[amsat-bb] Re: SEDSAT keps or freq off

[Astronautic Technology <tiung@xxxxxxxxxxxx>]

N8deu@aol.com wrote:
> A few observations were made:
> 1. It is nearly impossible to zero the antenna on this bird to verify the
>     KEP's since it only transmits a short burst of data at approximately
>     1 minute intervals.

Yup - this is a problem for everyone.  We won't be able to determine exact
freqencies on orbit until we upload new software, and begin to download
images,
which will give us longer data runs to center on.

> 2. No data or signal was received after the middle of the pass, indicating
>     an update may be needed on the KEP's or it stopped transmitting at
>     that point.  It was certainly in darkness at that point and the solar
>     panels would not have been seeing the sun.

There are new keps for SEDSAT, from Orbit 67.  However, it may have stopped
transmitting at that moment.  The KEPS are below for reference:

SEDSAT-1                
1 25509U 98061B   98302.25157598  .00000339  00000-0  57250-4 0   123
2 25509  31.4474   8.5741 0369771 290.9722  65.1725 14.23728456   676
DELTA 2 R/B 1           
1 25510U 98061C   98302.24900539  .00001178  00000-0  22624-3 0   101
2 25510  31.4484   8.5534 0373472 290.9265  65.1763 14.24509590   673

> 3. The frequency was measured to be approximately 3.4 KHz higher than
>     anticipated using the KEP's posted on the SEDSAT web page, indicating
>     that the KEP's need adjusted.  I am no expert in this area and have not
>     performed any calculations, but judging by the frequency offset
accounting
>     for the Doppler shift I would estimate that the KEP's may be about 2
> minutes
>     from those published on the SEDSAT site.  Any and all comment on this
>     best guess is welcomed.  This assumes that the frequency on SEDSAT is
>     true to 437.91 MHz.

I only noticed about a 6 second difference between the last element set and
this
one, so you may need to adjust your computer clock as well.



-- 
------------------------------------------------------------------------------
Christopher A. Lewicki KC7NYV 520.977.0758 Maintainer of SEDS.LPL.Arizona.EDU
     Project Manager, University of Arizona Student Satellite Project
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Sangat Singh, 9M2SS
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