The Observatory of Paris will be on board STEREO, mission of NASA

In 2004, a new monitoring system of the activity of the Sun, STEREO, composed of two identical probes, will be launched by NASA. They will carry each one four instruments which were selected by the American agency on December 8, 1999. One of them, WAVES, whose construction is financed by the National Center of Space Studies, is under the responsibility of the Observatory of Paris (Department of Space Search, UMR-CNRS 8632). The international team, which has the responsability of it, is directed by Dr. J.L. Bougeret (Observatory of Paris, CNRS). The objective of mission STEREO is to determine the origin, the propagation in the interplanetary medium and the consequences for the Earth, of the Coronal Mass Ejection, or CME, which are among the most significant disturbances frequently occurring in the Solar system and which can project towards the Earth up to 10 million tons of gas ionized at a speed of more than 1 million km/h. The observations of the current satellites give too brief information of these phenomena. The simultaneous use of two probes identical around the Sun placed on the orbit of the Earth, on both sides of the latter, will make it possible to obtain a stereoscopic vision of the structure and dynamics of the coronal plasma, and in particular of the CME, their emission on the surface of the Sun until the orbit of the Earth. The knowledge of the characteristics in 3D of these ejections will lead to a better determination of their speed and a much more precise forecast of the arrival of the cloud of plasma in the vicinity of the Earth. WAVES is a radio wave detector which will allow the diagnosis of the appearance and the propagation of the radio disturbances. Three other instruments were selected : SECCHI (U.S. Naval Observatory) will provide images in ultraviolet and in the visible ; IMPACT (Univ. of California, Berkeley) will sample the 3D distribution of the high energy solar particles and of the local magnetic field ; PLASTIC (Univ. of New Hampshire) will distinguish between the plasma of the CME and the ambient coronal plasma. This selection is the result of a fruitful co-operation of the international scientific community. The budget of the mission is 150 million dollars including 64 for the instruments.   Enquiry contact : Jean-Louis Bougeret  Observatory of Paris (DESPA)  e-mail :Jean-Louis.Bougeret obspm.fr