Successful RAFT transponder activation

Hi All,

On the 0600 UTC western pass on Sunday (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 KF6RTB

RAFT Fence Doppler Plot Posted

RAFT-REENTRY CAMPAING web page now has a Doppler Plot against TIME:
http://www.ew.usna.edu/~bruninga/craft/save-raft.html

To our surprise, the RAFT XP-217 radar receiver hears the Radar sidelobes as long as it is above the horizon! I guess that makes sense for a 700 KW transmitter. Even if we are not in the 80 Meggawatt main beam, the radar receiver does still hear it (even though its RX sensitivity was intentially only designed to be only - 40 dBm? or so)...

Now, is there anyone on the AMSAT-BB that would like to analyze this portion of the Doppler Plot and prove the timing. The only thing I'd like to confirm is the added inflection point at the start (probably due to the bistatic radar situation) which makes this different than the usual "S" plot with only a 3rd order curve.

Bob WB4APR

RAFT packet operator assistance desparately needed
http://www.southgatearc.org/news/may2007/raft_help_needed.htm

ANDE and RAFT limited USER operations authorized
http://www.southgatearc.org/news/december2006/
ande_open_for_xmas.htm

AMSAT-UK - ANDE Satellite Telemetry Page
http://www.southgatearc.org/news/december2006/
ande_telemetry_page.htm

RAFT and ANDE are APRS satellites
http://www.southgatearc.org/news/december2006/
satellites_to_deploy_thursday.htm