Switzerland is taking part in what could be one of the most revealing NASA missions, exploring the explosive release of energy in solar flares.

On Tuesday, the American space agency, NASA, is launching its High Energy Solar Spectroscopic Imager, or HESSI, to determine the sun's energetic X-ray and gamma-ray emissions.

The satellite will be launched aboard an orbital science Pegasus rocket, which will be dropped from the belly of the Orbital Sciences' L-1011 "Stargazer" aircraft 39,000 feet above the Atlantic Ocean, some 60 miles east of the Florida coastline.

Switzerland's Paul Scherrer Institute is playing a major part in the mission by providing instruments, such as the imaging telescope and optical aspect system.

The institute created vibration tests at Örlikon Contraves Space in Zurich in August 1999.

Postponed launch

Other investigators of the HESSI project include the University of California, Berkeley, Space Sciences Laboratory (SSL), NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland and Spectrum Astro in Gilbert, Arizona.

However, the launch of HESSI had already been postponed several times as its virgin flight in July 2000 was disrupted when the satellite was significantly damaged in ground vibration testing, which required major repairs.

The second launch had been scheduled for last June; however, the $85 million (SFr 145 million) project had to be abandoned once again due to the failure of a modified Pegasus first stage rocket booster carrying NASA's X-43A hypersonic test aircraft.

If HESSI's mission succeeds this time, it will enable researchers to find out the basic physics of particle acceleration and energy release in solar flares.

That is expected to advance their understanding of the fundamental high-energy processes at the core of the solar flare problem.

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