[amsat-bb] Re: O/OREOS TLE errors ?

Ryan Caron rcaron at gmail.com
Tue Nov 30 10:21:58 PST 2010

The O/OREOS TLEs consistently do not have valid checksums (last digit of 
each line). I submitted a comment about this on their website but I have 
not heard back. The correct checksums are 2 & 3, and not the 6 & 5 that 
is listed.

If, by the time you read this, the posted TLEs are not 6 & 5, then the 
TLEs have been updated and you'll have to generate new checksums. The 
formula is a sum of all numerical characters on the line, including the 
line number, treating minus signs as a one and everything else (letters, 
+, spaces) as a 0. Then take modulus 10 of the sum (i.e. last digit of 
the sum). Look it up on wikipedia for more details.

I've made a spreadsheet to fix this, but it is still a manual operation 
for me (got to write a script at some point). Some programs disregard 
the the checksum, which is why HRD & the website still work and your 
tracking tool doesn't. Predict/GPredict, my tools of choice, require 
valid checksums, making proper TLEs a pet peeve of mine. I don't know 
what NOVA's up to.

In terms of "swarm spread" (i.e. how small delta-V between spacecraft 
that shared the same ride, which in this case is just done by compressed 
springs, translates into spatial differences), 35 minutes of separation 
is pretty high for just 10 days after launch. With all the latest TLEs 
from the three websites, I show O/OREOS being 3.5 minutes ahead of RAX, 
and RAX being a 1.33 minutes ahead of FAST1/2.

Ryan, KB1LKI

On 11/30/10 4:54 AM, amsat-bb-request at amsat.org wrote:
> ------------------------------
> Message: 4
> Date: Mon, 29 Nov 2010 22:55:16 +0100
> From: PA3GUO<pa3guo at upcmail.nl>
> Subject: [amsat-bb]  O/OREOS TLE errors ?
> To:amsat-bb at amsat.org
> Message-ID:<19767175.1291067716437.JavaMail.root at viefep21.chello.at>
> Content-Type: text/plain; charset=utf-8
> Dear all,
> I keep on having troubles with the O/OREOS kepler sets.
> RAX and the others are fine.
> With todays version (as from the O/OREOS dashboard on the web)
> - NOVA gives O/OREOS just a bit behind RAX
> - HamRadioDeluxe give O/OREOS 35 minutes behind RAX
> - The O/OREOS web (dashboard graphic) shows O/OREOS 35 minutes behind RAX
> - My private antenna tracking tool does not recognize the keplerset of O/OREOS
> Anyone else has experienced this (and maybe even a solution) ?
> Henk
> --
> Henk, PA3GUO

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