9 January 1984 Test Results And In-Orbit Operation Of The Infrared Astronomical Satellite Circumvention Circuit
Author Affiliations +
The Infrared Astronomical Satellite (IRAS) is a satellite which is mapping the celestial sphere for infrared (IR) sources. One of the critical electronic circuits in the instrument is the circumvention circuit which eliminates the unwanted charged particle pulses from the IR signal. The circumvention circuit was designed to allow IRAS to function throughout its orbit and into part of the South Atlantic Anomaly (SAA), through most of the north and south polar horns, and in the presence of cosmic x-rays. This paper describes the operation of the circumvention circuit along with preflight and in-orbit testing. Ground testing of the brassboard circuit, using a simulated preamplifier output, showed the circuit would perform the circumvention function as designed. The initial testing of the IRAS flight circumvention, circuit and remaining electronics was done using ten prototype detectors and preamplifiers. This testing showed that the system noise exceeded the 0.5 millivolt detection threshold set for the circumvention circuit. Increasing the threshold to 2 millivolts was the only change required to the flight circumvention circuit. When all the flight detectors and preamplifiers became available the circuit was tested using a gamma source to simulate charged particle sources. With the low energy deposited in the detectors (20 keV average) the noise was reduced by up to 5 times with the circumvention circuit turned on. In-orbit results show the circumvention circuit decreases the unwanted charged particle background noise up to two orders of magnitude. The difference in the results with the circumvention off and on are so great that the science team has recommended that no data be taken with the circumvention circuit off. Figures are presented showing in-flight results with and without the circumvention circuit.
© (1984) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
E C Long, E C Long, D Langford, D Langford, } "Test Results And In-Orbit Operation Of The Infrared Astronomical Satellite Circumvention Circuit", Proc. SPIE 0445, Instrumentation in Astronomy V, (9 January 1984); doi: 10.1117/12.966156; https://doi.org/10.1117/12.966156


Infrared Astronomy Satellite
Proceedings of SPIE (September 26 1979)
Source Detection For The Infrared Astronomical Satellite
Proceedings of SPIE (November 20 1980)
A Telescope For The Infrared Astronomical Satellite (IRAS)
Proceedings of SPIE (November 14 1976)
Scanning infrared earth sensor for INSAT-II
Proceedings of SPIE (June 30 1991)

Back to Top