NASA’s Dawn space probe resumed its activities moving down to an altitude of about 3.900 kilometers (about 2,400 miles) over the dwarf planet Ceres in order to proceed with the mapping operations that will provide images at unprecedented resolution. This task was supposed to start at the end of June but due to an anomaly the spacecraft entered the “safe mode” in which it stops its activities awaiting instructions.

On June 30, the Dawn space probe activated its ion engine to begin the maneuver that was supposed to bring it down and enter the low altitude orbit chosen to map the dwarf planet Ceres. Shortly after, an anomaly triggered the safe mode and NASA engineers started the work of analyzing the data to understand its cause.

In early July, from NASA’s mission control center instructions were sent to return the Dawn space probe to its normal operation mode. However, the mapping operation was postponed to find the problem that caused the triggering of the safe mode.

The data analysis allowed to establish that there was a discrepancy between the intended orientation for the Dawn space probe and the actual one during the June 30 manoeuvers. That’s the anomaly that triggered the safe mode and from there NASA engineers were able to identify the problem in the system of gimbals that allow the ion engine #3 to swivel.

The Dawn space probe has three ion engines, mounted on different gimbal systems. This ensures sufficient redundancy to compensate for any faults or even only temporary problems. For example, due to a problem with an engine during the journey from the giant asteroid Vesta to the dwarf planet Ceres, another one was quickly activated.

In this case, NASA engineers activated the ion engine #2 and in the last week tested it to verify that the mechanical systems were working properly. Once they made sure  that the Dawn space probe can operate correctly, it was decided to resume its mission.

Now Dawn is maneuvering to enter the orbit called HAMO (High-Altitude Mapping Orbit). The ion engine isn’t very powerful so it will take some more days but in August the probe will start taking photographs of the dwarf planet Ceres with a quality better than those available. This will improve our understanding of its geology and perhaps solve the mystery of the bright spots.

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