Cooldown of Planck flight model spacecraft
This plot shows the evolution of the temperatures of the different elements of Planck's cooling system during the cooldown of the spacecraft at Centre Spatial de Liège (CSL). The plot covers the period 17 June to 29 July 2008. The different elements are colour coded:
|Black graph:||Three V-grooves providing passive cooling to 50 K|
|Red graph:||Sorption cooler which reduces the temperature to 18-20 K for the HFI and LFI focal plane units (FPUs) respectively|
|Purple graph:||Joule-Thomson cooler brings the HFI FPU to 4 K|
|Blue graph:||3He and 4He tanks for dilution cooling the HFI bolometers to 0.1 K|
|Green graph:||The 1.6 K plate that lies within the 4 K enclosure of HFI FPU, used to keep different filters of the instrument at 1.6 K.|
A heat switch between two adjacent temperature stages can be used to thermally connect or thermally isolate the two stages. The times at which the heat switch between the 20 K and 4 K stage was switched on (thermally connecting) and off (isolating) is also indicated in this plot. The heat switch between the 4 K and 1.6 K stages was also switched on and off on several occasions, with the first and last time indicated in the plot.
After a stage reached its operational temperature it was maintained at that temperature, seen in this plot with the graphs of the different elements branching off at progressively lower temperatures.
A detailed plot of the 0.1 K stage (blue graph) reaching its operational temperature is available from the right-hand navigation under related images.