Planck (spacecraft)

Planck (spacecraft)
Name	Planck
Mission type	Space observatory
Operator	European Space Agency (ESA)
Cospar id	2009-026A
Satcat	34925
Mission duration	4 years (nominal)
Manufacturer	Astrium, Thales Alenia Space
Launch mass	1950 kg
Dry mass	1100 kg
Power	1,500 W
Launch date	2009-05-14
Launch site	Guiana Space Centre
Launch contractor	Arianespace
Orbit reference	Sun–Earth L2
Instruments	High Frequency Instrument, Low Frequency Instrument
Programme	Herschel–Planck (mission)

Planck (spacecraft) Planck was a European Space Agency space observatory mission designed to map the anisotropies of the Cosmic Microwave Background (CMB) across the entire sky with unprecedented sensitivity, angular resolution, and frequency coverage. Developed by industry partners including Astrium and Thales Alenia Space and supported by national agencies such as CNES and DLR, Planck combined cryogenic detectors and a Gregorian telescope to produce full-sky surveys that informed cosmology, astrophysics, and particle physics. Launched in 2009 aboard an Ariane 5 from the Guiana Space Centre, Planck operated near the Lagrange point L2 before returning transformative datasets to the community.

Overview

Planck was conceived in response to long-standing questions in cosmology and followed earlier CMB missions like COBE and WMAP. The spacecraft carried two complementary instruments—one optimized for low frequencies and one for high frequencies—covering multiple bands to separate CMB anisotropy from astrophysical foregrounds such as emissions from Milky Way, interstellar medium, Sunyaev–Zel'dovich effect sources, and extragalactic dusty galaxies catalogued by surveys like IRAS and Herschel Space Observatory. Managed by ESA with scientific leadership from the Planck Collaboration, the mission aimed to constrain parameters in models associated with inflationary cosmology, dark matter, dark energy, and the ΛCDM model.

Mission and Objectives

Primary objectives included measuring temperature and polarization anisotropies of the CMB with arcminute-scale resolution, enabling precise estimation of cosmological parameters used in frameworks such as the Lambda-CDM model. Planck sought to test predictions from inflationary models, constrain the spectral index and non-Gaussianity linked to theories advanced by researchers like Alan Guth and Andrei Linde, and refine the Hubble constant value relative to local measurements by teams led by Adam Riess and Sharon G. The mission also targeted secondary science: mapping the Sunyaev–Zel'dovich effect in galaxy clusters identified in surveys by XMM-Newton and Chandra X-ray Observatory, studying polarized emission from Galactic magnetic fields relevant to work by J. L. Han and others, and producing legacy catalogs for follow-up by facilities such as Atacama Large Millimeter Array and James Webb Space Telescope.

Spacecraft Design and Instruments

The spacecraft bus and cryogenic systems were delivered by contractors including Astrium and integrated with instrument teams from research institutions like Max Planck Institute for Astrophysics and University of Cambridge. The optical system was a two-mirror off-axis Gregorian telescope providing low sidelobe response, developed drawing on heritage from missions such as IRAS and Herschel Space Observatory. The Low Frequency Instrument (LFI), developed by an international consortium coordinated by Istituto Nazionale di Fisica Nucleare and Jet Propulsion Laboratory, used coherent radiometers based on HEMT amplifiers to observe at 30, 44, and 70 GHz. The High Frequency Instrument (HFI), led by Institut d'Astrophysique Spatiale teams, used bolometric detectors cooled to 0.1 kelvin by a dilution refrigerator to measure bands at 100–857 GHz. Cryogenics involved stages maintained by partners including Air Liquide and utilized technologies refined for missions like Herschel. Onboard systems for attitude control and thermal shielding incorporated designs common to missions from European Space Agency collaboration with national space agencies.

Launch, Orbit, and Operations

Planck launched on 14 May 2009 on an Ariane 5 jointly with the Herschel Space Observatory from the Guiana Space Centre in Kourou. After separation, Planck executed a transfer to a halo orbit around the Sun–Earth Lagrange point L2, where it conducted continuous sky surveys with a spin-stabilized scanning strategy similar to that used by WMAP. Ground operations were handled by ESA's European Space Operations Centre and science operations by the Planck Science Office with data processing centers across institutions such as Max Planck Institute for Astrophysics, University of California, Berkeley, and University of Milano. Nominal mission lifetime was extended beyond four years due to efficient cryogen use and robust subsystems, allowing deeper integrations and additional sky surveys.

Data Processing and Key Results

Data reduction was performed by the Planck Data Processing Centres coordinated by the Planck Collaboration, producing calibrated frequency maps, component-separated CMB maps, and extensive catalogs of compact sources and galaxy clusters. Planck's first cosmological results tightened constraints on parameters like the Hubble constant, matter density, and scalar spectral index, providing strong support for the ΛCDM model while setting limits on primordial non-Gaussianity relevant to inflationary scenarios proposed by Andrei Linde and Alan Guth. The mission delivered high-fidelity polarization maps that informed studies of reionization epoch constraints linked to research by Wilkinson Microwave Anisotropy Probe predecessors and improved foreground models used by experiments such as BICEP2 and Keck Array. Planck catalogs of galaxy clusters via the Sunyaev–Zel'dovich effect enabled cross-comparison with surveys by SDSS, ROSAT, and XMM-Newton.

Legacy and Impact

Planck left a comprehensive legacy of full-sky maps and catalogs used by cosmologists, astronomers, and particle physicists, underpinning subsequent analyses by collaborations associated with Atacama Cosmology Telescope and South Pole Telescope. Its precise parameter constraints informed debates involving the Hubble tension highlighted by teams including Adam Riess and Wendy Freedman, stimulated theoretical work in inflationary model building, and guided instrument design for missions such as the proposed LiteBIRD and facilities planned by European Southern Observatory. The Planck dataset continues to serve as a reference for multiwavelength studies involving observatories like Spitzer Space Telescope and Fermi Gamma-ray Space Telescope, cementing its role in 21st-century observational cosmology.

Category:European Space Agency spacecraft Category:Cosmic microwave background