Ade, P.A.R. and Savini, G. and Sudiwala, R. and Tucker, C. and Catalano, A. and Church, S. and Colgan, R. and Desert, F.-X. and Gleeson, E. and Jones, W.C. and Lamarre, J.-M. and Lange, A. and Longval, Y. and Maffei, B. and Murphy, J.A. and Noviello, F. and Pajot, F. and Puget, J.-L. and Ristorcelli, I. and Woodcraft, A. and Yurchenko, V.
Planck pre-launch status: The optical architecture of the HFI.
Astronomy & Astrophysics, 520 (A11).
The Planck High Frequency Instrument, HFI, has been designed to allow a clear unobscured view of the CMB sky through an offaxis
Gregorian telescope. The prime science target is to measure the polarized anisotropy of the CMB with a sensitivity of 1 part
in 106 with a maximum spatial resolution of 5 arcmin (Cl ∼ 3000) in four spectral bands with two further high-frequency channels
measuring total power for foreground removal. These requirements place critical constraints on both the telescope configuration and
the receiver coupling and require precise determination of the spectral and spatial characteristics at the pixel level, whilst maintaining
control of the polarisation. To meet with the sensitivity requirements, the focal plane needs to be cooled with the optics at a few
Kelvin and detectors at 100 mK. To limit inherent instrumental thermal emission and diffraction effects, there is no vacuum window,
so the detector feedhorns view the telescope secondary directly. This requires that the instrument is launched warm with the cooler
chain only being activated during its cruise to L2. Here we present the novel optical configuration designed to meet with all the above
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