The joint NASA-ESA Solar and Heliospheric Observatory (SOHO) was launched in December 1995 and placed at L1 Lagrangian point, at about 1.5 million kilometers from the earth. The goals are to observe the sun without interruption and analyze, with the 12 different instruments onboard,  its different layers, from the very center to the outermost coronal layers including the solar wind, with unprecedented details.

The EIT (Extreme ultraviolet Imaging Telescope) is one of these instruments; it  is a Ritchey-Chrétien telescope that provides a continuous coverage of various coronal layers by making high resolution images of the sun at 4 different ultraviolet wavelengths (30.4, 28.4, 19.5 and 17.1 nm) allowing to highlight atmospheric matter at different temperatures from 80.000 K to more than 2 millions K.


CSL has played a very important role in managing the whole project under the scientific responsibility of the Institut d’Astrophysique Spatiale (Orsay, France).  In collaboration with an international consortium (different centers in France and USA, Observatoire Royal de Belgique), CSL was also deeply involved in the instrument design and development, in the calibrations as well as in the tests of the instrument.

In the early years of its mission the CCD detector of EIT has been somewhat damaged by too long an exposure to UV radiation. In order to recalibrate the instrument, a sounding rocket with a replica of EIT (EIT-CALROC) has been launched in October 1997, from White Sands (USA). CSL was responsible for updating this new instrument to a rocket flight, making new vibration tests, bringing support to the launch campaign and participating in the cross calibration with the SOHO-EIT instrument.



   EITquadsA s
EIT instrument   Sun in four wavelengths seen by EIT




Contact(s) : Pierre Rochus