This was all planned, but somehow it is still sad: European Space Agency’s Herschel space telescope is officially dead, its observations have been brought to a permanent end. HSO has exhausted all of its cryogen, there is no more superfluid liquid helium in the cryostat. This ends the more than three years of pioneering observations of the cool Universe, ESA reports.
The Herschel telescope allowed astronomers to look deep into space by detecting light emitted in the far-infrared and sub-millimetre regions of the spectrum. Earth's atmosphere prevents most of this light from reaching ground-based telescopes, but Herschel could see the coldest and dustiest objects in space: cool star formations, massive black holes and dusty galaxies with newborn stars.
The Herschel telescope is a classic Cassegrain design with a 3.5-m primary mirror — the largest ever launched into space — and a smaller secondary mirror. From orbit around the second Lagrange point of the Sun-Earth system, L2, 1.5 million kilometres from Earth, Herschel bridges the gap between previous infrared observatories and ground-based radio telescopes. This picture of the satellite was taken during testing at ESA’s European Space Research and Technology Centre, ESTEC, the Netherlands. Photo: ESA.
At 15:12:02 CEST on 14 May 2009, at the beginning of a 55-minute launch window, the Herschel and Planck satellite pair lifted off on board an Ariane 5 from Europe’s Spaceport in French Guiana. Photo: Optique Video CSG, P. Baudon/ESA/CNES/ARIANESPACE
The Herschel cryostat was filled up and superfluid helium was produced in Kourou in April 2009. A final helium top-up was done just a day before the 14 May 2009 launch. In July 2009, only two months after launch when Herschel had thermalised in space, the "In-Orbit Commissioning Review" took place. A lifetime prediction based on the thermal mathematical model and measured inflight temperatures was provided by industry. It predicted end-of-helium end of February 2013, but with an error bar of more than half a year. So every single day in operation since February was a gift.
Here are a few images we thank to Herschel:
Baby stars in the Rosette Cloud
Close-up of the Aquila / W40
Galactic plane at L=316 deg
Herschel’s view of the Horsehead Nebula
Jets Carve Out Big Hole
Stellar Gestation and Birth in the Milky Way
The spine of the swan
The star Fomalhaut and its debris disc
All images by ESA/OSHI