Reaching 100 mK within the HFI focal plane unit
This plot shows the temperature evolution of the 100 mK stage within the High Frequency Instrument (HFI) focal plane unit as measured by the dedicated fine thermometers during the thermal balance test between 22 July and 6 August 2008.
The HFI bolometers require an operational temperature of 100 mK to achieve the required detector efficiency. Over a period of five weeks the Planck spacecraft and its payload were cooled down to operational temperatures and the 100 mK for HFI was finally reached on 22 July 2008 at 19:30 UT.
A plot of the temperature evolution of all the cooling system stages during the entire cooldown is available from the right-hand menu under related images. The cooldown was performed inside the FOCAL-5 chamber at Centre Spatial de Liège.