Planck (ESA)

Planck (ESA)
Name	Planck
Mission type	Space telescope
Operator	European Space Agency
Cospar id	2009-026A
Satcat	34930
Mission duration	4.5 years (extended)
Launch mass	1830 kg
Launch date	2009-05-14
Launch rocket	Ariane 5 ECA
Launch site	Guiana Space Centre
Orbit reference	Sun–Earth L2
Instruments	High Frequency Instrument, Low Frequency Instrument
Programme	Horizon 2000

Planck (ESA) was a European Space Agency European Space Agency mission to measure the anisotropies of the Cosmic Microwave Background across the entire sky with unprecedented sensitivity, angular resolution, and frequency coverage. A successor in scientific lineage to the COBE and WMAP missions, Planck combined cryogenic detectors operated by teams from Centre National d'Études Spatiales, Max Planck Society, and Jet Propulsion Laboratory among others to map temperature and polarization of the microwave sky. The mission produced datasets that reshaped constraints on Lambda-CDM cosmology, the Hubble constant, and models of inflation.

Overview

Planck was developed under ESA's Horizon 2000 long-term programme and involved industrial leadership by Thales Alenia Space and scientific consortia including the European Space Research and Technology Centre and the Institute of Space Astrophysics and Planetology. The spacecraft carried two complementary instruments: the Low Frequency Instrument built by a consortium led by Istituto Nazionale di Astrofisica and Université Paris-Sud, and the High Frequency Instrument led by Agence Spatiale Européenne partners and the Max Planck Institute for Astrophysics. Launched on an Ariane 5 from the Guiana Space Centre into a halo orbit around the Sun–Earth L2 Lagrangian point, Planck surveyed the sky repeatedly to separate primordial cosmological signals from astrophysical foregrounds such as galactic dust, synchrotron radiation, and emission from extragalactic sources.

Mission Design and Instruments

The mission's optical design used a 1.5-metre off-axis reflector system developed by Rutherford Appleton Laboratory and Astrium to feed arrays of detectors spanning 30–857 GHz. The Low Frequency Instrument employed coherent radiometers based on indium-phosphide HEMT amplifiers developed with teams from NRAO and SRON, while the High Frequency Instrument used bolometric detectors cooled to 0.1 K by a sorption cooler and a dilution refrigerator designed by Cryogenic Engineering Group contractors with contributions from Centre National de la Recherche Scientifique and National Aeronautics and Space Administration. Onboard calibration referenced the orbital dynamics provided by European Space Operations Centre and attitude control systems derived from heritage at de Havilland and Airbus Defence and Space. The instrument suite allowed multifrequency component separation techniques developed by groups at Princeton University, University of Cambridge, University of Oxford, and Yale University.

Launch and Operations

Planck launched on 14 May 2009 atop an Ariane 5 ECA along with the Herschel Space Observatory, marking a dual-payload mission coordinated by Arianespace and operated from the Mission Control Centre at European Space Operations Centre. After a transfer to the Sun–Earth L2 halo orbit, mission operations including pointing, thermal control, and science scheduling were managed by ESA teams with science support provided by the Planck Science Office and instrument consortia coordinated through the European Space Agency Science Programme Committee. Routine observations began after instrument commissioning and cryogenic checkout, with survey strategies informed by experience from COBE and WMAP and data downlinks through the New Norcia Station and Cebreros Station ground networks. The nominal mission lasted until 2013 with extended operations enabled by consumables and cryogen lifetime management.

Scientific Results and Discoveries

Planck delivered high-precision measurements of the Cosmic Microwave Background angular power spectrum, refining parameters of the Lambda-CDM model such as the baryon density, cold dark matter density, scalar spectral index, and optical depth to reionization. The mission's polarization maps constrained models of cosmic inflation, placing limits on the tensor-to-scalar ratio that impacted theories by researchers at Harvard University, California Institute of Technology, and University of Chicago. Planck detected the imprint of the Sunyaev–Zel'dovich effect across known galaxy cluster catalogues compiled by teams including ROSAT and XMM-Newton, enabling cross-correlation studies with Sloan Digital Sky Survey and Dark Energy Survey datasets. High-frequency channels illuminated the properties of interstellar dust in the Milky Way, informing models used by ALMA and SOFIA observers, while Planck's compact source catalogues intersected with surveys by VLA, ATCA, and Spitzer.

Data Processing and Releases

Data reduction relied on sophisticated timelines, mapmaking, and component-separation pipelines developed by the Planck Collaboration and hosted at the European Space Astronomy Centre and distributed through coordinated data centres at Institute of Astrophysics of Canarias and Max Planck Institute for Radio Astronomy. Major public releases in 2013, 2015, and 2018 provided temperature and polarization maps, likelihood codes adopted by the Particle Data Group and cosmology teams at University of Toronto and Imperial College London, and associated catalogue products like the Second Planck Catalogue of Sunyaev–Zel'dovich Sources used by Planck Consortium science working groups. The releases included beam characterization, noise simulations, and systematic error assessments performed by instrument teams from Space Research Institute and Laboratoire de Physique Subatomique et de Cosmologie.

Legacy and Impact

Planck's legacy reshaped modern cosmology, setting benchmarks for precision cosmological parameters used by Large Hadron Collider phenomenologists, Euclid mission planners, and theorists at Institute for Advanced Study. The mission influenced design choices for successor experiments such as LiteBIRD, CMB-S4, and Simons Observatory, and its foreground separation techniques informed analyses in gamma-ray and submillimetre communities including observers at Herschel Space Observatory and James Webb Space Telescope teams. Planck datasets continue to be cross-used with surveys like Gaia, Pan-STARRS, and LSST pathfinder projects, underpinning studies of large-scale structure, primordial non-Gaussianity, and astrophysical processes from interstellar medium physics to galaxy evolution.

Category:European Space Agency spacecraft Category:Cosmic microwave background experiments