The Rosetta probe of the European Space Agency (ESA) ran into trouble during a March 28 flyby near the nucleus of comet 67P/Churyumov Gerasimenko.

The fault is being analyzed by ground controllers after the spacecraft's encounter with comet dust confused its navigation system.

Rosetta moved past the comet's icy core at a distance of about 14 kilometers, or 8.7 miles during the March 28 flyby. According to ESA, the probe aimed for a flyby point over the larger of comet 67P's two lobes.

Since the comet is swinging closer to the sun, it is heating up and triggering plumes of outgassing water vapor and dust particles. The dust grains pushed against Rosetta's long power-generating solar arrays as it approached the comet.

However, more serious effect on Rosetta's star trackers were observed by ground controllers. The spacecraft uses small cameras to locate bright stars in the sky. It uses the stellar fixes to determine its orientation in space.

Star trackers find guide stars to self-monitor the Rosetta's alignment with Earth and the sun. But the guidance system confused the flecks of dust for stars, which left the trackers not in a position to set navigation fix.

Although various attempts were made to recover tracking capabilities, there was too much background noise due to activity close to the comet nucleus. The spacecraft's star trackers registered hundred of 'false stars'. It took almost 24 hours to properly re-establish the tracking.

In a blog post on ESA's website, officials wrote, "During the most recent flyby, a number of issues were reported, starting with the primary star tracker encountering difficulties in locking on to stars on the way in towards closest approach".

The spacecraft went into a temporary safe by switching off its scientific instruments mode and halted non-essential functions. Although engineers at the Rosetta control center in Darmstadt, Germany, restored the spacecraft to normal status by March 30, science operations remain mostly suspended.