context: In February 2007, the fourth and last satellite of the BeiDou-1 system, BeiDou-1D (sometimes called BeiDou-2A, serving as a backup satellite), was sent up into space. It was reported that the satellite had suffered from a control system malfunction but was then fully restored.
question: నాలుగో బీడూ-1 ఉపగ్రహం పేరేమిటి?
answers: BeiDou-1D