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Schedule for this lecture.
Goddard Space Flight Center Engineering Colloquium
Date: Monday, September 20, 1999
The Solar and Heliospheric Observatory (SOHO) is a joint program between the European Space Agency (ESA) and NASA. After a launch (by an Atlas IIAS rocket) on December 2, 1995, SOHO was certified fully operational, at its vantage halo orbit around the first Lagrangian point, in April 1996. The instruments on-board SOHO brought a wealth of discoveries such as flows of gas inside the Sun; rivers of plasma beneath the surface of the sun; more than 70 sungrazing comets; spectacular images and movies of Coronal Mass Ejections, which could allow forecasts of space weather. At the beginning of a 1-week long series of maneuvers, the control of the spacecraft was lost on June 25, 1998. Based on the last telemetry data received from SOHO, engineers had reasons to believe that the spacecraft was slowly spinning in such a way that its solar arrays do not receive adequate sunlight to generate power. The subsequent efforts to recover the satellite will be described, efforts that led to one of the most remarkably space recoveries ever. Following a re-commission of the equipment and station-keeping maneuvers, SOHO was back into normal operations mode on Sept 25. The instruments were finally tested and were found to work surprisingly well. After a few months SOHO lost the last of its three gyros and needed to be kept stable using considerable amounts of fuel. The SOHO engineers found a new way of controlling the SOHO spacecraft without gyros and without consuming fuel. SOHO is now in a more or less normal operating mode, and its operational life has been extended to March 2003.
Dr. Paal Brekke joined the European Space Agency in January 1999 as the new SOHO Deputy Project Scientist. He earned a PhD in Solar Physics from the University of Oslo in 1992, with main interest in UV observations from the Sun working with UV spectra from the sun obtained from the US Naval Research Laboratory's HRTS instrument flown on rockets and on the Shuttle Spacelab 2. He became part of the Norwegian involvement in the SOHO spectrometers "CDS" and "SUMER" in 1993 and was responsible for the data display software and part of the operations team for CDS.
Colloquium Committee Sponsor: Barbara Pfarr
Engineering Colloquium home page: https://ecolloq.gsfc.nasa.gov