Planck Pre-Launch Status Papers - APC - Université Paris Diderot ...
Planck Pre-Launch Status Papers - APC - Université Paris Diderot ... Planck Pre-Launch Status Papers - APC - Université Paris Diderot ...
A&A 520, A5 (2010)70 GHz44 GHz30 GHzFig. 6. Calibrated differential radiometric outputs (downsampled to 1 Hz) for all LFI detectors during the long duration test. Temperature sensordata in antenna temperature units are superimposed (thin black line) on the calibrated radiometric data.Table 6. White noise sensitivities per frequency channel in µK· s 1/2 .Meas. Rad. Req.noise eq.70 GHz 146 130 10544 GHz 174 177 11330 GHz 135 149 1162015M-00M-01S-10S-11RequirementNotes. Sensitivity values have been extrapolated at CMB input usingthe two methods outlined in the text and detailed in Appendix D. Thethird column reports the LFI requirement.greater temperature stability, especially compared to the 70 GHzreceivers cryofacility (Villa et al. 2010).Summarised in Table 7,theresultsshowverygood1/ f noisestability of the LFI receivers, almost all with a knee frequencywell below the required 50 mHz.E bw (GHz)1055.2.5. Spurious frequency spikesDuring the FM test campaign, we found unwanted frequencyspikes in the radiometeric data at frequencies of the order of afew hertz. The source of the problem was recognised to be inthe backend data acquisition electronics box, where unexpectedcrosstalk between the circuits handling housekeeping and radiometricdata affected the radiometer voltage output downstreamof the detector diode.In Fig. 8, thisisclearlyshowninspectraofunswitcheddata acquired from the 70 GHz detector LFI18S-10 with thehousekeeping data acquisition activated and deactivated.0LFI18 LFI19 LFI20 LFI21 LFI22 LFI23 LFI24 LFI25 LFI26 LFI27 LFI28Fig. 7. Noise effective bandwidths calculated during instrument-levelmeasurements. The three lines indicate the 70 GHz, 44 GHz, and30 GHz requirements.Because the disturbance is added to receiver signal at the endof the radiometric chain it acts as a common mode effect on boththe sky and reference load data so that its effect in differenceddata is reduced by several orders of magnitude bringing it wellbelow the radiometer noise level.Page 8 of 16
A. Mennella et al.: LFI calibration and expected performanceTable 7. Summary of knee frequency and slope.DAE noise with housekeeping sequencer ONf knee (mHz)M-00 M-01 S-10 S-1170 GHzLFI18 ... ... 61 59LFI19 25 32 27 37LFI20 21 19 23 28LFI21 28 30 41 38LFI22 46 39 41 76LFI23 30 31 58 7544 GHzLFI24 ... ... 39 46LFI25 31 31 21 30LFI26 61 61 61 1430 GHzLFI27 30 30 27 26LFI28 37 31 37 39slopeM-00 M-01 S-10 S-1170 GHzLFI18 ... ... −1.12 −1.12LFI19 −1.27 −1.22 −1.11 −1.02LFI20 −1.47 −1.64 −1.27 −1.24LFI21 −1.48 −1.61 −1.15 −1.17LFI22 −1.18 −1.26 −1.19 −1.01LFI23 −1.11 −1.19 −1.15 −1.1244 GHzLFI24 ... ... −1.06 −1.11LFI25 −1.07 −1.03 −1.10 −1.00LFI26 −1.01 −1.01 −1.05 −1.5530 GHzLFI27 −1.06 −1.13 −1.25 −1.13LFI28 −0.94 −0.93 −1.07 −1.06(a)(b)(c)DAE noise with housekeeping sequencer OFFRadiometer noise with housekeeping sequencer ONRadiometer noise with housekeeping sequencer OFFFurther analysis of these spikes has shown that the disturbanceis synchronized in time. By binning the data synchronously,we obtain a template of the disturbance, which allowsits removal in the time-domain (Meinhold et al. 2009). Thefeasibility of this approach has been proven using data acquiredduring the full satellite test campaign in Liege, Belgium duringJuly and August, 2008.Therefore, because the only way to eliminate the disturbancein hardware would be to operate the instrument withoutany housekeeping information, our baseline approach is that, ifnecessary, the residual effect will be removed from the data inthe time domain after measuring the disturbance shape from theflight data.5.3. Radiometric suceptibility to front-end temperatureinstabilitiesThermal fluctuations in the receivers result in gain changes in theamplifiers and noise changes in the (slightly emissive) passivecomponents (e.g., horns, OMTs, waveguides). These changesmimic the effect of changes in sky emission, expecially at fluctuationfrequencies near the satellite spin frequency. The mostimportant source of temperature fluctuations for LFI is the sorptioncooler (Bhandari et al. 2004; Wade et al. 2000).For small temperature fluctuations in the focal plane, the radiometricresponse is linear (Seiffert et al. 2002; Terenzi et al.2009b), so the spurious antenna temperature fluctuation in thedifferential receiver output can be written asδT out = f trans δT phys , (5)(d)Fig. 8. DAE-only and radiometer noise amplitude density spectra inV/ √ Hz (from LFI18S-10 unswitched data) with and without activationof the housekeeping acquisition. These data clearly show that thesource of the disturbance is in the data acquisition electronics box andis correlated with the status of the housekeeping data acquisition.where the transfer function f trans can be estimated analyticallyfrom the differential power output given in Eq. (1):f trans = ∂p out∂T phys(∂pout∂T sky) −1· (6)The analytical form of f trans (discussed in detail in Terenzi et al.2009b) dependsprimarilyonthefront-endamplifiersusceptibilityparameters, ∂G/∂T phys and ∂T noise /∂T phys ,aswellasotherinstrument and boundary condition parameters such as the insertionloss of passive components and the sky input temperature.If we consider the systematic error budget in Bersanelli et al.(2010), it is possible to derive a requirement for the radiometrictransfer function, f trans 0.1, in order to maintain the finalpeak-to-peak error per pixel < ∼ 1 µK (seeAppendixF). Duringinstrument-level calibration activities, dedicated tests werePage 9 of 16
- Page 47 and 48: A&A 520, A3 (2010)Horizon 2000 medi
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- Page 67 and 68: A&A 520, A3 (2010)GUI = graphical u
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- Page 134 and 135: A&A 520, A8 (2010)inflation, giving
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A&A 520, A5 (2010)70 GHz44 GHz30 GHzFig. 6. Calibrated differential radiometric outputs (downsampled to 1 Hz) for all LFI detectors during the long duration test. Temperature sensordata in antenna temperature units are superimposed (thin black line) on the calibrated radiometric data.Table 6. White noise sensitivities per frequency channel in µK· s 1/2 .Meas. Rad. Req.noise eq.70 GHz 146 130 10544 GHz 174 177 11330 GHz 135 149 1162015M-00M-01S-10S-11RequirementNotes. Sensitivity values have been extrapolated at CMB input usingthe two methods outlined in the text and detailed in Appendix D. Thethird column reports the LFI requirement.greater temperature stability, especially compared to the 70 GHzreceivers cryofacility (Villa et al. 2010).Summarised in Table 7,theresultsshowverygood1/ f noisestability of the LFI receivers, almost all with a knee frequencywell below the required 50 mHz.E bw (GHz)1055.2.5. Spurious frequency spikesDuring the FM test campaign, we found unwanted frequencyspikes in the radiometeric data at frequencies of the order of afew hertz. The source of the problem was recognised to be inthe backend data acquisition electronics box, where unexpectedcrosstalk between the circuits handling housekeeping and radiometricdata affected the radiometer voltage output downstreamof the detector diode.In Fig. 8, thisisclearlyshowninspectraofunswitcheddata acquired from the 70 GHz detector LFI18S-10 with thehousekeeping data acquisition activated and deactivated.0LFI18 LFI19 LFI20 LFI21 LFI22 LFI23 LFI24 LFI25 LFI26 LFI27 LFI28Fig. 7. Noise effective bandwidths calculated during instrument-levelmeasurements. The three lines indicate the 70 GHz, 44 GHz, and30 GHz requirements.Because the disturbance is added to receiver signal at the endof the radiometric chain it acts as a common mode effect on boththe sky and reference load data so that its effect in differenceddata is reduced by several orders of magnitude bringing it wellbelow the radiometer noise level.Page 8 of 16
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