Herschel has been a fantastically successful mission, and the best is most definitely yet to come as the various teams working on Herschel data stop dealing with the torrent of new observations and are able to delve deeper into what they’ve got. But we always knew that its life was limited. The instruments need to be kept very cold – our own instrument SPIRE needs its detectors cooled to 0.3 K to work – and a reservoir of liquid Helium is used for this. But the Helium is limited, and we’re now getting to the point where the Helium is running out.
When the Helium is gone, the instruments can’t work and the mission is over.
Herschel was launched in May 2009 and had a design lifetime for the Helium of 3 and a half years, allowing full science operations for 3 years. We’ve done rather better than that, but things can’t go on forever. Current estimates suggest that the Helium will be gone in the next few weeks.
Work doesn’t stop there. We in the instrument teams will be pulling all the observations and calibration together to produce a uniform, well processed archive for the future. Herschel is sure to have a huge legacy, some hints of it can be found here, and I fully expect it to match the legacy of the IRAS satellite, launched in 1984, whose data I use nearly every day.
What do we do next? There are ground-based instruments like SCUBA2, working at the JCMT in Hawaii, that work in a similar waveband – though JCMT itself is threatened with closure – and followup with the wonderful new ALMA telescope provides some fantastic new possibilities.
But the far-infrared bands that Herschel observes can only be observed from space. Future missions are planned, the closest of which is the Japanese led SPICA mission, which should have significant ESA involvement. This isn’t yet fully funded, but hopefully things will clarify over the next year. Sadly the UK has not yet decided to back this project, so we risk losing the technological and scientific base that has grown over the last 20 years in far-IR and submm astronomy, thanks to Herschel, SCUBA, JCMT and other projects. Beyond SPICA are ambitious projects such as FIRI, unsuccessfully proposed for the first ESA Cosmic Visions large mission, but now being brought up to speed as a candidate for round two.
It will be sad to see Herschel go, but it will leave us a lot of work to be getting on with, and plenty more results for me to report here.
Many thanks to Colum whose email subscription to this blog saved this vanished post!