NEAR-INFRARED CAMERA WITH A HGCDTE 128X128 ARRAY AT THE CRL-1.5M TELESCOPE

An infrared camera has been designed and constructed for the 1.5 m tel escope of the Communications Research Laboratory (CRL) using a 128 x 1 28 HgCdTe array detector with a switched C-MOS multiplexer (TCM 1000B) . The large storage capacity (3 x 10(7) e-) of the array is advantageo us for astronomical observations with long exposure in order to store many photo-electrons and under high-background conditions. We have des igned a cooled optical system with a field of view of 4'.2 x 4'.2 and a resolution of 2'' pixel-1 at the Nasmyth focus of the telescope. The large field of view is important for studying large extended astronom ical objects. The cooled optical system and a kTC-noise limited readou t circuit has achieved high efficiency of the camera system. The array detector has been found to have a small nonlinearity in the responsiv ity, increasing with the stored charge, which is different from a decr ease of the responsivity due to a change in the capacitance of detecto r, which is common in arrays without an external integration capacitan ce. The magnitudes of infrared standard stars taken by this infrared c amera at the CRL 1.5 m telescope are compared with those of the CIT (C alifornia Institute of Technology) system, in which observations were made using a single detector; the magnitude and color transformation f ormulas were obtained as a function of infrared colors. The difference between the two photometric systems is small in both magnitude and co lor. The infrared camera system has been used to take two-dimensional infrared images of galaxies, planets, and comets, and has also been co mbined with a Fabry-Perot spectrometer to observe interstellar gas in a star-formation region and a supernova remnant.