Tim Furniss
The mysterious loss of contact with the European Space Agency's (ESA) Solar and Heliospheric Observatory (SOHO) last June was caused by mistakes by ground controllers, ESA reported yesterday.
The highly successful SOHO had been providing excellent data about the sun for over two years from its unique orbit between the Earth and sun in which it appears stationary.
The spacecraft fell silent on 25 June but contact has now been re-established, thanks to NASA's help, and ESA hopes that SOHO will soon be back to normal.
Flight controllers appear to have ignored procedures, allowing SOHO to lose its orientation. The craft's solar panels could not produce electricity and its batteries soon drained, preventing radio commands from Earth from being picked up.
The official investigation report says that "an erroneous decision", disabled part of the craft's failure detection system and controllers at first misunderstood what had happened to SOHO, and obtained false readings about its status. Too rapid a response was then made to correct the situation, making it harder to regain control.
SOHO was saved by using NASA's powerful Deep Space Network antennas which detected some faint signals from SOHO and enabled new commands to be sent to the craft to reposition it.
The next steps will be to complete the thawing of the craft's propellants so that its attitude control thrusters can work again.
Source: Flight Daily News
