Planck Pre-Launch Status Papers - APC - Université Paris Diderot ...

F. Villa et al.: Calibration of LFI flight model radiometersFig. 15. Setup of the RCA_SPR tests. The picture and the sketch on the left report the test setup of the 30 and 44 GHz RCAs. The flexible waveguideis clearly visible on the picture on the side of the horn. The picture and the sketch on the right report the setup of the 70 GHz RCAs. There thesignal was injected infront of the horn through the sky load, and copper rigid waveguides were used to carry the signal form the generator to theRCAs.Fig. 16. Measured relative gain function (bandpass) of the 8 detectorsat 30 GHz. The curves that show big ripples are those caused by thesetup problem (see text). The bandpasses are normalized to the area asexplained in the text.44 GHz and 70 GHz, where the tuning has second order effectson the overall frequency response.4.6. SusceptibilityAny variation in physical temperature of the RCA, T phys ,willproduce a variation of the output signal that mimics the variationof the input temperature, T sky ,sothatδT sky = T f · δT phys , (26)Fig. 17. Measured relative gain function (bandpass) of all 12 detectorsat 44 GHz. The bandpasses are normalized to the area as explained inthe text.where T f is the transfer function. A controlled variation of FEMtemperature was imposed to calculate the transfer function ofthe front end modules, T FEMf.ThiswasdoneforallRCAsandalldetectors. The chief results are given in Table 9,whilethedetailsof the applied method and of the measurements are reported byTerenzi et al. (2009c).The susceptibility of the radiometer signal to temperaturevariations in the BEM and 3rd V-groove were measured onlyfor the 30 and 44 GHz chains, because at 70 GHz it wasnot possible to control the temperatures of these interfaces intheir cryofacility. Here we report on the BEM susceptivity testsPage 11 of 14