IRAS (shown here by its engineering mockup in the National Air and
Space Museum) carried a 60-cm, cryogenically cooled telescope into
sun-synchronous orbit for an 11-month mission in 1983. Its detectors
scanned the sky at 12, 25, 60, and 100 microns (1,000 microns = 1 mm),
detecting as many as a million sources of far-infrared radiation and
at one stroke making far-IR astronomy a rational field of inquiry.
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