Power beaming to communication satellites in GEO

Batteries normally provide power to geosynchronous satellites during earth eclipse 90 times each year, but the heavy charge-discharge cycle decreases their life expectancy. Battery life, and thus satellite life, could be extended by providing power during eclipses via laser illumination of the photovoltaic array. For a spin-stabilized satellite this would require 35 kill using an 8-m diameter transmission mirror (and 850-nm light) or 180 kW using a 3.5-m mirror. A 3-axis stabilized satellite has a larger span and requires an elongated spot to use a comparable laser. At present, 70 satellites are scheduled to be replaced by the year 2000 at a cost of almost $10 billion. Power beaming could save a substantial portion of this cost. Laser illumination also could augment solar power to increase the power available to new satellites. Increased power could boost the signal strength or allow more channels on the satellite. In addition, high-frequency channels (which require higher power to penetrate the atmosphere) could be used. Removal of waste heat from the satellite limits the amount of power that can be transmitted. Nevertheless, a spin-stabilized satellite with power beaming could generate 0.9 kill per square meter of the collector array, which is six times thatmore » of an equivalent conventional satellite using the same size solar panel. A 3-axis stabilized satellite could generate 0.6 kW/m[sup 2] (four times conventional).« less