Sky Substraction

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Once flat-fielded, the 1 or 2 min frames have been sky subtracted. Thejitter data reduction procedure estimates the low-frequency infrared skyfrom the input data set by discriminating sky from object signal on atemporal basis, assuming the offsets between frames are correctlyscattered. One estimated sky frame is produced per input raw frame fromtypically ten time adjacent frames. They are immediately subtractedout to produce a sky-cleaned set of frames.