Sub-degree CMB anisotropy from space

Abstract

Abstract. In the context of the COBRAS/SAMBA mission study 1 , we discuss in-flight calibration of extended sky maps of the microwave sky using celestial sources. We simulate the observations in order to assess the accuracy obtainable for absolute and relative calibration of the Low Frequency Instrument (LFI), operating in the 30 − 130 GHz range. Accurate calibration can be achieved using the CMB dipole signal, ∆T D . With conservative assumptions on the effect of Galactic contamination, we find that the CMB dipole will provide absolute calibration accuracy ∼ 0.7% (limited by the COBE-DMR uncertainty on ∆T D ) on time-scales of about 10 days at all frequencies and for the entire mission lifetime. Long-term calibration with accuracy < 0.2% can be obtained using the spacecraft orbital velocity. Additional, independent calibration will be provided by the observation of external planets. We also describe the capability of the proposed scanning technique to detect and remove long-term instrumental drifts, and show that these effects, if present, can be controlled and removed with an overall negligible impact on the data uncertainty.

The Planck Mission: Recent Results, Cosmological and Fundamental Physics Perspectives

“…LFI is a coherent differential array based on 20 K InP HEMT amplifiers e covering the 30-70 GHz range in three bands centered at approximately 30, 44 and 70 GHz. 8 HFI is an array of bolometers cooled to 0.1 K in nine frequency bands centered at 100, 143, 217, 353, 545 and 857 GHz. 9 LFI and HFI accumulated data together up to the consumption of the cryogenic liquids on January 2012, achieving 29.5 months of integration, corresponding to about five complete sky surveys.…”

Wide-field imaging and polarimetry for the biggest and brightest in the 20-GHz southern sky

“…Bright, highly polarized sources are also necessary for upcoming CMB instruments, in particular, the ESA Planck satellite mission's Low Frequency Instrument (LFI), which will observe in bands between 30 and 70 GHz (Bersanelli & Mandolesi 2000). Among the source types that have been pursued as potential flux density and polarization calibrators for the instrument are extragalactic sources; however, as the spectral behaviour of the bright extragalactic population at high frequency is difficult to model, sources selected at lower frequency are not certain to be suitable calibrator candidates.…”

Planckpre-launch status: ThePlanckmission

“…the modulation of the CMB due to the motion of the solar system barycenter with respect to the cosmological comoving frame, has an amplitude of ∼3.4 mK which is known to an accuracy of ∼0.3% (Hinshaw et al 2009); it is further modulated by the motion of the Earth around the Sun, with an amplitude (∼10% of the dipole itself) which can be very accurately calculated from the orbital velocity of the satellite with respect to the Earth (which can be estimated in flight with an accuracy better than 1 cm/s), and that of the Earth around the Sun (which is extremely accurately known). These variations are visible in the Planck time-ordered data at periods of one minute and 6 months respectively, and are sufficient to calibrate the responsivity to large-scale CMB emission of all Planck detectors up to 353 GHz with an accuracy better than 1% (see Bersanelli et al 1997;Cappellini et al 2003, for LFI, Piat et al 2002. -at the highest frequencies of HFI, namely 545 and 857 GHz, the CMB dipole signal is too faint to be a good photometric calibrator.…”