Format change of tles

From: Bart De Pontieu <BDP_at_MPE.MPE-GARCHING.MPG.DE>
Date: Sun, 28 May 1995 14:26:07 -0400
These messages originally appeared on Compuserve. I think the subject will
interest most of you as well though. Thanks to Chris Steyaert for forwarding
it to me.

----------------------------------------------------------------------------
#: 220456 S3/Viewing Satellites
    27-May-95  17:51:10
Sb: #New Kepele Format
Fm: Conrad Kirksey, SS3 71575,1677
To: All Satellite Viewers

USSPACECOM has made a change in its two line Keplerian element format.

NASA/GSFC receives its data from USSPACECOM. NASA/GSFC TLEs are now the
new USSPACECOM format.

1. The checksum is not added to the end of each line.

2. Some zeros have been eliminated.

3. The International Designator has gone back to its original format
   (the piece number [letter] is right justified).

Since most tracking software will have problems with the new format, I
have converted the TLEs downloaded today from NASA/GSFC to the old format
before uploading them to CIS.

Here is a comparison of the new and the old formats:

Mir
1 16609U 86 17  A 95144.12750572 0.00003953  00000 0  57842-4     49
2 16609  51.6459 278.0913 0003976 349.9089  10.2052 15.5660711852928
Mir
1 16609U 86017A   95144.12750572 0.00003953  00000 0  57842-4 0   491
2 16609  51.6459 278.0913 0003976 349.9089  10.2052 15.56607118529287

The first set is the new format.
The second set is the old format.

In line 1:

The Int'l ID (column 10-17) does not have the zero between "86" and "17."

The piece number of the Int'l ID ("A") is now right justified.

The leading zero of the drag term "IS STILL" present (column 34).

The zero in column 63 (ephemeris type) is no longer present.

There is no checkusum number at the end of the line (column 69).

In line 2:

There is no checksum number at the end of the line (column 69).

Con

----------------------------------------------------------------------------
#: 220477 S3/Viewing Satellites
    27-May-95  19:35:11
Sb: #220456-#New Kepele Format
Fm: Paul Hirose 71202,2014
To: Conrad Kirksey, SS3 71575,1677 (X)

Thanks for the warning.  This is the first I've heard of the change. Kelso
probably has a notice posted on his BBS, but I haven't been on there in a
couple weeks.

Deletion of the checksum would break my programs.  Since I write my own
software, it would be no great bother to rework them (or make a program to
"fix" the elements as you are doing), but a lot users would be left in the
lurch with elements in the new format.  Wonder why they deleted the checksum.
It's not that big a space saving, after all.

------------------------------------------------------------------------------
#: 220549 S3/Viewing Satellites
    28-May-95  06:51:10
Sb: #220477-New Kepele Format
Fm: Conrad Kirksey, SS3 71575,1677
To: Paul Hirose 71202,2014

Paul,

You're right. The changes shouldn't have been made.

The reason given was that the checksum wasn't necessary any more because
error-checking protocols are used nowadays. It was said that the checksum
originated back in the teletype days when errors were more frequent and
couldn't be corrected.

Kelso's BBS uses ASCII for the Bulletin TLEs, so the checksum is certainly
necessary there. I download from the RAID BBS in ASCII. I don't download
the user file. I depend on the checksum.

Right justifying the piece number was just going back to the way it used to
be done.

Some zeros were eliminated, but the leading zero in the decay was not!

The changes seem to be so frivolous. A standard had been adopted worldwide
and then it was changed for such unimportant reasons.

NASA/GSFC had to go along with USSPACECOM because USSPACECOM supplies the
element sets.

I will continue to download TLEs from NASA/GSFC, convert them to the old
format, and upload them to CIS

Con
Received on Sun May 28 1995 - 13:30:31 UTC

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