Exploring Cosmic Origins with CORE:Survey requirements and missiondesign
(2018) Journal of Cosmology and Astroparticle Physics — Vol. 2018, p. APRIL 2018 (2017)
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- Abstract
- Future observations of cosmic microwave background (CMB) polarisation have the po-tential to answer some of the most fundamental questions of modern physics and cosmology,including: What physical process gave birth to the Universe we see today? What are thedark matter and dark energy that seem to constitute 95% of the energy density of the Uni-verse? Do we need extensions to the standard model of particle physics and fundamentalinteractions? Is the ΛCDM cosmological scenario correct, or are we missing an essentialpiece of the puzzle? In this paper, we list the requirements for a future CMB polarisationsurvey addressing these scientific objectives, and discuss the design drivers of theCOREspace mission proposed to ESA in answer to the “M5” call for a medium-sized mission. Therationale and options, and the methodologies used to assess the mission’s performance, areof interest to other future CMB mission design studies.COREhas 19 frequency channels,distributed over a broad frequency range, spanning the 60–600 GHz interval, to control astro-physical foreground emission. The angular resolution ranges from 2′to 18′, and the aggregateCMB sensitivity is about 2μK.arcmin. The observations are made with a single integratedfocal-plane instrument, consisting of an array of 2100 cryogenically-cooled, linearly-polariseddetectors at the focus of a 1.2-m aperture cross-Dragone telescope. The mission is designed to minimise all sources of systematic effects, which must be controlled so that no more than10−4of the intensity leaks into polarisation maps, and no more than about 1% ofE-typepolarisation leaks intoB-type modes.COREobserves the sky from a large Lissajous orbitaround the Sun-Earth L2 point on an orbit that offers stable observing conditions and avoidscontamination from sidelobe pick-up of stray radiation originating from the Sun, Earth, andMoon. The entire sky is observed repeatedly during four years of continuous scanning, witha combination of three rotations of the spacecraft over different timescales. With about 50%of the sky covered every few days, this scan strategy provides the mitigation of systematiceffects and the internal redundancy that are needed to convincingly extract the primordialB-mode signal on large angular scales, and check with adequate sensitivity the consistency ofthe observations in several independent data subsets.COREis designed as a “near-ultimate”CMB polarisation mission which, for optimal complementarity with ground-based observa-tions, will perform the observations that are known to be essential to CMB polarisationscience and cannot be obtained by any other means than a dedicated space mission. It willprovide well-characterised, highly-redundant multi-frequency observations of polarisation atall the scales where foreground emission and cosmic variance dominate the final uncertaintyfor obtaining precision CMB science, as well as 2′angular resolution maps of high-frequencyforeground emission in the 300–600 GHz frequency range, essential for complementarity withfuture ground-based observations with large telescopes that can observe the CMB with thesame beamsize.
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Ringeval, C., & et al. (2018). Exploring Cosmic Origins with CORE:Survey requirements and missiondesign. Journal of Cosmology and Astroparticle Physics, 2018, APRIL 2018. https://doi.org/10.1088/1475-7516/2018/04/014 (Original work published 2017)