Flight performance of the Mid-Infrared Spectrometer on the Infrared Telescope in Space mission

Abstract

The mid-infrared spectrometer (MIRS) was one of four focal- plane science instruments that flew aboard the orbiting infrared telescope in space (IRTS). This telescope was a joint NASA/Japanese Scientific Space Agency (ISAS) project that was launched on March 18, 1995 aboard a Japanese HII expendable launch vehicle and was subsequently retrieved by the space shuttle. The telescope itself was liquid helium- cooled with a 15 cm aperture and surveyed approximately 7% of the sky over the course of its 26 day mission life before its cryogen expired and it began to warm up. The MIRS was developed jointly by NASA, the University of Tokyo, and ISAS and operated over a wavelength range of 4.5 to 11.7 microns with a spectral resolution of 0.23 to 0.36 microns. The MIRS has a conventional entrance aperture, so that spectral studies could be made of extended as well as point-sources. A cold shutter and an internal calibrator allowed accurate absolute flux determinations. The realized in-flight performance of the MIRS followed the pre-launch calibration performance as measured on the ground, with the exception of some degradation in the spectrometer throughput, some unanticipated detector behavior due to the passages through the South Atlantic anomaly, and to unavoidable observations of the moon.