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Mid-Infrared Spectrometer (MIRS)

MIRS had 32 discrete Si:Bi photoconductor detectors. The output signals of 32 detectors were multiplexed by two multiplexers in the cold stage and sent to he warm electronics. The signals were read by the integrating amplifiers. The amplifiers were automatically reset when the signal of one of the two channels most sensitive to the zodiacal emission(#15: 7.765 μm and #16: 7.990 μm channels) became 75% of the maximum in ADU (16 bits). Each detector was read every 0.512 sec (2Hz mode) or 1.024 sec (1Hz mode) depending on the telemetry rate. In the first period of the observations the low rate (1Hz mode) was used occasionally, but in the later phase of the mission the data were read all in the 2Hz mode. The period of 0.512 sec corresponded to about 2' on the sky at the scan rate of the IRTS. Therefore for those areas observed at the low sampling rate the data had less spatial information. The sampling speed of each individual detector was 2 msec. Since the aperture size of MIRS was 8' x 8', the difference in the signal acquisition timing of the detectors was negligible.


Wavelength range4.495 - 11.703 micron
Resolution0.23 - 0.36 micron
Size210 x 137 x 75 mm3 (overall)
Weight805 g
Electrical power dissipation Cold electronics : 4 mW
Warm electronics : 2.9 W
Detectors32 Si:Bi photoconductors, Aerojet Electro Systems
Entrance Aperture1.4 x 1.4 mm2 (0.14 x 0.14 deg2 on sky)
Integrating AmplifiersModel JF-4, IR Labs
Cold MultiplexersCD4067B, RCA Electronics Corp.
Warm electronics packageHamamatsu Photonics K.K.
MIRS data rate 1188 bits/sec (standard operating mode)
594 bits/sec (reduced data-rate mode)
Photograph of the MIRS
Photograph of the MIRS


For more details, refer to the following documents.

MIRS Explanatory Supplement [PDF]

"Flight performance of the Mid-Infrared Spectrometer (MIRS) on the Infrared Telescope in Space mission"
T. L. Roellig, K. Mochizuki, T. Onaka, T. Tanabe, and I. Yamamura
1996, in SPIE Proc.2817, Infrared Spaceborne Remote Sensing IV ed. M. S. Scholl and B. F. Andresen, p.258-266 [ SPIE ] [ ADS ]
"The Mid-Infrared Spectrometer on the Infrared Telescope in Space (IRTS) Mission"
Thomas L. Roellig, Takashi Onaka, Thomas J. McMahon, and Toshihiko Tanabe
1994, The Astrophysical Journal, vol.428, p. 370-376 [ ADS ]

Last Modified: 20 July 2023