<title>Infrared And Visible Detector Electronics For The Infrared Astronomical Satellite (IRAS)</title>

Abstract

The Infrared Astronomical Satellite (IRAS) launched in January of 1983 utilizes a super-fluid helium cooled IR telescope and detector Focal Plane Array (FPA) to perform an all-sky survey in four wavelength bands from 8 to 118 micrometers. Temperatures at which different portions of the electronics must operate range from 2.5 to 280 K. The FPA consists of 62 infrared channels and 8 visible channels operating at 2.5 K. The IR detectors are grouped in eight 7 or 8 channel staggered linear suharrays with shared bias voltage; the visible detectors are grouped in two 4 channel skewed arrays, also with shared bias. Each IR channel detector is DC coupled to a TIA preamplifier through a very low power thermally isolated JFET source follower operating at approximately 65 K within the FPA housing. The TIA preamplifiers and bias supplies are located outside the telescope dewar and operate at approximately 280 K. The signal outputs from the preamplifiers are further processed by additional DC coupled gain amplifiers, filters and multiplexers prior to being digitized by a 16 bit analog to digital converter. The visible channel detectors are AC coupled to TIA preamplifiers and signal chain electronics using MOSFET source followers operating at approximately 2.5K within the FPA housing. This paper describes the detectors, preamplifiers and processing electronics, the system characterization test methods and results, and finally the performance of the detectors and electronics during the first month of on-orbit operation of the IRAS telescope.