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Program MAK2LINE
Make 2-Line Elements using Keplerian Elements
(C) Copyright 1992, All Rights Reserved
by David H. Ransom, Jr.
Rancho Palos Verdes, CA
Version 9208
February 16, 1992
BBS: (310) 541-7299
MAK2LINE Program Documentation Page 1
INTRODUCTION
------------
This program provides a means to individuals without modems to receive
the so-called "Keplerian Orbital Elements" and reliably prepare "2-Line
Orbital Elements" as required by satellite tracking programs such as my own
STSORBIT and STSORBIT PLUS as well as Paul Traufler's excellent TRAKSAT and
other similar programs. However, more information is included in the 2-line
orbital element set than is usually included in the Keplerian orbital
elements; this means that the "missing" information must either be obtained
from other sources or be set to a specified value or zero. These
instructions and the example and sample form which follows will help the
unskilled user to do these tasks.
The current version of MAK2LINE is always available on my RPV
ASTRONOMY BBS at (310) 541-7299 in Rancho Palos Verdes, CA near Los
Angeles. It is a very busy system, so please be patient (especially during
Space Shuttle missions).
Program MAK2LINE is copyrighted software. Use it if you like it,
discard it if you don't. There are no warranties of any kind. Program
registration is not required; however, if you use and enjoy Program
MAK2LINE, a donation of US$10.00 will be much appreciated and will encourage
me to continue supporting the amateur radio and satellite tracking
communities with software big and small. A donation of US$10.00 will also
bring you the latest version of the program on disk. Please specify disk
size, 5-1/4" 360K or 3-1/2" 720K.
David H. Ransom, Jr.
7130 Avenida Altisima
Rancho Palos Verdes, CA 90274
MAK2LINE Program Documentation Page 2
PROGRAM NOTES
-------------
Program MAK2LINE has but a single purpose: to prepare 2-line orbital
elements from Keplerian orbital elements by means of user keyboard input.
Since the program is designed only to transcribe valid data from one format
to another, no error checking is performed and the program makes no tests
of the "reasonableness" of the various data and parameters. The user is
therefore cautioned to check his data before using this program, or to use
the resulting data with caution until it has been verified.
The information shown below is usually included in the Keplerian
orbital elements as received via modem or via voice (amateur radio or
telephone). This sample is an actual file from Space Shuttle Flight STS-42
in January of 1992 and received via modem direct from the NASA Johnson
Space Center:
Satellite: STS-42
Catalog number: 21846
Epoch time: 92024.87908918 (24 JAN 92 21:05:53.31 UTC)
Element set: JSC-005
Inclination: 56.9720 deg
RA of node: 233.8707 deg Space Shuttle Flight STS-42
Eccentricity: .0009197 SGP4 Keplerian Elements
Arg of perigee: 264.4174 deg from NASA flight Day 3 vector
Mean anomaly: 95.5875 deg
Mean motion: 15.91353638 rev/day G. L. Carman
Decay rate: 2.10000e-03 rev/day^2 NASA Johnson Space Center
Epoch rev: 37
If you compare the information requested by Program MAK2LINE (as shown
on the example on the following page) with that above, several items are
missing or may be in a slightly different format. Here are some
suggestions.
1. A sample form is included in this documentation which will assist you
when receiving Keplerian orbital information by voice line or when it
is transmitted by amateur radio link. Note that the form includes
lines for "IAU Designation" and "BSTAR Drag"; these items are
frequently omitted from voice transmissions.
2. The NORAD Number is assigned by the U. S. Space Command at Cheyenne
Mountain after a satellite has been successfully launched. Initial or
pre-launch Keplerian elements may use the mission number or some other
convenient number for this item. Most tracking programs will accept
any number here.
3. The IAU (International Astronomical Union) Designation is often not
assigned until well after a flight is in progress; press ENTER to use
all spaces for this item.
4. For the 2-line orbital element set, the element set number (shown as
"JSC-005" in the example above) MUST be numeric. For this example,
enter "5" or "005". Most tracking programs will accept any number for
this item, up to a maximum of FOUR DIGITS.
MAK2LINE Program Documentation Page 3
5. The "Epoch Rev/Orbit" is the orbit number at the epoch (the instant
when the data is taken). Up to FOUR DIGITS may be entered here but
except for the orbit number on displays, this number has no effect on
the propagated orbit.
6. When MAK2LINE asks for "NDOT2 Drag/Decay", the information being
requested is the "Decay rate" in the Keplerian elements. It may be
entered in the form shown in the example or as a decimal fraction such
as ".0021" (which is identical to the "2.10000e-03" in scientific
notation as used in the example).
7. When MAK2LINE asks for "NDDOT6 Drag", press ENTER to insert a value of
zero. This should be satisfactory for most tracking programs.
8. When MAK2LINE asks for "BSTAR", you may press ENTER to insert a value
of zero. This will be satisfactory for times very close to the Epoch
Time for the elements. However, as time progresses the satellite may
lag behind the propagated (projected) ground track if no value is
avaialble for BSTAR. It may be satisfactory to use a value from a
similar satellite or a prior set of 2-line elements in order to
achieve more accurate long term results.
9. After the last data item has been entered, MAK2LINE will request the
filename to which the 2-line orbital data is to be written. Enter the
full file name such as "TESTSAT.TXT". The file will be written to the
current drive and directory by default. A drive and/or path may
optionally be included in the filename entered. Any prior file by the
same name will be overwritten.
10. If you make a mistake during the data entry process, you may use the
BACKSPACE key until ENTER has been pressed. If you wish to cancel the
program without writing the data to a file, press CTRL-C.
Finally, a word about the NDOT2 and BSTAR parameters. Both the U. S.
Space Command (formerly NORAD) and Johnson Space Center have been known to
"tweak" these values for a variety of reasons. Usually it is because the
orbit is in a state of change due, perhaps, to maneuvers or excessive drag.
A positive value for BSTAR, which indicates positive acceleration and is
somewhat unusual (and often also an indication of "tweaking"), is NOT
handled correctly by MAK2LINE at this point and must be manually edited. If
this proves troublesome, it will be corrected in a future release of the
program.
MAK2LINE Program Documentation Page 4
PROGRAM MAK2LINE EXAMPLE
------------------------
Enter 2-LINE ELEMENTS
Enter the required data as prompted. Most essential data is
so-called Keplerian Orbital Data available to amateur radio
enthusiasts. Other data may be inserted if available or may
be omitted if not. Accuracy may be affected, see documentation.
Enter Satellite Name (15 chars max): sts-42
Enter NORAD Number (NNNNN): 21846
Enter IAU Designation (8 chars max): 92 2 A
Enter Epoch Time (YYDDD.TTTTTTTT): 92024.87908918
Enter Element Set Number (NNN): 5
Enter Inclination (DDD.DDDD): 56.972
Enter RA of Ascend Node (DDD.DDDD): 233.8707
Enter Eccentricity (.NNNNNNN): .0009197
Enter Arg of Perigee (DDD.DDDD): 264.4174
Enter Mean Anomaly (DDD.DDDD): 95.5875
Enter Mean Motion (NN.NNNNNNNN): 15.91353638
Enter Epoch Rev/Orbit (NNN): 37
Enter NDOT2 Drag/Decay (.NNNNNNNN): .0021
Enter NDDOT6 Drag (NNNNN-N):
Enter BSTAR (NNNNN-N): 61700-3
Satellite Name (15 chars max): Sts-42
NORAD Number (NNNNN): 21846
IAU Designation (8 chars max): 92 2 A
Epoch Time (YYDDD.TTTTTTTT): 92024.87908918
Element Set Number (NNN): 5
Inclination (DDD.DDDD): 56.9720
RA of Ascend Node (DDD.DDDD): 233.8707
Eccentricity (.NNNNNNN): .0009197
Arg of Perigee (DDD.DDDD): 264.4174
Mean Anomaly (DDD.DDDD): 95.5875
Mean Motion (NN.NNNNNNNN): 15.91353638
Epoch Rev/Orbit (NNN): 37
NDOT2 Drag/Decay (.NNNNNNNN): .00210000
NDDOT6 Drag (NNNNN-N): 00000-0
BSTAR (NNNNN-N): 61700-3
Sts-42
1 21846U 92 2 A 92024.87908918 .00210000 00000-0 61700-3 0 59
2 21846 56.9720 233.8707 0009197 264.4174 95.5875 15.91353638 379
MAK2LINE Program Documentation Page 5
RECEIVED KEPLERIAN ORBITAL DATA
-------------------------------
This form is provided as a convenience to users receiving Keplerian
orbital data via voice link (amateur radio or telephone). Each set of
underline characters indicates an expected character; the decimal point is
shown where expected (if appropriate for the item). Make multiple copies of
this form prior to a mission.
Satellite: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
Catalog Number: __ __ __ __ __
IAU Designation: __ __ __ __ __ __ __ __
Epoch Time: __ __ __ __ __ . __ __ __ __ __ __ __ __
Element Set: __ __ __ __
Inclination: __ __ __ . __ __ __ __
RA of Node: __ __ __ . __ __ __ __
Eccentricity: . __ __ __ __ __ __ __
Arg of Perigee: __ __ __ . __ __ __ __
Mean Anomaly: __ __ __ . __ __ __ __
Mean Motion: __ __ . __ __ __ __ __ __ __ __
Decay Rate: . __ __ __ __ __ __ __ __
BSTAR Drag: __ __ __ __ __ - __
Epoch Rev: __ __ __ __
MAK2LINE Program Documentation Page 6
MAK2LINE REVISION HISTORY
-------------------------
Each released version of MAK2LINE uses a four digit revision code such
as 9208. 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 occuring within the same week. A partial
week at the beginning or end of the year is counted as a full week. Using
this method, a year will typically have 53 weeks although it is possible to
have 54 weeks in a leap year (1972 is an example). The current year-week
revision code is shown on the Julian Date display, Display Mode 7, using my
program ASTROCLK.
This section records the revision history of program MAK2LINE through
all of the minor twists and turns that usually accompany the evolution of
such a program. It illustrates the tortuous process of maintaining and
refining a program as ideas and problems are reported from every quarter.
It may also be helpful to users who are upgrading from one version to
another to find out what has changed. This section may also describe recent
changes not included in the main documentation.
Version 9208 02/16/92
----------------------
-Initial public release of the program.
-User comments and suggestions are welcome.