IRTS observation of the mid-infrared spectrum of the zodiacal emission

T. Ootsubo, T. Onaka, I. Yamamura, T. Tanabé, T. L. Roellig, K. W. Chan, T. Matsumoto

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16 Citations (Scopus)


We present the mid-infrared spectrum (3-12 μm) of the zodiacal emission obtained by the Infrared Telescope in Space (IRTS), the first Japanese cryogenically cooled orbital infrared telescope. The Near-Infrared Spectrometer (NIRS) on board IRTS provided the spectrum of 3-4 μm, while that of 4.5-11.7 μm has been observed by the Mid-Infrared Spectrometer (MIRS). In this paper we present the data reduction and results of the observations by MIRS. Spectra of the background emission at high galactic latitudes (ζbζ > 30°) have been extracted from the MIRS observations by excluding point sources. The observed sky brightness has a clear dependence on the ecliptic latitude, indicating that the zodiacal emission dominates in the mid-infrared sky brightness. On the other hand, the spectral shape does not show any appreciable dependence on the ecliptic latitude for β = 0°-75°. The spectrum combining the NIRS and MIRS observations can be fitted by a grey body radiation at 250 K, but excess emission is seen in the 3-6 μm range. Alternatively, the spectrum of the zodiacal emission can be reproduced fairly well by a grey body at 280 K with an excess around 10 μm. In this case the excess may be attributed to a silicate emission band. Other than these excesses, no spectral features above the 10% level are seen in the MIRS spectrum.

Original languageEnglish
Pages (from-to)507-511
Number of pages5
Journalearth, planets and space
Issue number6-7
Publication statusPublished - 1998
Externally publishedYes

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science


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