Yesterday it was afternoon at ESA’s ESOC (European Space Operations Centre of ESA) in Darmstadt, Germany, when the last command was sent to the Planck Surveyor, the space telescope that provided us with the most detailed map of the early universe. This marked the end of its mission after being “parked” into a heliocentric orbit.

The Planck project was developed in collaboration with NASA after the merger of the projects COBRAS, which became the Low Frequency Instrument (LFI) instrument, and SAMBA, which became the High Frequency Instrument (HFI) instrument. It’s the successor of other missions which in previous years examined the cosmic background radiation.

The Planck space telescope was launched on May 14, 2009 atop an Ariane 5 rocket together with another important astronomical instrument, the Herschel space telescope. Both were placed on Lissajous orbits in the second Lagrange point of the Sun-Earth system, about one and a half million kilometers (about 930,000 miles) from Earth.

Planck’s instruments of  were cooled to very low temperatures with a sophisticated system to limit the amount of electromagnetic radiation emitted by them, thus avoiding interference with their operation: LFI was brought to a temperature of about 20 Kelvin, HFI down to 0.1 Kelvin.

The major findings of the Planck Surveyor mission arrived in March 2013, when ESA presented a map of the early universe created thanks to the surveys of this space telescope. It’s a result that had important consequences in astrophysics and will affect the search for much longer.

The HFI instrument became unusable in January 2012 with the depletion of liquid helium that refrigerated it. The LFI instrument was still used until the beginning of October 2013. After the end of its scientific operations, ESA started the complex process for putting the Planck Surveyor into hibernation.

The propellant still available was used to move Planck. The procedure called in jargon passivating was initiated with the disconnection of the batteries, the trasmission system switch off and the complete emptying of the tanks of propellant and refrigerant.

In the end, a final version of the software has been loaded to inhibit the possibility of radio transmission for the Planck Surveyor. At that point, the space telescope has become a dead body drifting around the Sun. It accomplished its mission in an extraordinary way and scientists will keep on examining the data it collected for a long time.

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