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Program ORBITEL
Verify and Sort 2-Line Orbital Elements
(C) Copyright David H. Ransom, Jr., 1992,1993
All rights reserved.
Version 9303
January 14, 1993
by David H. Ransom, Jr.
Rancho Palos Verdes, California, USA
Bulletin Board Systems
----------------------
RPV ASTRONOMY BBS
(310) 541-7299 @ 14400/9600/2400 Baud
RPV HOTLINE BBS
(310) 544-8977 @ 2400/1200 Baud
Program ORBITEL Verify & Sort Orbital Elements Page i
ORBITEL
Verify and Sort 2-Line Orbital Elements
by David H. Ransom, Jr.
Introduction
------------
Program ORBITEL is a utility program to verify, merge, and sort
standard 2-line orbital elements files such as those posted on my bulletin
board systems and elsewhere. I use the program routinely to produce the
NASAnnn.TXT and GSFCnnn.TXT files from "raw data" obtained from TS Kelso's
Celestial BBS and the Goddard Space Flight Center's OIG RBBS respectively.
In both cases, the "raw data" consists of two or more files with differing
names and sometimes non-standard format (OIG RBBS) which must be merged and
then sorted to produce the final output file. Perhaps from force or habit,
most sources are sorted in ascending order of NORAD number; I prefer to
sort in descending order so that more recent satellites are near the
beginning of the file.
ORBITEL can also be used simply to verify and correct the checksums at
the end of each line of a 2-line element set. For individuals who create or
modify their own 2-line elements, this avoids the tedious and error-prone
task of doing the job manually. Be aware, however, that a file with one or
more checksum errors may contain data errors and should be carefully
checked before use.
It is important that the checksums be set correctly; while certainly
not foolproof, the checksums do provide a quick check of the data and can
detect single digit errors. Unfortunately, the simple checksum method used,
modified modulo ten on each data line, will not detect digit transpositions
-- one of the more common manual errors. Nor will it necessarily detect
multiple digit errors on a single line. Far better error detection and
correction techniques are now available but the 2-line element format was
devised many years ago (as "2-Card Elements", harking back to the days of
punched cards) and the format is deeply imbedded in many programs. Changing
the format at this late date is thus unlikely.
ORBITEL has progressed by fits and starts over the past several years
as I find a need for various tools to work with NASA/NORAD 2-line elements.
ORBITEL does not test the validity of the orbital data itself, only the
structure of the file and the checksums for each data line. Various sort
and batch mode options are included.
David H. Ransom, Jr.
7130 Avenida Altisima
Rancho Palos Verdes, CA 90274
Program ORBITEL Verify & Sort Orbital Elements Page i
Running Program ORBITEL Interactively
-------------------------------------
ORBITEL may be executed either interactively or in batch mode. To use
the program interactively, enter "ORBITEL" at the DOS prompt. The following
menu appears:
Program ORBITEL: Verify/Sort NASA 2-Line Orbital Elements
Version 9245 by David H. Ransom, Jr.
F1 Display Information on 2-Line Elements
F2 Display 2-Line Element Data by Satellite
F3 Verify line checksums and file structure
F4 Write new sorted file with corrected checksums
ESC Quit program ORBITEL
Enter desired function:
Press the indicated Function Key to perform the desired function or press
the key marked "ESC" to return to DOS.
F1 Display Information on 2-Line Elements
------------------------------------------
This function displays a series of brief help screens describing the
structure of 2-line orbital elements. See the section "2-Line Orbital
Elements" below for similar information.
F2 Display 2-Line Element Data by Satellite
--------------------------------------------
This function displays the orbital data for a specific satellite. Two
prompts are displayed:
Enter 2-Line Elements FILENAME:
Enter desired SATELLITE NAME:
For the FILENAME, enter the name of the 2-line elements file; if you omit
the filetype, ".TXT" will be used automatically. For the SATELLITE NAME,
enter sufficient letters to unambiguously identify the desired satellite;
for example, "STS" will normally be sufficient to identify a space shuttle
mission. For either prompt, upper or lower case may be used.
ORBITEL searches through the specified file and attempts to locate a
satellite whose name matches the one requested. If found, the 2-line
orbital elements data is displayed as read from the file:
Element Record: 1 STS-44
2-Line Elements for STS-44 [STS44N01.TXT]
0 Satellite Number 21795
1 Launch Year 0
2 Launch Number 0
Program ORBITEL Verify & Sort Orbital Elements Page i
3 Piece of Launch
4 Epoch Year 91
5 Epoch, JD+frac 329.35841039
6 1st Deriv Mean Mot'n .00038
7 2nd Deriv Mean Mot'n 0
8 BSTAR Drag .000275
9 Ephemeris Type 0
10 Element Number 1
11 Inclination 28.4689
12 RA of Ascending Node 248.6938
13 Eccentricity .0024211
14 Argument of Perigee 196.5249
15 Mean Anomaly 163.4609
16 Mean Motion 15.62614298
17 Rev # at Epoch 7
Press any key to continue ...
Press any key (except non-typing keys such as SHIFT or CTRL) to view
additional derived data for the satellite:
Derived data:
Epoch JD#: 2448585.8584104
Epoch Time (UTC/GMT): 8.6018494
8:36:06.66
Epoch Date (DD/MM/YYYY): 25/11/1991
Launch JD#: 2448584.4216158 (estimated)
Launch Time (UTC/GMT): 22.1187790
22:07:08
Launch Date (DD/MM/YYYY): 23/11/1991
Mean Orbit Time: 92.1533 min
Osc Orbital Time: 92.2412 min
Mean SemiMajor Axis: 6758.2500 km
Orbital Altitude: 380.1150 km 204.8778 nm
Orbital Perigee: 363.7526 km 196.0586 nm
Orbital Apogee: 396.4774 km 213.6969 nm
Press any key to continue ...
Press any key (except non-typing keys such as SHIFT or CTRL) to return to
ORBITEL's Main Menu.
The Epoch JD#, Time, and Date restate the time of Epoch for the
elements (the instant for which the elements were calculated) in more
conventional notation. The Launch JD#, Time, and Date calculate an
estimated launch date based upon the Rev # (orbit number) at Epoch.
CAUTION: NORAD is not always consistent in the way in which it assigns
orbit numbers and some very strange dates can result. At best, the launch
calculations will yield a very rough approximation of the actual time and
date for the launch of the satellite.
The orbital data contained in the 2-line elements are adjusted in a
variety of ways for use with the SGP4 and SDP4 mathematical orbital models.
The additional derived orbital data take into account these adjustments and
Program ORBITEL Verify & Sort Orbital Elements Page i
are calculated as of the Epoch time for the elements. Orbital altitude,
perigee, and apogee are given in both kilometers and nautical miles and
assume a spherical Earth with a mean Earth radius of 6378.135 kilometers.
F3 Verify line checksums and file structure
--------------------------------------------
This function verifies the checksums on the two data lines and
validates the structure of the 2-line elements file. You will be prompted
for the filename to check; if you omit the filetype, ".TXT" will be used
automatically.
Enter 2-Line Elements FILENAME:
As ORBITEL checks each record in the file, a brief listing is displayed for
each satellite:
Record 836: 00047 TRANSIT 2A R/B Launched 1960
Record 837: 00046 SOLRAD 1 (GREB) Launched 1960
Record 838: 00045 TRANSIT 2A Launched 1960
Record 839: 00029 TIROS 1 Launched 1960
Record 840: 00022 EXPLORER 7 Launched 1959
Record 841: 00020 VANGUARD 3 Launched 1959
Record 842: 00016 VANGUARD 1 R/B Launched 1958
Record 843: 00012 VANGUARD 2 R/B Launched 1959
Record 844: 00011 VANGUARD 2 Launched 1959
Record 845: 00005 VANGUARD 1 Launched 1958
END-OF-FILE. Press any key to continue ...
Reading from the left, the colums are: record number within the file; NORAD
number for the satellite; satellite name (15 characters max); and launch
year if specified. The sample, taken from the end of a large file,
indicates that 2-line elements for a total of 845 satellites is included in
the file. Press any key (except non-typing keys such as SHIFT or CTRL) to
return to ORBITEL's Main Menu.
F4 Write new sorted file with corrected checksums
--------------------------------------------------
This function sorts a specified 2-line elements file, correcting any
bad checksums in the process. You are first asked to select a sort method:
Sort and check 2-line elements file:
A = ASCENDING sort
D = DESCENDING sort
N = NO sort
Enter desired sort method:
Sorting is performed using the NORAD number for each satellite in the file.
You may choose to sort in ascending or descending order or you may elect
not to sort the file. Press the letter corresponding to the desired sort
Program ORBITEL Verify & Sort Orbital Elements Page i
method. I recommend using the descending sort method since more recent
satellites will then be placed near the beginning of the file and will be
accessed more rapidly by other programs. You are then asked to select the
file to process:
Enter 2-Line Elements FILENAME: NASA085.TXT
Enter the name of the desired file. If you omit the filetype, ".TXT" will
be used automatically.
ORBITEL then reads and optionally sorts the file, displaying the
following information during the process:
14:20:44 Now reading satellite records ...
845 Satellite Records read
14:20:55 Now sorting by DESCENDING satellite number ...
2 Sorting passes
14:20:56 Now checking for duplicate satellites ...
14:20:56 Now writing satellite records ...
845 Satellite Records written
14:21:05 Press any key to continue ...
In this example, 845 satellites were included in the 2-line elements file
and the file was already sorted (no duplicate satellites were found). The
complete process required 21 seconds; more time will be required if sorting
must be performed and will depend upon the size of the file and the speed
of your computer. In this case, the new file will be named "NASA085.TXT"
and the original file will be renamed "NASA085.BAK". Press any key (except
non-typing keys such as SHIFT or CTRL) to return to ORBITEL's Main Menu.
Running Program ORBITEL in Batch Mode
-------------------------------------
Like myself, the phrase "Batch Mode" is a holdover from earlier days
when computer programs and their data were often submitted to be run "as a
batch" and the user received the results (or sometimes just a series of
error messages if the program was being debugged) some considerable time
later. Today, the phrase usually means that the program executes in
response to a series of instructions contained in a batch file, a file
whose filetype is ".BAT". The phrase is also sometimes used to refer to the
use of a program when all parameters required are entered on the command
line (the characters following the program name typed at the DOS prompt).
The use of ORBITEL from the DOS prompt is similar to the F4 selection
when using the program interactively. The form of the command is:
ORBITEL <filename> [options]
where "<filename>" is the name of the 2-line elements file to process and
[options] may be one or both of the following:
/A Sorts output file in ASCENDING order of NORAD Numbers. The
default is to sort in DESCENDING order of NORAD Number, placing
Program ORBITEL Verify & Sort Orbital Elements Page i
the most recent satellites (those with higher NORAD numbers) at
the beginning of the output file.
/N Does NOT remove TLE's with duplicate NORAD Numbers. This allows
merged files and "LAST5" files to be sorted while retaining all
TLE's. TLE's for the same satellite are grouped together in
ascending order of Epoch Date. See example below.
/O Adds orbit data to Line 0. The data is formatted as apogee in km
followed by perigee in km (e.g. "364 x 355") beginning in column
50 of the line. NOTE: This is the letter OH not the digit zero!
/U Unsorted output. The order of satellites in the output file is
the same as the input file. Duplicate satellites will NOT be
removed (as with the "/N" command line option).
Multiple options may be used:
ORTIBEL NASA.LST /O/U
will add apogee and perigee to Line 0 and generate unsorted output.
By default, ORBITEL will remove all duplicate 2-line elements except the
most recent. Using the "/N" command line option performs the same as the
"NO Sort" option when used interactively and will process elements for the
same satellite in ascending order of Epoch Date, as shown in the following
example:
Intelsat 6
1 20523U 90 21 A 92039.04552756 .00008522 00000-0 60373-3 0 6706
2 20523 28.3318 282.7030 0016740 137.2451 222.9377 15.02964371104940
Intelsat 6
1 20523U 90 21 A 92040.04160086 .00003959 00000-0 27372-3 0 6711
2 20523 28.3168 276.1581 0017876 144.3411 215.7910 15.02948478105097
Intelsat 6
1 20523U 90 21 A 92042.03371371 .00009772 00000-0 69437-3 0 6732
2 20523 28.3301 263.1098 0016731 168.2365 191.4355 15.02942356105392
Intelsat 6
1 20523U 90 21 A 92043.16265899 .00008101 00000-0 57361-3 0 6743
2 20523 28.3308 255.7126 0016553 180.5935 179.4275 15.02955973105565
Intelsat 6
1 20523U 90 21 A 92043.95950791 .00004471 00000-0 31092-3 0 6752
2 20523 28.3286 250.4967 0016496 189.4170 170.5602 15.02953000105688
Using .LST and .SEL Key Files
-----------------------------
ORBITEL may also use several "key files" when operated in the batch
mode. These key files have filetypes ".LST" and ".SEL". If the filename
specified has filetype ".LST", ORBITEL assumes that the file contains a
list of files to process. For example, a list file called "NAVSTAR.LST"
might include the following lines:
*
* Convert .DAT files for NAVSTAR data ...
Program ORBITEL Verify & Sort Orbital Elements Page i
*
NASA085.TXT
INTEREST.DAT
NAVIGATN.DAT
THIRTY.DAT
/NAVSTAR.TXT
Files which contain 2-line elements are listed with a SPACE at the left and
are sequentially read by ORBITEL. The output file is designaged with the
"/" character at the left. Comment lines, lines which will be displayed but
otherwise ignored, are designated with the "*" character at the left.
By popular request, ORBITEL has been enhanced to allow the user to
specify a list of satellites to include when used in the batch mode. When
the filename specified in the command line has the filetype ".LST" and
ORBITEL detects a file with the same filename and filetype ".SEL", that
second file is interpreted as a list of NORAD Numbers to include in the
output file; all other TLE's will be skipped. If "NAVSTAR.LST" is the list
file and if select file "NAVSTAR.SEL" is found, the output file will
contain 2-line elements only for those satellites whose NORAD numbers are
included in the second file. File "NAVSTAR.SEL" might contain:
11054 1978 093A NAVSTAR 3/ 6
11783 1980 032A NAVSTAR 6/ 9
14189 1983 072A NAVSTAR 8/11
15039 1984 059A NAVSTAR 9/13
15271 1984 097A NAVSTAR 10/12
16129 1985 093A NAVSTAR 11/ 3
19802 1989 013A NAVSTAR 14/14
20061 1989 044A NAVSTAR 13/ 2
20185 1989 064A NAVSTAR 16/16
20302 1989 085A NAVSTAR 19/19
20361 1989 097A NAVSTAR 17/17
20452 1990 008A NAVSTAR 18/18
20533 1990 025A NAVSTAR 20/20
20724 1990 068A NAVSTAR 21/21
20830 1990 088A NAVSTAR 22/15
20959 1990 103A NAVSTAR 23/23
21552 1991 047A NAVSTAR 24/24
ORBITEL will read the numeric value at the left of each line in file
"NAVSTAR.SEL" (ignoring the balance of the line), interpret it as a NORAD
number, and include ONLY the resulting list of 2-line elements in the
output file. In this case, assuming no "/N" command line option, the four
specified source files will be loaded and only the most recent TLS's for
the 17 GPS NavStar satellites specified will be included in the output file
"NAVSTAR.TXT".
Beginning with Version 9303, the .SEL file may be specified as an entry
within the .LST file and does not need to have the same file name. In
addition, multiple .SEL and output files may be specified so that several
sets of elements may be extracted from the same "master file". I use two
files, SELECT.BAT and SELECT.LST to automatically generate several selected
groups of elements. SELECT.BAT performs the primary task and also generates
ZIP files for the selected sets of elements:
Program ORBITEL Verify & Sort Orbital Elements Page i
ORBITEL SELECT.LST
PKZIP -A -O ALLSAT ALLSAT.TXT
PKZIP -A -O AMATEUR AMATEUR.TXT
PKZIP -A -O GPS GPS.TXT
PKZIP -A -O TVRO TVRO.TXT
PKZIP -A -O VISUAL VISUAL.TXT
PKZIP -A -O WEATHER WEATHER.TXT
SELECT.LST is then used by ORBITEL to control the actual file reading,
sorting, and selection processes:
NASA.TXT <-- Note leading SPACE!
GSFC.TXT <-- Note leading SPACE!
/ALLSAT.TXT
SAMATEUR.SEL
/AMATEUR.TXT
STVRO.SEL
/TVRO.TXT
SGPS.SEL
/GPS.TXT
SVISUAL.SEL
/VISUAL.TXT
SWEATHER.SEL
/WEATHER.TXT
Briefly, this process reads two 2-line elements files, NASA.TXT and
GSFC.TXT, to form a composite sorted master file called ALLSAT.TXT. The
same 2-line elements data are then used in succession to produce
AMATEUR.TXT, TVRO.TXT, GPS.TXT, VISUAL.TXT, and WEATHER.TXT according to
the contents of the respective .SEL files. When all .TXT files have been
written, each .TXT file is then archived into a ZIP file using PKWARE's
program PKZIP to minimize the file size. Sample files are included in the
standard distribution package.
Program ORBITEL Verify & Sort Orbital Elements Page i
2-Line Elements from Celestial BBS
----------------------------------
Major T.S. Kelso, USAF, operates the Celestial BBS in Fairborn, Ohio
and regularly posts 2-line orbital elements in a variety of files. The
satellite tracking community owes "TS" a considerable debt. His Celestial
BBS was the first relaible electronic source of 2-line elements and, in
addition, he has made information and program code available on the SGP4
and SDP4 orbital models which permit the data to be used to produce
accurate satellite position predictions and has written several such
programs himself. Major Kelso also teaches celestial mechanics and related
subjects for the USAF.
The following background information is posted on the Celestial BBS
and is reproduced here for the information of users.
- Two-Line Orbital Element Sets [26 January 1991] -
Contents
History
Where To Find Data
Frequency of Updates
Format Description
Source of Orbital Data
NORAD Orbital Models
Special Orbital Element Requests
Satellite Frequencies
Information on Specific Satellites
Reposting Data Found Here
=======
History
=======
Effective January 1986, this system began posting the most recent two-line
orbital element sets 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, Progress, US Space
Shuttle, NAVSTAR (GPS), Glonass, GOES, Meteor, and NOAA.
==================
Where To Find Data
==================
These elements will be maintained in ASCII format in the file BULLETIN.TXT
which may be viewed with the 'B'ulletin command. This file is available
for downloading from the System directory. The bulletins are also
maintained in an archive, BULLETIN.ARC; this file is in the Satellite
directory. Additional sets of elements may be found in files in the
Satellite directory with a name of GROUP*.*. These files are groups of
special distribution (see Special Orbital Element Requests).
====================
Program ORBITEL Verify & Sort Orbital Elements Page i
Frequency of Updates
====================
The data provided on this system is generally updated three times a week.
Updates are scheduled to be performed on Monday, Wednesday, and Friday
evening, subject to the availability of the data. Difficulties in the
process of obtaining the data result in frequent delays in this schedule
(see Source of Orbital Data).
==================
Format Description
==================
Data for each satellite will consist of three lines in the following format
(not including the two line "ruler):
1 2 3 4 5 6
123456789012345678901234567890123456789012345678901234567890123456789
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 0 is an eleven-character name.
Lines 1 and 2 are the standard Two-Line Orbital Element Set Format
identical to that used by NASA and NORAD. The format description is:
Line 1
Column Description
01-01 Line Number of Element Data
03-07 Satellite Number
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
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 2
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]
Program ORBITEL Verify & Sort Orbital Elements Page i
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
Note that the International Designator fields are frequently blank. All
epochs are UTC (Coordinated Universal Time).
Satellites will be ordered by their Catalog (Satellite) 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.
Hopefully, this service will provide a central location for users to obtain
this data in a timely manner and help eliminate the tedious process of
entering data by hand directly from the NASA Prediction Bulletins.
======================
Source of Orbital Data
======================
Many people have inquired as to the original source of the data provided
here, so I feel compelled to provide some background. Until 1990, *all* of
the data available on this system came directly from the NASA Prediction
Bulletins provided by NASA Goddard on *paper*. That means for over four
years I entered all the data by hand using software specially designed to
ensure the data was in the proper format and to perform maximal error
checking. At the time I began this effort, satellite tracking by both
professionals and amateurs was in its infancy and development and
application was being severely hampered by the lack of data. After trying
to convince NASA for several years to set up a system for electronic
dissemination of orbital data, I decided to undertake the task myself.
If you are interested in obtaining this data directly from NASA, it is free
but it usually takes several weeks to have requests or changes processed.
And there will be a mail delay between the time the data is updated and you
receive it, depending on how far you are from NASA Goddard (Greenbelt, MD).
Also, there are limitations on the number of packages that any one person
can receive. The address is:
National Aeronautics and Space Administration
Code 513
Goddard Space Flight Center
Greenbelt, MD 20771
Note that anything you can get from NASA on paper you can get here much
sooner and in electronic form -- just follow the procedures for requesting
data outlined below.
Program ORBITEL Verify & Sort Orbital Elements Page i
Beginning in 1990, I began obtaining data indirectly from NORAD for the
entire catalog of objects on orbit. This data is provided on a daily basis
in electronic form and it makes the actual process of updating the various
sets of data provided here much simpler. However, the network of computer
links required to transfer the data from NORAD to this system is somewhat
complex and subject to frequent breakdowns. As a result, it often takes me
several hours to get the data each time I perform an update. When I am
unable to obtain the data from this source, I must fall back to the
original method of entering the data by hand.
The question which inevitably arises is, "How can I get the data from NORAD
directly?" The simple answer is, "You can't." Obtaining this data is not
a simple process of linking into a NORAD computer system and downloading
the data. The data is sent through a network of about half a dozen
computer links with at least one manual transfer along the way.
Considering the amount of time I take each week to obtain this data, you
should be thankful you don't have to repeat the process.
The next question which arises is, "How can I obtain the entire database of
two-line orbital element sets?" Again, I must answer, "You can't." There
are several reasons for this restriction. First, there are some
limitations on disseminating the entire catalog over which I have no
control. In addition, the size of the file would be prohibitive. There
are currently over 1500 users on this system and, as I'm sure you're aware,
the system is frequently busy. If I could make the entire database
available, even in compressed form, many people would want to download the
entire database (many on a daily basis, whether they really needed it or
not), making it nearly impossible to access the system for the majority of
users. While I would like to have multiple 9600-bps lines to service this
system to relieve this congestion, that goal is incompatible with the goal
of keeping the system open to the maximum number of users (i.e., no access
charges).
====================
NORAD Orbital Models
====================
You may be unaware of the special relationship of the two-line element sets
provided here to the NORAD orbital models (SGP and SGP4) discussed in
Spacetrack Report Number 3 (see SPACETRK.ZIP online in the Satellite
directory). To get accurate predictions with the data provided here, you
MUST use a program which uses these NORAD orbital models. Here's why. The
two- line orbital element sets are generated using these models and they
incorporate the various orbital perturbations (due to atmospheric drag, the
"shape" of the earth's gravity field, lunar and solar gravitational
effects, etc.) in a specific way that ONLY these models will properly
interpret.
One way to think about what's going on here is that you wouldn't expect to
use one compression algorithm to compress data and another one to
uncompress it and get good results! Most compression programs (PKZIP, PAK,
etc.) check for these incompatibilities but most tracking programs don't.
It is up to the user to ensure the proper orbital model is used. You may
use any other orbital model you feel appropriate, but you should not expect
to get very accurate results. Depending on the orbit of the satellite you
Program ORBITEL Verify & Sort Orbital Elements Page i
are working with, errors of many minutes may result.
The good news is that after five years of making the NORAD orbital models
and two-line element sets available, most tracking software (either
commercial or public domain) now incorporate these orbital models. And
there are many of the best such programs online this system in the
Satellite directory (use the WHATSFOR option in the File Section and use
"NORAD" or "SGP" as keywords to search on).
================================
Special Orbital Element Requests
================================
If you wish to receive elements for satellites other than those already
included in the master list, please read the article on Special Orbital
Element Requests. If you have any suggestions for improvements in these
data dissemination procedures, please leave a message or comment for the
SYSOP and I will get back to you. Please be aware that some plans are
already underway for improvements; these plans are described in the article
on the Celestial
BBS Upgrade.
=====================
Satellite Frequencies
=====================
Oftentimes, users request lists of the frequencies used by the satellites
contained in two-line element sets. While there are some lists online for
amateur radio and weather satellites and the space shuttle (use the
WHATSFOR option in the File Section and use "frequency" as a keyword to
search on), it would be impossible for me to keep up with a list of
frequencies for any large number of satellites. All satellites operate on
a number of different frequencies and many of them change frequencies on a
regular basis. Which frequencies you are interested in depends upon what
you are trying to do. If you cannot find the information you need here,
ask a specific question (e.g., What frequency does NOAA 11 transmit APT
data on?) in a message addressed to ALL; that should get you started. I
welcome the assistance of anyone willing to provide frequency information
on satellites with which they are familiar; I will take whatever inputs I
receive and compile them into a master listing.
==================================
Information on Specific Satellites
==================================
If you are interested in finding out more about some of the satellites for
which two-line element sets are available here (such as size, weight,
etc.), the following books are ideal references. Check your local
bookstore or library for them.
Nicholas L. Johnson, "The Soviet Year in Space 19xx", Teledyne Brown
Engineering, 19xx.
Giovanni Caprara, "The Complete Encyclopedia of Space Satellites",
Portland House, 1986.
Program ORBITEL Verify & Sort Orbital Elements Page i
Phillip Clark, "The Soviet Manned Space Program", Orion Books, 1988.
Kenneth Gatland, "The Illustrated Encyclopedia of Space Technology",
Harmony Books, 1981.
Douglas Hart, "The Encyclopedia of Soviet Spacecraft", Exeter Books,
1987.
D.G. King-Hele, et al., "The RAE Table of Earth Satellites 1957--19xx",
Wiley-Interscience, 19xx.
Reginald Turnill, "Jane's Spaceflight Directory 19xx-xx", Jane's
Publishing Company Limited, Fifth Edition, 19xx.
Bill Yenne, "The Encyclopedia of US Spacecraft", Exeter Books, 1985.
Bill Yenne, "The Pictorial History of World Spacecraft", Exeter Books,
1988.
=========================
Reposting Data Found Here
=========================
Finally, if you are reposting the two-line element set data provided by
this system to another BBS, I ask that you download the file TLE-POST.HDR
and add it to the beginning of your file before reposting. Doing so will
ensure that the Celestial BBS gets proper credit for providing these
elements in electronic form.
- TS Kelso
SYSOP, Celestial BBS
Program ORBITEL Verify & Sort Orbital Elements Page i
1-Line Element Sets (OLE)
-------------------------
The One Line Element (OLE) format is a somewhat abbreviated set of orbital
data used by the Navy at the Naval Research Laboratory (NRL) and perhaps
others. Some useful information which is included in the 2-Line Element
format is omitted, such as the Revolution Number at Epoch. Other
information, such as the International Designator, can often be obtained
from other sources using the satellite number (NORAD catalog number). The
only virtue to this format is its brevity, 60 characters for the single
line of data, as shown in the following format (which does not include the
"ruler" and the line beginning "nnnnn..."):
1 2 3 4 5 6
123456789012345678901234567890123456789012345678901234567890
nnnnnyydddffffffddddddiiiiiinnnnnneeeeeeaaaaaammmmmmxxxxxxxx
206399019071772000014705251829684400765901146334880715202450
Columns 1-5 NORAD catalog number
Columns 6-7 year
Columns 8-10 day number
Columns 11-16 fraction of a day
Columns 17-22 drag term (Implied decimal left)
Columns 23-28 inclination (Implied decimal in the middle)
Columns 29-34 ascending node (Implied decimal in the middle)
Columns 35-40 eccentricity (Implied decimal left)
Columns 41-46 argument of perigee (Implied decimal in the middle)
Columns 47-52 mean anomaly (Implied decimal in the middle)
Columns 53-60 mean motion (Implied decimal 2 from the left)
Example:
206399019071772000014705251829684400765901146334880715202450
The following values are obtained:
20639 catalog number
90 year
190 day number
.717720 fraction of a day
.000147 drag term
52.518 inclination
296.844 ascending node
.007659 eccentricity
011.463 argument of perigee
348.807 mean anomaly
15.202450 mean motion
The input of elements in this form may be terminated by a line which
contains a zero for the catalog number.
One-Line Element format information courtesy Mike McCants.
Program ORBITEL Verify & Sort Orbital Elements Page i
ORBITEL Revision History
------------------------
Each released version of STSPLUS uses a four digit revision code such
as 9245. The first two digits indicate the year and the second two digits
indicate the week of the year. In some cases, an additional letter suffix
is added to distinguish changes occurring within the same week or to
identify special versions. A partial week at the beginning or end of the
year is counted as a full week. Using this method, a year will typically
have 53 weeks although it is possible to have 54 weeks in a leap year (1972
is an example). The current year-week revision code is shown on the Julian
Date display, Display Mode 7, in my program ASTROCLK.
This file records the revision history of program STSPLUS through all
of the minor twists and turns that usually accompany the evolution of such
a complex program. It illustrates the tortuous process of maintaining and
refining a program as ideas and problems are reported from every quarter.
These notes may also be helpful to users who are upgrading from one version
to another to find out what has changed.
David H. Ransom, Jr.
Version 9302 -- January, 1993
-----------------------------
-Added the "/U" command line option to disable sorting. The order of
satellites in the output file is the same as in the input file. Duplicate
satellites will NOT be removed.
-Added the "/O" (letter OH, for Orbit data) command line option to cause
ORBITEL to add the apogee and perigee in km to Line 0 of each 2-line
element set starting at column 50.
-Corredted a bug that caused the select function (when a .SEL file was used
to select specific NORAD numbers) to fail unless the NORAD number was
followed by a space. The trailing space and optional name are now not
required and the .SEL file will be handled correctly whether or not these
items are present. Thanks to Paul Traufler for the report!
-Various cosmetic changes.
-Documentation completely rewritten.
Version 9214 -- April, 1992
---------------------------
-A bug was discovered in Version 9209 and before which caused the last set
of 2-line elements to be omitted from the final file after sorting, etc.
-The screen now displays the number of satellites in the current input
file, rather than the cumulative total number of satellites read so far (as
in prior versions). When in batch mode, the total number of satellites is
now displayed following the output file name.
Version 9209 -- February, 1992
------------------------------
-Finally, after much nagging by friends and acquaintances, I have done some
"serious work" on the sort algorithm. On my 386/20 and using files of 989
satellites total arranged in just about a "worst case" order, the sort time
went from about 3.5 minutes to 1 minute.
Program ORBITEL Verify & Sort Orbital Elements Page i
Version 9208 -- February, 1992
------------------------------
-ORBITEL modified to accept the "/A" and "/N" command line switches in the
batch mode.
-By popular request, ORBITEL has been enhanced to allow the user to specify
a list of satellites to include when used in the batch mode.
Version 9207 -- February, 1992
------------------------------
-This version has been updated to process Joel Runes' Space Object
Catalogs. The Catalog is divided into sections, each of which includes data
on 2000 sequential NORAD Catalog numbers and TLE data when available. If
ORBITEL is given a filename of "NORADCAT.nnn", all text and data will be
removed and a new file, "NORADCAT.TXT" will be created containing only the
TLE data. The original file will not be altered.
NORADCAT files may also be included in batch files but note that since there
are currently some 6300+ objects for which NORAD maintains TLE's, ORBITEL
cannot make a single composite catalog; its present limit is 1800 TLE's.
Version 9203 -- January, 1992
-----------------------------
-Thanks to a bug report by Tom Hayhurst, Version 9203 substitutes "0" for
spaces in the DAY portion of the Epoch in Line 1. Thus, an Epoch such as
"92 9.004999123" will be changed to "92009.004999123". The program does
not sort/select properly at year changes when spaces are present.
Version 9153 -- December, 1991
------------------------------
-In accordance with TS Kelso and Celestial BBS, RPV Astronomy BBS is
returning to checksum calculations for 2-line elements which count "+" as
ZERO rather than as TWO. Let us hope that NASA and NORAD can manage to keep
heading in the same direction on checksums for a while now.
-Beginning on January 1, 1992, all 2-line elements posted on RPV ASTRONOMY
BBS will be checked by this version of ORBITEL (or later) to verify
checksums.
Version 9148 -- November, 1991
------------------------------
-Fixes a file naming problem. Sometimes the output file was left with a
file type of ".$$$".
Version 9147B -- November, 1991
-------------------------------
-This version fixes a minor bug that caused problems if the entries in the
".LST" file were not all upper case. Case no longer is significant.
-The cross reference (.DAT files only) and sort times have been
significantly improved. Still not Really Fast, but MUCH better ...
-The running total for checksum errors is now shown as each input file is
Program ORBITEL Verify & Sort Orbital Elements Page i
processed. The number of errors in a given file is the difference between
the number shown and the number shown for the prior file. If no errors are
detected, the message is omitted.
Version 9147A -- November, 1991
-------------------------------
-Somehow an intermediate version of 9147 was released instead of the
correct version. In that release, F2 and F3 did not work and the output
file using the .LST batch file was incorrectly named. Version 9147A
corrects these problems.
-Added file list capability to batch mode. If the file specified on the
command line has filetype ".LST", ORBITEL assumes that it contains a list
of input filenames and an output filename. Input filenames must be
preceeded by a space and the output filename must be preceeded by the "/"
character. All other lines in the file are considered comments and are
echoed to the screen.
-Renamed the cross--reference file to ORBITEL.XRF to avoid confusion with
files of the same name from other programs. This file was inadvertently
omitted from the Version 9144 distribution. Sorry ...
Version 9144 -- October, 1992
-----------------------------
-Version 9144 will automatically add filetype ".TXT" if no filetype (or
".") is included in the filename. This applies to both interactive mode and
batch mode operations. (This feature in Version 9144 was previously
undocumented.)
-Repairs a bug in Version 9134 that caused duplicate satellites to not
always be removed depending upon the epoch time difference and the order of
appearance in the file. The sort routine now correctly orders all duplicate
satellites by epoch and retains only the most recent elements.
-Adds a batch file capability. If a filename is included on the command
line, the file will automatically be verified and rewritten as if the "W"
command had been entered. Satellites are sorted in DESCENDING order. If the
filetype entered automatically or with the "W" command is ".N2L", the
original file will remain unmodified and a new file with filetype ".TXT"
will be created which does NOT contain the beginning and ending comments
(marked by lines "startn2l" and "endn2l" respectively); this permits
automatic checking, sorting, and editing of Ted Molczan's NORAD 2-line
element files.
-ORBITEL is now able to process the 2-line format from the GSFC Orbital
Information Group RBBS. If the filetype is ".DAT", the extraneous second
text line is removed and the satellite ID number is compared against the
file ORBITEL.XRF (provided by Paul Traufler and which must be in the same
directory as ORBITEL) and replaced with the ASCII name if found; if the
satellite ID number is NOT found in the SATNAMES.XRF file, the name in the
output file is the satellite ID number. Note that this search and replace
requires additional time for each satellite! The original file will remain
unmodified and a new file with the same filename but filetype ".TXT" will
be written. ORBITEL may now be used with the GSFG OIG "Last 5" element sets
BUT only the most recent element set for each satellite will be written to
the output file. A sample batch file I use with the GSFC files is included.
Version 9134
Program ORBITEL Verify & Sort Orbital Elements Page i
------------
-Removed excess spaces on the first line of each satellite. Users had
complained that those spaces "confused" some tracking programs.
Version 9118
------------
-Initial public release. Added sort feature which is still slow but
improved. This is because I store the complete ASCII file in internal
arrays AND because I use a quick and dirty "brute force" method to do the
sorting. Improvements and suggestions are welcome.