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R.L. Kremens (Questra Consulting), J.H. Kastner (Cernter for Imaging Science, Rochester Inst. of Technology), K.M. Merrill (National Optical Astronomy Observatory), C. Kaminski (Center for Astrophysical Research in Antarctica, U. of Chicago)
We report on observing conditions in the thermal infrared at the Center for Astrophysical Research in Antartica (CARA) South Pole observing site, using the 60-cm SPIREX telescope during the 1999 austral winter. The telescope was equipped with a 1024x1024 InSb ALADDIN focal plane array and support electronics. Our analysis concentrates on images of standard stars, skydip observations, and background measurements at L (3.5 microns) and L' (3.8 microns) wavebands. These calibration data were obtained in support of a general investigator program managed jointly by CARA and National Optical Astronomy Observatories and supported by a data pipeline reduction and analysis system developed and run at Rochester Institute of Technology.
During the 200 day observing season, nearly 13,000 raw images were captured in L, L', PAH, Ba, and H2 wavebands. Our investigation was undertaken primarily in L and L' wavebands, where close to 6,500 raw images were acquired. We demonstrate that the L-band background sky count rate alone provides an excellent metric of observing conditions in general and of photometric reliability in particular. Data of high photometric quality in L and L' wavebands (RMS deviation < 5 observing days. Finally, we describe a method that uses measurements of L-band background to correct photometry obtained under less than optimal observing conditions.
CARA is funded by a grant from the National Science Foundation.