France in Space # 359

Status Report From: Centre National d'Etudes Spatiales (CNES)
Posted: Wednesday, November 8, 2006


With CNES' CoRoT (Convection, Rotation & planetary Transits) Space Telescope mission steadily advancing towards its December 21st, 2006, launch date, we the editors at France In Space thought that we would use this week's edition to describe this one-of-a-kind spacecraft and its remarkable mission. The mission, first proposed by CNES in December 1996 was finally given the green light in March of 2000 after three years of research and feasibility studies and a call for potential European partners in September1999. Once launched, CoRoT will be the first spacecraft devoted to the search for rocky planets outside our Solar System; its goal is to find inhabitable, Earth-like planets orbiting other stars. The spacecraft will also be studying stellar vibrations which will give scientists insight on the interiors and physics of stars.


The CoRoT Space Telescope has a dual mission: it will be studying stellar seismology (i.e. the detection and measurement of stellar vibrations), as well as searching for small, rocky, Earth-like planets orbiting stars outside our Solar System. These two objectives were grouped together in the same mission as they use the same technique of extremely high precision photometry and continuous observations of the same part of the sky over long periods of time (up to 150 days). Both of these techniques are impossible here on Earth given the Earth's rotation around the Sun and around the poles which only allows for observation of the same part of the sky for two to three months, and only at night. From the Earth, scientists and astronomers have only been able to detect giant, gaseous planets, several times the diameter of our planet. However, CoRoT, as it will not be affected by the distorting effects of the Earth's atmosphere will be capable of discovering small, rocky bodies, which are yet undiscovered outside of our Solar System. Every 150 days CoRoT will move to a new field and begin new observations. CoRoT's mission is expected to last a minimum of two and a half years. The spacecraft will be launched from Baikonur via Soyuz 2.1B.


CoRoT is a CNES-led European mission, of which CNES acts as the prime contractor. CoRoT's payload consists primarily of a telescope (2 mirrors off axis) and two cameras, one for each of the two mission objectives. The telescope, developed under the responsibility of Laboratory of Astrophysics (LAM) in Marseille, France, contains two parabolic mirrors, each with a 1.1 meter focal length. The field of view is two degrees≤, half for the seismology mission and half for the exoplanet mission. The telescope also includes an external "baffle", designed by ESA's ESTEC facilities in the Netherlands, to shield the lens from light pollution. The two cameras were developed under the leadership of the Space Studies and Astrophysics Instrumentation Laboratory (LESIA) in Paris, France, and manufactured by ESA's ESTEC. The satellite itself is based on the PROTEUS multi-mission platform, developed in partnership between CNES and, what is today, Alcatel Alenia Space. It is the same platform used for the Franco-American oceanographic satellite JASON-1 (launched in December 2001), the CNES-NASA CALIPSO mission (launched in April 2006), the OSTM/JASON-2 satellite and CNES' Megha-Tropiques satellite. CoRoT will have a total mass at launch of 630 kg.


The innovative nature of this mission led CNES to collaborate with a number of international countries. ESA had a crucial role in that it provided the optics for the telescope as well as tested the payload. Scientists from Denmark, Switzerland, the UK and Portugal, among other European countries, were selected as Co-Investigators. Other participating countries are Austria, Spain, Germany, Belgium and Brazil. As a result of ESA's participation in the CoRoT program, scientists from ESA's Member States will have access to the spacecraft's data.


Over the thousands of years that scientists and astronomers have been observing and studying the stars, they have come to understand that stars are spheres of ionized gas which tend to oscillate in different ways depending on their spherical structure. These oscillations are important as they are the only signal that comes from the interior of the star, thus the only way to "see" to the star's core. The CoRoT mission was designed to observe these vibrations in a number of different sized stars. By observing the vibrations of various stars of differing age, mass and chemical composition, scientists will have new information to aid in their determination of how the Universe has evolved, its age and its future.


It was only 11 years ago that the first exoplanet, 51 Pegasi b, was discovered, however since then, more than 200 other planets have been detected from ground-based observatories. All of these planets were discovered by measuring the perturbation produced by the planet on the star's motion with respect to the Earth, and all are large, Jupiter-like planets. Scientists are convinced that smaller, "extrasolar" planets, similar to Earth exist yet detecting them from Earth remains impossible due to interference from the Earth's atmosphere. CoRoT will help solve this problem. Using its highly accurate photometer, CoRoT will be the first spacecraft to detect "transits", or the attenuation of the light of the parent star when a "small" planet passes in front of the stellar disk. Observing this phenomena is not easy in the least and is dependant on having the telescope pointed in the right direction, being perfectly aligned with the star and the planet and observing a very large number of objects. Scientists estimate that given the specifics of CoRoT's telescope they will be able to observe a few hundred planetary systems and a few dozen "small" planets.

[CNES 10/12/06, ESA 10/24/06, 11/07/06


France In Space is a weekly synthesis of French space activities based on French press. Its content does not reflect an official position of the French Government or CNES. It is provided by the CNES office and the Office of Science and Technology of the French Embassy in Washington, D.C.

Editors: Jean-Jacques Tortora, NoŽlle Miliard and Timothťe Verwaerde

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About CNES

"CNES develops and leads national space programmes. The main thrust of its action is to serve France's ambition to sustain a strong space capability and contribute to scientific discovery at the highest levels. CNES is committed to fostering innovative space technologies that meet the current and future needs of society. Most programmes are pursued in cooperation with international partners. CNES also plays a central role in programmes initiated by ESA, the European Space Agency, to which it is a major contributor. It is thus a driving force behind ESA programmes and activities".

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