The High Energy Telescopes for the STEREO Mission

We describe the High Energy Telescopes (HETs), which are part of the IMPACT investigation for the STEREO mission (Principal Investigator: Janet Luhmann, University of California atBerkeley). The two STEREO spacecraft were launched from Cape Canaveral, FL on October 25, 2006. High energy electrons (~ 0.7 -6 MeV) and nuclei from hydrogen to iron (~ 13 – 200MeV/nucleon) are detected by the HETs, one on each spacecraft. Observations from one pass through the Earth's magnetosphere and from four X-class solar events in December, 2006 are presented to illustrate the capabilities of the HETs. The HET observations are also compared with observations from other spacecraft. The event of December 13th was the first Ground Level Event in almost two years.