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# Re: TMSAT Status

• Subject: Re: [amsat-bb] TMSAT Status
• From: Roy Welch <rdwelch@xxxxxxxxxx>
• Date: Sat, 11 Jul 1998 14:51:50 +0000

```I also had no trouble loading the keps here.  Be sure that when you edit
the message to get rid of the text that you delete the > character at
the beginning of each line of the keps and that you don't leave a blank
in it place.

I have received a data carrier here just a few minutes ago on a low
elevation pass to the east.  The next pass will be better since this one
was too weak to capture any data.  I have found the frequency about 4 Khz
higher here than I expected through out the pass.

--
73, Roy

Internet: w0sl@amsat.org

Chris Hill wrote:
>
> Hi Norm and All,
>
> I was able to load the two-line elements for TMSAT-1 into my satellite
> program OK...
>
> In any case, I thought I'd respond to the "How is the modulo-10 checksum
> calculated";
>
> 1.  Add up the value of the first 68 characters (numbers) in each line.
> 2.  Ignore non-numeric characters, except a minus sign ('-') counts as a 1
> (one).
> 3.  Divide the total by 10.
> 4.  The modulus is the remainder.
>
> For example, the line;
>
> 1 25395U 98043B   98191.87373682 -.00000045  00000-0  00000+0 0    24
>
> adds to 134.
> Dividing by 10 gives 13 (discard the 13), with a remainder of 4.  Hence 134
> MOD 10 = 4.
>
> The simple check is that the 69th character in the line should be the
> modulo-10 result as described above.  In the example, the 69th character is
> 4, hence the line is (probably) good.
>
> Here is a function taken from a Pascal program written by Dr T.S Kelso;
>
> +----------------------------------------------------------------------+
> Function Checksum_Good(line : line_data) : boolean;
>   var
>     i,checksum,check_digit : integer;
>   begin
>   checksum := 0;
>   for i := 1 to 68 do
>     case line[i] of
>       '0'..'9' : checksum := checksum + Ord(line[i]) - Ord('0');
>            '-' : checksum := checksum + 1;
>       end; {case}
>   checksum := checksum mod 10;
>   check_digit := Ord(line[69]) - Ord('0');
>   Checksum_Good := (checksum = check_digit);
>   end; {Function Checksums_Good}
> +----------------------------------------------------------------------+
>
> I used this routine in a little program I wrote, which allows the user to
> edit some of the two-line elements in a text editor...  my program then
> calculates the mod-10 check digit and inserts it into each line, so that the
> keps will check out OK in any program....  of course, the keps are false,
> but it allows the user to experiment with some "what if's" like "what if a
> LEO like KO-23 was in an essentially identical orbit to it's current one,
> but inclined at zero degrees to the equator?".
>
> I've been meaning to clean it up a bit and describe it on a web page on the
> Amsat site...  if you would be interested in such a program, please let me know.
>
> 73 Chris VK6KCH
>
> p.s  what version of InstantTrack are you running?
>
> At 19:29 11/07/98, you wrote:
> >At 06:58 11/07/1998 +0100, you wrote:
> >Snip.....
> >>The following keps are accurate for tracking the spacecraft (Note that the
> >>object number is not the final TMSAT object).
> >>
> >>TMSAT-1
> >>1 25395U 98043B   98191.87373682 -.00000045  00000-0  00000+0 0    24
> >>2 25395  98.7944 261.8948 0001516   6.1903 313.0257 14.22263117    96
> >>----
> > Ok, so when I load these into Instantrack I get the "mon 10 line checksum
> >failed message. When compared to other elsets the checksum even looks
> >wrong. Am I stupid and missing something... it has been a long day?
> >
> >BTW, how is the mod(ulus?)10 checksum calculated? I seem to recall having a
> >similar problem with some Iridium elsets.
> >
>  +-------------------------------------------------+
>  |  Chris Hill            email : vk6kch@amsat.org |
>  |  CRH Telnet PTY LTD          A.C.N. 008 922 530 |
>  |  Phone : +61 8 9354 8416  Fax : +61 8 9354 8826 |
>  +-------------------------------------------------+
>
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```

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