|Frequency (GHz)||No. det.||Angle Uncertainty (deg)b||Cross-polar level (%)c||X-Y Mismatchd (%)|
Notes. (a) The data presented
correspond to monchromatic beams at band centre. The HFI spider-web
bolometers are slightly polarised and therefore they are also included
in this table.
(b) The uncertainty in the angle of the principal plane of polarisation, at focal plane level (the systematic uncertainty of a rigid rotation of the focal plane is very low as it will be measured in-flight very accurately, see Sect. 7). The differences between the design angle and the angle measured at focal plane level are within 3 for HFI; the measurement was made using a source which filled the beam to -20 dB. For LFI the 1 angle uncertainty is estimated from the mechanical manufacture and assembly tolerances, plus a model of thermoelastic deformations. However, the total angle uncertainty for LFI detectors may be dominated by cross-polar effects in the optical chain (telescope, horn, and mainly OMT) rather than the mechanical tolerances (see Sect. 4 and Leahy et al. 2010).
(c) The fraction of power detected from incident radiation linearly polarised in the direction orthogonal to the principal plane of polarisation and hence contributing to apparent depolarisation.
(d) Maximum RF power reaching one detector minus that reaching the orthogonal detector, normalised to the highest of the two (this definition is a factor of 2 larger than the leakage of Stokes I to Q ( ) defined in Leahy et al. 2010).
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