PR 33-1998: SOHO pointing at the Sun again
17 September 1998The SOHO solar spacecraft yesterday, 16 September 1998, obeyed commands that turned its face fully towards the Sun. For the first time since 25 June, when SOHO spun out of control and communication was lost, it points the right way. The SOHO flight operations team reported success in the manoeuvre, which is called attitude recovery, at 18:30 UT on 16 September 1998.
"It's a big step forward in our recovery plan for SOHO," says ESA's Francis Vandenbussche, head of the SOHO recovery team at GSFC. "We were never quite sure that we would manage to make the spacecraft point back towards the Sun, which is essential for its proper operation." John Credland, ESA's head of Scientific Projects says: "We have really got to congratulate our joint ESA/NASA team, helped by our industrial contractors, who have accomplished this great job."
"This is the best news we have had from SOHO in a long time," said Dr. George Withbroe, Director of the Sun-Earth Connection science theme at NASA Headquarters, Washington, DC. "Despite the gloomy early days after the loss we always stayed hopeful that the resourceful people on the team could save the day. We are not there yet -we still have to see if the scientific instruments survived. But this gives us reason to hope."
ESA's project scientist for SOHO, Dr. Bernhard Fleck, explains what will happen next. "Now we start a comprehensive check of all the spacecraft's systems and scientific instruments. We shall take our time and go step by step, in consultation with the 12 scientific teams in Europe and the USA who provided the instruments. In some cases the instruments have been through an ordeal of heat or cold, with temperatures approaching plus or minus 100 degrees Celsius. But I'm cautiously optimistic that SOHO can win back much of its scientific capacity for observing the Sun."
SOHO, the Solar and Heliospheric Observatory, operates at a special vantage point 1.5 million kilometers out in space, on the sunward side of the Earth. It is a joint project of ESA and NASA. The spacecraft was built in Europe but it carries some American as well as European instruments. NASA launched SOHO and has responsibility for operations.
After its launch on 2 December 1995, SOHO worked a revolution in solar science by its special ability observe simultaneously the interior and atmosphere of the Sun, and particles in the solar wind and the heliosphere. Apart from amazing discoveries about flows of gas inside the Sun, giant "tornadoes" of hot, electrically charged gas, and clashing magnetic field-lines, SOHO also proved its worth as the chief watchdog for the Sun, giving early warning of eruptions that could affect the Earth.
In April 1998, SOHO's scientists celebrated two years of successful operations, and the decision of ESA and NASA to extend the mission to 2003. The extension would enable SOHO to observe intense solar activity, expected when the count of sunspots rises to a maximum around the year 2000. It would remain the flagship of a multinational fleet of solar spacecraft, including the ESA/NASA Ulysses and Cluster II missions.