European spacecraft prepared for safe, inert 'retirement'

Controllers of a European spacecraft said they fired its thrusters Monday to empty its fuel tanks, preparing to "retire" it in a permanently safe condition. The European Space Agency's Planck mission, which mapped the relic radiation from the Big Bang -- the Cosmic Microwave Background, or CMB -- in unprecedented detail, will be switched off in two days, a release from the Paris headquarters of ESA said. Planck has completed eight full-sky surveys using two instruments -- a high-frequency one and its low-frequency partner -- since its launch in 2009. Its high-frequency instrument exhausted its liquid helium supply in January 2012, with surveys since made with the low-frequency version before all science operation came to an end on Oct. 3. "In the past weeks, we've been working to prepare Planck for permanent safe disposal," said ESA's Steve Foley, Spacecraft Operations Manager at the European Space Operations Centre in Darmstadt, Germany. "This includes 'passivating' the spacecraft and placing it onto a disposal trajectory that will keep it in a parking orbit around the sun well away from the Earth-moon system for hundreds of years," he said. On Oct. 9 controllers commanded Planck to perform a two-day maneuver to begin slowly drifting away from Earth, and Monday's thruster burn was intended to deplete the spacecraft's fuel to render it inert. "We've already programmed the onboard software so that it will no longer try to automatically reactivate the transmitters, and next we will disconnect the batteries and disable the onboard protection mechanisms," Foley said. "The final step will be the simple act of switching off the transmitters: we will witness the silencing of Planck and we will never receive a signal from her again."