Nimbus was a research program conducted by NASA in the 1960s and 1970s to study the Earth's atmosphere and weather via satellites in polar orbit. This artifact, an engineering protype of SIRS-A (Satellite Infrared Spectrometer), is representative of a key research instrument, called a sounder, used to measure temperature and water vapor at different levels in the atmosphere.
A SIRS-A sounder flew on Nimbus 3, launched in 1969, and was the first space-based instrument to acquire a temperature profile of the atmosphere. Its first reading occured over Kingston, Jamaica, which, as a test of the sounder's performance, was compared with readings acquired by a balloon radiosonde.
The National Oceanic and Atmospheric Administration transferred this artifact to the Museum in 1987.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.