NASA lost contact with its Deep Impact probe on August 8 and has been unable to reestablish communication.
Mission controllers postulate that there was an anomaly generated by the spacecraft’s software which left the vehicle’s computers in a condition where they are continuously rebooting themselves. If this is the case, the computers would not continue to command the vehicle’s thrusters to fire and hold attitude. Lack of attitude hold makes attempts to reestablish communications more difficult because the orientation of the spacecraft’s antennas is unknown. It also brings into question the vehicle’s electrical power status, as the spacecraft derives its power from a solar array that is fixed, with its cells pointing in one direction.
Nature reports that, according to Deep Impact principal investigator Michael A’Hearn of the University of Maryland, a prolonged spin with solar panels pointed in the wrong direction could run down the spacecraft’s power, permanently. Nature writes:
One casualty of the mishap is that scientists have not received any of the expected images the craft was scheduled to take in August of Comet ISON, the icy space rock that could make a spectacle in the inner Solar System this fall before diving into the Sun, A’Hearn says.
Deep Impact launched in 2005 to study the comet Tempel 1. When that mission was complete, the probe went on to study the comet Hartley 2 and Garradd. It has travelled 431 million kilometers.
Image caption: An image of comet Tempel-1 taken buy Deep Impact just after it collided with the body to study its ejecta (Credits: NASA).