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1992-09-14
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Documentation for
Pass Update
Developed by
Dr TS Kelso
Version 2.50
1992 September 13
Copyright (C) 1989, 1990, 1992
All rights reserved
Pass Update is a program which will allow the you to automatically update
groups of two-line element sets. This program supports the maintenance of
user-defined special groups of satellites for easy use in other packages and
allows you to update any or all of these files at one time. For example, you
may want to maintain separate .TLE (two-line element) files on groups of
weather satellites (e.g., NOAA.TLE, METEOR.TLE) or amateur radio (e.g.,
AMATEUR.TLE).
The program PASSUPDT.EXE (Two-Line Element Set Update) can be run stand-alone
or from within Pass Scheduler. After an initial information screen, PASSUPDT
will present a screen listing up to 49 .TLE files which you can select to
update.
Files are selected for update by positioning the highlight on the file to be
selected (using the cursor keys, Home to move to the first file, or End to
move to the last file) and toggling with the space bar. All files may be
selected using the 'A' key (which actually toggles the selection status of all
files). All files can be deselected by pressing the 'U' key.
Once the files to be updated are selected, press <ENTER> to begin the update
process. PASSUPDT will go through each file selected, showing its status as
it goes. You can abort this process (after the current file is processed) by
pressing the <ESC> key at any time.
During the update process, the program will show the two-line elements for
each satellite in the file to be updated. The color of the elements indicates
their age. Elements 0 to 15 days old are green, 16 to 30 days old are yellow,
31 to 45 days are red, and anything over 45 days is brown (on the rare
occasion where elements are released before the current date, these show up as
blue).
If a matching element set is found in the update database, it is shown using
the same color scheme. If the element sets are identical or the update data
is older, no change is made. If the update data is newer, an update is
performed. Since the program checks both the epoch date and the element set
number, you will be prompted if the two do not agree (e.g., when the
element set number wraps around from 999 to 000). No update will be performed
if the new element set does not pass the modulo-10 checksum or does not
conform to the standard two-line format.
If no update is available or the data is older than 30 days, you will be
prompted to determine whether that element set should be deleted.
After all the selected files have been updated, PASSUPDT will check for the
existence of the file PASSUPDT.CAT containing a list of NORAD Catalog Numbers
(in increasing numerical order, each number having leading zeros, if
necessary). If this file exists, PASSUPDT will check for the existence of
files of the form SATcatnr.Dyy (in the default data directory), where catnr is
the NORAD Catalog Number and yy is the epoch year of the two-line element
set(s). PASSUPDT will add new element sets to existing files or create new
files, as appropriate. This option makes it easy to maintain catalogs of
element sets for programs which require them. An example of such a program is
one which registers satellite imagery to a geodetic grid; each image to be
registered requires the two-line data closest to the time of the image, not
the most recent data.
OPTIONS
Many users prefer to be able to allow PASSUPDT to run without being prompted
for old data, epoch/elset discrepancies, and missing data. While this mode of
operation is not recommended, the user has the option of configuring PASSUPDT
to process without prompting through the configuration file PASSUPDT.CFG. A
sample configuration file is shown below.
Sample PASSUPDT.CFG file
==============================================================================
% Default data drive
\SAT\DATA\ % Default data directory
C:\COMM\TLE.TXT % Default update database
100 % Program delay (milliseconds)
Y % Ask to update data
Y % Ask to delete old data
Y % Ask to delete missing data
3 % Lines per record (2 or 3)
==============================================================================
This file MUST be present to run; the program will present an error message
stating that PASSUPDT.CFG is missing and abort if it cannot find the file in
the working directory.
The first two lines of this file are used to specify the default drive and
directory containing the .TLE files to be updated. If either line is blank,
the current drive and/or directory is assumed (the sample above assumes the
.TLE files are to be found on the active drive in the subdirectory \SAT\DATA).
If no .TLE files are found, an error message to that effect will be printed
and the program will abort.
The next line specifies the drive, path, and filename of the master update
file to be used. For example, if you download the file TLE.TXT into the \COMM
directory on your C: drive (you can get a current copy of TLE.TXT from the
Celestial BBS listed at end of this document), you can run PASSUPDT using this
new data without moving or otherwise manipulating the file. In fact, PASSUPDT
will search the file for the first line beginning with '1 ' to find where the
data starts, for those of you who receive the data with some kind of header
attached. Once again, if this file cannot be found, an error message is
reported and the program will abort.
The next line sets the pause (in milliseconds) after each element set update
before continuing the program. The primary purpose for this delay is to allow
the user to become more familiar with the update process by slowing the
program down enough to watch. If you are not interested in watching, you can
set this value to some small positive number.
The next three lines are used to specify whether you want to be asked to
update data when there is a discrepancy between element sets (e.g., newer
epoch but older element set number) or to delete when the data is over 30 days
old or no new data is available. If you answer No to these questions,
PASSUPDT will do the safe thing, that is, it will NOT update questionable
data and it will NOT delete old or missing data. If you choose to disable
these prompts, it will be left to you to decide how you want to resolve any
discrepancies which occur in your databases.
The final line in PASSUPDT.CFG is used to indicate whether the master update
file contains only two-line element sets or contains a name followed by a two-
line element set. If only two-line data is used, a 2 should be entered; files
including satellite names (such as TLE.TXT) should have a 3. Any other value
will result in a 3 being assumed.
CONCLUSION
That should about do it. This code has been thoroughly tested and validated
to ensure it works (this new version has been used since May 1992 for my daily
updates) and you should have no problems with it. I believe that this version
corrects many of the difficulties and potential pitfalls of Version 1.00 and
hope you will find it useful. However, if you note any difficulties or would
like to make suggestions as to future features, please feel free to do so.
Simply leave me a message on the Celestial BBS or via Internet. In a
continuing effort to promote standardization of orbital calculations, I will
endeavor to continue to improve this package and will gratefully accept user
feedback or contributions to this effort.
NOTE: The previous release of this program was packaged with the Pass
Scheduler -- that program will be updated soon and released separately.
This program should, however, still run with the original version of
PASSCHED.
- Dr TS Kelso
Internet: tkelso@afit.af.mil
anonymous ftp at archive.afit.af.mil
in the directory pub/space
SYSOP, Celestial BBS
513/427-0674 (modem)
Operating 24 hours/day
No parity, 8 data bits, 1 stop bit
300, 1200, 2400, 4800, and 9600 bps
v.32/32bis, v.42/42bis
2340 Raider Drive
Fairborn, OH, USA 45324-2001