HFI performance summary

The HFI operated 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 52 bolometers collected data in very stable conditions during the whole mission, and practically all of the data were correctly recorded.

The noise performance of HFI bolometers is measured on timelines which have been cleaned of features such as glitches, and from which the signal has been removed. The figures below show an example (from Planck-Early-V) of this process.

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The essential characteristics of the HFI are gathered in the table below. The extreme sensitivity provided by the 100 mK bolometers and the HFI architecture provided a new view of the submillimetre and millimetre sky, with a noise level not far from the fundamental limits set by the photon noise of the observed source. However, expected and unexpected systematic effects were seen, the most noticeable of them being the spikes in the signal produced by cosmic rays hitting the bolometers and their immediate surroundings. The sensitivity here is obtained from the half difference of the half rings. The overall sensitivity for the 2013 release was around that announced as the goal in the "bluebook" , i.e. 2 times better than the required sensitivity. These numbers improved by about √2 when the whole mission data become 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 [FWHM, 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-1 (*)	0.013 MJy sr-1 (*)
Goal sensitivity	2.5 µK/K	2.2 µK/K	4.8 µK/K	14.7 µK/K	0.023 MJy sr-1	0.041 MJy sr-1

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