A problem with the SKYRAD IRT that itermittantly produced a gradual increase in the sky
temperature measurement then a sudden correction, as compared to AERI, appears to have been
caused by a combination of a failing IR detector, a poor signal cable, a contaminated
(with condensation or frost) mirror or lens, and low ambient temperatures. The positive
bias was apparently not consistant in either frequency or duration but on days when the
unusual behavior is observed, it usually occurred from about 00:00 to 06:00 local time.
The instrument was repaired and recalibrated and the signal cable replaced.