Beam mismatch effects in Cosmic Microwave Background polarization measurements

Measurement of cosmic microwave background polarization is today a major goal of observational cosmology. The level of the signal to measure, however, makes it very sensitive to various systematic effects. In the case of Planck, which measures polarization by combining data from various detectors, the beam asymmetry can induce a temperature leakage or a polarization mode mixing. In this paper, we investigate this effect using realistic simulated beams and propose a first-order method to correct the polarization power spectra for the induced systematic effect.Comment: Accepted by Astronomy & Astrophysic

Polarization experiments

Possible instrumental set--ups for the measurement of CMB polarization are reviewed in this article. We discuss existing and planned instruments, putting special emphasis on observational, instrumental, and data processing issues for the detection of very low polarization signals of prime cosmological interest. A short prospective summary is included

CMB Polarization as complementary information to anisotropies

The origin of CMB polarization is reviewed. Special emphasis is placed on the cosmological information encoded in it: the nature of primordial fluctuations, the connection with the inflation paradigm. Insights into more recent epochs are also discussed: early reionization and high redshift matter distribution from CMB lensing.Comment: 9 pages, 6 figures, One reference added in section 6.

Euclid Near Infrared Spectrometer and Photometer instrument concept and first test results obtained for different breadboards models at the end of phase C

The Euclid mission objective is to understand why the expansion of the Universe is accelerating through by mapping the geometry of the dark Universe by investigating the distance-redshift relationship and tracing the evolution of cosmic structures. The Euclid project is part of ESA's Cosmic Vision program with its launch planned for 2020 (ref [1]). The NISP (Near Infrared Spectrometer and Photometer) is one of the two Euclid instruments and is operating in the near-IR spectral region (900- 2000nm) as a photometer and spectrometer. The instrument is composed of: - a cold (135K) optomechanical subsystem consisting of a Silicon carbide structure, an optical assembly (corrector and camera lens), a filter wheel mechanism, a grism wheel mechanism, a calibration unit and a thermal control system - a detection subsystem based on a mosaic of 16 HAWAII2RG cooled to 95K with their front-end readout electronic cooled to 140K, integrated on a mechanical focal plane structure made with molybdenum and aluminum. The detection subsystem is mounted on the optomechanical subsystem structure - a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an instrument control unit that interfaces with the spacecraft via a 1553 bus for command and control and via Spacewire links for science data This presentation describes the architecture of the instrument at the end of the phase C (Detailed Design Review), the expected performance, the technological key challenges and preliminary test results obtained for different NISP subsystem breadboards and for the NISP Structural and Thermal model (STM)

Contribution à la mesure de la polarisation du fond diffus cosmologique dans le cadre des programmes ARCHEOPS et PLANCK

The work presented here deals with the measurement of the polarization of the cosmic microwave background. We first recall the basement of the standard model of cosmology, with particular focus on the main interests of the polarization of the cosmic background radiation for cosmology. We then describe the Archeops and Planck experiments, and their detectors. The calibration of the Planck high frequency instrument needs an optical system for which we have searched for a scattering surface and a polarizer adapted for millimetric wavelengths. We have also studied the influence of instrumental parameters on the measurement of polarization, especially the effects related to the beams. We thus show the importance of time constants and relative calibration. Finally, we finish with the analysis of Archeops data and show the presence of polarized galactic clouds at 353 GHz at more than 10%, using an original intercalibration method.Le travail présenté ici se place dans le cadre de la mesure de la polarisation du rayonnement de fond cosmologique. Nous commençons par rappeler les fondements du modèle standard de la cosmologie, en insistant sur les intérêts de la polarisation du fond diffus pour la cosmologie. Nous décrivons ensuite les expériences Archeops et Planck et leurs détecteurs. L'étalonnage de l'instrument hautes fréquences de Planck nécessite un système optique pour lequel nous avons recherché une surface diffusante et un polariseur adaptés au rayonnement millimétrique. Nous avons ensuite étudié l'influence de différents paramètres instrumentaux sur la mesure de la polarisation, notamment les effets liés aux lobes. Nous montrons ainsi l'importance des constantes de temps et de la calibration relative. Enfin, nous terminons par l'analyse des données d'Archeops, et montrons la présence de nuages galactiques polarisés à 353 GHz à plus de 10%, grâce à une méthode originale d'intercalibration

La mesure de la polarisation avec Planck HFI (calibration, effets systématiques et sources compactes)

L'étude des anisotropies de température du rayonnement fossile durant les vingt dernières années a permis d'assoir notre modèle standard cosmologique, et de contraindre fortement ses paramètres. En dépit de la robustesse du modèle proposé, de nombreuses questions persistent, et la mesure de la polarisation de ce rayonnement pourrait permettre de répondre à certaines de ces questions. En particulier, une détection des modes B de polarisation permettrait de sonder la phase d'inflation qui se serait produite dans l'univers primordial. Mesurer la polarisation du fond diffus cosmologique est l'un des objectifs de la mission spatiale européenne Planck. En raison de l'échelle d'amplitude relative du signal en température, modes E et modes B de polarisation, cette mesure requiert un contrôle drastique des effets systématiques liés à l'instrument. Cette thèse présente mon travail sur la calibration et l'étude des effets systématiques affectant la mesure de polarisation pour l'instrument Planck HFI, ainsi que l'étude de sources compactes. Une nouvelle méthode de photométrie des sources, basée sur les données temporelles plutôt que sur les cartes, est proposée et utilisée pour étudier la polarisation et les variations temporelles de sources astrophysiques observées par Planck (en particulier la nébuleuse du Crabe). Cette étude de sources compactes a aussi permis de tester la calibration de l'instrument et d'étudier certains effets systématiques (forme des lobes, bandes passantes des détecteurs, fonction de transfert des bolomètres ...) pouvant affecter cette calibration. Enfin, une méthode pour la calibration polarisée est proposée et testée sur des simulations.During the last couple of decades, studying the cosmic microwave background (CMB) temperature ani has been the most powerful probe to establish our current standard cosmological model and to constraint its parameters. In spite of the impressive agreement between the model and a large variety of observation: there are still some remaining issues that polarization measurement of the CMB could help disentangle. In particular primordial B-modes of polarisation are widely considered as being a smoking gun of the hypothetical period of inflation, and detecting them is one of the most important goal in cosmology for the next few years.The measurement of CMB polarisation is one of Planck's ESA mission goals. Measuring polarisation is challenging though; the relative amplitudes of the signals in temperature and polarisation require a strict control of systematic effects. This thesis present my work on calibration and characterization of the systematic effects for the Planck HFI instrument, as well as a study of compact sources. I propose a new method to extract compact sources photometry, based on time domain analysis instead of maps, and apply it to study polarisation and time variability of astrophysical sources seen by Planck; a particular attention is dedicated to the Crab nebula. This analysis is also used to test the HFI calibration and study various systematic effects, such as beam shapes or bandpass effects, that can affect this calibration. A method to calibrate the polarisation parameters of HFI detectors (polarization efficienciescand orientations in the focal plane) is also proposed and tested on simulations.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Contribution à la mesure de la polarisation du fond diffus cosmologique dans le cadre des programmes Archeops et Planck

STRASBOURG-Bib.Central Recherche (674822133) / SudocPARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

healpy: equal area pixelization and spherical harmonics transforms for data on the sphere in Python

International audienc

Random telegraph signal (RTS) in the Euclid IR H2RGs

International audienceEuclid is an ESA mission to map the geometry of the dark Universe with a planned launch date in 2021. Euclid is optimised for two primary cosmological probes, weak gravitational lensing and baryonic acoustic oscillations. They are implemented through two science instruments on-board Euclid, a visible imager (VIS) and a near-infrared photometer/spectrometer (NISP), which are being developed and built by the Euclid Consortium instrument development teams. The NISP instrument contains a large focal plane assembly of 16 Teledyne HgCdTe H2RG detectors with 2.3 μm cut-off wavelength and SIDECAR readout electronics. The performance of the detector systems is critical for the science return of the mission and extended on-ground tests are being performed for characterisation and calibration purposes. Special attention is given also to effects even on the scale of individual pixels, which are difficult to model and calibrate, and to identify any possible impact on science performance. This paper discusses the known effect of random telegraph signal (RTS) in a follow-on study of test results from the Euclid NISP detector system demonstrator model [1], addressing open issues and focusing on an in-depth analysis of the RTS behaviour over the pixel population on the studied Euclid H2RGs

Detector chain calibration strategy for the Euclid Flight IR H2RGs

International audienceEuclid is an ESA mission to map the geometry of the Dark Universe with a planned launch date in 2021.1 Two primary cosmological probes, weak gravitational lensing and baryonic acoustic oscillations, are implemented through a VISible imager (VIS) and a Near-Infrared Spectrometer and Photometer (NISP).2 The ground characterization of the NISP Flight Sensor Chip Systems (SCS) followed by the pixel response calibration aims to produce all informations to correct and control the accuracy of the signal. This work reports on the ground characterization of the NISP detector chain. The detector and electrical effects are likely to generate statistical fluctuations and systematic errors on the final flux measurement. The analysis strategies to maintain the pixel relative response accuracy within 1% is proposed in this work. The Euclid NISP test ow is presented and the main concerns of the detector chain calibration, such as non-linearity, charge trapping and de-trapping are discussed on the basis of the analysis of the flight detectors characterization data