Planck Pre-Launch Status Papers - APC - UniversitÃ© Paris Diderot ...

More documents

Recommendations

Info

M. Bersanelli et al.: Planck pre-launch status: Design and description of the Low Frequency Instrumentscanning strategy, a higher knee frequency ( f k < 50 mHz) is acceptableas robust destriping and map making algorithms canbe successfully applied to suppress the effects of low-frequencyfluctuations. Because a total power HEMT receiver would havetypical knee frequencies of 10 to 100 Hz, a very efficient differentialdesign is needed for LFI to meet the 50 mHz requirement.2.5. Systematic effectsThroughout the design and development of LFI a key driverhas been the minimisation and control of systematic effects,i.e., deviations from the signal that would be produced by aninstrument with axially symmetric Gaussian beams, with idealpointing and pure Gaussian white noise. These include opticaleffects (e.g., straylight, misalignment, beam distortions), instrumentintrinsic effects (e.g., non-stationary and correlated noisefeatures such as 1/ f noise, spikes, glitches, etc.), thermal effects(e.g., temperature fluctuations in the front-end or otherinstrument interfaces), and pointing errors. In particular, theLFI receiver (discussed in Sect. 3) wasdesignedwiththeprimaryobjective of minimising the impact of 1/ f noise, thermalfluctuations, and systematic effects due to non-ideal receivercomponents.The quantitative evaluation of various potential systematiceffects required a complex iterative process involving designchoices, knowledge and stability of the interfaces (with HFI andwith the satellite), testing and modelling of the instrument behaviour,and simulations and simplified data analysis to evaluatethe impact of each effect on the scientific output of the mission(Mennella et al. 2004). Furthermore, dedicated analyses wererequired to evaluate the impact of instrument non-idealities onpolarisation measurements (Leahy et al. 2010).Limits on systematic effects impacting the effective angularresolution (beam ellipticity, alignment, pointing errors) wereused, together with those coming from HFI, as input to the designof the Planck telescope and focal plane, as well as to setpointing requirements at the system level. Regarding signal perturbations,for LFI we set an upper limit to the global impactof systematic effects of
A&A 520, A4 (2010)Fig. 2. Schematic of the LFI system displaying the main thermal interfaceswith the V-grooves and connections with the 20 K and 4 K coolers.Two RCAs only are shown in this scheme. The radiometer arrayassembly (RAA) is represented by the shaded area and comprises thefront-end unit (FEU) and back-end unit (BEU). The entire LFI RAAincludes 11 RCAs, with 11 feeds, 22 radiometers, and 44 detectors.Fig. 1. Top: schematicofaradiometerchainassembly(RCA).TheLFI array has 11 RCAs, each comprising two radiometers carrying thetwo orthogonal polarisations. The RCA is constituted by a feed horn,an orthomode transducer (OMT), a front-end module (FEM) operatedat 20 K, a set of four waveguides that connect FEM to the back-endmodule (BEM). The notations “0” and “1” for the two radiometers inthe RCA denote the branches downstream of the main and side armsof the OMT, respectively. Each amplifier chain assembly (ACA) comprisesa cascaded amplifier and a phase switch. Bottom: pictureofa30 GHz RCA integrated before radiometer-level tests.3.2. Radiometer array assemblyAschematicoftheradiometerarrayassembly(RAA),isshownin Fig. 2. EachRCAhasbeenintegratedandtestedseparately,and then mounted on the RAA without de-integration to ensurestability of the radiometer characteristics after calibrationat RCA level (Villa et al. 2010).A“mainframe”supportstheLFI20Kfrontend(withfeeds,OMTs, and FEMs) and interfaces the HFI 4 K front-end box inthe central portion of the focal plane. The HFI 4 K box is linkedto the 20 K LFI mainframe with insulating struts and providesthe thermal and mechanical interface to the LFI reference loads.Forty-four waveguides connect the LFI front-end unit (FEU) tothe back-end unit (BEU), which is mounted on the top panel ofthe Planck service module (SVM) and is maintained at a temperatureof ∼300 K. The BEU comprises the eleven BEMs andthe data acquisition electronics (DAE) unit. After on-board processing,provided by the radiometer box electronics assembly(REBA), the compressed signal is down-linked to the groundstation with housekeeping data.Amajordesigndriverhasbeentoensureacceptablylowconductive and radiative parasitic thermal loads at the 20 Kstage, particularly those introduced by the waveguides and cryoharness.As we discuss below, sophisticated design solutionswere implemented for these units. In addition, three thermalsinks were used to largely reduce the parasitic loads in the 20 Kstage, and these are the three conical shields (V-grooves) introducedin the Planck payload module to thermally isolate thecold telescope enclosure from the SVM at ∼300 K (Tauber et al.2010a). The V-grooves also provide multiple precool temperaturesto all of the Planck coolers, as well as intercepting parasiticsfrom the cooler piping and HFI equipment. The threeV-grooves are expected to reach in-flight temperatures of approximately170 K, 100 K, and 50 K.The FEU is aligned in the focal plane of the telescope andsupported by a set of three thermally insulating bipods attachedto the telescope structure. The back-end unit is fixed on top of thePlanck service module, below the lower V-groove. In Fig. 3 weshow a detailed drawing of the RAA, including an exploded viewshowing its main subassemblies and units. After integration, theRAA was first tested in a dedicated cryo-facility (Mennella et al.2010) forinstrumentleveltests(Fig.4), and then inserted intoPage 6 of 21
Page 1 and 2:
A&A 520, E1 (2010)DOI: 10.1051/0004
Page 3 and 4:
ABSTRACTThe European Space Agency
Page 5 and 6:
A&A 520, A1 (2010)Fig. 2. An artist
Page 7 and 8:
A&A 520, A1 (2010)Fig. 4. Planck fo
Page 9 and 10:
A&A 520, A1 (2010)Fig. 6. The Planc
Page 11 and 12:
A&A 520, A1 (2010)Table 4. Summary
Page 13 and 14:
A&A 520, A1 (2010)three frequency c
Page 15 and 16:
A&A 520, A1 (2010)Fig. 12. The left
Page 17 and 18:
A&A 520, A1 (2010)Fig. 14. Left pan
Page 19 and 20:
A&A 520, A1 (2010)flux limit of the
Page 21 and 22:
A&A 520, A1 (2010)- University of C
Page 23 and 24: A&A 520, A1 (2010)57 Instituto de A
Page 25 and 26: A&A 520, A2 (2010)Fig. 1. (Left) Th
Page 27 and 28: A&A 520, A2 (2010)Fig. 3. (Top)Twos
Page 29 and 30: A&A 520, A2 (2010)Table 2. Predicte
Page 31 and 32: Table 3. Predicted in-flight main b
Page 33 and 34: A&A 520, A2 (2010)materials. Theref
Page 35 and 36: A&A 520, A2 (2010)Fig. 11. Comparis
Page 37 and 38: A&A 520, A2 (2010)Table 5. Inputs u
Page 39 and 40: A&A 520, A2 (2010)Fig. 16. Three cu
Page 41 and 42: A&A 520, A2 (2010)Table 7. Optical
Page 43 and 44: A&A 520, A2 (2010)Fig. A.1. Dimensi
Page 45 and 46: A&A 520, A2 (2010)5 Università deg
Page 47 and 48: A&A 520, A3 (2010)Horizon 2000 medi
Page 49 and 50: A&A 520, A3 (2010)Fig. 1. CMB tempe
Page 51 and 52: A&A 520, A3 (2010)Ω ch 2τn s0.130
Page 53 and 54: A&A 520, A3 (2010)Fig. 6. Integral
Page 55 and 56: A&A 520, A3 (2010)Table 2. LFI opti
Page 57 and 58: 3.3.1. SpecificationsThe main requi
Page 59 and 60: A&A 520, A3 (2010)Fig. 11. Schemati
Page 61 and 62: A&A 520, A3 (2010)features of the r
Page 63 and 64: A&A 520, A3 (2010)Fig. 13. Level 2
Page 65 and 66: A&A 520, A3 (2010)Fig. 15. Level 3
Page 67 and 68: A&A 520, A3 (2010)GUI = graphical u
Page 69 and 70: A&A 520, A3 (2010)23 Centre of Math
Page 71 and 72: A&A 520, A4 (2010)In addition, all
Page 73: A&A 520, A4 (2010)Table 2. Sensitiv
Page 77 and 78: A&A 520, A4 (2010)Fig. 6. LFI recei
Page 79 and 80: A&A 520, A4 (2010)Fig. 9. Schematic
Page 81 and 82: A&A 520, A4 (2010)Table 4. Specific
Page 83 and 84: A&A 520, A4 (2010)Fig. 15. DAE bias
Page 85 and 86: A&A 520, A4 (2010)Fig. 19. Picture
Page 87 and 88: A&A 520, A4 (2010)Table 10. Main ch
Page 89 and 90: Table 13. Principal requirements an
Page 91 and 92: A&A 520, A5 (2010)DOI: 10.1051/0004
Page 93 and 94: A. Mennella et al.: LFI calibration
Page 105 and 106: D.1. Step 1-extrapolate uncalibrate
Page 107 and 108: A&A 520, A6 (2010)DOI: 10.1051/0004
Page 109 and 110: F. Villa et al.: Calibration of LFI
Page 121 and 122: A&A 520, A7 (2010)DOI: 10.1051/0004
Page 123 and 124: M. Sandri et al.: Planck pre-launch
Page 126 and 127:
A&A 520, A7 (2010)Fig. 8. Footprint
Page 128 and 129:
-30-40-30-6-3-20A&A 520, A7 (2010)0
Page 130 and 131:
A&A 520, A7 (2010)Table 4. Galactic
Page 132 and 133:
A&A 520, A7 (2010)Fig. A.1. Polariz
Page 134 and 135:
A&A 520, A8 (2010)inflation, giving
Page 136 and 137:
A&A 520, A8 (2010)estimated from th
Page 138 and 139:
A&A 520, A8 (2010)ways the most str
Page 140 and 141:
unmodelled long-timescale thermally
Page 142 and 143:
A&A 520, A8 (2010)Fig. 5. Polarisat
Page 144 and 145:
A&A 520, A8 (2010)Table 3. Band-ave
Page 146 and 147:
A&A 520, A8 (2010)where S stands fo
Page 148 and 149:
A&A 520, A8 (2010)Fig. 11. Simulate
Page 150 and 151:
stored in the LFI instrument model,
Page 152 and 153:
A&A 520, A8 (2010)Table 5. Statisti
Page 154 and 155:
A&A 520, A8 (2010)comparable in siz
Page 156 and 157:
A&A 520, A8 (2010)Table B.1. Main b
Page 158 and 159:
A&A 520, A8 (2010)Bond, J. R., Jaff
Page 160 and 161:
A&A 520, A9 (2010)- (v) an optical
Page 162 and 163:
A&A 520, A9 (2010)Fig. 2. The Russi
Page 164 and 165:
A&A 520, A9 (2010)Table 3. Estimate
Page 166 and 167:
A&A 520, A9 (2010)Fig. 7. Picture o
Page 168 and 169:
A&A 520, A9 (2010)Fig. 9. Cosmic ra
Page 170 and 171:
A&A 520, A9 (2010)Fig. 13. Principl
Page 172 and 173:
A&A 520, A9 (2010)Fig. 16. Noise sp
Page 174 and 175:
A&A 520, A9 (2010)Table 6. Basic ch
Page 176 and 177:
A&A 520, A9 (2010)with warm preampl
Page 178 and 179:
A&A 520, A9 (2010)20 Laboratoire de
Page 180 and 181:
A&A 520, A10 (2010)Table 1. HFI des
Page 182 and 183:
A&A 520, A10 (2010)based on the the
Page 184 and 185:
A&A 520, A10 (2010)Fig. 6. The Satu
Page 186 and 187:
A&A 520, A10 (2010)5. Calibration a
Page 188 and 189:
A&A 520, A10 (2010)Fig. 16. Couplin
Page 190 and 191:
A&A 520, A10 (2010)217-5a channel:
Page 192 and 193:
A&A 520, A10 (2010)10 -310 -495-The
Page 194 and 195:
A&A 520, A11 (2010)DOI: 10.1051/000
Page 196 and 197:
P. A. R. Ade et al.: Planck pre-lau
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
A&A 520, A12 (2010)Table 1. Summary
Page 204 and 205:
arrangement was also constrained by
Page 206 and 207:
A&A 520, A12 (2010)frequency cut-of
Page 208 and 209:
A&A 520, A12 (2010)Fig. 9. Gaussian
Page 210 and 211:
A&A 520, A12 (2010)the horn-to-horn
Page 212 and 213:
A&A 520, A12 (2010)Fig. 15. Composi
Page 214 and 215:
A&A 520, A12 (2010)Fig. 19. Broad-b
Page 216 and 217:
A&A 520, A13 (2010)DOI: 10.1051/000
Page 218 and 219:
C. Rosset et al.: Planck-HFI: polar
Page 220 and 221:
Page 222 and 223:
of frequencies and shown to have po
Page 224 and 225:
Page 226 and 227:
show all

Planck Pre-Launch Status Papers - APC - UniversitÃ© Paris Diderot ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?