Sep. 19, 1998 Spacecraft controllers successfully regained control of the Solar and Heliospheric Observatory (SOHO) spacecraft Sept. 16 after sending a series of commands directing the spacecraft to fire thrusters and turn its face and solar power panels fully towards the Sun.
The SOHO flight operations team reported success in the maneuver, which is called attitude recovery, at 2:29 p.m. EDT Wednesday, the first time the joint European Space Agency (ESA) and NASA spacecraft has been controlled from the ground since SOHO spun out of control and communication was lost on June 24.
"It's a big step forward in our recovery plan for SOHO," says Dr. John Credland, ESA's head of scientific projects. "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. I congratulate our joint ESA-NASA team, helped by our industrial contractors, who have accomplished it."
"This is the best news we've 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're not there yet -- we still have to see if the scientific instruments survived. But this gives us reason to hope."
"Now we start a comprehensive check of all the spacecraft's systems and scientific instruments," said Dr. Bernhard Fleck, ESA's project scientist for SOHO. "We shall take our time and go step by step, in consultation with the 12 scientific teams in Europe and the United States, 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 (212 degrees Fahrenheit). But I'm cautiously optimistic that SOHO can win back much of its scientific capacity for observing the Sun."
SOHO operates at a special vantage point 1.5 million kilometers (about one million miles) out in space, on the sunward side of the Earth. The spacecraft was built in Europe and it carries both American and European instruments, with international science teams. NASA launched SOHO and has responsibility for operations at NASA's Goddard Space Flight Center, Greenbelt, MD.
After its launch on Dec. 2, 1995, SOHO revolutionized solar science by its special ability to 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.
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