On 29 April 2013, the ESA Herschel Space Observatory ran out of liquid helium. Launched on 14 May 2009, the 3.5-m infrared telescope was the largest and most sensitive infrared space telescope. Operating from 55 to 670 microns, Herschel observed in the far-infrared and sub-millimetre parts of the electromagnetic spectrum, specifically designed to study the cool Universe – cold and dusty regions of our and other galaxies where stars form and astrochemistry in the interstellar medium. Herschel had three science instruments: two medium resolution cameras plus spectrographs: PACS (the Photodetector Array Camera and Spectrometer) and SPIRE (the Spectral and Photometric Imaging REceiver), and HIFI (the Heterodyne Instrument for the Far Infrared).
The 2300 litres of liquid helium was used to cool the instruments to nearly zero Kelvin to ensure that the instruments operated with great sensitivity. The mission was planned for three years and managed to last almost four. During that time, Herschel acquired 25,000 hours of data, covering 35 000 scientific observations from almost 600 programmes since science operations started in December 2009. The rich dataset, which is publicly available after a 12 month propriety period, will keep astronomers busy for many years to come!
For more details, see
- Herschel closes it eyes to the Universe, ESA Herschel press release
- Observation gives way to examination as Herschel coolant runs out, ESA Sci&Tech press release
- Herschel Science Centre, ESA website
- Herschel Space Observatory, UK outreach site