The Planck mission WiP

The Planck mission

Planck is a mission of the European Space Agency - ESA. The Planck satellite carried instruments provided by two scientific Consortia funded by ESA member states (in particular the lead countries: France and Italy) with contributions from NASA (USA), and telescope reflectors provided in a collaboration between ESA and a scientific Consortium led and funded by Denmark.

The main objective of Planck was to measure the spatial anisotropies of the temperature of the Cosmic Microwave Background radiation (CMB), with an accuracy set by fundamental astrophysical limits. Its level of performance enables Planck to extract essentially all the information in the CMB temperature anisotropies. Planck also measured to high accuracy the polarisation of the CMB anisotropies, which encodes not only a wealth of cosmological information, but also provides a unique probe of the thermal history of the Universe during the time when the first stars and galaxies formed. In addition, the Planck sky surveys produce a wealth of information on the properties of extragalactic sources and on the dust and gas in our own Galaxy. The scientific objectives of Planck as conceived in 2005 (4 years before launch) were described in detail in Blue Book.

Planck was conceived in 1992, in the wake of the release of the results from the Cosmic Background Explorer (COBE) satellite, notably its measurement of the shape of the spectrum of the CMB, and its detection 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.

The development of Planck began with two proposals presented to the European Space Agency (ESA) in May of 1993, for the Cosmic Background Radiation Anisotropy Satellite (COBRAS) and the Satellite for Measurement of Background Anisotropies (SAMBA, ). Each of these proposed a payload formed by an offset Gregorian telescope focussing light from the sky onto an array of detectors (based on High Electron Mobility Transistor [HEMT] Low Noise Amplifiers for COBRAS and very low temperature bolometers for SAMBA) fed by corrugated horns. The two proposals were used by an ESA-led team to design a payload where a single COBRAS-like telescope fed two instruments, a COBRAS-like Low Frequency Instrument (LFI), and a SAMBA-like High Frequency Instrument (HFI) sharing a common focal plane. A period of study of this concept culminated in the selection by ESA in 1996 of the COBRAS/SAMBA satellite (described in the so-called Redbook) into its programme of scientific satellites. At the time of selection the launch of COBRAS/SAMBA was expected to be in 2003. Shortly after the mission was approved, it was renamed in honor of the German scientist Max Planck (1858-1947), winner of the Nobel Prize for Physics in 1918.

Shortly after its selection, the development of Planck was joined with that of ESA's Herschel Space Telescope, based on a number of potential commonalities, the most important of which was that both missions targeted orbits around the second Lagrangian point of the Sun-Earth system and could therefore share a single heavy launcher. In practice the joint development has meant that a single ESA engineering team has led the development of both satellites by a single industrial prime contractor, leading to the use of many identical hardware and software subsystems in both satellites, and a synergistic sharing of engineering skills and manpower. The industrial prime contractor, Thales Alenia Space France, was competitively selected in early 2001. Thales Alenia Space France was supported by two major subcontractors: Thales Alenia Space Italy for the Service Module of both Planck and Herschel, and EADS Astrium GmbH for the Herschel Payload Module, and by many other industrial subcontractors from all ESA member states (industrial team ).

In early 1999, ESA selected two Consortia of scientific institutes to provide the two Planck instruments which were part of the payload described in the Redbook: the Low Frequency Instrument was developed by a consortium led by N. Mandolesi of the Istituto di Astrofisica Spaziale e Fisica Cosmica (CNR) in Bologna (Italy); and the High Frequency Instrument by a consortium led by J.-L. Puget of the Institut d'Astrophysique Spatiale (CNRS) in Orsay (France). More than 40 European institutes, and some from the USA, have collaborated on the development, testing, and in-flight operations of these instruments, as well as the ensuing data analysis and initial scientific exploitation.

In early 2000, ESA and the Danish National Space Institute (DNSI) signed a Letter of Agreement for the provision of the two reflectors that are used in the Planck telescope. DNSI led a Consortium of Danish institutes, which together with ESA subcontracted the development of the Planck reflectors to EADS Astrium GmbH (Friedrichshafen, D), who have manufactured the reflectors using state-of-the-art carbon fibre technology.

The development history of the Planck satellite is summarised here. It culminated with the successful launch of Planck and Herschel on 14 May 2009. After a period dedicated to Commissioning and Performance Verification, Planck started its planned observations on 13 August 2009. It carried on observing for a period of about 30 months, about twice the span originally required, and completed five full-sky surveys with both instruments. Able to work at slightly higher temperatures than HFI, the Low Frequency Instrument (LFI) continued to survey the sky for a large part of 2013, providing even more data to improve the Planck final results. The last command to the Planck satellite was sent on the 23 October 2013, marking the end of operations.

The Planck Data Products

The Data Products of Planck have been released in four different stages of increasing scope and quality:

• The first set of scientific data, the Early Release Compact Source Catalogue (ERCSC; Template:Planck2011-1.10), was released in January 2011. At the same time, a set of 26 papers related to astrophysical foregrounds were published in a special issue of Astronomy and Astrophysics (Vol. 536, 2011).
• The second set of data products (sometimes referred to as Planck Release 1 or “PR1,” because it was the first release of cosmologically useful data) was based on data acquired during the so-called nominal mission, i.e. from start of routine operations to 28 November 2010. These products were based on temperature analysis of the whole sky, and were released in March of 2013. The data and associated scientific results are described in a set of 32 papers in another special issue of A&A (Vol. 571, 2014).
• The third set of data products (and second set of cosmological data, hence “PR2”) and scientific results released by Planck, was based on the data acquired during the complete Planck mission from 12 August 2009 to 23 October 2013, and hereafter referred to as the “2015 products.” They are based on both temperature and polarization analysis of the entire sky, and were released between February and July 2015. The data and associated scientific results are described in a set of 28 papers published in a third special issue of A&A (Vol. 594, 2016).
• The fourth set of scientific data (and third set of cosmological data, hence "PR3") ...

Since then, 40 “Intermediate” (i.e., between the major data releases) papers have been submitted to A&A containing further astrophysical investigations by the Collaboration.

The Planck Legacy Archive

The Planck Legacy Archive (PLA) contains all public products originating from the Planck mission, and provides an online interface to select and retrieve them. The majority of the scientific data products from Planck have been produced by the LFI and HFI Data Processing Centres on behalf of the Planck Collaboration.

The Planck collaboration institutes and agencies.

For more information

A complete overview of the Planck mission and its science programme can be found in the Blue Book.

More details on the Planck mission performance can be found in , .

A complete list of Planck publications can be found here.