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... :-) Congratulations! Bob, WB4APR USNA Satellite Lab
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Matt Bennett Sent: Sunday, May 27, 2007 8:09 PM To: [email protected] Subject: [amsat-bb] SUCCESSFUL RAFT Transponder Activation!
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:
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!
Matt Bennett KF6RTB
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