[amsat-bb] AO-92 camera mode more info plse
zleffke at vt.edu
Wed Apr 29 14:18:37 UTC 2020
When in camera mode the VT camera follows the following basic sequence: Snap a picture, check how much 'earth' is in the frame, if it meets the 'earth detection' threshold, compress it with JPEG algorithms, break up the result into smaller data frames (8 pixel lines) and send the frame to the flight computer. If the 'earth detection' threshold is not met, the image is discarded and another one is taken, check if there is earth, rinse repeat. There is no long term storage of any given image and the earth detection step is part of the NOAA license. If an image is received by a station, it's a shot from roughly 'overhead', and the AMSAT page has a nifty feature that shows the subsatellite point based off timestamp information from each image downloaded.
I believe there is a 45 minute timer (roughly half of one orbit, the command folks can double check my number there) for the general 'camera mode' of the spacecraft (which is both 'high speed mode' and 'camera on'), with the command stations that start that process in NA. After the timeout the spacecraft goes back into transponder mode (or safe mode, again command stations can correct me there). So it might be tricky to pick up in New Zealand. I know early on in the life of AO-92 there were some experiments to trigger camera mode right as the spacecraft set over the horizon (I believe on ascending passes) by command stations at higher latitudes so that the camera would be active and received by Japanese hams. A similar experiment might work for descending passes and southerly command stations, but it would be smart to look at the footprint/ground track to see which pass might put New Zealand in the footprint within the timer window.
Aerospace & Ocean Systems Lab
Ted & Karyn Hume Center for National Security & Technology
Virginia Polytechnic Institute & State University
Work Phone: 540-231-4174
Cell Phone: 540-808-6305
From: AMSAT-BB <amsat-bb-bounces at amsat.org> On Behalf Of Rob Ramsey via AMSAT-BB
Sent: Wednesday, April 29, 2020 12:39 AM
To: amsat-bb at amsat.org
Subject: [amsat-bb] AO-92 camera mode more info plse
A little more info please on the camera mode of AO-92 , Is this just a real time transmission as the satellite is overhead or close by? is it stored and sent continuously for a predetermined time? I had my station on remote all day got nothing here in New Zealand ZL3TCM _______________________________________________
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