# Re: mmccants tles and sattrack.

From: Russ Bessom (russbessom@desurf.com)
Date: Fri Mar 15 2002 - 05:23:23 EST

• Next message: raymundo@reaiche.com: "Obs Mar 14"

```Very Nice Ralph,
And now for the rest of us dummy's, go to Windows calculator, select
scientific view, enter the total per TLE line i.e. 157, push the "Mod"
button, then push the 10 button.  Then push equals.  Hey look it dat!

Russ Bessom - russbessom@desurf.com
Zweibruecken Germany
Lat 49.14.0 N / Long 7.19.0 E - 325m

----- Original Message -----
From: "Ralph McConahy" <rmcconahy@earthlink.net>
To: "SeeSat-L" <SeeSat-L@satobs.org>
Sent: Friday, March 15, 2002 6:53 AM
Subject: Re: mmccants tles and sattrack.

> Atul Sowani wrote:
>
> > When I use tles downloaded from mmccant's site with SatTrack,
> > I am getting "checksum error in line[2]" for all satellites.
>
> Can't help with the error you are getting, but I can answer your
question...
> > What is "checksum" and how it is calculated?
>
> The checksum digit is the last digit on the TLE.
> Example:
> TRMM
> 1 25063U 97074A   02073.54250259  .00066661  00000-0  92646-3 0  5707
> 2 25063  34.9757 236.9292 0000682 267.5731  92.5406 15.55953514246813
>
> The checksum for the first line is "7", and "3" for the second line.
>
> It is calculated by adding the digits of the first 68 characters, modulo
10
> (the checksum digit is in column 69). For non-numbers: Blanks, letters,
> decimal points and "+" each equal zero, the minus sign ("-") equals one.
In
> the first line above, adding the digits (don't add the 7 on the end), and
> remembering to add one for each "-", you get 157 (157 modulo 10 = 7). For
> the second line you get 223 (223 modulo 10 = 3).
>
>   Ralph McConahy
>   34.8829N  117.0064  670m

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```

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