COROT

COROT

Model of the Corot satellite
General information
NSSDC ID	2006-063A
Organization	Centre National d'Etudes Spatiales European Space Agency
Launch date	2006-12-27 14:24:00 UTC
Launched from	Baikonur Cosmodrome Kazakhstan
Launch vehicle	Soyuz 2.1b/Fregat
Mission length	≥2.5 years (4 years,  1 month, and 18 days elapsed)
Mass	630 kg
Type of orbit	Polar
Orbit height	827 km
Location	Earth orbit
Telescope style	Afocal
Diameter	27 cm
Website	smsc.cnes.fr/COROT

COROT (COnvection ROtation and planetary Transits) is a space mission led by the French Space Agency (CNES) in conjunction with the European Space Agency (ESA) and other international partners. The mission's two objectives are to search for extrasolar planets with short orbital periods, particularly those of large terrestrial size, and to perform asteroseismology by measuring solar-like oscillations in stars.^[1] It was launched at 14:28:00 UTC on 27 December 2006, atop a Soyuz 2.1b carrier rocket.^[2][3][4] COROT subsequently reported first light on 18 January 2007.^[5] COROT is the first spacecraft dedicated to extrasolar planet detection. It detected its first extrasolar planet, COROT-1b, in May 2007.^[6] Mission flight operations were originally scheduled to end 2.5 years from launch but apparently flight operations were extended to January, 2010^[7] and then to 2013^[8].

Overview

Spacecraft design

The COROT optical design minimizes stray light coming from the Earth and provides a field of view of 2.7° by 3.05°. The COROT optical path consists of a 27 cm (10.6 in) diameter off-axis afocal telescope housed in a two-stage opaque baffle specifically designed to block sunlight reflected by the Earth and a camera consisting of a dioptric objective and a focal box. Inside the focal box is an array of four CCD detectors protected against radiation by aluminum shielding 10mm thick. The asteroseismology CCDs are defocused by 760μm toward the dioptric objective to avoid saturation of the brightest stars. A prism in front of the planet detection CCDs gives a small spectrum designed to disperse more strongly in the blue wavelengths.^[9]

The four CCD detectors are model 4280 CCDs provided by E2V Technologies. These CCDs are frame-transfer, thinned, back-illuminated designs in a 2048 pixel by 2048 pixel array. Each pixel is 13.5 × 13.5μm² in size which corresponds to an angular pixel size of 2.32 arcsec. The CCDs are cooled to −40 °C (233.2 K; −40.0 °F). These detectors are arranged in a square pattern with two each dedicated to the planetary detection and asteroseismology. The data output stream from the CCDs are connected in two chains. Each chain has one planetary detection CCD and one asteroseismology CCD. The field of view for planetary detection is 3.5°.^[9]

The satellite, built in the Cannes Mandelieu Space Center, has a launch mass of 630 kg, is 4.10 m long, 1.984 m in diameter and is powered by two solar panels.^[7]

Mission design

Over its planned 2½ year mission it will observe perpendicular to its orbital plane, meaning there will be no Earth occultations, allowing 150 days of continuous observation. During the northern summer it will observe in an area around Serpens Cauda and during the winter it will observe in Monoceros. During the remaining 30 days between the two main observation periods, COROT will observe 5 other patches of sky. Four fixed areas of the sky have been identified for study:

• LRa01 in the constellation of Monoceros
• LRc01 in the constellation of Aquila
• SRc01 in the constellation of Serpens Cauda
• IRa01 in the constellation of Monoceros

The probe will monitor the brightness of stars, watching for the slight dimming that happens in regular intervals when planets transit their primary sun. COROT will be sensitive enough to detect rocky planets several times larger than Earth; it is also expected to discover new gas giants, which currently comprise almost all of the known extrasolar planets.^[10]

COROT will also undertake asteroseismology. It can detect luminosity variations associated with acoustic pulsations of stars. This phenomenon allows calculation of a star's precise mass, age and chemical composition and will aid in comparisons between the sun and other stars.

In each field of view there will be one main target star for the asteroseismology as well as up to nine other targets. Simultaneously, it will be recording the brightness of 12,000 stars brighter than apparent magnitude 15.5 for the extrasolar planet study. It is expected that a few dozen planets will be found as a result of this project.

The mission began on 27 December 2006 when a Russian Soyuz 2-1b rocket lifted the satellite into a circular polar orbit with an altitude of 827 km . The first scientific observation campaign started on 3 February 2007.^[11]

Development

The primary contractor for the construction of the COROT vehicle was CNES,^[12] to which individual components were delivered for vehicle assembly. The COROT equipment bay, which houses the data acquisition and pre-processing electronics, was constructed by the LESIA Laboratory at the Paris Observatory and took 60 person-years to complete.^[12] The COROT camera, also constructed by the LESIA Laboratory, took 25 person-years to complete.^[12]

Potential

Before the beginning of the mission, the team stated with caution that COROT would only be able to detect planets a few times to several times larger than Earth and that it was not specifically designed to detect habitable planets (it would instead assess their potential for habitability). According to the press release announcing the first results, COROT's instruments are performing with higher precision than had been predicted, and may be able to find planets down to the size of Earth.^[6]

COROT should be assumed to only detect a small percentage of planets within its detection range due to the low percentage of existing planets that would likely make transits from the angle of observation from our Solar System. Expectations are that any planetary systems detected within a suitable range for further observations will be followed up by the future Darwin and Terrestrial Planet Finder spacecrafts or other projects like Kepler (NASA), New Worlds Mission, or Space Interferometry Mission.

Discoveries

On May 3, 2007, it was reported that COROT had discovered a hot Jupiter COROT-1b orbiting a sun-like star 1,500 light years away. This planet has a radius approximately 1.78 times that of Jupiter, a mass approximately 1.3 times that of Jupiter, and orbits its parent star once every 1.5 days.^[6][13] On the 300th day of operations ESA reported that "CoRoT is discovering exo-planets at a rate only set by the available resources to follow up the detections".^[14] On 20 December 2007, additional results were published, declaring that a second exoplanet, COROT-2b had been discovered, this time with a radius 1.4 times and a mass 3.5 times that of Jupiter. The orbital period is less than two days. Results on asteroseismology were published in the same press release.^[15] Three papers describing the two exoplanets, with radial-velocity follow-up, appeared in Astronomy and Astrophysics in May 2008 (Barge 2008, Alonso 2008 and Bouchy 2008).

In May 2008, findings of two new exoplanets, as well as an unknown celestial object COROT-3b were announced by ESA. COROT-3b appears to be "something between a brown dwarf and a planet."

In February 2009, COROT-7b was announced. It is the smallest exoplanet to have its diameter confirmed at 1.7 Earth's diameter.

In March 2010 CoRoT-9b was announced. This is the first temperate planet found known to be similar to those within our own Solar System.^[16]

COROT has found three far stars which show Sun-like seismology (oscillations and granulations), although hotter.^[17]

Planets discovered by COROT

The following planetary objects have been announced by the mission.

Failure of Data Processing Unit #1

On March 8, 2009 the satellite suffered a loss of communication with Data Processing Unit #1, processing data from one of the two photo-detector chains on the spacecraft. Science operations resumed early April with Data Processing Unit #1 offline while Data Processing Unit #2 operating normally. The loss of photo-detector chain number 1 results in the loss of one CCD dedicated to asteroseismology and one CCD dedicated to planet detection. The field of view of the satellite is thus reduced by 50%. The loss of channel 1 appears to be permanent.^[21]

See also

• List of extrasolar planets
• Kepler Mission, a NASA space mission, launched in March 2009, to also discover planets using the transit method.
• Eddington mission, now canceled, was to have been a followup mission.
• MOST, an operational asteroseismology satellite built by Canada and launched in June 2003.
• List of space telescopes

References

External links

• CoRoT N2 Public archive

News

• Six new planets discovered