We had an exciting two hours back when the STEREO solar telescope satellites were first launched. The first summed image of several hours of first-light data showed a clear distortion in one of the ten SECCHI detectors. Doom! Tragedy! Can we compensate for it?
It was almost like the sky was a bathtub draining to the lower left. All the light warped and bended in that direction. Opinions varied as to the cause... was it a bad CCD, misalignment of the scope, or satellite pointing issue? Was that detector totally FUBARed? Could it be saved!?!?!
Mundanely, a programmer reran the data with better handling of offsets and the distortion disappeared. It was just due to not compensating for the satellite rotation-- a space-borne version of the star trails any ground long exposure sees. On Earth, turn a camera onto the night sky for a long exposure and you'll see the stars trace out their path across the sky (due to Earth's rotation). Same thing happens on satellites, which not only orbit like the Earth, but rotate, reposition, and occassionally wiggle.
Only one scientist pegged it before the reprocess, and he's a pure theorist. I think that means he trusts the data less than the rest of us, and that's a good lesson to remember. Observational data is the basic measure of reality, yes, but even observations have issues. Seeing isn't believing-- knowing is.
Life as a Daytime Astronomer: Star Trails
By Alex "Sandy" Antunes | February 6th 2009 04:39 AM | Print | E-mail