The Solar and Heliospheric Observatory (SOHO) is a cooperative effort of NASA the European Space Agency (ESA). The spacecraft carries scientific instruments to study the solar atmosphere, helio-seismology, and solar wind. It was launched on December 2, 1995 and reached stable observation position (1 million miles from the Earth where the pulls of the Earth and the Sun balance) to began uninterrupted solar observations. It has been keeping a steady watch on the Sun since April 1996. Keeping the Sun under constant observation, allows to warn Earth about approaching Sun’s coronal mass ejections that could potentially disrupt communications. The spacecraft has  also discovered dozens of comets. One of SOHO’s most important discoveries has been locating the origin of the fast solar wind near the Sun’s poles.

A USC-designed and -built (under leadership of astronautics faculty Prof. Darrell Judge) sensor SEM (Solar EUV Monitor designed to measure the ultraviolet light and X-rays produced by the sun), a part of the  instrument CELIAS, is installed in the SOHO spacecraft. Another USC-based part of the mission was a multi-year Sounding Rocket Program for SOHO cross-calibration (using (SEM)  of the solar ultraviolet radiation. Astronautics faculty Prof. Mike Gruntman studied signatures of interplanetary dust as a Guest Investigator on SOHO Program.

SOHO spacecraft in full view.

Solar Eclipse on 29 March 2006 taken by SOHO spacecraft.