I want to know the answer to the following question:
When was the fourth satellite for the BeiDou-1 system launched?
All the background I'm provided with is that "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.". Is that enough to answer the question?