CoRoT

Lore & Background

CoRoT was led by the French Space Agency (CNES) in conjunction with the European Space Agency (ESA) and other international partners. The satellite was built at the Cannes Mandelieu Space Center, with a launch mass of 630 kg, length of 4.10 m, and diameter of 1.984 m, powered by two solar panels. Its optical design minimized stray light from Earth and provided a field of view of 2.7° by 3.05°, using a 27 cm diameter off-axis afocal telescope housed in a two-stage opaque baffle. The camera contained four CCD detectors (model 4280 from E2V Technologies), each a 2,048 by 2,048 pixel array, cooled to −40 °C, with two dedicated to planetary detection and two to asteroseismology.

The satellite observed perpendicular to its orbital plane, allowing up to 150 days of continuous observation in 'Long Runs'. After the loss of half the field of view due to failure of Data Processing Unit No. 1 in March 2009, the observation strategy changed to 3-month runs. CoRoT observed in two main sky regions: around Serpens Cauda toward the Galactic Center in northern summer, and in Monoceros in the Galactic anticenter during winter. The mission suffered a computer failure on 2 November 2012 that made data retrieval impossible; repair attempts failed, and on 24 June 2013 it was announced that CoRoT had been retired and would be decommissioned, lowered in orbit to burn up in the atmosphere.

Reader's Guide

CoRoT was notable as the first spacecraft dedicated to detecting transiting extrasolar planets, establishing the technique later used by Kepler and TESS. It detected its first extrasolar planet, CoRoT-1b, in May 2007, just three months after observations began. Among its most significant discoveries was CoRoT-7b, discovered in 2009, which became the first exoplanet shown to have a rock or metal-dominated composition. The mission monitored thousands of stars in the V-magnitude range 11 to 16 for planet detection, and was sensitive enough to detect rocky planets with a radius twice that of Earth orbiting stars brighter than magnitude 14. For asteroseismology, CoRoT measured luminosity variations from acoustic pulsations, allowing calculation of a star's precise mass, age, and chemical composition. The mission's cost was €170 million, with 75% paid by CNES and 25% by Austria, Belgium, Germany, Spain, Brazil, and ESA. CoRoT observed numerous fields from 2007 to 2012, with the final run (LRc10) interrupted by the fatal computer failure in November 2012.

Mission Purpose & Scientific Objectives

CoRoT, an acronym for Convection, Rotation et Transits planétaires, was a space telescope mission conceived with a dual scientific mandate. Its first goal was to hunt for extrasolar planets on short orbital periods, with particular emphasis on bodies of large terrestrial size—worlds that might hint at rocky compositions beyond our solar system. Its second goal was asteroseismology: the precise measurement of solar-like oscillations in stellar surfaces, a technique that reveals the internal structure of stars much as seismology reveals Earth's interior. The mission was spearheaded by France's CNES in partnership with ESA and a broader circle of international collaborators. Though it flew for only seven years, CoRoT holds a singular distinction: it was the very first spacecraft built and deployed with the explicit purpose of detecting transiting exoplanets. In that capacity it paved the conceptual and technical runway for the far more ambitious Kepler and TESS missions that followed, proving that a dedicated transit survey could yield genuine, characterizable discoveries rather than mere statistical candidates.

Engineering & Spacecraft Design

The CoRoT spacecraft was a carefully engineered instrument built at the Cannes Mandelieu Space Center, weighing 630 kilograms at launch and measuring 4.10 meters in length with a 1.984-meter diameter, powered by twin solar panels. At its heart sat a 27-centimeter off-axis afocal telescope, enclosed in a two-stage opaque baffle purpose-built to suppress stray sunlight reflected off Earth's surface. The optical path terminated in a focal box housing four E2V Technologies model 4280 CCD detectors—frame-transfer, thinned, back-illuminated arrays of 2,048 by 2,048 pixels, each pixel 13.5 micrometers square, corresponding to 2.32 arcseconds on the sky. These detectors were cooled to minus 40 degrees Celsius and shielded by 10-millimeter-thick aluminum plates against radiation. Two CCDs were dedicated to planet detection, preceded by a prism that dispersed blue wavelengths more strongly to produce a small spectrum; the other two served asteroseismology and were deliberately defocused by 760 micrometers to prevent the brightest stars from saturating the sensor. The resulting field of view spanned 2.7 by 3.05 degrees.

Key Discoveries & Scientific Legacy

CoRoT's most celebrated finding came in 2009 with the detection of CoRoT-7b, which became the first exoplanet confirmed to possess a rock- or metal-dominated composition—a milestone that reshaped expectations about what kinds of worlds could orbit other stars. The mission's first planetary detection, CoRoT-1b, arrived in May 2007, a mere three months after science operations commenced on 2 February, demonstrating the instrument's readiness almost immediately. Over its operational life, CoRoT cycled through numerous observation fields—designated IRa01, SRc01, LRc01, and so on—monitoring anywhere from roughly 5,000 to over 11,000 stars per run. These fields were drawn from the CoRoTsky database, assembled between 1998 and 2005 through ground-based preliminary surveys of two sky patches: Serpens Cauda near the Galactic Center during northern summer, and Monoceros toward the Galactic anticenter in winter. Selection criteria demanded dense populations of dwarf stars for transit searches and brighter, diverse stellar types for asteroseismology, while avoiding fields that were either too sparse or too crowded. By proving that a dedicated space-based transit survey could deliver concrete, characterizable planets, CoRoT directly opened the door to the Kepler and TESS missions that would follow.

Mission Timeline, Setbacks & Retirement

CoRoT lifted off at 14:28:00 UTC on 27 December 2006, riding a Soyuz 2.1b rocket into orbit. First light was achieved on 18 January 2007, and the spacecraft began collecting science data on 2 February. The original flight plan called for operations to conclude roughly two and a half years after launch, but the mission's scientific productivity prompted an extension that carried it into 2013. The satellite observed perpendicular to its orbital plane, eliminating Earth occultations and enabling continuous Long Run observation stretches of up to 150 days, interspersed with shorter Short Run campaigns aimed at asteroseismology. In March 2009, a failure in Data Processing Unit No. 1 cost the spacecraft half its field of view, forcing a shift to three-month observing cycles to preserve detection efficiency. The final blow came on 2 November 2012, when a computer failure rendered it impossible to retrieve any data from the telescope. Despite repair efforts, the mission was formally retired on 24 June 2013. CoRoT was lowered from orbit to re-enter and burn up in Earth's atmosphere, ending a career that had nonetheless reshaped exoplanet science.