One of astronomy's great orbiting observatories has breathed its last. On 14 January, the liquid helium cooling one of the two photon sensors onboard the Planck space telescope ran dry, ending a mission to map the big bang's echo.
The European Space Agency telescope has been measuring the cosmic microwave background (CMB) with unprecedented accuracy since 2009.
The helium was due to run out when it did. "The supplies lasted almost until the day we predicted when it first launched," says Jan Tauber of the European Space Research and Technology Centre in Noordwick, the Netherlands. He plans to operate the telescope's uncooled sensor for a further year to calibrate the observatory but the mission is effectively over.
Planck's data will help tease apart the large-scale structure of the universe and determine how it formed. It will also provide the most detailed views of nearer phenomenon, such as galactic dust and magnetic fields, which are superimposed on the spacecraft's view of the CMB. This data will be released in early 2013, once it has been processed.
Planck is the last in a line of observatories studying the CMB, which date back to 1989. As yet, there is no successor. "We want to know what the spacecraft will reveal before planning the next mission," says Tauber.
Justin Mullins, New Scientist