They're on the air today. I just had a pass with a maximum elevation of 6 degrees, and the signal was almost full-quieting! Unfortunately the timing was bad and I got the last half of one image and the first half of the next one, with a 3-minute break between to allow for transmitter cooling or whatever. Higher passes coming up the rest of the day! (Unfortunately that'll probably bring fading when overhead, because I'm just using a simple groundplane antenna.)