CRYOGENIC ASPECTS OF ISOPHOT, THE PHOTOMETER FOR THE ISO SATELLITE

ISOPHOT is a focal plane instrument aboard the European Infrared Space Observatory (ISO) satellite to be launched in 1995. This versatile astronomical instrument allows for photometry, polarimetry, spectrophotometry and imaging in the far infrared region. Because its highly sensitive detectors are operated in the 1.8-3.2 K range, several cryogenic devices such as filter change wheels, a chopper and electrical components have been developed and space qualified. Stringent requirements had to be met in terms of opto-mechanical precision, low heat dissipation, minimal number of electrical drive lines, high reliability and tolerance against vibrational loads. Test equipment has been developed to verify the performance under simulated cryogenic and low photon background conditions and to calibrate the instrument.