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Published December 2011 | Published + Submitted
Journal Article Open

Planck early results. IV. First assessment of the High Frequency Instrument in-flight performance


The Planck High Frequency Instrument (HFI) is designed to measure the temperature and polarization anisotropies of the cosmic microwave background and Galactic foregrounds in six ~30% bands centered at 100, 143, 217, 353, 545, and 857 GHz at an angular resolution of 10′ (100 GHz), 7′ (143 GHz), and 5′ (217 GHz and higher). HFI has been operating flawlessly since launch on 14 May 2009, with the bolometers reaching 100 mK the first week of July. The settings of the readout electronics, including bolometer bias currents, that optimize HFI's noise performance on orbit are nearly the same as the ones chosen during ground testing. Observations of Mars, Jupiter, and Saturn have confirmed that the optical beams and the time responses of the detection chains are in good agreement with the predictions of physical optics modeling and pre-launch measurements. The Detectors suffer from a high flux of cosmic rays due to historically low levels of solar activity. As a result of the redundancy of Planck's observation strategy, theremoval of a few percent of data contaminated by glitches does not significantly affect the instrumental sensitivity. The cosmic ray flux represents a significant and variable heat load on the sub-Kelvin stage. Temporal variation and the inhomogeneous distribution of the flux results in thermal fluctuations that are a probable source of low frequency noise. The removal of systematic effects in the time ordered data provides a signal with an average noise equivalent power that is 70% of the goal in the 0.6−2.5 Hz range. This is slightly higher than was achieved during the pre-launch characterization but better than predicted in the early phases of the project. The improvement over the goal is a result of the low level of instrumental background loading achieved by the optical and thermal design of the HFI.

Additional Information

© 2011 ESO. Received: 10 January 2011. Accepted: 29 June 2011. The Planck HFI instrument (http://hfi.planck.fr/) was designed and built by an international consortium of laboratories, universities and institutes, with important contributions from the industry, under the leadership of the PI institute, IAS at Orsay, France. It was funded in particular by CNES, CNRS, NASA, STFC and ASI. The authors extend their gratitude to the numerous engineers and scientists, who have contributed to the design, development, construction or evaluation of the HFI instrument. A description of the Planck Collaboration and a list of its members, indicating which technical or scientific activities they have been involved in, can be found at http://www.rssd.esa.int/index.php?project=PLANCK\&page=Planck_Collaboration. The Planck Collaboration acknowledges financial support from: ESA; CNES and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC and MICINN (Spain); Tekes and AoF (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); Swiss Funding Agency (Switzerland); Norwegian Funding Agency (Norway); and FCT/MCTES (Portugal).

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Submitted - 1101.2039.pdf


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August 19, 2023
October 18, 2023