Paris

Only a few years after the discovery of giant, extrasolar planets, a proposed French mission to extend the search to smaller planets in ‘habitable’ orbits is at risk of being axed. The project (see Nature 400, 316–317; 1999) looks set to fall foul of cuts imposed on the national space agency CNES by the science ministry.

The main scientific goal of the proposed Corot space telescope, which was due for launch in 2002, is to use seismology to study the internal structure of stars other than the Sun. But, with the telescope designed to fix the same part of the sky for 150 days at a time, astronomers built into the mission a second goal — detecting extrasolar eclipses.

Observing such eclipses would yield the orbital period and size of any planets with precision, says Frederic Bonneau, head of the mission at CNES.

But the mission, costed at a modest FF350 million (US$55 million), including launch costs, is considered the primary target for cuts worth FF200 million to be imposed on CNES next year. The agency's science programme committee plans an emergency meeting next week to discuss Corot's future.

One member of the panel says it is likely to confirm its support for the mission, with pressure to axe Corot coming from the science ministry, which is keen to trim France's commitments to big science programmes, and national projects in particular.

The panel member adds that space agency officials are in discussions with the ministry to try to win a reprieve for the mission. Other options to be considered at next week's meeting of the committee include postponing Corot, trying to reduce its costs, and searching for partners.

David Hughes, an astrophysicist at the University of Sheffield in the United Kingdom, is sceptical of Corot's chances of detecting planets, arguing that extrasolar eclipses are rare, even when one is looking at 6,000 stars. By definition, an eclipse would also be irreproducible, he points out. But he agrees it is a worthwhile secondary scientific objective. “If there is a reduction in brightness of the star, the data will hit them in the face anyway.”

But Hughes describes Corot's main scientific goal as “super science”. He argues that solar seismology has revolutionized stellar science by allowing researchers to “probe in depth” into the interior of stars, yielding information on pressure and temperature.

Because Corot would take the technique to other stars for the first time, “it is one of these space missions that has to happen,” says Hughes. “If the French don't do it first, someone else will.”