From: European Space Agency
Posted: Friday, March 16, 2012
ESA's Venus Express spacecraft has returned to routine operation after its startracker cameras were temporarily blinded last week by radiation from a pair of large solar flares.
Science observations by ESA's Venus Express were temporarily suspended on 7 March after the two startrackers - used to help navigate and orient the spacecraft - were overwhelmed by excessive proton radiation. The proton storm stemmed from the Coronal Mass Ejections (CMEs) emitted by the Sun, which were associated with a pair of massive solar flares that occurred early in the morning on 7 March.
With the startrackers unable to function properly, mission controllers at ESOC, ESA's European Space Operations Centre, Darmstadt, had to place the spacecraft into a special mode to ride out the storm.
This meant that all instruments were switched off and routine scientific observations and data gathering were stopped. "As the radiation faded, the startrackers began functioning normally again on 9 March," said Octavio Camino, ESA's Spacecraft Operations Manager. "After taking some time to conduct a series of thorough spacecraft health checks, Venus Express returned to regular science operations on 12 March at 20:20 GMT."
Waiting out the storm
This month, Venus Express is going through 'quadrature': a period of about five weeks during which the Sun-spacecraft-Earth angle is between 75* and 95*. They occur twice every 19 months. During quadrature, the spacecraft must maintain a special orientation so that certain instruments are not over-exposed to sunlight and the radio antenna can still be pointed to Earth.
"At any time, if a problem is autonomously detected onboard, the spacecraft might place itself into 'safe mode'," says Octavio. However, if a safe mode were to happen during quadrature operations, and the startrackers were not operating, it would be much more difficult to return the spacecraft to normal operations. "To be very cautious, we simply stopped science activities to wait out the proton storm," says Octavio.
The mission operations team used the gyroscopes to maintain a safe attitude while waiting for the startrackers to return to normal.
Venus Express: a very robust mission
"There were no permanent effects; Venus Express is in excellent condition and the operations team performed very well," said Paolo Ferri, responsible for interplanetary mission operations at ESOC. "Yes, orbiting Venus means we're closer to the Sun - and in a potentially hazardous environment." "But we have a very robust mission that is once again returning a large amount of valuable scientific data."
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