Planck was a space observatory operated by the European Space Agency (ESA) from 2009 to 2013, which mapped the anisotropies of the cosmic microwave background (CMB) at microwave and infrared frequencies, with high sensitivity and small angular resolution. The mission substantially improved upon observations made by the NASA Wilkinson Microwave Anisotropy Probe (WMAP). Planck provided 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. Since the end of its mission, Planck has defined the most precise measurements of several key cosmological parameters, including the average density of ordinary matter and dark matter in the Universe and the age of the universe. The project was started around 1996 and was initially called COBRAS/SAMBA: the Cosmic Background Radiation Anisotropy Satellite/Satellite for Measurement of Background Anisotropies. It was later renamed in honour of the German physicist Max Planck (1858–1947), who became the originator of quantum theory by deriving the formula for black-body radiation. Built at the Cannes Mandelieu Space Center by Thales Alenia Space, and created as a medium-sized mission for ESA's Horizon 2000 long-term scientific programme, Planck was launched in May 2009. It reached the Earth/Sun by July 2009, and by February 2010 it had successfully started a second all-sky survey. On 21 March 2013, the mission's first all-sky map of the cosmic microwave background was released with an additional expanded release including polarization data in February 2015. The final papers by the Planck team were released in July 2018. At the end of its mission Planck was put into a heliocentric graveyard orbit and passivated to prevent it from endangering any future missions. The final deactivation command was sent to Planck in October 2013. Objectives The mission had a wide variety of scientific aims, including: high resolution detections of both the total intensity and polarization of primordial CMB anisotropies, creation of a catalogue of galaxy clusters through the Sunyaev–Zel'dovich effect, observations of the gravitational lensing of the CMB, as well as the integrated Sachs–Wolfe effect, observations of bright extragalactic radio (active galactic nuclei) and infrared (dusty galaxy) sources, observations of the Milky Way, including the interstellar medium, distributed synchrotron emission and measurements of the Galactic magnetic field, and studies of the Solar System, including planets, asteroids, comets and the zodiacal light. Planck had a higher resolution and sensitivity than WMAP, allowing it to probe