ESA Science & Technology - Publication Archive

A&A doi http://dx.doi.org/10.1051/0004-6361/200912911

Planck is a scientific satellite that represents the next milestone in space-based research related to the cosmic microwave background, and in many other astrophysical fields. Planck was launched on 14 May of 2009 and is now operational. The uncertainty in the optical response of its detectors is a key factor allowing Planck to achieve its scientific objectives. More than a decade of analysis and measurements have gone into achieving the required performances. In this paper, we describe the main aspects of the Planck optics that are relevant to Planck science, and the estimated in-flight performance, based on the knowledge available at the time of launch. We also briefly describe the impact of the major systematic effects of optical origin, and the concept of in-flight optical calibration. Detailed discussions of related areas are provided in accompanying papers.

A&A doi http://dx.doi.org/10.1051/0004-6361/200913203

Context. The Planck satellite was successfully launched on May 14th 2009. We have completed the pre-launch calibration measurements of the High Frequency Instrument (HFI) on board Planck and their processing.
Aims. We present the results ot the pre-launch calibration of HFI in which we have multiple objectives. First, we determine instrumental parameters that cannot be measured in-flight and predict parameters that can. Second, we take the opportunity to operate and understand the instrument under a wide range of anticipated operating conditions. Finally, we estimate the performance of the instrument built.
Methods. We obtained our pre-launch calibration results by characterising the component and subsystems, then by calibrating the focal plane at IAS (Orsay) in the Saturne simulator, and later from the tests at the satellite level carried out in the CSL (Liege) cryogenic vacuum chamber. We developed models to estimate the instrument pre-launch parameters when no measurement could be performed.
Results. We reliably measure the Planck-HFI instrument characteristics and behaviour, and determine the flight nominal setting of all parameters. The expected in-flight performance exceeds the requirements and is close or superior to the goal specifications.

A&A doi http://dx.doi.org/10.1051/0004-6361/200913054

The High Frequency Instrument of Planck will map the entire sky in the millimeter and sub-millimeter domain from 100 to 857 GHz with unprecedented sensitivity to polarization (DP/T_cmb ~4 x 10^-6 for P either Q or U and T_cmb~2.7 K) at 100, 143, 217 and 353 GHz. It will lead to major improvements in our understanding of the Cosmic Microwave Background anisotropies and polarized foreground signals. Planck will make high resolution measurements of the E- mode spectrum (up to l~1500) and will also play a prominent role in the search for the faint imprint of primordial gravitational waves on the CMB polarization.

A&A doi http://dx.doi.org/10.1051/0004-6361/200912860

The Low Frequency Instrument (LFI) on-board the ESA Planck satellite carries eleven radiometer subsystems, called Radiometer Chain Assemblies (RCAs), each composed of a pair of pseudo-correlation receivers. We describe the on-ground calibration campaign performed to qualify the flight model RCAs and to measure their pre-launch performances. Each RCA was calibrated in a dedicated flight-like cryogenic environment with the radiometer front-end cooled to 20K and the back-end at 300K, and with an external input load cooled to 4K. A matched load simulating a blackbody at different temperatures was placed in front of the sky horn to derive basic radiometer properties such as noise temperature, gain, and noise performance, e.g. 1/f noise. The spectral response of each detector was measured as was their susceptibility to thermal variation. All eleven LFI RCAs were calibrated. Instrumental parameters measured in these tests, such as noise temperature, bandwidth, radiometer isolation, and linearity, provide essential inputs to the Planck-LFI data analysis.

A&A doi http://dx.doi.org/10.1051/0004-6361/200912855

We present a system-level description of the Low Frequency Instrument (LFI) considered as a differencing polarimeter, and evaluate its expected performance. The LFI is one of the two instruments on board the ESA Planck mission to study the cosmic microwave background. It consists of a set of 22 radiometers sensitive to linear polarisation, arranged in orthogonally-oriented pairs connected to 11 feed horns operating at 30, 44 and 70 GHz. In our analysis, the generic Jones and Mueller-matrix formulations for polarimetry are adapted to the special case of the LFI. Laboratory measurements of flight components are combined with optical simulations of the telescope to investigate the values and uncertainties in the system parameters affecting polarisation response. Methods of correcting residual systematic errors are also briefly discussed.

(Abbreviated abstract)
New large-scale CO surveys of the first and second Galactic quadrants and the nearby molecular cloud complexes in Orion and Taurus, obtained with the CfA 1.2 m telescope, have been combined with 31 other surveys obtained over the past two decades with that instrument and a similar telescope on Cerro Tololo in Chile, to produce a new composite CO survey of the entire Milky Way. The survey consists of 488,000 spectra that Nyquist or beamwidth (1/8 °) sample the entire Galactic plane over a strip 4°-10° wide in latitude, and beamwidth 1/4 ° sample nearly all large local clouds at higher latitudes. Compared with the previous composite CO survey of Dame et al. (1987), the new survey has 16 times more spectra, up to 3.4 times higher angular resolution, and up to 10 times higher sensitivity per unit solid angle.

This publication, often referred to as the Blue Book, provides a introduction to the Planck mission and a comprehensive overview of the scientific capabilities of the mission.

A&A doi http://dx.doi.org/10.1051/0004-6361/200912983

The Planck mission was conceived in 1992, in the wake of the release of the results from the Cosmic Background Explorer (COBE) satellite (Boggess et al. 1992), notably the measurement by the FIRAS instrument of the shape of the spectrum of the Cosmic Microwave Background (CMB), and the detection by the DMR instrument of the spatial anisotropies of the temperature of the CMB. The latter result in particular led to an explosion in the number of ground-based and suborbital experiments dedicated to mapping of the anisotropies, and to proposals for space experiments both in Europe and the USA.

Only a few decades ago, the origin of the Universe was a scientific topic lacking reliable data. However, scientists now know where to look for answers, and they are steadily gaining the means to do so. ESA' s ambitious Planck mission is the next step in solving many of cosmology's biggest questions.

For any space mission, the 'ground segment' is vital for operating a spacecraft and processing data received from its instruments. Planck is no different, with hardware software, telecommunications and other operations reaching from Spain to Australia.

The big bang: The universe bursts into existence, an infinitely dense and hot soup of subatomic particles and radiation. In a fraction of a nanosecond, it doubles its size again and again, in a faster-than-light growth spurt known as inflation. That bizarre, hypothetical stretching evens out the universe but also sets off ripples in space and time called gravitational waves, which 13.7 billion years later should have left traces in the afterglow of the big bang, the cosmic microwave background (CMB). The 400 researchers working with the European Space Agency's (ESA's) Planck satellite hope to spot those traces - subtle patterns in the polarization of the microwaves called "B modes" -before anyone else does.

In 2008, an Ariane-5 will lift off from French Guiana carrying ESA's two pioneering Herschel and Planck deep space observatories to explore previously unknown regions of the Universe. Their target is the 'bright' part of the far-infrared spectrum that has tantalised scientists for decades. Until now, the technology has not existed to make precise observations of a distant domain that touches the very beginning of time.

Planck is the third Medium-Sized Mission (M3) of ESA's Horizon 2000 Scientific Programme. It is designed to image the anisotropies of the Cosmic Microwave Background (CMB) over the whole sky, with unprecedented sensitivity (DeltaT/T ~ 2 x 10^-6) and angular resolution (better than 10 arcminutes). Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early universe and the origin of cosmic structure. The ability to measure to high accuracy the angular power spectrum of the CMB fluctuations will allow the determination of fundamental cosmological parameters such as the density parameter (Omega₀) and the Hubble constant H₀, with an uncertainty of order a few percent. In addition to the main cosmological goals of the mission, the Planck sky survey will be used to study in detail the very sources of emission which "contaminate" the signal due to the CMB, and will result in a wealth of information on the properties of extragalactic sources, and on the dust and gas in our own galaxy. One specific notable result will be the measurement of the Sunyaev-Zeldovich effect in many thousands of galaxy clusters. We will present an overview of the Planck mission, its scientific objectives, the key elements of its technical design, and its current status.

COBRAS/SAMBA: Report on the Phase A Study, ESA D/SCI (96)3, 1996,

(Note that at the time the Study was written, the Planck project was still referred to as COBRAS/SAMBA, so you will find the latter name extensively used.)

Planck is the third Medium-Sized Mission (M3) of ESA's Horizon 2000 Scientific Programme. It is designed to image the anisotropies of the Cosmic Microwave Background (CMB) over the whole sky, with unprecedented sensitivity (DeltaT/T ~ 2 x 10^-6) and angular resolution (better than 10 arcminutes). Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early universe and the origin of cosmic structure. The ability to measure to high accuracy the angular power spectrum of the CMB fluctuations will allow the determination of fundamental cosmological parameters such as the density parameter (Omega₀) and the Hubble constant H₀, with an uncertainty of order a few percent. In addition to the main cosmological goals of the mission, the Planck sky survey will be used to study in detail the very sources of emission which "contaminate" the signal due to the CMB, and will result in a wealth of information on the properties of extragalactic sources, and on the dust and gas in our own galaxy. One specific notable result will be the measurement of the Sunyaev-Zeldovich effect in many thousands of galaxy clusters. We will present an overview of the Planck mission, its scientific objectives, the key elements of its technical design, and its current status.

The decrease of brightness temperature of relic radiation in the direction of the cluster of galaxies identically testifies to the existence of hot intergalactic gas in clusters.