Planck/Herschel Cryogenic Testing from Elements to Spacecraft in CSL Premises 2004-01-2307
Both Planck and Herschel satellite are cryogenic payloads, the first one having a cold point around 0.1 [K], the second one around 0.3 [K]. Not only the detectors are cooled, but also major subsystems and systems of the spacecraft’s.
The Centre Spatial de Liège (CSL) is involved in the testing of several parts of the spacecraft’s, starting from optical tests on the mirrors or on the telescopes, going on with cryogenic vibration testing of scientific focal plane instruments, ending with the full Planck spacecraft testing. Each test requires temperature lower than 20 [K], in volumes ranging from 1 [m3] to 60 [m3], cooling down several kilograms to more than one ton, and withstanding heat load up to 150 [W] in stabilization.
These tests are done is 4 different facilities of CSL, linked to a common cold Helium network. This latter allows full flexibility for operation of the different facilities quasi independently. Dedicated specifications are fulfilled by adding at specific locations liquid Helium systems, providing colder and stable shroud panels.
All tests related to mirrors or telescopes are using optical metrology, with the dedicated problems due to very high stability and optical openings. The vibration testing has to find a specific compromise between support stiffness and thermal insulation. The overall spacecraft test challenge is very high, as it will be the unique way to check end-to-end the cooling chain of the spacecraft. The space conditions reproduction must be as perfect as possible to avoid the test set-up influence on the spacecraft performances, especially linked to radiative cooling and mechanical perturbations.
The different cryogenic set-up and tests to be done are presented, with a highlight on the specific challenges, and on the CSL solutions adopted.