IRAS stayed aloft for over a year gathering infrared data. The signals in the galactic plane were expected, but the signals in the ecliptic plane were surprising because a peakof emissions at about 20 microns was observed from dust, etc. in the ecliptic plane. Treating it as blackbody radiation and using the Wien displacement law, an effective temperature of about145 K was obtained for this solarsystem debris.

Some engineering details about IRAS
Estimation of temperatures from IRAS data.
Earth satellites
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Estimation of the temperature of solar system dust from IRAS infrared data

Using the Wien displacement law on the peak of the observed infrared emission:

Comparison plot

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The Technology of IRAS

The IRAS satellite was cooled by 720 liters of superfluid liquid helium which is pumped to keep the temperature at 1.6 K. The pumping uses the superfluid property, diffusing out through a porous brass plug to achieve the pumping. The helium vents are symmetric and matched to one part in 1000 to prevent the application of torque to the satellite.
Communication of data from the satellite was an interesting application of geosynchronous communication satellites.
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