(20 10? The Beidou-1 satellite navigation system independently developed by China played an important role in the earthquake relief in Wenchuan, Sichuan.

1. According to the equation that gravity equals gravity on the earth's surface:

GMmR2=mg？ ①

According to the centripetal force provided by gravity, list the equations:

GMmr2=ma？ ②

From ① ②: a=R2gr2, so A is correct.

B, the satellite 1 is injected backward, so the speed of the satellite 1 will increase in a short time, and the centripetal force required by the satellite 1 will also increase. At this time, the magnitude of gravity is almost constant, which is less than the required centripetal force. Then satellite 1 made a centrifugal motion, deviating from the original orbit, and satellite 1 could not catch up with satellite 2.

C, according to the centripetal force provided by gravity, list the equation:

GMmr2=mω2r，ω=GMr3=gR2r3。

The time required for satellite 1 to move from position A to position B is t=π3ω=πr3Rrg, so c is correct.

D when the satellite 1 moves from position a to position b, gravity provides centripetal force, and the direction of force is always perpendicular to the speed direction, so the work is zero. Therefore, d is correct.

So choose ACD. ..