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

A&A 520, A5 (2010)Table 1. Main instrument parameters and stages at which they have been measured.Category Parameters Additional Individual Integrated Satellite In flightReference radiometers instrumentBias tuning Front-end amplifiersCuttaia et al. (2009) Y Y Y YPhase switches Cuttaia et al. (2009) Y Y Y YCalibrationBasic calibration Photometric calibrationVilla et al. (2010) Y Y Y YLinearity Mennella et al.(2009)Y Y N NIsolation Villa et al. (2010) Y Y N NIn-band response Zonca et al. (2009) Y N N NNoise performance White noise Meinhold et al.(2009)Knee frequency Meinhold et al.(2009)1/ f slope Meinhold et al.(2009)Y Y Y YY Y Y YY Y Y YSusceptibilityFront-end temperaturefluctuationsTerenzi et al.(2009b)Y Y Y YBack-end temperaturefluctuationsY Y N NFront-end bias fluctuationsY Y N NNotes. In bodface, we highlight calibration parameters defining the instrument scientific performance that are discussed in this paper.Table 2. Summary of main thermal conditions.Temperatures Flight Receiver Instr.Sky ∼3K 8K 18.5 KRef. ∼4.5 K 8K 18.5 KFront-end ∼20 K ∼20 K ∼26 KBack-end ∼300 K ∼300 K ∼300 KNotes. The table reports thermal conditions achieved in-flight and in thevarious testing facilities.Table 3. LFI cryo-facility thermal performance.Avg. Temp. (K) Stability (K)Sky load 18–35 0.10Focal plane unit 26 0.03Reference loads 22 0.08Back end unit 315 0.65Notes. The temperature stability listed in the second column refers tothe measured peak-to-peak during one day.At the end of the test campaign and just before instrument deliveryto ESA, the radiometer LFI18M-0 was replaced with aflight spare. In the second case, the problem was a defectiveelectrical contact to the amplifier V g2 (gate 2 voltage) line,which was repaired after the end of the test. Subsequentroom-temperature tests as well cryogenic ground satellite tests(Summer 2008) and in-flight calibration (Summer 2009) showedfull functionality, confirming the successful repair of LFI18M-0and LFI24M-0. Becausethesetworadiometerswereinafailedstate during the test campaign, we generally show no results forthem. The only exception is the calibrated noise per frequencychannel reported in Table 6,where:– for LFI18M-0, weassumethesamenoiseparametersobtainedfor LFI18S-1;and– for LFI24M-0,weusethenoiseparametersmeasuredduringsingle-receiver tests before integration into the instrument array.5.1. Basic calibration5.1.1. Experimental setupThese parameters were determined by means of tests in whichthe radiometric average voltage output, V out ,wasrecordedforvarious input antenna temperature levels, T in .Althoughstraightforwardin principle, these tests required the following conditionsin the experimental setup and in the measurementPage 4 of 16