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Far Infrared Absolute Spectrophotometer (FIRAS)

NSSDCA ID: 1989-089A-01

Mission Name: COBE
Principal Investigator:Dr. John C. Mather

Description

The far-IR absolute spectrophotometer (FIRAS) is a cryogenically cooled polarizing Michelson interferometer used as a Fourier transform spectrometer. The instrument points along the spin axis and has a 7-deg field of view. This device measures the spectrum to a precision of 1/1000 of the peak flux at 1.7 mm for each 7-deg field of view on the sky (over the range 0.1 to 10 mm). The FIRAS uses a special flared trumpet horn flux collector having very low sidelobe levels and an external calibrator covering the entire beam; precise temperature regulation and calibration are required. The instrument has a differential input to compare the sky with an internal reference at 3 deg K. This feature provides immunity from systematic errors in the spectrometer, and contributes significantly to the ability to detect small deviations from a blackbody spectrum. The instrument weighs 60 kg, uses 84 W and has a data rate of 1200 bps.

Alternate Names

  • COBE/FIRAS
  • FIRAS

Facts in Brief

Mass: 30 kg
Power (avg): 84 W
Bit rate (avg): 1.2 kbps

Funding Agency

  • NASA-Office of Space Science (United States)

Discipline

  • Astronomy: Infrared

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Samuel GulkisOther InvestigatorNASA Jet Propulsion Laboratorysamuel.gulkins@jpl.nasa.gov
Dr. Rainer WeissOther InvestigatorMassachusetts Institute of Technologyweiss@ligo.mit.edu
Dr. George F. Smoot, IIIOther InvestigatorLawrence Berkeley Laboratoriessmoot@astra.lbl.govsmoot@cosmos.lbl.gov
Dr. David T. WilkinsonOther InvestigatorPrinceton University
Dr. Michael G. HauserOther InvestigatorNASA Goddard Space Flight Centerhauser@stsci.edu
Dr. John C. MatherPrincipal InvestigatorNASA Goddard Space Flight Centerjohn.c.mather@nasa.gov

Selected References

  • Mather, J. C., et al., Early results from the far infrared absolute spectrophotometer (FIRAS), in "After The First Three Minutes" AIP Conference, Preprint No. 90-06, Proc. 222, pp. 161-178, doi:10.1063/1.40411, Oct. 15-17, 1990.
  • Wright, E. L., Preliminary results from the FIRAS and DIRBE experiments on COBE, Preprint No. 91-05, Proc. The Infrared and Submillimetre Sky After COBE, Les Houches, doi:10.1007/978-94-011-2448-5_13, Mar. 1991.
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