ESA Science & Technology - Publication Archive
A brief description of the methodology of construction, contents and usage of the Planck Early Release Compact Source Catalogue (ERCSC), including the Early Cold Cores (ECC) and the Early Sunyaev-Zeldovich (ESZ) cluster catalogue is provided. The catalogue is based on data that consist of mapping the entire sky once and 60% of the sky a second time by Planck, thereby comprising the first high sensitivity radio/submillimetre observations of the entire sky. A Monte-Carlo algorithm based on the injection and extraction of artificial sources into the Planck maps was implemented to select reliable sources among all extracted candidates such that the cumulative reliability of the catalogue is >=90%. The 10sigma photometric flux density limit of the catalogue at |b|>30 deg is 0.49, 1.0, 0.67, 0.5, 0.33, 0.28, 0.25, 0.47 and 0.82 Jy at each of the nine frequencies between 30 and 857 GHz. Sources which are up to a factor of ~2 fainter than this limit, and which are present in "clean" regions of the Galaxy where the sky background due to emission from the interstellar medium is low, are included in the ERCSC if they meet the high reliability criterion. The Planck ERCSC sources have known associations to stars with dust shells, stellar cores, radio galaxies, blazars, infrared luminous galaxies and Galactic interstellar medium features. A significant fraction of unclassified sources are also present in the catalogs. In addition, two early release catalogs that contain 915 cold molecular cloud core candidates and 189 SZ cluster candidates that have been generated using multi-frequency algorithms are presented. The entire source list, with more than 15000 unique sources, is ripe for follow-up characterisation with Herschel, ATCA, VLA, SOFIA, ALMA and other ground-based observing facilities.
The European Space Agency's Planck satellite was launched on 14 May 2009, and has been surveying the sky stably and continuously since 13 August 2009. Its performance is well in line with expectations, and it will continue to gather scientific data until the end of its cryogenic lifetime. We give an overview of the history of Planck in its first year of operations, and describe some of the key performance aspects of the satellite. This paper is part of a package submitted in conjunction with Planck's Early Release Compact Source Catalogue, the first data product based on Planck to be released publicly. The package describes the scientific performance of the Planck payload, and presents results on a variety of astrophysical topics related to the sources included in the Catalogue, as well as selected topics on diffuse emission.
This A&A issue features 13 articles describing the pre-flight status of the European Space Agency Planck mission, launched together with the Herschel satellite on 14 May 2009. The Planck mission is designed to image the anisotropies of the cosmic background radiation field over the whole sky, with unprecedented sensitivity and angular resolution, as well as a wide frequency range. As a byproduct of that main goal, it will simultaneously address a wide range of galactic and extragalactic science. The mission involves more than four hundred scientists, who are currently working on data processing, calibration, and data analysis.
The satellite is scheduled to continuously acquire high-quality science data until the end of 2011. An early release of the compact source catalogue will be delivered in January 2011, together with a small set of science papers related to foreground astrophysical sources. The first major cosmology results will be delivered in December 2012.
In this special feature, the telescope's optical system and the design, ground calibration, and performance of the Planck lowand high-frequency instruments are described in detail.
A&A doi http://dx.doi.org/10.1051/0004-6361/200912891
We describe the optical design and optimisation of the Low Frequency Instrument, one of two instruments onboard the Planck satellite, which will survey the cosmic microwave background with unprecedented accuracy. The LFI covers the 30 - 70 GHz frequency range with an array of cryogenic radiometers. Stringent optical requirements on angular resolution, sidelobes, main beam symmetry, polarization purity, and feed orientation have been achieved. The optimisation process was carried out by assuming an ideal telescope according to the Planck design and by using both physical optics and multi-reflector geometrical theory of diffraction. This extensive study led to the flight design of the feed horns, their characteristics, arrangement, and orientation, while taking into account the opto-mechanical constraints imposed by complex interfaces in the Planck focal surface.
A&A doi http://dx.doi.org/10.1051/0004-6361/200912837
This paper provides an overview of the Low Frequency Instrument (LFI) programme within the ESA Planck mission. The LFI instrument has been developed to produce high precision maps of the microwave sky at frequencies in the range 27-77 GHz, below the peak of the cosmic microwave background (CMB) radiation spectrum. The scientific goals are described, ranging from fundamental cosmology to Galactic and extragalactic astrophysics. The instrument design and development are outlined, together with the model philosophy and testing strategy. The instrument is presented in the context of the Planck mission. The LFI approach to ground and inflight calibration is described. We also describe the LFI ground segment. We present the results of a number of tests demonstrating the capability of the LFI data processing centre (DPC) to properly reduce and analyse LFI flight data, from telemetry information to calibrated and cleaned time ordered data, sky maps at each frequency (in temperature and polarization), component emission maps (CMB and diffuse foregrounds), catalogs for various classes of sources (the Early Release Compact Source Catalogue and the Final Compact Source Catalogue). The organization of the LFI consortium is briefly presented as well as the role of the core team in data analysis and scientific exploitation. All tests carried out on the LFI flight model demonstrate the excellent performance of the instrument and its various subunits. The data analysis pipeline has been tested and its main steps verified. In the first three months after launch, the commissioning, calibration, performance, and verification phases will be completed, after which Planck will begin its operational life, in which LFI will have an integral part.
A&A doi http://dx.doi.org/10.1051/0004-6361/200912853
In this paper we present the Low Frequency Instrument (LFI), designed and developed as part of the Planck space mission, the ESA programme dedicated to precision imaging of the cosmic microwave background (CMB). Planck-LFI will observe the full sky in intensity and polarisation in three frequency bands centred at 30, 44 and 70 GHz, while higher frequencies (100-850 GHz) will be covered by the HFI instrument. The LFI is an array of microwave radiometers based on state-of-the-art indium phosphide cryogenic HEMT amplifiers implemented in a differential system using blackbody loads as reference signals. The front end is cooled to 20K for optimal sensitivity and the reference loads are cooled to 4K to minimise low-frequency noise. We provide an overview of the LFI, discuss the leading scientific requirements, and describe the design solutions adopted for the various hardware subsystems. The main drivers of the radiometric, optical, and thermal design are discussed, including the stringent requirements on sensitivity, stability, and rejection of systematic effects. Further details on the key instrument units and the results of ground calibration are provided in a set of companion papers.
A&A doi http://dx.doi.org/10.1051/0004-6361/200913039
The Planck High Frequency Instrument, HFI, has been designed to allow a clear unobscured view of the CMB sky through an off-axis Gregorian telescope. The prime science target is to measure the polarized anisotropy of the CMB with a sensitivity of 1 part in 106 with a maximum spatial resolution of 5 arcmin (Cl ~ 3000) in four spectral bands with two further high-frequency channels measuring total power for foreground removal. These requirements place critical constraints on both the telescope configuration and the receiver coupling and require precise determination of the spectral and spatial characteristics at the pixel level, whilst maintaining control of the polarisation. To meet with the sensitivity requirements, the focal plane needs to be cooled with the optics at a few Kelvin and detectors at 100 mK. To limit inherent instrumental thermal emission and difraction effects, there is no vacuum window, so the detector feedhorns view the telescope secondary directly. This requires that the instrument is launched warm with the cooler chain only being activated during its cruise to L2. Here we present the novel optical configuration designed to meet with all the above criteria.
A&A doi http://dx.doi.org/10.1051/0004-6361/200912849
We present the calibration and scientific performance parameters of the Planck Low Frequency Instrument (LFI) measured during the ground cryogenic test campaign. These parameters characterise the instrument response and constitute our optimal pre-launch knowledge of the LFI scientific performance. The LFI shows excellent 1/f stability and rejection of instrumental systematic effects; its measured noise performance shows that LFI is the most sensitive instrument of its kind. The calibration parameters will be updated during flight operations until the end of the mission.
A&A doi http://dx.doi.org/10.1051/0004-6361/200912999
Planck is a European Space Agency (ESA) satellite, launched in May 2009, which will map the Cosmic Microwave Background anisotropies in intensity and polarisation with unprecedented detail and sensitivity. It will also provide full-sky maps of astrophysical foregrounds. An accurate knowledge of the telescope beam patterns is an essential element for a correct analysis of the acquired astrophysical data.We present a detailed description of the optical design of the High Frequency Instrument (HFI) together with some of the optical performances measured during the calibration campaigns.We report on the evolution of the knowledge of the pre-launch HFI beam patterns when coupled to ideal telescope elements, and on their significance for the HFI data analysis procedure.
A&A doi http://dx.doi.org/10.1051/0004-6361/200912975
Context. The High Frequency Instrument (HFI) is one of the two focal instruments of the Planck mission. It will observe the whole sky in six
bands in the 100 GHz - 1 THz range.
Aims. The HFI instrument is designed to measure the cosmic microwave background (CMB) with a sensitivity limited only by fundamental sources: the photon noise of the CMB itself and the residuals left after the removal of foregrounds. The two high frequency bands will provide full maps of the submillimetre sky, featuring mainly extended and point source foregrounds. Systematic effects must be kept at negligible levels or accurately monitored so that the signal can be corrected. This paper describes the HFI design and its characteristics deduced from ground tests and calibration.
Methods. The HFI instrumental concept and architecture are feasible only by pushing new techniques to their extreme capabilities, mainly: (i) bolometers working at 100 mK and absorbing the radiation in grids, (ii) a dilution cooler providing 100 mK in microgravity conditions, (iii) a new type of AC biased readout electronics and (iv) optical channels using devices inspired from radio and infrared techniques.
Results. The Planck-HFI instrument performance exceeds requirements for sensitivity and control of systematic effects. During ground-based calibration and tests, it was measured at instrument and system levels to be close to or better than the goal specification.