Dawn is back on track for Ceres

Although the CMEs that struck Earth were mostly cosmetic rather than damaging, another one may have gone Dawn’s way; the spacecraft, currently en route from Vesta to Ceres with the help of an ion drive, unexpectedly went into safe mode a week ago.  Engineers suspect a comic ray, either from the Sun or from deep space, struck a sensitive component in the ion propulsion system.  As a protective measure, the spacecraft is designed to shut down all nonessential systems and concentrate on maintaining adequate power and communications with Earth, which it did.  Worse, another system was also hit, causing it to lose lock on Earth with its high gain antenna.  Fortunately, another less directional (but weaker) antenna was still functioning and contact was restored.

JPL remotely commanded the spacecraft to swap to another ion engine and another electronic controller so it could resume thrusting while they analyze the fault and hopefully fix it.  The same thing happened three years ago, and they were able to recover all the systems.  The pointing issue may be due to an error in the main computer; a reboot appears to have resolved it, suggesting it was in working memory rather than the burned copy of the flight software.

This pushes back the timeline for arrival at Ceres by about a month, alas, but the good news is that the system is robust enough that this doesn’t compromise the mission.  It’ll just take a little bit longer. 😉  Currently, ETA is April, 2015.



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