The European Space Agency’s Herschel telescope is nearing the end of its life as its helium coolant runs out, bring an end to three years of infrared spectrum discoveries.
Launched in 2009, the ESA Herschel telescope was designed solely to observe in the far infrared band of radiation, looking inside cold dust and gas clouds, determining the composition of atmospheres and looking for galaxy and planetary formation.
In order to look for signs of these, it was necessary to cool the instruments on Herschel to just above absolute zero (-273 degrees Celsius) by providing the instruments with a supply of liquid Helium. 2,300 litres of Helium was launched aboard Herschel in a giant thermos flask called a Cryostat. As the instruments were used they were kept cool by transferring their heat to the Helium which slowly but steadily boiled off until now, when there is little Helium left for observing.
It is not possible to predict the exact day the helium will finally run out, but confirmation will come when Herschel begins its daily 3-hour communication period with ground stations on Earth. The fatal moment will be indicated when telescope instrument temperatures rise suddenly over the course of only a few hours. All is not lost, however, as Herschel has managed about 22,000 hours of observing time which is about 10% more than was originally planned. All the observations were done in order of highest priority, leaving a great deal of data for astronomers to sift through and study, and even now Herschel is performing some last observations to exploit every last drop of helium left.
After the helium runs out, Herschel will be in ground contact for several months until May, when it is expected to be put into a long term (millions of years) stable parking orbit around the Sun.
You can read some of our stories connected with Herschel here.
Image Credit: European Space Agency