would lift the demonstrator out of the cargo bay and release it along the velocity vector. After a safe distance between the two spacecraft had been achieved (e.g. 10 km), Astro-SPAS would deploy the rectenna package. This rectenna would be similar to that of the ASAP except it would be twice the size at about 25 m in diameter. The rectenna would, essentially, be a full-scale development model for a space station rectenna and would include the complete capability to rectify as much incident power as possible. It would also need to be equipped with a cold-gas attitude control system to ensure it was facing the demonstrator during power beaming experiments. Initially, however, the rectenna would align itself for minimum aerodynamic drag. For the experiment, it would perform a rotation manoeuvre to face the demonstrator. After successful deployment of the rectenna, the demonstrator would release the 3-4 m diameter solid reflector stowed for launch on the side of Astro-SPAS. Alternatively, a phase array system could be used, although the off-set reflector approach is likely to be less expensive. Once a systems checkout had been completed, Astro-SPAS would use its cold gas attitude control thrusters to station-keep within 3 kilometres in front of the rectenna. After the rectenna had rotated itself to face Astro-SPAS, the high-precision star trackers on the platform would lock onto three suitably positioned light sources on the rectenna (i.e. artificial stars). Once this had occurred, microwave power could be beamed to the rectenna. The microwave power level would be as high as 3-5 kW using a cluster of 15-25, 200 W TWTs mounted on a heat-sink structure within Astro-SPAS. Power supply would come from a group of Shuttle-rated lithium-based batteries, as with the ASAP demonstrator. Beaming would be shut down automatically if the power beam wandered beyond the rectenna. The ASAP mission will be critical in developing control algorithms to ensure the pointing system can compensate for non-linear space plasma interactions and the beam central peak never wanders outside the rectenna. Demonstrating such control
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