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Infrared Array Camera

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Here is a four-band IRAC image. Because its near-to mid infrared, the wavelengths the cameera see's are mapped to the visible colors that humans see for an image (See False color). In this image of the Trifid nebula 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8.0 microns (red).
IRAC filters

Infrared Array Camera (IRAC) is an instrument on the Spitzer Space Telescope.[1] It is an electronic infrared camera for astronomical imaging, and it can detect from the near to mid infrared.[2] The sensor can detect light with a wavelength of 3 microns to 8 microns when chilled.[3] The detectors have a resolution of 256 by 256 pixels, and there is four detectors that view four bands at the same time.[4][5] Each detector has 65000 pixels, which was a big increase over previous infrared telescopes.[6] The IRAC detector takes in light from the telescopes reflecting optics, which consits of a primary and secondary mirror made of beryllium metal.[7] IRAC was used with four bands until May 15, 2009 when the crygogen was depleted, and then as a 2-band camera until at least 2017.[8] The telescope has slowly drifted farther and farther from the Earth, and as of October 2016 entered its beyond mission, in which it faced increased challenges.[9]

Light bands IRAC can observe in wavelength microns:[10][11]

  • 3.6
  • 4.5
  • 5.8
  • 8.0

It can view all four wavelength bands at the same time, whats called a broad-band image.[12] The 3.6 and 4.5 micron bands use InSb (Indium antimonide) detectors, and the 5.8 and 8 micron bands use Si:As (Silicon doped with Arsenic) detectors[13][14][15] The 3.6 and 4.5 wavelengths band could be operated when the coolant runs out and the telescope warms up, whereas the 5.8 and 8 microns wavelength bands operated only when the coolant chilled the telescope to even colder temperatures.[16] The IRAC instrument is contained in the Spitzer Multiple Instrument Chamber with several other pieces of technology, including the other focal plane instruments.[17] In the MIC is the Infrared Array Camera, Infrared Spectrograph, and Multiband Imaging Photometer as well as the pointing calibration reference sensor.[18] The MIC is attached to the cryostat and it is intended to keep the science instruments cold, including IRAC, but also to keep stray light.[19] The IRAC, inside the MIC, is enclosed with the outer shell of the spacecraft/observatory, which also has a thermal shield to help keep the telescope cool.[20] Like the rest of the Spitzer, IRAC was launched into space in 2003 into a Earth-trailing heliocentric orbit (it is orbiting the Sun not Earth).[21]

Once the cryostat ran out the 3.6 and 4.5 bands stabilized to a temperature 28.7K, however they have nearly the same sensitivity as during the cold mission.[22] The telescope does operate a different temperature after the warm-up but it is still possible to be used for observations, and those bands could continue to be used.[23]

References

  1. ^ "The Infrared Array Camera (IRAC) - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  2. ^ "The Infrared Array Camera (IRAC) - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  3. ^ "The Infrared Array Camera (IRAC) - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  4. ^ [1]
  5. ^ [2]
  6. ^ "Infrared Detector Developments - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  7. ^ "Infrared Detector Developments - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  8. ^ [3]
  9. ^ [4]
  10. ^ Fazio, G. G.; team, the IRAC (2004-09-01). "The Infrared Array Camera (IRAC) for the Spitzer Space Telescope". The Astrophysical Journal Supplement Series. 154 (1): 10–17. doi:10.1086/422843. ISSN 0067-0049.
  11. ^ "The Infrared Array Camera (IRAC) - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  12. ^ Fazio, G. G.; team, the IRAC (2004-09-01). "The Infrared Array Camera (IRAC) for the Spitzer Space Telescope". The Astrophysical Journal Supplement Series. 154 (1): 10–17. doi:10.1086/422843. ISSN 0067-0049.
  13. ^ Fazio, G. G.; team, the IRAC (2004-09-01). "The Infrared Array Camera (IRAC) for the Spitzer Space Telescope". The Astrophysical Journal Supplement Series. 154 (1): 10–17. doi:10.1086/422843. ISSN 0067-0049.
  14. ^ [NULL]. "Spitzer: IRAC Instrument Handbook". irsa.ipac.caltech.edu. Retrieved 2017-01-12.
  15. ^ "The Infrared Array Camera (IRAC) - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  16. ^ "The Infrared Array Camera (IRAC) - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  17. ^ "The Multiple Instrument Chamber - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  18. ^ "The Multiple Instrument Chamber - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  19. ^ "The Multiple Instrument Chamber - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  20. ^ "The Outer Shell - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  21. ^ "Clever Choice of Orbit - NASA Spitzer Space Telescope". NASA Spitzer Space Telescope. Retrieved 2017-01-12.
  22. ^ [5]
  23. ^ [6]

See also

  • NIRCam (planned JWST camera for 0.6 to 5 micron light)
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