracking station horizon. The output
is in degrees, with the time and date formats the same as option
five. (The version number may be different in this display.)
******************
* IMPORTANT NOTE *
******************
No visibility methods, LOS or optical, are used in the multi-
track GROUND TRACK modes. THE TABULAR OUTPUT MODES WILL DETERMINE
THE VISIBILITY BASED OF THE SETTING OF THE MAIN MENU OPTION
SEVEN, (LOS or Optical). (The user can determine the LOS
visibility by looking at the elevation angles displayed when
using the ground track option.)
MULTI-TRACKING TABULAR OUTPUT MODE
As of TRAKSAT version 2.30 and above a tabular multi-tracking
mode has been included. The output is in text rather than a
graphic display mode. Below is an example of the multi-tracking
tabular output mode. The different satellites will be displayed
in different colors also, the colors are the same as the ground
track options.
TRAKSAT Satellite Tracking Program Page 33
╔═════════════════════╡ TRAKSAT Version 2.30 ╞═══════════════════════╗
║ Tabular Multi-Tracking Mode ║
║ Tracking Station: HUNTSVILLE, AL Input Data File: NASA707.TXT ║
║ UTC 00:10:00.0 Date 6/19/1990 ║
║ Local 00:10:00.0 Date 6/18/1990 ║
╟─────────────────────────────┤ Mir ├─────────────────────────────╢
║ Latitude -12.0376° Azimuth 283.3060° Range 11839.43 Km ║
║ Longitude 42.4516° Elevation -63.4864° NOT Visible ║
╟─────────────────────────────┤ Salyut 7 ├─────────────────────────────╢
║ Latitude -5.4339° Azimuth 249.6659° Range 7706.61 Km ║
║ Longitude 209.8406° Elevation -33.6718° NOT Visible ║
╟─────────────────────────────┤ HST ├─────────────────────────────╢
║ Latitude 21.5907° Azimuth 350.3650° Range 11762.57 Km ║
║ Longitude 102.0782° Elevation -60.0983° NOT Visible ║
╟─────────────────────────────┤ SeaSat 1 ├─────────────────────────────╢
║ Latitude 59.6848° Azimuth 328.8212° Range 7653.05 Km ║
║ Longitude 20.8611° Elevation -29.3966° NOT Visible ║
╟─────────────────────────────┤ EGP ├─────────────────────────────╢
║ Latitude -2.4094° Azimuth 106.5518° Range 8414.05 Km ║
║ Longitude 338.9396° Elevation -27.4664° NOT Visible ║
╟─────────────────────────────┤ IRAS ├─────────────────────────────╢
║ Latitude 57.6857° Azimuth 354.3749° Range 9450.31 Km ║
║ Longitude 82.8507° Elevation -39.6712° NOT Visible ║
║ ║
╚═══════════════════════════════════════════════════════════════════════════╝
The output of the multi-tracking mode is similar to the bottom
two lines of a ground track plot. The output will display only
satellites found in the element file.
TRAKSAT Satellite Tracking Program Page 34
QUITTING THE PROGRAM (MAIN MENU OPTION NINE)
This option will stop the TRAKSAT program and return the user to
DOS. If the tracking station data was changed during the program
execution, the user will be asked if the new data should replace
the old default data. That choice is up to the user to decide.
The old data will be displayed along with the current data to help
the user with the choice. THE DEFAULT IS NOT TO SAVE THE NEW
DATA.
USER DEFINED SATELLITE PLOTTING COLOR
TRAKSAT version 2.40 and above allows the user to choose what
color to plot the satellite in. The color is changed in the file
TRAKSAT.DEF. Below is an example of a TRAKSAT.DEF file with the
default satellite plotting color as light yellow (14). To change
the color edit the file TRAKSAT.DEF and change the Color = XX to
any of the colors allowed. (If a incorrect color is chosen the
light yellow will be used as a default.)
COLUMN NUMBER
123456789012345678901234567890123456789012345678901234567890123456
2447836.50000000 Color = 14 ed read.me
Printer Pins = 9
HUNTSVILLE, AL 34.7317000 273.4033000 228.60 -5 0 CDT
NASA678.TXT
Multi-Track Satellite Names
Satellite # 1: MIR
Satellite # 2: SALYUT 7
Satellite # 3: IRAS
Satellite # 4: SEASAT 1
Satellite # 5: EGP
Satellite # 6: NOAA 9
User Defined Satellite Names
IRAS
SALYUT 7
COSMOS 1686
COSMOS 1766
MIR
The user can choose from the pallette of;
2 = GREEN 9 = LIGHT BLUE
3 = CYAN 10 = LIGHT GREEN
4 = RED 11 = LIGHT CYAN
5 = MAGENTA 12 = LIGHT RED (sun term.)
6 = BROWN 13 = LIGHT MAGENTA
7 = WHITE (map land mass color) 14 = LIGHT YELLOW
8 = GRAY 15 = BRIGHT WHITE
TRAKSAT Satellite Tracking Program Page 35
ADVANCED FEATURES MENU OPTIONS
The advanced features option will control access to the "Advanced
Features" menu. If the user selects the zero option the advanced
features menu will appear;
╔═══════════════════════════════════════════════════════════════╗
║ ║
║ ║
║ ║
║ ╔═════════════════════════════════════════╗ ║
║ ║ ADVANCED FEATURES MENU ║ ║
║ ╠═════════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ (0) Reverse Solution ║ ║
║ ║ (1) All Satellites In Data File ║ ║
║ ║ (2) Analytical Rise & Set (LOS) ║ ║
║ ║ (3) Analytical Rise & Set (Optical) ║ ║
║ ║ (4) Return To Main Menu ║ ║
║ ║ Enter Option (0 - 4) ║ ║
║ ║ ║ ║
║ ╚═════════════════════════════════════════╝ ║
║ ║
║ ║
║ ║
╚═══════════════════════════════════════════════════════════════╝
The user has five options from this menu, the Reverse Solution,
All or User Defined Satellites, Analytical Rise & Set (LOS)
Solution, Analytical Rise & Set (Optical) Solution, and finally
the return to Main Menu options. If the user selects any other
options than 0 - 4 the program will return to the Main Menu.
TRAKSAT Satellite Tracking Program Page 36
REVERSE SOLUTION (ADVANCED FEATURES MENU OPTION ZERO)
The main menu option 0 will perform the "reverse solution", i.e.,
given a right ascension & declination (Ra & Dec) and time (UTC)
determine what satellite was observed. For this method to work the
user must take accurate right ascension, declination and UTC time
measurements. If the user selects this option a opening warning
screen will appear before entering into the reverse solution
menu. This warning is to remind the user that accurate
measurements (THREE ARE REQUIRED) are needed to obtain acceptable
results. The accuracy of the data should be within the abilities of
most users with a telescope that has Ra & Dec digital read out
or mechanical measurement devises. The observed data set WILL
NEED TO BE FROM THE SAME REVOLUTION NUMBER, i.e., A SINGLE PASS
NEAR THE TRACKING SITE.
TRAKSAT has been tested with several satellites, changing the
observed Ra & Dec and times to better determine the accuracy
requirements of the reverse solution option. The Ra & Dec can be off
about 2 minutes and still produce good results. If the Ra & Dec
is off more then 2 minutes the error grows linearly with time.
Remember that the closer the satellite element data set is to the
observed data the better the match will be. A brief description
of the methods used for the reverse solution is located in
section; (Program Limitations and Assumptions).
The user is given a choice to return to the Main Menu or continue
with the reverse solution from this warning message screen.
At any rate the reverse solution menu will appear as such;
╔═════════════════════════════════════════════════════════════╗
║ ╔═══════════════════════════════════════════════════════╗ ║
║ ║ REVERSE SOLUTION MENU ║ ║
║ ╠═══════════════════════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ Observation #1 Observation #2 Observation #3 ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ Month [ ] Month [ ] Month [ ] ║ ║
║ ║ Day [ ] Day [ ] Day [ ] ║ ║
║ ║ Year [ ] Year [ ] Year [ ] ║ ║
║ ║ Hour (UTC) [ ] Hour (UTC) [ ] Hour (UTC) [ ] ║ ║
║ ║ Minute [ ] Minute [ ] Minute [ ] ║ ║
║ ║ Second [ ] Second [ ] Second [ ] ║ ║
║ ║ Ra Hour [ ] Ra Hour [ ] Ra Hour [ ] ║ ║
║ ║ Ra Minute [ ] Ra Minute [ ] Ra Minute [ ] ║ ║
║ ║ Ra Second [ ] Ra Second [ ] Ra Second [ ] ║ ║
║ ║ Dec Degree[ ] Dec Degree[ ] Dec Degree[ ] ║ ║
║ ║ Dec Minute [ ] Dec Minute [ ] Dec Minute [ ] ║ ║
║ ║ Dec Second [ ] Dec Second [ ] Dec Second [ ] ║ ║
║ ║ ║ ║
║ ╚═══════════════════════════════════════════════════════╝ ║
╚═════════════════════════════════════════════════════════════╝
the user will "fill in the blanks". Data entered will be checked
for "correct" values, i.e., no 13th month or any other such
errors. The "full" year is used, i.e., 1990 NOT 90.
TRAKSAT Satellite Tracking Program Page 37
After all of the data has been entered the program will display
the search mode screen. The satellite data filename is displayed,
the current filename will be used. The screen will appear as;
╔═══════════════════════════════════════════════════════════════╗
║ ╔═══════════════════════════════════════════════════════╗ ║
║ ║ READING NASA 2-LINE SATELLITE FILE ║ ║
║ ╠═══════════════════════════════════════════════════════╣ ║
║ ║ Looking For Matching Data ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ File: NASA668.TXT ║ ║
║ ║ Possible Match Data Fit ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ╚═══════════════════════════════════════════════════════╝ ║
╚═══════════════════════════════════════════════════════════════╝
As the program finds any "matches", i.e., if the satellite could
be the observed one, the satellite name is displayed along with a
data fit. The data fit is simply the Root Sum Square (RSS) values
of the difference between the measured right ascension and
declination and the calculated values. The RSS value is then
converted into a percent and displayed. A data fit of 100% means
the observation data matched a particular satellite, i.e., the
observed data fit the predicted satellite position almost
perfectly. The data fit is displayed so the user can determine
any possible satellites that could have been seen.
******************
* IMPORTANT NOTE *
******************
If the user would like to change the default filename, FIRST run
main menu option 1 and select the new satellite filename and ANY
satellite data set in that file. This is important because the
reverse solution will search the default satellite data file, the
default data file being the currently loaded in memory or the
filename in the TRAKSAT.DEF file. For more information on
changing the default data file see main menu option one.
An example is included below to help user with the reverse
solution option. (This example is for a UNKNOWN satellite
using elements from the NASA668.TXT file.) The tracking station
coordinates were for Huntsville, Al..
TRAKSAT Satellite Tracking Program Page 38
╔═════════════════════════════════════════════════════════════╗
║ ╔═══════════════════════════════════════════════════════╗ ║
║ ║ REVERSE SOLUTION MENU ║ ║
║ ╠═══════════════════════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ Observation #1 Observation #2 Observation #3 ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ Month [3 ] Month [3 ] Month [3 ] ║ ║
║ ║ Day [27] Day [27] Day [27] ║ ║
║ ║ Year [1990] Year [1990] Year [1990] ║ ║
║ ║ Hour (UTC) [3 ] Hour (UTC) [3 ] Hour (UTC) [3 ] ║ ║
║ ║ Minute [1 ] Minute [3 ] Minute [6 ] ║ ║
║ ║ Second [0 ] Second [0 ] Second [0 ] ║ ║
║ ║ Ra Hour [2 ] Ra Hour [8 ] Ra Hour [13] ║ ║
║ ║ Ra Minute [38] Ra Minute [12] Ra Minute [10] ║ ║
║ ║ Ra Second [51] Ra Second [22] Ra Second [4 ] ║ ║
║ ║ Dec Degree[46 ] Dec Degree[56 ] Dec Degree[-21] ║ ║
║ ║ Dec Minute [47] Dec Minute [29] Dec Minute [17] ║ ║
║ ║ Dec Second [4 ] Dec Second [44] Dec Second [22] ║ ║
║ ║ ║ ║
║ ╚═══════════════════════════════════════════════════════╝ ║
╚═════════════════════════════════════════════════════════════╝
After all of the observed data was entered the next screen
will appear such as;
╔═══════════════════════════════════════════════════════════════╗
║ ╔═══════════════════════════════════════════════════════╗ ║
║ ║ READING NASA 2-LINE SATELLITE FILE ║ ║
║ ╠═══════════════════════════════════════════════════════╣ ║
║ ║ Looking For Matching Data ║ ║
║ ╟───────────────────────────────────────────────────────╢ ║
║ ║ File: NASA668.TXT ║ ║
║ ║ Possible Match Data Fit ║ ║
║ ║ Name: Salyut 7 100% ║ ║
║ ║ ║ ║
║ ║ End Of Data File ║ ║
║ ║ Number Of Matches = 1 ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ╚╡ Press Return ╞═══════════════════════════════════════╝ ║
╚═══════════════════════════════════════════════════════════════╝
In this example the observed satellite was the Salyut 7, matching
the observed data 100 percent.
******************
* IMPORTANT NOTE *
******************
Due to the fact that about 140 of the more than 8000 satellite
data sets are included in a typical data file, most of the
observed data sets will not find a matching satellite. The only
cure would be to have ALL 8000 satellite data sets, this seems
HIGHLY unlikely for the average user let alone the advanced user.
TRAKSAT Satellite Tracking Program Page 39
ALL/USER DEFINED SATELLITES (ADVANCED FEATURES MENU OPTION ONE)
The user has the choice with the analytical solution options to
select all of the satellites in the data file or some user
defined satellites. The default will be to read ALL of the
satellites for these options. The user can define his or her
"favorite" satellites, up to 25 satellites can be included. The
user will need to use a word processor to edit the TRAKSAT.DEF
file and add the satellites names to it. The word processor used
will need to save the file in PLAIN ASCII format, i.e., NO
SPECIAL CONTROL CHARACTERS EXCEPT THE END OF FILE MARKER. The
edlin or PC-Write word processors will do the job nicely for the
user. An example of the TRAKSAT.DEF file with user defined
satellites is included below;
column number
123456789012
2447836.50000000 Color = 14
HUNTSVILLE, AL 34.7317000 273.4033000 228.60 -5 0 CDT
NASA678.TXT
Multi-Track Satellite Names
Satellite # 1: MIR
Satellite # 2: SALYUT 7
Satellite # 3: IRAS
Satellite # 4: SEASAT 1
Satellite # 5: EGP
Satellite # 6: NOAA 9
User Defined Satellite Names
IRAS
SALYUT 7
COSMOS 1686
COSMOS 1766
MIR
******************
* IMPORTANT NOTE *
******************
Remember to start the user defined satellite name in column 2.
The next 12 characters make up the satellite name, upper or lower
case makes no difference. If a user defined satellite is NOT
located in the satellite data file a warning message will be
displayed. The user defined satellites can be ANY of the
satellites included in the data file, however, 25 satellites is
the maximum number allowed. If the user has more than 25
satellites then select the All Satellite Data Sets option.
The user defined option is a toggle switch, i.e., if the menu
shows "All Satellites In Data File" and the user presses option 1
the menu will reappear displaying the "User Defined Satellite"
message. The user can toggle back and forth between these two
options.
TRAKSAT Satellite Tracking Program Page 40
ANALYTICAL RISE & SET (ADVANCED FEATURES OPTION 2/3)
TRAKSAT version 2.00 and above has included a very powerful
option, Analytical Rise & Set. Many people have asked "why use
this analytical approach ?". Three reasons come to mind speed,
speed, and speed! The analytical approach used is a closed form
solution to the problem of determining when a satellite can be
seen (either LOS #2 or Optical #3) by a ground tracking station.
In effect, this problem usually involves the calculation of the
rise-and-set time (UTC) of a given satellite from a specific
ground tracking station.
In the past, it has been the custom to solve the problem by
letting the satellite run through its ephemeris, and checking at
each instant to see whether the elevation angle of the satellite
was greater than some minimum value. However, by attacking the
problem from a different point of view, that is, with the
eccentric anomaly taken to be the independent variable, it is
possible to obtain a closed-form solution to the satellite
visibility problem. Specifically, the closed-form solution is a
single transcendental equation in the eccentric anomalies
corresponding to a rise-and-set time for a given orbital pass of
a satellite. It is more difficult to solve the controlling
equation than the standard Keplerian equation. However, the
method offers the advantage that the controlling equation is
solved only once per orbit period as contrasted with the hundreds
of times the Keplerian equation must be solved with the standard
step-by-step technique.
"How much faster is the analytical solution ?" Several
"benchmarks" were run using the same satellite data sets and
starting times to determine the speed of each method. If the user
selects the Delta Time Mode and then the Analytical Solution the
speed difference will be obvious.
******************
* IMPORTANT NOTE *
******************
The analytical solution methods will use 10 DEGREES AS THE
MINIMUM ELEVATION ANGLE that the viewer can "see". In practice
that "assumption" is very well founded. The minimum is NOT user
selectable in this case.
An example of the speed comparison is in order to back-up these
claims. The user is invited to try this "test" to better
determine the speed advantage the analytical solution will
provide. The steps to complete this "test" are:
1. Edit the TRAKSAT.DEF file and place ONLY ONE satellite
name under the User Defined area.
2. Run TRAKSAT and select Main Menu option 1 (read in
satellite data) and select the satellite name.
3. The next step is to run Main Menu option 4 (delta time
mode) from say 4-20-1990 0 UTC for 24 hours by 1 minute
steps. (Any date can be substituted.)
TRAKSAT Satellite Tracking Program Page 41
4. Answer the prompts to place output into a File of only
the Visible passes and Yes to the Ra & Dec question.
5. Use a watch, or a stopwatch to time how long the
simulation takes and make a note of the time.
6. Now return to the Main Menu and select the Advanced
Features option 0, and press option 1 (User Defined
Satellites) and then option 2 or 3 (use the same LOS
or Optical visibility test as before). Answer Yes to the
question about the same times. The output MUST be
directed to a FILE. The program will display how long
the analytical solution method took to solve the SAME
TIME PERIOD as the delta time mode.
The conclusions will be easy to figure out; the Analytical
Solution will be some 20+ TIMES FASTER than the Delta Time Mode,
(OVER THE SAME TIME PERIOD).
On the machine used for testing (coprocessor installed) the
analytical solution runs about 4 seconds per satellite per 24
hours of simulation time vs. the 120 seconds per 24 hours in the
delta time mode. (This was on a 386/16 with a 287 coprocessor.)
(A 386/33 computer with a 387 can crank out 160 satellites per
minute in this "benchmark"!!!!)
Use the analytical solution for "rough" estimates and the delta
time mode for the detailed analysis. The term "rough" implies
that the analytical solution is not as accurate as the Delta Time
mode, and in fact that is true. The error (Delta Time mode vs.
Analytical Solution) is usually LESS then 1 minute for predicted
rise or set times. (Remember that the analytical solution will
display results for a satellite elevation ABOVE 10 degrees.) The
error is the price to pay for the speed advantage.
******************
* IMPORTANT NOTE *
******************
The analytical solution DOES INCLUDE THE DRAG EFFECTS in the
calculations, (as of TRAKSAT version 2.30). By including the
drag effects in the solution a long term prediction can be done
without a loss of accuracy.
It has proved helpful for several TRAKSAT users to predict
several weeks into the future any visible passes and make a note
of the dates. As the date approaches and newer elements become
available the user can "improve" the viewing times to finally
obtain a accurate prediction of the satellites. Using this
approach the user can mark "special" days when a particular
satellite should be seen.
The analytical solution will save the user from "looking" for
satellites that will not be seen, or unfavorable passes.
******************
* IMPORTANT NOTE *
******************
If the user selects the analytical solution AND the OPTICAL
TRAKSAT Satellite Tracking Program Page 42
visibility test then only satellites with a mean motion of
greater than 2.5 revs per day will be calculated. That is any
satellite that is "near geosync" will not be calculated. This
approach was necessary due to some of the limits of the
analytical solution. This should NOT be of to great importance to
most users as seeing ANY near geosync satellites is VERY
DIFFICULT. The line of sight (LOS) method will still work for the
near geosync satellites. If the user needs to "see" a near
geosync satellite than the delta time mode will be required.
That is enough "horn blowing" let us look at an example.
Below is and example output from the analytical solution using
the screen output option. The visibility method in this example
was LOS (line of sight) while the starting date was 4-20-1990 @ 0
UTC hours. The end time was 24 hours. The starting times are
entered through the same type method as used in the Delta Time
mode. (The time step is NOT entered.) The user is directed to the
section on Delta Time mode for further study on entering starting
times.
The "header" at the top of the display will show some vital
information to the user. The tracking station name and satellite
data file name along with the visibility method will be displayed
to remind the user of the current settings.
******************
* IMPORTANT NOTE *
******************
To change the input file name the user will need to return to the
Main Menu and select option 1, and enter the new satellite data
file name along with ANY satellite name in that file. (This name
will not have any special meaning to the analytical solution.)
(SCREEN OUTPUT OPTION)
TRAKSAT Version 2.00 Analytical Solution
Tracking Station: HUNTSVILLE, AL File: NASA678.TXT Visibility: LOS
Satellite UTC TIME LOCAL TIME AZIMUTH MAX MIN DURATION
DATE HR:MN:SC DATE HR:MN:SC ELE RANGE HR:MN:SC
Alouette 1 20Apr90 01:08:32 19Apr90 20:08:32 N TO SE 25 1905 00:10:32
20Apr90 02:54:12 19Apr90 21:54:12 NW TO S 43 1387 00:12:12
Cosmos 398 20Apr90 01:19:02 19Apr90 20:19:02 NW TO E 33 1970 00:16:02
20Apr90 03:34:48 19Apr90 22:34:48 NW TO SE 74 2069 00:26:48
20Apr90 05:54:02 20Apr90 00:54:02 W TO S 21 4272 00:23:02
20Apr90 20:54:16 20Apr90 15:54:16 NW TO N 10 1100 00:01:16
21Apr90 01:27:19 20Apr90 20:27:19 NW TO E 39 1879 00:18:19
Starlette 20Apr90 02:27:41 19Apr90 21:27:41 NW TO E 35 1582 00:13:41
Working ...
Press Esc to Quit
If the Optical method was selected the header message will
display so.
******************
* IMPORTANT NOTE *
******************
The user can NOT stop/start the screen as in the other modes,
TRAKSAT Satellite Tracking Program Page 43
i.e., pressing Esc will STOP the display and terminate the
analytical solution. This method was chosen to avoid
inadvertently waiting for the screen to update while in a pause
mode. The screen update can be slow on a Optical visibility test
and a NON-coprocessor equipped machine. (There may not be any
satellites optical visible at all!)
If a file output was selected the header placed in the file has
the same information as the screen header. Below is an example of
the analytical solution file output. (The same times as above
were used but this example used the optical visibility test.)
Below is the screen or file output option menu.
╔═══════════════════════════════════════════════════════════╗
║ ╔════════════════════════════════════╗ ║
║ ║ TRAKSAT ║ ║
║ ╠════════════════════════════════════╣ ║
║ ║ ANALYTICAL RISE & SET ║ ║
║ ╠════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ (F) Output To File ║ ║
║ ║ (S) Output To Screen ║ ║
║ ║ LOS Visibility ║ ║
║ ║ Enter Option (F,S) [F] ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ╚════════════════════════════════════╝ ║
╚═══════════════════════════════════════════════════════════╝
******************
* IMPORTANT NOTE *
******************
The default is to write output to the file TRAKSAT.OUT. This is
NOT user selectable, ANY OLD FILES WITH THIS NAME WILL BE
OVERWRITTEN.
(FILE OUTPUT OPTION)
TRAKSAT Version 2.00
Analytical Solution
Tracking Station: HUNTSVILLE, AL
[ Optical Visibility ]
Satellite UTC TIME LOCAL TIME AZIMUTH MAX MIN DURATION
DATE HR:MN:SC DATE HR:MN:SC ELE RANGE HR:MN:SC
Alouette 1 20Apr90 02:54:12 19Apr90 21:54:12 NW TO S 43 1387 00:12:12
Cosmos 398 20Apr90 01:19:02 19Apr90 20:19:02 NW TO E 33 1970 00:16:02
20Apr90 03:34:48 19Apr90 22:34:48 NW TO SE 74 2069 00:26:48
21Apr90 01:27:19 20Apr90 20:27:19 NW TO E 39 1879 00:18:19
Starlette 20Apr90 02:27:41 19Apr90 21:27:41 NW TO E 35 1582 00:13:41
20Apr90 02:30:13 19Apr90 21:30:13 NW TO E 55 1241 00:13:13
LAGEOS 20Apr90 04:57:34 19Apr90 23:57:34 NE TO W 47 6830 00:51:34
20Apr90 08:22:09 20Apr90 03:22:09 NE TO NW 27 8006 00:40:09
21Apr90 03:34:44 20Apr90 22:34:44 NE TO SW 70 6108 00:56:44
GPS-0001 20Apr90 02:33:52 19Apr90 21:33:52 W TO SE 65 20491 06:47:52
TRAKSAT Satellite Tracking Program Page 44
GPS-0002 20Apr90 05:05:15 20Apr90 00:05:15 NW TO NW 13 24419 01:15:15
GPS-0005 21Apr90 02:37:23 20Apr90 21:37:23 W TO SE 65 20533 06:47:23
GPS-0006 20Apr90 00:16:22 19Apr90 19:16:22 NW TO SW 57 20854 04:27:22
SME 21Apr90 02:15:21 20Apr90 21:15:21 S TO NW 29 812 00:05:21
Salyut 7 20Apr90 09:56:11 20Apr90 04:56:11 SW TO NE 71 413 00:06:11
Cosmos 1383 20Apr90 02:53:40 19Apr90 21:53:40 N TO S 50 1293 00:12:40
IRAS 20Apr90 01:52:33 19Apr90 20:52:33 S TO SW 23 1793 00:08:33
The screen below will be displayed when the file output mode is
selected and the simulation is over. This case took 423 seconds
to complete 112 satellite predictions for 24 hours.
╔═══════════════════════════════════════════════════════════╗
║ ╔════════════════════════════════════╗ ║
║ ║ TRAKSAT ║ ║
║ ╠════════════════════════════════════╣ ║
║ ║ ANALYTICAL RISE & SET ║ ║
║ ╠════════════════════════════════════╣ ║
║ ║ ║ ║
║ ║ (F) Output To File ║ ║
║ ║ (S) Output To Screen ║ ║
║ ║ LOS Visibility ║ ║
║ ║ Enter Option (F,S) [F] ║ ║
║ ║ Input File: NASA678.TXT ║ ║
║ ║ Record# 112 of 112 ║ ║
║ ║ Total Time: 423 Sec ║ ║
║ ╚════════════════════════════════════╝ ║
╚═══════════════════════════════════════════════════════════╝
TRAKSAT Satellite Tracking Program Page 45
ADVANCED FEATURES OPTION 4
To return to the Main Menu the user can press return or option 4.
The default will return the user to the Main Menu.
NORAD/NASA 2-LINE SATELLITE DATA
NORAD maintains general perturbation element sets on all resident
space objects. These element sets are periodically refined so as
to maintain a reasonable prediction capability on all space
objects. In turn, these element sets are provided to users.
The input file of current orbital elements can be obtained form
several BBS around the country. One such BBS is the Celestial BBS
at (513) 427-0674 in Fairborn, Ohio, the SYSOP is T.S. Kelso.
See section; Obtaining Satellite Data, for more information on
obtaining satellite data.
I have included a file of the latest elements for over 130
orbiting satellites. See section; Files Required To Run TRAKSAT.
******************
* IMPORTANT NOTE *
******************
The following was downloaded from Celestial BBS, T.S. Kelso SYSOP.
Effective January 1986, this system began posting the most recent
element sets received from NASA/Goddard Space Flight Center for
several categories of satellites: Amateur Radio, Earth
Resources, Manned Spacecraft, Navigation, Weather, and NASA's 30
Day Specials (which contain objects launched within the last 30
days and are often easy to spot visually). More specifically,
these include the following satellites or satellite series:
OSCAR, Radio Sputnik, UOSAT, Cosmos, LandSat, SeaSat 1, SPOT,
Mir, Salyut 7, Soyuz, LDEF, US Space Shuttle, NAVSTAR (GPS),
GOES, Meteor, and NOAA.
These elements will be maintained in ASCII format in the file.
Data for each satellite will consist of three lines in the
following format:
AAAAAAAAAAA
1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN
2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN
Line 1 is a eleven-character name. Lines 2 and 3 are the standard
Two-Line Orbital Element Set Format identical to that used by
NASA and NORAD. The format description is:
Line 2
Column Description
01-01 Line Number of Element Data
03-07 Satellite Number
TRAKSAT Satellite Tracking Program Page 46
10-11 International Designator (Last two digits of launch year)
12-14 International Designator (Launch number of the year)
15-17 International Designator (Piece of launch)
19-20 Epoch Year (Last two digits of year)
21-32 Epoch (Julian Day and fractional portion of the day)
34-43 First Time Derivative of the Mean Motion (rev/day^2)
or Ballistic Coefficient (Depending of ephemeris type)
45-52 Second Time Derivative of Mean Motion (Blank if N/A)
54-61 BSTAR drag term if GP4 general perturbation theory was used.
Otherwise, radiation pressure coefficient.
63-63 Ephemeris type
65-68 Element number
69-69 Check Sum (Modulo 10)
(Letters, blanks, periods = 0; minus sign = 1;
plus sign = 2)
Line 3
Column Description
01-01 Line Number of Element Data
03-07 Satellite Number
09-16 Inclination [Degrees]
18-25 Right Ascension of the Ascending Node [Degrees]
27-33 Eccentricity (decimal point assumed)
35-42 Argument of Perigee [Degrees]
44-51 Mean Anomaly [Degrees]
53-63 Mean Motion [Revs per day]
64-68 Revolution number at epoch [Revs]
69-69 Check Sum (Modulo 10)
All other columns are blank or fixed.
Example:
NOAA 6
1 11416U 86 50.28438588 0.00000140 67960-4 0 5293
2 11416 98.5105 69.3305 0012788 63.2828 296.9658 14.24899292346978
For a description of the mean orbital elements see section; What
Are The Mean Classical Elements.
Note that the International Designator fields are usually blank,
as issued in the NASA Prediction Bulletins. All epochs are UTC.
Satellites will be ordered by their NASA Catalog Number. The
data file will be updated as soon as possible after receipt of
new element sets or whenever element sets are received for the
Space Shuttle.
TRAKSAT Satellite Tracking Program Page 47
The following pages contain a brief overview of the methods used
in TRAKSAT and are included to help the reader understand the
mechanics of a orbiting satellite about the earth.
WHAT ARE THE MEAN CLASSICAL ELEMENTS
Five independent quantities called "orbital elements" are
sufficient to completely describe the size, shape and orientation
of an orbit. A sixth element is required to pinpoint the position
of the satellite along the orbit at a particular time. The
classical set of six orbital elements are defined as:
1. a, semi-major axis, a constant defining the size of
the conic orbit.
2. e, eccentricity, a constant defining the shape of the
conic orbit.
3. i, inclination, the angle between the Z axis, i.e.
like the North Pole, and the angular momentum vector,
h = R X V, i.e. the vector R crossed with the vector V.
4. Ω, longitude of the ascending node, the angle, in the
fundamental plane, between the direction of the
vernal equinox and the point where the satellite
crosses the fundamental plane in a northerly
direction, (ascending node). This angle is measured
counterclockwise when viewed from the north side of
the fundamental plane.
5. w, argument of periapsis, the angle, in the plane of
the satellite's orbit, between the ascending node and
the periapsis point, measured in the direction of the
satellite's motion.
6. T, time of periapsis passage, the time when the
satellite was at periapsis.
6a. Sometimes the time of periapsis passage is replaced
by the true anomaly, v, the angle, in the plane of
the satellite's orbit, between perigee and the
position of the satellite at the particular time, t0,
called the epoch.
* (To convert from T to v)
v = (360 deg) * t0 / T
TRAKSAT Satellite Tracking Program Page 48
The sharp reader will notice that the NORAD elements do NOT
include the semi-major axis, a. It is possible to calculate the
semi-major axis with the data in a NORAD elements set. The
approach would be;
1. Convert the mean motion into degrees per second.
and calculate the time to complete one orbit, this
will be called the period.
2. Using the period and the earth's gravitational
constant, mu, the semi-major axis can be calculated.
(equations used)
xn_s = (mean motion * 360)/86400
per = 360/xn_s
a = ((per^2 * mu)/(4*π^2))^(1/3)
mu = 3.986012d+14 km^3/sec^2.
The starting point for the study of motion of one body orbiting
another, such as an artificial satellite about the earth, is
always the two-body problem; i.e., two point masses attracted to
each other according to Newton's Law of Universal Gravitation,
the inverse square law. The solution is well-known; the two
bodies move about each other in conic sections. For bounded
motions, such as those of an earth satellite, this conic is
either a circle or an ellipse.
The problem can be formulated in different ways, but is always
convenient to chose a coordinate system with the origin centered
at one of the bodies. The position of the second body then can
be specified, for example, by giving its initial cartesian
position and velocity coordinates and then integrating the
equations of motion to find the future positions and velocities.
The cartesian system is not the most convenient one in which to
represent the motion because an analytic solution cannot be
obtained and the integrations must be done numerically.
By adopting a polar coordinate system, one is able to effect an
analytic solution referred to above which can be specified in
terms of six constants of motion; five orbital elements,
a,e,i,w,Ω and the time of pericenter passage T. The last
constant can be, and usually is, replaced by the mean anomaly M
which is a linear function of time. This is a very convenient way
to specify the initial position and velocity of a satellite and
it also allows an easy visualization of the motion. The position
and velocity of the satellite at any future time can be
specified in terms of these six constants, a,e,i,w,Ω,M and
time.
In realistic applications, such as artificial satellites about
the earth, there are forces acting on the satellite in addition
to the inverse square force although this is the dominate one.
Other gravitational forces are due to distant bodies such as the
moon and sun but the principal additional gravitational forces
are due to the non-sphericity of the earth. All of the
gravitational forces are conservative and can be represented by
a potential function. In addition to these extra gravitational
TRAKSAT Satellite Tracking Program Page 49
forces, there are non-conservative forces such as atmospheric
drag. All of these forces other than the inverse square force
are called perturbations. The prediction of motion considering
these additional forces is called Perturbation Theory.
The orbital elements, constant for pure two-body motion, become
slowly varying functions of time when the perturbations are
considered. Differential equations describing the time rates of
change of the elements are called the Lagrange Planetary
Equations, LPE and can be found in any standard book on
celestial mechanics. Considering conservative forces only, which
can be represented by a potential function, the part of the
potential other than the two-body part is conventionally called
the disturbing function, represented by R, and the LPE are:
.
a = 2 / n a * ( δR / δM )
.
e = (-(1-e²)^½ / na²e)*δR/δw+(1-e²/na²e)*δR/δM
.
i = cot i/(na²(1-e²)^½ * δR/δw - δR/(δΩna²(1-e²)½)
.
w = (1-e²)^½ * δR / na²eδe - cot i * δR/(na²(1-e²)^½)*δi)
.
Ω = δR/(na² sin i *(1-e²)^½) * δi)
M = n - 2δR/naδa - 1-e² * δR/(na²e * δe).
* where δ is the partial derivative
starting from the very simple representation of the gravitational
potential between two point masses of magnitude m0 and mi
separated by distance r as;
V = -G * (m0 * mi)/r
one can, by applying this to a satellite of mass m0 and to every
infinitesimal mass point mi of the earth and integrating over the
whole earth, arrive at the following potential function for the
earth;
∞ n ∞ n m
V=-µ/r(1-Σ JnPn (sinδ)(re/r)^ +Σ Σ Jnm (re/r)^ Pn^ (sinδ)cos(m(α-α))).
n=2 n=2m=1 mn
The first term is the one giving pure two-body motion and the
additional terms are the perturbing terms. The first sum, zonal
harmonics, represents the flattening and other distortions
relative to the equator and the second sum, tesseral harmonics,
represents the non-uniformity of the earth in longitude. If, as
is frequently done, one assumes that the earth possesses
rotational symmetry, then the second sum vanishes. The neglect of
the second sum usually produces no noticeable effects except in
the case of geosynchronous satellites. Then one must consider
those terms which cause slow long-period drifts of the
geosynchronous position.
TRAKSAT Satellite Tracking Program Page 50
For close earth satellites one can usually take about three terms
from the first sum and get very accurate results; even the first
term alone will produce very satisfactory results in most cases
for short-time periods.
The Jn are constants which depend on the mass distribution in the
earth and are deduced from analysis of observed satellite
motions. The currently accepted values of J2, J3, and J4, which
are used in TRAKSAT, are;
-3
J2 = 1.082616 X 10
-6
J3 = -2.53881 X 10
-6
J4 = -1.65597 X 10 .
The Pn (sin δ) are Legendre polynomials of index n and are even
functions of sin δ for n even and odd functions for n odd. The J2
term describes the flattening of the earth and the J3 term the
so-called pear shape. J2, which is three orders of magnitude
larger than J3, gives rise to secular changes in the elements w,
Ω, and M while J3 gives rise to long_period oscillations in e and w.
In general, even harmonics cause long-period and secular changes
in the elements, and odd harmonics cause long-period
oscillations.
Short-period oscillations can result from all terms; but since J2
is so much larger than the other coefficients, generally only the
J2 short-period terms are considered. Secular terms are those
which monotonically increase or decrease with time. For first
order solutions this change with time is linear. Long-period
terms are those which oscillate with a period of typically one to
two months, and short-period terms are those which oscillate with
a period of one orbital period or some rational fraction of it.
To finish formulating the problem, the disturbing function is
expressed in terms of the orbital elements and then the
appropriate partial derivatives are taken and substituted into
the LPE. One then has a coupled set of first order non-linear
ordinary differential equations. Because they are non-linear, they
can be solved only by various approximation methods. The usual
method is to assume that the solutions can be represented in some
type of power series expansion in a small parameter and arrive at
sets of approximation equations which can be a close
representation of the real motion, at least over short-time
periods.
The complete solution consists of the sum of the secular terms,
short-period terms, and the long-period terms; i.e.,
a = a + a + a .
osc s sp lp
TRAKSAT Satellite Tracking Program Page 51
******************
* IMPORTANT NOTE *
******************
I have NOT included the actual equations used in the program in
this document for obvious reasons, i.e. they are long and hard to
type in with a text based word processor. If you have an interest
in these equations they are in several references I have listed.
TRAKSAT Satellite Tracking Program Page 52
MODELS FOR PROPAGATION OF NORAD ELEMENT SETS
NORAD maintains general perturbation element sets on all
resident space objects. These element sets are periodically
refined so as to maintain a reasonable prediction capability on
all space objects. In turn, these element sets are provided to
users.
The most important point to be noted is that not just any
prediction model will suffice. The NORAD element sets are "mean"
values obtained by removing periodic variations in a particular
way. In order to obtain good predictions, these periodic
variations must be reconstructed (by the prediction model) in
exactly the same way they were removed by NORAD. Hence,
putting NORAD element sets into a different model (even though
the model may be more accurate or even a numerical integrator)
will result in degraded predictions.
All space objects are classified by NORAD as near-Earth (period
less than 225 minutes) or deep-space (period greater than or
equal 225 minutes). Depending on the period, the NORAD element
sets are automatically generated with the near-Earth or deep-
space model.
The PROGRAM will calculate the satellite period and know which
PREDICTION MODEL TO USE.
THE PROPAGATION MODELS
Two mathematical models for prediction are used by TRAKSAT. The
first of these, SGP4, was developed by Ken Cranford in 1970 (see
Lane and Hoots 1979) and is used for near-Earth satellites. This
model was obtained by simplification of the more extensive
analytical theory of Lane and Cranford (1969) which uses the
solution of Brouwer (1959) for its gravitational model and a
power density function for its atmospheric model (see Lane, et al
1962).
The next model, SDP4, is an extension of SGP4 to be used for
deep-space satellites. The deep-space equations were developed
by Hujsak (1979) and model the gravitational effects of the moon
and sun as well as certain sectoral and tesseral Earth harmonics
which are of particular importance for half-day and one-day
period orbits.
TRAKSAT Satellite Tracking Program Page 53
COMPATIBILITY WITH NORAD ELEMENT SETS
The NORAD element sets are currently generated with either SGP4
or SDP4 depending on whether the satellite is near-Earth or deep-
space.
For SGP4 and SDP4 users, the mean motion is first recovered from
its altered form and the drag effect is obtained from the SGP4
drag term (B*) with the pseudo-drag term being ignored. The
value of the mean motion can be used to determine whether the
satellite is near-Earth or deep-space (and hence whether SGP4 or
SDP4 was used to generate the element set). From this
information the program will decide whether to use SGP4 or SDP4
for propagation and hence be assured of agreement with NORAD
predictions.
TRAKSAT Satellite Tracking Program Page 54
PROGRAM LIMITATIONS AND ASSUMPTIONS
The ephemeris equations DO include the zonal harmonics, through
2nd order, of the gravitational potential. This implies a
gravitational field produced by an oblate spheroidal earth
unsymmetrical with respect to the equator, pear-shaped. In other
words, the ephemeris equations contain J2, J3, and J4 terms. The
currently accepted values of J2, J3, and J4, which are used in
TRAKSAT, are;
-3
J2 = 1.082616 X 10
-6
J3 = -2.53881 X 10
-6
J4 = -1.65597 X 10 .
The earth equatorial radius used by TRAKSAT is; 6378.135 Km,
while the flattening factor used is 1/298.257 (both are from the
1972 WGS models).
The program TRAKSAT models only ELLIPTICAL orbital motion about
the earth. That is, the orbital eccentricity MUST BE LESS THAN
ONE and GREATER THAN ZERO. Very small eccentricities are
acceptable, i.e., such as 1.0E - 5.
STARS USED IN TRAKSAT
The star background option will use the following list of stars
for the display. The star data values are from USNO Floppy
Almanac 1988, Version 2.11.88, file STAR1.CAT using Epoch J2000
coordinates.
Bayer Name Proper Name
---------- -----------
Ursae Minoris Polaris
Andromedae Alpheratz
Phoenicis Ankaa
Cassiopeiae Schedar
Ceti Diphda/Deneb Kaito
Eridani Achernar
Arietis Hamal
Eridani Acamar
Ceti Menkar
Persei Mirfak
Tauri Aldebaran
Orionis Rigel
Aurigae Capella
Orionis Bellatrix
Tauri Elnath
TRAKSAT Satellite Tracking Program Page 55
Orionis Alnilam
Orionis Betelgeuse
Carinae Canopus
Canis Majoris Sirius
Canis Majoris Adhara
Canis Minoris Procyon
Geminorum Pollux
Carinae Avior
Lambda Velae Suhail
Carinae Miaplacidus
Hydrae Alphard
Leonis Regulus
Ursae Majoris Dubhe
Leonis Denebola
Corvi Gienah
Crucis ACrux
Crucis GaCrux
Ursae Majoris Alioth
Virginis Spica
Ursae Majoris Alkaid
Centauri Hadar
Centauri Menkent
Boötes Arcturus
Centauri A Rigil Kentaurus
Librae Zubenelgenubi
Ursae Minoris Kochab
Coronae Borealis Alphecca
Scorpii A Antares
Triangulii Atria
Ophiuchi Sabik
Lambda Scorpii Shaula
Ophiuchi Rasalhague
Draconis Eltanin
Sagittarii Kaus Australis
Lyrae Vega
Sagittarii Nunki
Aqilae Altair
Pavonis Peacock
Cygni Deneb
Pegasi Enif
Gruis Al Na ir
Piscis Austrini Fomalhaut
Pegasi Markab
USER DEFINED STAR DATA
The option of using your own star data in TRAKSAT is
included. Up to 1500 stars can be included in a data file.
** ALL STAR DATA WILL NEED TO BE FOR EPOCH J2000. **
The following description of the data base format is included
for the user. All star data files are in standard ASCII code. See
section; Files Required To Run TRAKSAT for a sample star data
file.
TRAKSAT Satellite Tracking Program Page 56
User defined star data has the following format:
GGGCCC HHMMD+DDMM +M.M +C.CC
----------------------------
GAMCAS 00567+6043 +2.4 -0.15
GA2AND 02039+4220 +2.3 +1.37
39 ARI 02479+2915 +4.5 +1.11
HR961 03203+7744 +5.5 +0.19
where GGG is the first three characters of the Greek name of the
star OR the first two characters and a superscript number OR the
Flamsteed number of the star. Alpha is ALP, beta is BET, gamma is
GAM, and so on. Omicron and Omega are abbreviated OI and OE to
distinguish them. CCC is the standard three-letter abbreviation
of the constellation name -- ORI for Orion, UMA for Ursa Major,
CVN for Canes Venatici. If the star has neither Greek letter nor
Flamsteed number, then GGGCCC becomes is "HR" plus the four-digit
Yale Bright Star Catalog number.
HHMMD+DDMM is the star's location in right ascension and
declination coordinates for Epoch J2000. HH is hours, MM is
minutes, and D is decimal minutes of RA. +DD is declination
degrees and MM is declination minutes. The coordinates, as given,
are precise enough for virtually any computer graphics
application. +M.M is the star's visual magnitude in yellow light,
essentially how bright the star appears to the eye. The sign is
necessary because some of the brightest stars, like Sirius, have
negative magnitudes.
Finally +C.CC is the B-V "color index" of the star. This number
ranges from -0.25 to +2.5. The "bluest" stars have the lower or
negative B-V color, while red stars have color indices over 1.6
or so. The Sun has a B-V of +0.62, and is a yellow-white star.
TRAKSAT does not use the color data for any calculations. We thus
decode the examples as: Gamma Cassiopeiae, a medium-bright blue
star at 0 hours 56.7 minutes right ascension and +60 (degrees)
43' declination; Gamma-2 Andromedae as a reddish star of
approximately the same brightness; 39 Arietis doesn't have a
Greek letter name; and HR 961 is the 961st entry in the Yale
Bright Star Catalog, barely visible to the naked eye.
The user defined star data option will NOT display the star
names. (There would not be any room on the screen to see the
orbital track!) The format used is popular with several star map
programs and should be available to the user. (A star file is now
included with TRAKSAT.)
METHOD DESCRIPTION FOR REVERSE SOLUTION
The reverse solution is a very powerful and useful option for the
satellite observer. May times I have looked up to the skies only
to see a unknown satellite fly-by. Determining which satellite I
saw was almost impossible. The approach I used was to run TRAKSAT
in the multi-track mode until I either ran out of satellite data
sets or I found a possible match. This could prove very tedious
and not very practical on a day to day basis.
This "lacking" provided the desire for the reverse solution
option in TRAKSAT. The next step was to determine a method to use
TRAKSAT Satellite Tracking Program Page 57
and what would be required from the user. Several methods of
converting observed data into orbital elements are in use today,
such as Gauss, f & g series, Lambert, and true anomaly iteration
are just a few. It is difficult to be specifically precise in a
statement of which of the previous methods can be termed "the
best". Certainly a method which best decrees the problem at hand
should be chosen for the determination of a particular orbit.
There are, however, several points of interest that should be
known to the analyst before choosing a particular method. For
example, which method is the fastest from a computational point
of view? Which method has the least numerical error? Which method
experiences the least convergence difficulties? Numerical studies
upon many orbits of varying eccentricity and semi-major axis have
provided a very partial answer to these questions.
To answer the first question, that is, which is the fastest
computational method, several sources were consulted. The fastest
method proved to be the true anomaly with the Gauss method
following close behind. The f & g series was the slowest method.
The second question, which method has the least numerical error,
is difficult to answer, and, as might be expected, indicates that
every method is optimum in the computation of a particular
element. It is, however, possible to segregate the overall
results of the numerical studies into three categories: high,
medium, and low accuracy. The Gauss and Lambert methods display a
high accuracy rating while the true anomaly and f & g series have
only a medium accuracy rating.
The last question, ease of convergence, is not as difficult to
answer. The Gauss and f & g series methods are called "self-
perpetuating" in their convergence. That is, from a easily
estimated first guess an iterative loop is initiated which
converges automatically to the desired result. The Gauss method
suffers from instability of convergence for radial spreads of
greater than 90 degrees. This should NOT prove a problem because
most observed satellite data sets will be viewed in less than a
90 radial spread.
The natural conclusion to this analysis was to use the method of
Gauss. This document will NOT develop this method as MANY of the
references listed go into great detail on the subject. I would
suggest the reader to investigate further if interested.
ACCURACY OF TRAKSAT
Several people have asked the question; " How accurate is
TRAKSAT ?". To answer such a question one must define a set of
limits. The real "acid test" is to have a prediction from TRAKSAT
and then go outside and observe that satellite, taking note of
the time and position of the satellite. A comparison between
actual observed data and predicted can then be determined.
Another approach is to compare the output from TRAKSAT against
several other satellite tracking programs. Both the public domain
and the commercial markets have several good tracking programs
that the user could compare with.
The later approach, that is the comparison between tracking
TRAKSAT Satellite Tracking Program Page 58
programs, has been carried out by several people including
myself. The output from TRAKSAT compares very well with many of
the "current" tracking programs (both commercial and public
domain). It could be concluded from a simple test of TRAKSAT that
it agrees with several other tracking programs. (Gee we all can't
be wrong!)
The next step is one of comparing predicted output and observed
data. The most popular use for TRAKSAT has been in the optical
sighting options. The optical sighting of a satellite will be the
"acid test" used for this accuracy test.
First a note about NASA 2-line elements, low earth satellites
(about 15 rev per day satellites) have larger disturbances from
the atmosphere than higher satellites. The drag on a satellite
can cause purtubations greater than the J2 terms therefore the
drag term is of great importance. The very latest elements for
the low earth satellite can greatly improve the prediction
process, while the higher satellites do not require as current of
elements. (The term low will be in the range of 250 - 375
kilometers altitude.)
Reports about TRAKSAT (and its predictions) have been made on the
MIR satellite along with several other low earth satellites. The
bottom line being LESS THAN 30 SECONDS ERROR (prediction vs.
actual) for 10 day old satellite element sets. If the satellite
elements are 20 days old the error is about 60 seconds. If the
elements a only a day or two old, errors of less than 10 seconds
are possible (several reports have been made about 2-10 seconds
of error).
The position data is on the money, it is the time at that
position that usually drives the accuracy of the observation.
The higher earth satellites generally have less than 30 seconds
of error for 20 day old elements.
A NOTE MUST BE MADE ABOUT THE ERROR ANALYSIS, THE ASSUMPTION IS
MADE THAT NO ORBITAL MANEUVERING WAS DONE TO THE SATELLITE DURING
THE "TEST" PERIOD. (The STS-31, the Hubble launch, was a prime
example of several orbital maneuvers changing the predicted
observed times).
In general it can be said that the most current elements are the
best ones for planning the evenings viewing. (Elements over 30
days old can have a very large error to them). Element sets 7 -14
days old will be acceptable for most users.
NORAD/NASA updates the satellite elements for this very reason,
to keep the prediction process accurate.
TRAKSAT Satellite Tracking Program Page 59
A BRIEF EDITORIAL
One of the first decisions to be made when setting out to write a
program is the choice of a programming language. I'm an Aerospace
Engineer working for a company in Huntsville, Al. My job title
is; Trajectory Analysis Engineer. I work with NASA, mostly the
shuttle program, and design trajectories for several upcoming
shuttle missions. I have written large trajectory simulations
programs, for the most part they were written in FORTRAN.
I know FORTRAN is not the best language to use for programs that
use graphics, but Microsoft has come up with the ideal solution.
Microsoft FORTRAN, version 4.0 and higher, can call BASIC, C, and
PASCAL routines. Microsoft FORTRAN version 5.0 also contains graphic
routines that were used in TRAKSAT, these graphic routines are the
same as used in QuickC version 2.0.
Most (95%) of the TRAKSAT program is written in FORTRAN to get
the best speed and high precision mathematics and C, Microsoft C
version 6.0, for some useful utilities. I have found this
combination to be very powerful and useful for program
development.
TRAKSAT Satellite Tracking Program Page 60
SPECIAL THANKS
I would like to take this opportunity to thank the many people
who helped me either directly or indirectly on this program.
First of all my wife, Anita, who understands why I have a hobbie
like computers and enjoy working with them. She has not
complained about the many hours, in excess of 500 hours, I have
spent working on TRAKSAT. TRAKSAT version 2.45 has some 21,000
lines of code and IS STILL GROWING.
Dave Ransom Jr., of Rancho Palos Verdes, CA. has kept me going
when my interest in the program was slipping away. I did use the
city data from his excellent program ASTROCLOCK. I also used
several of the references Dave listed in his program. I would
highly recommend his program to any person interested in
astrodynamics. The documentation supplied with ASTROCLOCK is in
itself very interesting reading and very well done. I could only
hope that someday TRAKSAT will have that level of
professionalism. My thanks to Dave and his wife Vicki.
John Williams and Dr. Jeff Wallach, from the Dallas DataLink BBS,
have been very helpful in this project also. They have offered
data and a helping hand with TRAKSAT. The DataLink BBS has a
vast amount of satellite information along with other interests.
I would recommend it to others interested in satellite tracking.
The DataLink BBS is THE place to learn about obtaining satellite
images. My thanks to John and his family.
I would also like to thank T.S. Kelso, SYSOP of the Celestial BBS
where current satellite data can be downloaded. Several satellite
tracking programs are also available on his BBS along with a vast
amount of satellite information.
TRAKSAT Satellite Tracking Program Page 61
QUESTIONS AND COMMENTS
I would very much like to hear from anyone interested in
this program and astrodynamics in general. I have not included
the source code to TRAKSAT mainly because most people do not have
a Microsoft FORTRAN compiler nor a working knowledge of FORTRAN.
The high cost ($500.00) of both the FORTRAN and C compilers makes
the cost of working on a project like TRAKSAT expensive also.
As for the choice of FORTRAN compiliers there are many fine
products out and I have used many of them. However, the only
compilier that supports mixed language is Microsoft. For this
reason alone I would recommend it to others interested in
programming.
At this time I feel that TRAKSAT is still going through some
"growing pains" and I would like the chance to improve it and
add new features. The only way this can happen is if you, the
user, takes the time to leave me messages or mail on problems or
suggestions. I will try to answer your messages in a timely
manor.
One of the major goals of this project is to make the finest,
easiest to use, satellite tracking program available. A program
the average person can use and successfully track satellites.
I would suggest the user to OBTAIN A COPROCESSOR if they do not
have one already. A coprocessor speeds up math intensive
programs, such as TRAKSAT, to a level that was only dreamed about
a few years ago.
Please feel free to contact me to discuss TRAKSAT or other
computer problems. I can reached through the RPV BBS;
RPV BBS
Rancho Palos Verdes, Ca.
213-541-7299
24 hours, 2400/1200 baud.
This BBS is owned and operated by Dave Ransom Jr.. I call up the
BBS three or four times a week to check my mail and do some file
transfers. This BBS is geared towards Astronomical interests. The
latest version of ASTROCLOCK can be downloaded from this BBS
also.
Other BBS's I frequent are;
Celestial RCP/M DataLink RBBS System
Fairborn, Ohio Dallas, Texas
513-427-0674 214-394-7438
24 hours, 2400/1200 baud, 24 hours, 9600/2400/1200 baud.
I can also be reached at work or home, please no calls after 10
PM Central Time. Please leave a phone number and the best time to
call on any messages that require by personal attention. My work
number has an answering machine pick-up if I can not be reached.
TRAKSAT Satellite Tracking Program Page 62
The last, and slowest method to reach me is with the U.S. mail
service, I will respond with a phone call if at all possible.
Paul E. Traufler
111 Emerald Dr.
Harvest, Al. 35749
Phone (work) 205-726-5511
Phone (home) 205-830-8450
TRAKSAT Satellite Tracking Program Page 63
FUTURE UPGRADES
To obtain the latest version of TRAKSAT, several BBSs around the
country keep it online. The BBSs listed under section; Questions
and Comments list several places to obtain the current version.
Compuserve has TRAKSAT and many other releated files also. If you
would like to save on the long distance charges, contact myself
and I will try to find a local BBS that I can upload TRAKSAT to.
For a small fee ($10.00) I will mail TRAKSAT on a disk, 360K,
1.2M, if that is the easiest way to obtain the latest version,
(1.2M is best for me). Please contact the author for more
information.
If you send a SELF ADDRESSED AND STAMPED DISK-MAILING PACKAGE,
with the proper disk format, I will return mail it free of
charge.
TRAKSAT and its companion files is being distributed as
shareware. YOU ARE ENCOURAGED TO SHARE THIS SOFTWARE WITH OTHERS
PROVIDED THAT IT IS DISTRIBUTED COMPLETE WITH DOCUMENTATION AND
IN UNMODIFIED FORM AND THAT NO FEE OR OTHER CONSIDERATION IS
CHARGED OR ACCEPTED.
*****************************************************************
*****************************************************************
THERE IS NO CHARGE FOR THIS PROGRAM, but in the spirit of the
shareware concept, if the end user finds this package useful, and
would like to help fund development of enhancements to this
package, any amount that the end user feels is appropriate for
the value received in using this package will be gladly accepted
(perhaps $15.00). Please mail any donations to the above address.
ANYONE WHO SENDS A DONATION WILL RECEIVE A PERSONALLY REGISTERED
COPY OF TRAKSAT AND BE PLACED ON THE UPDATE LIST FOR FUTURE
UPDATES TO THE PROGRAM. This copy will give the user credit for
supporting the shareware concept.
*****************************************************************
*****************************************************************
TRAKSAT Satellite Tracking Program Page 64
OBTAINING NORAD SATELLITE DATA SETS
The following BBS's have the current satellite data files;
Celestial RCP/M
Fairborn, Ohio
SYSOP: T.S. Kelso
513-427-0674
24 hours, 2400/1200 baud,
8 bit NO parity 1 stop.
Datalink RBBS System
Dallas, Texas
SYSOP: Dr. Jeff Wallach
214-394-7438
24 hours, 9600/2400/1200 baud,
8 bit NO parity 1 stop.
RPV BBS
Rancho Palos Verdes, Ca.
SYSOP: Dave Ransom Jr.
213-541-7299
24 hours, 2400/1200 baud,
8 bit NO parity 1 stop.
To obtain the elements from the Celestial RCP/M BBS, (with the
least amount of trouble), just dial up the BBS and login. The
next step is to type "F" (without the quotes) to go to the Files
section, then to area #1. The next step is to type "D", for
download and then type "BULLETIN.ARC" as the file to download,
open an XMODEM file transfer mode with your telecommunications
software. This will transfer the NASA 2-line elements to a file
on the users computer. Log out of the BBS and then unarchive the
file using several of the unarchiving programs, (PAK, ARC,
PKZIP, etc.).
The downloaded file will have some characters at the
top of the file that will need to be removed with a word
processor (this MUST save the file in pure ASCII, i.e., PC-Write,
Edlin etc. works very well).
(This method assumes that an account is available to the user).
NASA can provide up to 20 satellite data sets (HARD COPY FORM
ONLY) if the user writes and requests them. This service is free
but the user will need to enter the elements into a file for use
with TRAKSAT. (This is done the old fashion way, you TYPE them!)
NASA Goddard Space Flight Center
Control Center Support Section
Code 513.2
Greenbelt, Md. 20771
TRAKSAT Satellite Tracking Program Page 65
FILES REQUIRED TO RUN TRAKSAT
The following files should have been included in the archive
file;
TRAKSAT.EXE The program.
TRAKSAT.DEF The default data for the tracking station.
TRAKSAT.CTY The city file for tracking stations.
TRAKSAT.DOC TRAKSAT program documentation.
EARTH.DAT World map data file.
NASA724.TXT This is the latest NORAD satellite data set,
(as of 26 July, 1990, element set #724).
READ.ME Latest notes about the program.
MSHERC.COM This utility is used for Hercules graphics.
MODERN.FON This is a font file used for the graphics.
STARS.DAT This is a star data base that is NOT required
to run TRAKSAT, it is optional. This data file
can be used in the user defined star data
option.
STARS.DAT is almost identical to the star
database used with Richard Berry's (Editor of
ASTRONOMY) program STARS.BAS. For
compatibility, I have retained the same
database format. According to Mr. Berry's
documentation file STARS.DOC, his database is
essentially the same database used for the
StarDome map printed in the center spread of
ASTRONOMY every month.
TRAKSAT Satellite Tracking Program Page 66
BIBLIOGRAPHY
THe following sources were used to prepare and test the
TRAKSAT program.
Meeus, Jean, ASTRONOMICAL FORMULAE FOR CALCULATORS, 3rd Edition,
Willmann-Bell, Inc., Richmond, VA. 1985.
Duffett-Smith, Peter, PRACTICAL ASTRONOMY WITH YOUR PERSONAL
COMPUTER, Cambridge University Press, New York, NY. 1986.
Danby, John, FUNDAMENTALS OF CELESTIAL MECHANICS, 2nd Edition,
Willmann-Bell, Inc., Richmond, VA. 1988.
Bate-Mueller-White, FUNDAMENTALS OF ASTRODYNAMICS, Dover
Publications, Inc. New York, NY. 1971.
Forsythe-Malcolm-Moler, COMPUTER METHODS FOR MATHEMATICAL
COMPUTATIONS, Prentice-Hall, Inc. Englewood Cliffs, NJ. 1977.
USAF-Ford Aerospace Corporation, ORBITAL MECHANICS, O&M Training
Section, Sunnyvale, CA. 1982.
Moulton, F. R., CELESTIAL MECHANICS, Macmillan Company, New York,
NY. 1960.
Brand, L., VECTOR ANALYSIS, John Wiley and Sons, New York, NY.
1957.
Geyling-Westerman, INTRODUCTION TO ORBITAL MECHANICS, Addison
Wesley, Whippany, NJ. 1971.
Brouwer, D., "Solution of the Problem of Artificial Satellite
Theory without Drag", Astronomical Journal 64, 378-397, November
1959.
Hilton, C.G. and Kuhlman, J.R., "Mathematical Models for the
Space Defense Center", Philco-Ford Publication No. U-3871, 17-28,
November 1966.
Hoots, F.R., "A Short, Efficient Analytical Satellite Theory".
AIAA Paper No. 80-1659, August 1980.
Hoots, F.R., "Theory of the Motion of an Artificial Earth
Satellite", accepted for publication in Celestial Mechanics.
Hujsak, R.S., "A Restricted Four Body Solution for Resonating
Satellites with an Oblate Earth", AIAA Paper No. 79-136, June
1979.
Hujsak, R.S. and Hoots, F.R., "Deep Space Perturbations Ephemeris
Generation", Aerospace Defense Command Space Computational Center
Program
Documentation, DCD 8, Section 3, 82-104, September 1977.
TRAKSAT Satellite Tracking Program Page 67
Kozai, Y., "The Motion of a Close Earth Satellite", Astronomical
Journal 64, 367-377, November 1959.
Lane, M.H. and Cranford, K.H., "An Improved Analytical Drag
Theory for the Artificial Satellite Problem", AIAA Paper No. 69-
925, August 1969.
Lane, M.H., Fitzpatrick, P.M., and Murphy, J.J., "On the
Representation of Air Density in Satellite Deceleration Equations
by Power Functions with Integral Exponents", Project Space Track
Technical Report No. APGC-TDR-62-15, March 1962, Air Force
Systems Command, Eglin AFB, FL.
Lane, M.H. and Hoots, F.R., "General Perturbations Theories
Derived from the 1965 Lane Drag Theory", Project Space Track
Report No. 2, December 1979, Aerospace Defense Command, Peterson
AFB, CO.
Bellman, R. and Kalaba, R.E., "Modern Analytic Computational
Methods in Science and Mathematics", American Elsevier Publishing
Company, Inc. 1967.
Escobal, P.R., "Mehtods of Orbit Determination", John Wiley and
Sons, New York, NY. 1965.
Craig, C. John, "Microsoft QuickC Programmer's Toolbox",
Microsoft Press, Redmond Washington 1990.
El'yasberg, P. E., "Theory of Flight of Artificial Earth
Satellites", Israel Program for Scientific Translations Ltd.,
1967. (Translated from Russian)
King-Hele, Desmond, "Observing Earth Satellites", Van Nostrand
Reinhold Co. Inc., 1983.