HFI performance summary

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The HFI(Planck) High Frequency Instrument has been operating flawlessly for 30 months, the maximum autonomy expected for the helium of the dilution cooler. The telescope pointing was achieved with an accuracy better than expected and reconstructed to a few seconds of arc. Fifty of the fifty-two bolometers have collected data in very stable conditions during the whole mission, and practically all of the data was correctly recorded.

The essential characteristics of the HFI(Planck) High Frequency Instrument are gathered in the table below. The extreme sensitivity provided by the 100 mK bolometers and the HFI(Planck) High Frequency Instrument architecture has provided a new view of the submillimetre and millimetre sky with a noise not far from the fundamental limits set by the photon noise of the observed source. Expected and unexpected systematic effects were evidenced. The most noticeable of them are the spikes in the signal produced by cosmic rays hitting the bolometers and their immediate surrounding. The sensitivity is obtained from the half difference of the half rings. The overall sensitivity is finally around that announced as the goal in the "bluebook"[1] , i.e. twice better than the required sensitivity. One can expect to improve these numbers by about root two when the whole mission data is available.

Beam size and sensitivity of maps for the nominal mission (15 months)
Frequency 100 GHz 143 GHz 217 GHz 353 GHz 545 GHz 857 GHz
Beam size (FWHMFull-Width-at-Half-Maximum, arcmin) 9.66 7.27 5.01 4.86 4.84 4.63
Sensitivity per fiducial pixel 3.95 µK/K 2.35 µK/K 4.58 µK/K 15.17 µK/K 0.013 MJy/sr (*) 0.013 MJy/sr (*)
Goal sensitivity 2.5 µK/K 2.2 µK/K 4.8 µK/K 14.7 µK/K 0.023 MJy/sr 0.041 MJy/sr

(*) These sensitivities are only valid for high galactic latitude.


  1. The Scientific Programme of Planck, Planck Collaboration, ESA publication ESA-SCI(2005)/01, (2005).