Space environment and detection : lessons learned from PLANCK/HFI

1. Space environment and detection : lessons learned from PLANCK/HFI François PAJOT Institut d'Astrophysique Spatiale Beyond CoRE, June 26th 2012

2. Introduction • Planck/HFI first mission with • NEP ~10-17 WHz-1/2 bolometers • 100 mK uninterrupted operation for nearly 30 months • 0.01 Hz- 100 Hz flat noise requirement • polarization sensitive bolometers • high precision calibration • at SE Lagrangian L2 • Outline • cosmic rays interactions • impact on design and tests • EMI/EMC • note on ground calibrations (spectral, ADC,...)

3. Glitches

4. Planck/HFI data processing glitches templates glitches removal 1 s

5. High glitch rate on bolo and thermo 100/mn

6. Cosmic ray impact on HFI • CR on detectors • thermometer • grid • wafer • CR on 100 mK plate • CR secondary and showers • higher energy CR interacting with HFI or satellite then with bolometers or 100 mK plate • correlated events on many bolometers, big events on the 100 mK plate (elephants: still lacking an interpretation)

7. CR on bolometers • Cosmic Rays primary and secondary, hits thermometer, grid and wafer • NEP ~10-17 WHz-1/2 means sensitivity down to a few 10 eV on grid or thermometer, but tens of keV on the wafer

8. CR on bolometers total short very long long

9. CR hits impact on 100 mK stage • Low frequency thermal fluctuations • CR hits on bolometer housing (many s) • CR hits and showers on bolometer cold plate (10 s and more) • CR hits on thermometers used by the PIDs (depends on PID)

10. Cosmic ray hits on 100 mK stage: long term trend • Solar activity minimum means higher CR rate below ~500 MeV bolometer plate PID bolometer plate SREM count (AU) dilution plate PID

11. Cryochain stability: long term trend • About 4 nW power change on 100mK bolometer plate / 2 years PID dilution EOL EOL correlated with SREM data (ie: sun waking up) 30 nW The power follows the Helium pressures at the pressure regulators PID bolo EOL EOL PID 1.6K PID 4K SCS switch over

12. Cosmic ray energy distribution -> solar minimum est. -> solar maximum

13. Planck/HFI noise PSD

14. Impact on design and tests • Minimize detector sensitivity to CR • minimize cross section to CR for absorber (grid,..) and thermometer • minimize beams / frame thermal coupling to thermometer • fast time response • differential measurements • model and test under representative environment (instrument + high energy particles : proton accelerators up to few 100 MeV – on going work in Orsay IAS and Grenoble LPSC & INéel) • Cryochain design • passive / active thermal regulation • need design sub-K stages more immune to cosmic rays showers.

15. EMI/EMC • Strict EMI/EMC design of Planck • no pertubation from transmitters • no perturbation from other subsystems • except from known 4K cooler drive electronics • synchronization with modulation of bolometer readout gives very narrow lines • requires design at system level (ex SPICA/SAFARI)

16. Thoughts on ground calibrations • Temporal response • direct impact on C(l) • more characterisations • ADC calibration • large dynamics, but usefull range on a few bits • Spectral transmission calibration • the best achievable on ground may not be enough • check with multiband sky measurement • Polarization calibration...

17. Thank You !

18. The results presented here are a product of the Planck Collaboration, including individuals from more than 50 scientific institutes in Europe, the USA and Canada Planck is a project of the European Space Agency -- ESA -- with instruments provided by two scientific Consortia funded by ESA member states (in particular the lead countries: France and Italy) with contributions from NASA (USA), and telescope reflectors provided in a collaboration between ESA and a scientific Consortium led and funded by Denmark.