[amsat-bb] Re: SUCCESSFUL RAFT Transponder Activation! ASSESSMENT

Robert Bruninga bruninga at usna.edu
Sun May 27 20:43:28 PDT 2007

Finaly got into work to replay the audio, and since the signal
is so much stronger at the end, I am convinced you were just
about into the main radar beam.  So you really got close to
perfect!   My guess is the 1 minute of the transponder was just
prior to hitting the main beam!

I'm catching up on email.  My opinion may change... :-)
USNA Satellite Lab

> -----Original Message-----
> From: amsat-bb-bounces at amsat.org 
> [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Matt Bennett
> Sent: Sunday, May 27, 2007 8:09 PM
> To: amsat-bb at amsat.org
> Subject: [amsat-bb] SUCCESSFUL RAFT Transponder Activation!
> Hi All,
> On the 0600 UTC western pass this morning (5/27), the
> UCISAT ground station crew successfully activated
> RAFT's radar transponder as it approached the Texas
> radar fence!  After several days of unsuccessful
> attempts, the success of this pass was largely
> attributed to NORAD obtaining a fresh set of Keps for
> RAFT's degrading orbit just before the pass started.
> The epoch of the elset was less than 3 hours, so our
> pointing was much more accurate than in previous low
> EL passes. 
> I threw together a simple website with the audio
> recording files and audio spectrum analysis of the
> transponder tone from the successful pass. The site
> also has tips and tricks for operators who want to
> help record the transmission within the footprint: 
> http://ucisat.eng.uci.edu/RAFT.php
> According to Bob Bruninga (WB4APR), the audio
> recording on the website is in fact the transponder
> picking up the ground radar signal. However, he
> pointed out that we did not catch the narrow beam of
> the radar which would have sounded like a bird chirp
> in the middle of an open FM carrier. He believes this
> could be because RAFT may have been too far west of
> the radar station and only catching side lobes, or
> because the transponder was activated a bit too early
> (difficult to tell due to a last minute configuration
> change at our station to accommodate the new elset).
> Because of this uncertainty, we absolutely need
> additional operators within the eastern and western
> pass footprints to help record the transponder audio!!
> For the next couple of days, two command stations will
> activate the transponder just before the radar fence
> penetration on the eastern and western passes around
> 0400 and 0530 UTC respectively. These times are MUCH
> earlier than they were at the beginning of last week
> because of the orbit decay (no longer 2-4 AM). Plus,
> all you have to do is record the audio! If you're
> interested, a procedure for recording stations willing
> to volunteer on the website above. For specific info
> on RAFT and its mission/operations, please see their
> website at
> http://www.ew.usna.edu/~bruninga/craft/save-raft.html
> Please feel free reply with questions if you're
> interested in helping with the recording in the next
> few days and one of us will get back to you. Thanks
> again to all for your reports and support throughout
> this week!
> 73,
> Matt Bennett
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