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End in sight for Herschel Space Telescope

Ben Gilland
Feb 21, 2012, 0:00 UTC

The Herschel Space Observatory has entered what could be its last year of service.

Launched by the European Space Agency (ESA) in 2009, Herschel boasts the biggest mirror ever launched into space and can pierce the dustiest and earliest stages of planet, star and galaxy formation.

For visible-light telescopes like Hubble, the coolest objects in the universe appear as dark blobs (or not at all) making it impossible to find out what happens within.

Herschel sees the Universe in the far-infrared spectrum and, as such, has been able to see objects as cold as -263 Celsius. This has allowed the telescope to pierce cold clouds of dust and gas to study the newborn stars hiding within.

But to see super-cold objects, Herschel has to be kept at an even colder -271 Celsius, otherwise its own heat would obscure its readings.

To keep its instruments at this temperature, Herschel relies upon its supply of liquid helium, which cools the craft by evaporating at a rate of about 200g per day.

The telescope now has only 100kg of helium remaining – meaning that the craft will run out in about a year.

Unlike Hubble, which, at a mere 600km (373 miles) above Earth, is close enough to be serviced, Herschel is positioned 1.5 million kilometres from Earth.

At this distance, a helium top-up is out of the question and, when it is all gone, the craft’s temperature will rise and Herschel will go blind.