After previously suggesting that the Phobos-Grunt sample/return mission to the Martian moon Phobos had been the victim of some kind of radar jamming or interference - possibly intentional - the head of Russia's Roscosmos space agency, Vladimir Popovkin, noted that charged particles from the Sun affecting imported components in the spacecraft was the most probable cause of the memory/computer fault that left the craft stranded in a low Earth orbit. Popovkin subsequently blamed a lack of radiation testing of the imported components, which may have been substandard or counterfeit.
The formal investigation found that the components had not been qualified for spaceflight and that this led to an unnecessary simultaneous rebooting of two of the channels of the onboard computer and control system. The net effect of this was to put the spacecraft into a sun-seeking safe mode which meant that the craft could not make its orbit raising and transfer trajectory firings as planned. These main engine firings were to have been done on a timer system as the craft was out of contact with mission control when they were to have taken place.
The automated attitude control system did make some thruster firings to keep the spacecraft orientated correctly, slightly raising the orbit, but these were not significant. Unfortunately, apart from some intermittent contacts with the craft using European Space Agency ground stations, engineers were unable to regain control of the craft and it re-entered the Earth’s atmosphere in January along with the small Chinese Mars orbiter, Yinghuo-1, it was carrying.