NASA’s Herschel Space Observatory Shuts Down

As of April 29, NASA’s Herschel space observatory has exhausted its supply of liquid helium coolant, ending its more than three years of observations of the universe. The mission began with over 2,300 liters of liquid helium, which has been slowly evaporating since Herschel’s launch on May 14, 2009. The liquid helium was essential to cool the observatory’s instruments to close to absolute zero. Herschel’s detectors were designed to pick up the glow from celestial objects with infrared wavelengths as long as 625 micrometers, which is 1,000 times longer than what we can see with our eyes. Because heat interferes with these devices, they were chilled to temperatures as low asminus 271 degrees Celsius using the liquid helium.

During its operations, Herschel made over 35,000 scientific observations and collected more than 25,000 hours worth of science data.