Planck’s Spacecraft Operations Manager, Steve Foley, at ESOC sent in this note on Saturday, 12 October. He mentions the Sorption Cooler; Planck’s H2 Sorption Cooler is the first stage of the active cryogenic chain.

The Planck H2 Sorption Cooler is the first stage of the active cryogenic chain: its task is to maintain the LFI down to the operating temperature while providing a pre-cooling stage for the HFI refrigerators.

The Planck H2 Sorption Cooler is the first stage of the active cryogenic chain: its task is to maintain the LFI down to the operating temperature while providing a pre-cooling stage for the HFI refrigerators.

Its task is (was) to maintain the LFI instrument down to the operating temperature while providing a pre-cooling stage for the HFI refrigerators.

Steve’s wrote:

Another significant moment in the mission tonight as we stopped the Sorption Cooler, the last active cooler of Planck, and start the warm-up to the passive temperature of the payload module of around 46K. Cooler was transitioned to READY Mode at 17:30Z. Pressure in the cooler is dropping and the warm up has commenced.

It’s a milestone in the sad but necessary shut down of a magnificent mission! In a follow up mail, Steve added;

[Planck’s] exquisite dataset lives on and will feed many minds and solve many puzzles, as well as presenting many challenging questions, for many many years to come. This is our heritage. Well done Planck!