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Dawn spacecraft malfunctions ahead of Ceres observation

NASA's protoplanet probe's third reaction wheel has failed in the lead-up to observations of Ceres' weird bright patch.


Illustration of Dawn's ion thrusters, which enabled it to leave Vesta's orbit and enter Ceres'.


NASA's Dawn, currently in orbit around dwarf planet Ceres in the asteroid belt between Mars and Jupiter, is still busily collecting data. It's been manoeuvering into position for its next task: observing Ceres from an "opposition" position, directly between the Occator crater and its mysterious bright spot and the sun.

While this is still going ahead, the spacecraft is struggling. The third of its four reaction wheels, which help orient the probe in space, has malfunctioned. The first malfunctioned in 2010, and the second in 2012. This leaves just one reaction wheel operational.

However, the team was prepared ahead of time. When the wheel malfunctioned, in between manoeuvres, the craft entered safe mode and the team reassigned orientation control to its hydrazine thrusters. This means Dawn can still complete its observations without significant problems. These are due to take place on April 29.

Dawn's primary mission concluded on June 30, 2016. It doesn't have much fuel left, and isn't expected to remain operational much longer.

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