A missing satellite, dormant and thought to have been lost in space, has been brought back to life by European and American space scientists who have begun the slow process of coaxing the errant spacecraft back on line.
Radio contact with the Solar and Heliospheric Observatory (SOHO), a joint satellite mission of the European Space Agency and NASA, was broken on June 25th. SOHO had already sent back much valuable information about the sun and its very hot atmosphere. Its mission had recently been extended to 2003, so the loss of the satellite was a serious blow.
SOHO was effectively lost and the ESA and NASA had no way of knowing whether the spacecraft remained in one piece. The assumption was that the satellite had lost its orientation and could not keep the solar arrays that charge its batteries pointed towards the sun. Then the spacecraft was relocated three weeks ago using the 305-metre diameter radio telescope in Puerto Rico, part of NASA's deep space tracking network. The telescope's role is usually to pick up faint radio signals from distant galaxies - or perhaps communicating aliens - but instead it was used to beam a radio signal towards the satellite and then watch for its faint echo.
Controllers were able to track SOHO for about an hour, long enough to tell them that it was in the correct orbit and that a radio signal from Earth might just break its silence.
On August 2nd the rescue team managed to coax a tentative response from the spacecraft delivered in 10-second radio signal bursts. It wasn't much but the SOHO team knew the satellite could still communicate.
On August 8th more data was sent by SOHO, giving information about its temperature and electrical status. "This is the best news I've heard since we lost contact with SOHO," according to Dr Roger Bonnet, director of science for ESA.
"I never gave up hope of some recovery of this fantastic mission. We should just hope that the damage sustained by SOHO's enforced period of deep freeze does not affect the scientific payload too much."
The August 8th message was made possible after commands sent by controllers enabled a partial charging of one of SOHO's onboard batteries. After 10 hours of charging, a command turned on the telemetry and seven full sets of data were sent.
The team is now working to get a second battery fully charged and to find a way to defrost the spacecraft's hydrazine fuel which could be used to realign SOHO with the sun.