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Technology Through Time: Issue #24, rhessi

Solar flares are the most powerful explosions in the solar system. Scientists are still not sure why they occur, or how to accurately predict them.


RHESSI was launched on February 5, 2002 into a circular Earth-orbit with an altitude of 600 kilometers.


The satellite has a height of 2.16 m (85 in) and a maximum width of 5.76 m (227 in) after solar panel deployment. Its total mass 293 kg (645 lb) and it consumes 414 watts of power.


Researchers think that much of the energy released during a solar flare is used to accelerate electrons, protons and other ions to very high speeds. During a single 5-minute flare, temperatures as high as 30 million degrees can be reached, making solar flares much hotter than the core of the Sun - at least for a few seconds! The RHESSI mission combines high-resolution imaging of high energy X-rays and gamma rays with high-resolution spectroscopy, so that a detailed energy spectrum can be obtained at each point of the image. This enables researchers to find out where these particles are accelerated and to what speeds.

The most important scientific goals of RHESSI include 1) Determine the frequency, location, and evolution of solar flares 2) Study the acceleration of electrons, protons, and heavier ions in flares, 3) Study the heating of plasma to tens of millions of degrees and determine its relationship to particle acceleration; and 4) Determine the mechanisms that accelerate both electrons and ions to high speeds so rapidly and efficiently.



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RHESSI Website