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CoRoT reaches end of mission life after more than seven years in orbit

06/19/2014 | By CNES
Tags : CNES CoRoT

After more than seven years in orbit, the CoRoT satellite has reached the end of its mission life. Decommissioning operations begun in December last year, driven by engineering teams at CNES’s Toulouse Space Centre, were wrapped up on 17 June, when the last command was uplinked to the satellite. This pioneering space astronomy mission leaves a rich legacy of achievements.

Started in 1993, the CoRoT project was conceived with two main scientific goals in mind: to observe stellar vibrations and search for extrasolar planets. But as the quality of its measurements became apparent, it soon proved a valuable source of data in other fields of physics and for studying the evolution of stars. As a result, similar photometric measurements from the same mission but used for very different applications would create synergies between two very active astrophysics communities.

CoRoT’s space telescope continuously counts the number of photons received from distant stars, over long periods and with a very high level of precision. The resulting ‘light curves’, which can only be generated with a space-based instrument, then require complex processing and comparison with observations from the ground.During the course of its mission, CoRoT pointed its telescope at various regions of our Galaxy, providing astrophysicists with precious information on the structure and evolution of stars, their position and their attendant cortege of planets.

In measuring the frequency and amplitude of stellar vibrations with unprecedented precision, CoRoT has opened a whole new field of study. The vibration modes of stars yield unique information about their structure, inner workings and age. From its orbital perch able to observe a wide stellar field for several months, CoRoT was the first instrument to apply knowledge previously acquired about the inner vibrations of the Sun to other extremely varied stars.

For example, CoRoT discovered vibrations comparable to those of the Sun in red giants and showed how their properties are precise indicators of their mass, radius and age. Combined with positional and velocity measurements from GAIA, this major result will give us deeper insights into the history and future of these distant regions of the Milky Way.

By detecting occulting planetary ‘transits’ in front of stars, CoRoT paved the way to search for small planets with the discovery of the first confirmed Earth-like exoplanet orbiting a star similar to our own Sun, thereby proving the value of space-based observation. In all, it has since revealed 32 planets and 100 more are awaiting confirmation.

Supported by a vast array of complementary observing telescopes on the ground, scientists have obtained precious information about the planets discovered by CoRoT, such as their radius, mass and density—information which reveals their inner structure and composition—and the inclination and eccentricity of their orbit. Numbers aside, what is striking about these planets is their extraordinary diversity, especially in the domain of gas giants.

CoRoT and ground telescopes also broke new ground through the combined study of stars and their planets, looking at their interactions, tidal effects in stars and the impact of a star’s brightness on a planet’s structure.

CoRoT’s most spectacular discoveries include:
- the first confirmed rocky exoplanet orbiting close to its star, with a density and composition similar to Earth’s
- the first temperate planet with an orbital period near to 100 days
- an object somewhere between a planet and a star
- a first planetary system with two small planets

The CoRoT space telescope was launched on 27 December 2006. Construction was overseen by CNES as prime contractor, with responsibility for design entrusted to the Paris Observatory, supported by researchers from the French national scientific research centre CNRS and academia. The Paris Observatory also chaired the science committee with representatives from many French and international laboratories1. CoRoT operated for nearly six years, twice as long as planned. In the last months of the mission, CNES conducted a series of technology experiments before shutting down the satellite.

The PROTEUS spacecraft bus conceived in the 2000s by CNES to fly medium-sized science instruments for ambitious low-cost space missions worked without a hitch throughout the mission. Experiments conducted included testing of new control and guidance methods, and the many technology lessons learned will prove useful for future generations of satellites.

Alongside these experiments, operations to decommission the CoRoT satellite were performed from CNES’s control centre in Toulouse. They began at the end of last December by lowering the satellite’s orbit to bring it back into Earth’s atmosphere as quickly as possible, in accordance with the French Space Operations Act (FSOA), and then emptying its fuel tanks.
Lastly, teams at the control centre completed the final phase of decommissioning on 17 June, when they passivated the satellite’s electrical systems to minimize the risk of generating debris in the event of a collision with another object. The final shutdown of the satellite was duly noted a few hours after the last command was sent.

CoRoT’s rich harvest of data holds the prospect of many more discoveries ahead, both in stellar seismology and exoplanets. Data analysis is set to continue long after decommissioning of the satellite, which is why CNES and the laboratories involved in the mission have decided to archive them for the benefit of the scientific community for decades to come.

Data received directly from the instrument will be stored at the SERAD archive at CNES, while the light curves extracted from them will be archived at the CDS astronomy data centre in Strasbourg, designed to give the international community access to the corpus of astronomy knowledge through a ‘virtual observatory’.

CoRoT was a pioneering satellite that blazed the trail for numerous other space astronomy missions. NASA’s Kepler satellite used the same detection principle as CoRoT, operating from 2009 to 2012, and the TESS mission has since been selected to succeed it.
ESA’s CHEOPS mission, selected in 2012, is scheduled to launch in 2017, while the PLATO mission selected at the start of this year will launch in 2024. All of them will continue to explore and develop the new fields of investigation opened up by CoRoT.

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