The work described in this report was performed by the Telecommunications Science and Engineering Division of the Jet Propulsion Laboratory. An active retrodirective array (ARA) electronically points a microwave beam back at the apparent source of an incident pilot signal. ARA’s are particularly suitable as solar power satellite antennas because they are inherently Failsafe. Because of the obvious difficulty in mechanically pointing a 1.0 km diameter antenna with accuracy, the proponents of the SPS suggest using an ARA for the spacecraft antenna with the pilot source located at the center of the rectenna. An equally important reason for using an ARA for the SPS is safety, specifically, the need to protect the public from exposure to the high-power beam. Although no beam pointing system is infallible, the ARA would seem to be the most inherently reliable system for this application since its retrodirectivity is inseparable from the beam forming process itself.