This document was directly transfered over and combined from the PDS3 IRAS catalog spacecraft description files. PDS_VERSION_ID = PDS3 RECORD_TYPE = "STREAM" LABEL_REVISION_NOTE = " 2003-10-07, S.McLaughlin, Added paragraphs for satellite attitude and optical system; moved instrument summary to INSTRMNT.CAT. 2004-12-15, S.McLaughlin, Resolved liens. " OBJECT = INSTRUMENT_HOST INSTRUMENT_HOST_ID = "IRAS" OBJECT = INSTRUMENT_HOST_INFORMATION INSTRUMENT_HOST_NAME = "INFRARED ASTRONOMICAL SATELLITE" INSTRUMENT_HOST_TYPE = "SPACECRAFT" INSTRUMENT_HOST_DESC = " Instrument Host Overview ======================== The IRAS satellite consisted of two main parts, the spacecraft and the telescope system. The overall dimensions of the satellite with deployed solar panels were 3.60 meters in height, 3.24 meters in width, and 2.05 meters in depth. The mass of the satellite at launch was 809 kilograms. The satellite attitude was controlled by three orthogonal reaction wheels. Excess momentum was dumped by magnetic coils to the Earth's magnetic field as necessary. The attitude, and changes in attitude, were sensed by a combination of a horizon sensor, a sun-sensor, and three orthogonal gyros. The z-axis gyro was used in all modes of control and was duplicated to provide a redundant backup. The telescope system comprised the upper part of the satellite. The system was mounted within a toroidal superfluid helium tank, which in turn was mounted within the evacuated main shell. The telescope was a f/9.6 Ritchey-Chretien design with a 5.5 meter focal length and a 0.57 meter aperture. The mirrors were made of beryllium and cooled to approximately 4 K. The optical system was protected from contamination before launch and during the first week of the mission by an aperture cover cooled with supercritical helium. After the cover was ejected, the sunshade limited heat flow to the aperture by blocking direct solar radiation and reflecting away terrestrial infrared radiation. The telescope was cooled by contact with the superfluid helium tank to temperatures ranging from 2 to 5 K. The surfaces of the sunshade which could be viewed by the telescope aperture were cooled by a three-stage radiator to about 95 K. The focal plane assembly contained the survey detectors, visible star sensors for position reconstruction, a Low Resolution Spectrometer (LRS) and a Chopped Photometric Channel (CPC). The focal plane assembly was located at the Cassegrain focus of the telescope and was cooled to about 3 K. The survey array consisted of 62 rectangular infrared detectors arranged in staggered rows such that any real point source crossing the focal plane as the satellite scanned would be seen by at least two detectors in each wavelength band. Most of the detectors in each band had standard size apertures, with one or two being half-sized. The LRS was a slitless spectrometer sensitive from 7.5 to 23 microns with a resolving power of about 20. The CPC operated during some pointed observations. It mapped sources simultaneously at 50 and 100 microns, and used a cold internal chopper for flux reference. However, the focal plane temperature was lower than expected, which resulted in CPC detector anomalies that rendered CPC data very difficult to use. For more information about the instrument, see Beichman et al. 1988 [BEICHMANETAL1988] and Neugebauer et al. 1984 [NEUGEBAUERETAL1984]." END_OBJECT = INSTRUMENT_HOST_INFORMATION OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = { "BEICHMANETAL1988", "NEUGEBAUERETAL1984" } END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO END_OBJECT = INSTRUMENT_HOST END PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "NULL" OBJECT = INSTRUMENT_HOST INSTRUMENT_HOST_ID = "IRAS" OBJECT = INSTRUMENT_HOST_INFORMATION INSTRUMENT_HOST_NAME = "INFRARED ASTRONOMICAL SATELLITE" INSTRUMENT_HOST_TYPE = "SPACECRAFT" INSTRUMENT_HOST_DESC = " Instrument Host Overview ======================== The Infrared Astronomical Satellite (IRAS) was a spacecraft with a telescope mounted in a liquid helium cooled cryostat. The telescope was a f/9.6 Ritchey-Chretien design with a 5.5 m focal length and a 0.57 m aperture. The mirrors were made of beryllium and cooled to approximately 4 K. The focal plane assembly contained the survey detectors, visible star sensors for position reconstruction, a Low Resolution Spectrometer (LRS) and a Chopped Photometric Channel (CPC). The focal plane assembly was located at the Cassegrain focus of the telescope and was cooled to about 3 K. The survey array consisted of 62 rectangular infrared detectors arranged in staggered rows such that any real point source crossing the focal plane as the satellite scanned would be seen by at least two detectors in each wavelength band. Most of the detectors in each band had standard size apertures (see table below), with one or two being half-sized. The LRS was a slitless spectrometer sensitive from 7.5 to 23 microns with a resolving power of about 20. The CPC operated during some pointed observations. It mapped sources simultaneously at 50 and 100 microns, and used a cold internal chopper for flux reference. However, the focal plane temperature was lower than expected, which resulted in CPC detector anomalies that rendered CPC data very difficult to use. Instrument Summary ------------------ In the table below, the center wavelengths are in microns. For the survey array, the FOV is determined by the rather large detector mask size and is roughly the native 'resolution' of the data in that band. The resolution of the IRAS image data is not governed by the resolution of the telescope, which was diffraction limited longwards of 12 microns, but by the size of the detectors. ------------------------------------------------------------------ SURVEY ARRAY Center # working FOV Bandpass Detector Average 10-sigma Wavelength detectors (arcmin) (micron) Material Sensitivity (Jy) 12 16 .75 x 4.5 8.5- 15 Si:As 0.7 25 13 .75 x 4.6 19 - 30 Si:Sb 0.65 60 15 1.5 x 4.7 40 - 80 Ge:Ga 0.85 100 13 3.0 x 5.0 83 -120 Ge:Ga 3.0 ------------------------------------------------------------------ CPC Center # working FOV Bandpass Detector Average 10-sigma Wavelength detectors (arcmin) (micron) Material Sensitivity (Jy) 50 1 1.2 41 - 63 Ge:Ga 7.0 100 1 1.2 84 -114 Ge:Ga 7.0 ------------------------------------------------------------------ LRS Slit width Wavelength Range Detector Resolving (arcmin) (micron) Material Power 5.0 8 - 13 Si:Ga 14-35 7.5 11 - 23 Si:As 14-35 ------------------------------------------------------------------" END_OBJECT = INSTRUMENT_HOST_INFORMATION OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "NEUGEBAUERETAL1984" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "BEICHMANETAL1988" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO END_OBJECT = INSTRUMENT_HOST END