Simulations of the submillimeter-wave telescope on the ESA PLANCK surveyor

The PLANCK surveyor utilizes a special dual-reflector submillimeter-wave telescope of a non-conventional Gregorian configuration. Both the design and simulation of such a telescope are extremely challenging. Firstly, the telescope is electrically large, the primary mirror having a projected aperture diameter of D=1500 mm while the minimal wavelength involved is only X=0.35 mm (D/λ=4300). Secondly, it is an axially asymmetric system that consists of two essentially defocused ellipsoidal reflectors providing a very large field of view at the focal plane where two arrays of 76 horn antennas feeding low-temperature detectors are located . To add to the complexity, the 14 channels operating at the highest frequencies of 545 and 857 GHz are based on multi-moded horns designed for receiving maximum microwave power within the required angular resolution of 5 arcminutes on the sky. The polarization characteristics of the microwave background should be measured in different channels as well. The goal of our analysis is the optimization of six high-frequency channels of the High-Frequency Instrument (HFI) covering the range from 100 GHz to 857 GHz