Planckearly results. II. The thermal performance ofPlanck

Abstract

The performance of the Planck instruments in space is enabled by their low operating temperatures, 20 K for LFI and 0.1 K for HFI, achieved through a combination of passive radiative cooling and three active mechanical coolers. The scientific requirement for very broad frequency coverage led to two detector technologies with widely different temperature and cooling needs. Active coolers could satisfy these needs; a helium cryostat, as used by previous cryogenic space missions (IRAS, COBE, ISO, Spitzer, AKARI), could not. Radiative cooling is provided by three V-groove radiators and a large telescope baffle. The active coolers are a hydrogen sorption cooler (<20 K), a 4 He Joule-Thomson cooler (4.7 K), and a 3 He-4 He dilution cooler (1.4 K and 0.1 K). The flight system was at ambient temperature at launch and cooled in space to operating conditions. The HFI bolometer plate reached 93 mK on 3 July 2009, 50 days after launch. The solar panel always faces the Sun, shadowing the rest of Planck, and operates at a mean temperature of 384 K. At the other end of the spacecraft, the telescope baffle operates at 42.3 K and the telescope primary mirror operates at 35.9 K. The temperatures of key parts of the instruments are stabilized by both active and passive methods. Temperature fluctuations are driven by changes in the distance from the Sun, sorption cooler cycling and fluctuations in gas-liquid flow, and fluctuations in cosmic ray flux on the dilution and bolometer plates. These fluctuations do not compromise the science data.

Nuclear spin assisted quantum tunnelling of magnetic monopoles in spin ice

“…However, it is more problematic to cool samples containing Ho, due to the large Ho nuclear spin which results in a Schottky heat capacity of 7 J mol −1 K −1 at 300 mK. Indeed this anomaly has been exploited by the Planck telescope where the bolometers are attached to the cold plate by yttrium–holmium feet thus allowing passive filtering with a several hour time constant that was crucial to the operation of the system 21 . For Ho 2 Ti 2 O 7 this means difficulty in cooling.…”

Exploring cosmic origins with CORE: The instrument

“…In the 60-600 GHz frequency range this corresponds to minimum background loads in the range of 100-200 fW. Achieving this sensitivity requires continuously cooling the detector array to ∼ 100 mK, and the mirrors down to 40 K-100 K. The CORE cryogenic chain leverages on the ultra-low temperature space missions heritage (Planck [57], Hitomi) and ongoing developments (MIRI/JWST, XIFU/Athena) to succeed. The CORE cryogenic architecture minimizes the development risk for a continuous low temperature cooling chain, and is open to potential evolutions of the instrument needs or configurations during the phase-A study.…”

“…This passive cooling system is made possible by the large surface area of the instrument baffle. With our telescope configuration, V-Grooves similar to the ones proposed for the Planck mission [57], or the SPICA [59] and Ariel studies, can be re-proposed. Given the impact of the scan strategy on the requirements for these V-grooves, their optimization is discussed in detail in the mission companion paper [5].…”

Dense Dark Matter Hairs Spreading Out From Earth, Jupiter, and Other Compact Bodies

“…One highly developed technology for space missions is refrigeration for experiments requiring very low temperatures typical of axion searches (Asztalos et al 2010). The cosmic microwave background (CMB) Planck satellite mission relied on active cooling to lower the temperature of the High Frequency Instrument bolometer plate to 93 mk (Ade et al 2011) which is similar to the temperature goal for the ADMX apparatus upgrade. Generally speaking, axion searches and CMB space telescopes broadly share a reliance on microwave science and engineering which would make it more likely that a space-based axion detection mission could recycle welltested CMB technology.…”