Planck cooling system
The key elements of the Planck spacecraft's passive cooling system are the three V-groove thermal shields and the telescope baffle.
The V-grooves are a set of three specular, conical thermal shields with an opening angle of 5° between adjacent shields. They are located between the service module, which operates at ambient temperatures and houses all spacecraft's warm elements, and the telescope that is at about 50 K or -220 °C.
The Planck spacecraft with its characteristic V-grooves and telescope baffle (26 Feb 2009)
Each V-groove is composed of six 60° sections. The layout of the V-grooves with their reflective surfaces and the opening angle make them efficient insulators (any radiated heat is reflected out into space). The V-grooves are at progressively colder temperatures, dropping in three steps from the 300 K of the service module to about 45 K at the topmost V-groove, closest to the payload.
The telescope baffle surrounds the telescope and the focal plane. It is a high-efficiency radiator made of aluminium honeycomb and painted black on the outside. The baffle is fully reflective inside and also acts as a straylight shield, preventing unwanted radiation from entering the telescope and the instrument detectors located in the focal plane underneath the telescope's primary mirror.
Together, the baffle and V-grooves provide a thermal environment at about 45 K for the telescope and the focal plane units (FPU) of the LFI and HFI instruments. This passive cooling is an important pre-cooling stage for the active cooling system.
An important factor for the effectiveness of the spacecraft's passive cooling is that Planck is operated at the second Lagrange point L2 of the Sun-Earth system, where the lower side of the spacecraft is continuously oriented towards the Sun, keeping the V-grooves and the telescope always in the shadow with direct view to cold space.
||Active cooling system
Last Update: 17 Sep 2009