Operations and Performance of the PACS Instrument 3He Sorption Cooler on board of the Herschel Space Observatory

摘要

A 3He sorption cooler produced the operational temperature of 285mK for thebolometer arrays of the Photodetector Array Camera and Spectrometer (PACS)instrument of the Herschel Space Observatory. This cooler provided a stablehold time between 60 and 73h, depending on the operational conditions of theinstrument. The respective hold time could be determined by a simple functionalrelation established early on in the mission and reliably applied by thescientific mission planning for the entire mission. After exhaustion of theliquid 3He due to the heat input by the detector arrays, the cooler wasrecycled for the next operational period following a well established automaticprocedure. We give an overview of the cooler operations and performance overthe entire mission and distinguishing in-between the start conditions for thecooler recycling and the two main modes of PACS photometer operations. As aspin-off, the cooler recycling temperature effects on the Herschel cryostat 4Hebath were utilized as an alternative method to dedicated Direct Liquid HeliumContent Measurements in determining the lifetime of the liquid Helium coolant.