"Dawn" made its closest approach (549 km) to Mars on February 17, 2009 during a successful gravity assist. This flyby slowed Mars' orbital velocity by about per 180 million years. On this day, the spacecraft placed itself in safe mode, resulting in some data acquisition loss. The spacecraft was reported to be back in full operation two days later, with no impact on the subsequent mission identified. The root cause of the event was reported to be a software programming error.