2) Accordingly, existing or known technology should be used whenever possible, unless identifiable severe cost impacts result. 3) Transportation logistics and space construction operations are not intended as subjects for the study. Bidders should assume that costs of space transport from Earth to GEO are not greatly different than those attainable through use of Shuttle/Centaur capabilities, i.e., no fleet of high-capacity, low-cost heavy lift systems. 4) The primary power conversion method is not limited to photovoltaic; any solar conversion system may be considered. A preferred design will minimize the total mass of components or materials required from the Earth. 5) Mass should not be a design driver. Mass is not necessarily to be ignored, but rugged, simple, high-mass designs are much more practical for an SPS derived from lunar materials than for SPS concepts based on Earth launch. 6) The hardware making up the design concept should be adaptable to automated production in space or on the Moon. A commercially- feasible concept will require that annual mass throughput of finished hardware from production machines far exceeds the mass of the machines themselves. 7) Power transmission to Earth may use RF or coherent infrared means. Preferred wavelengths fall in the range of about 5 micrometers to 12 centimeters. Some wavelengths in this general range are, of course, precluded by excessive atmospheric absorption. Transmission maximum beam intensities must be non-destructive nominally 30 mW/cnr (300 watts/m^) for RF bands and 200 mW/cm? (2 kW/m^) for IR bands. 8) Earth-based receiving stations need not be defined beyond the area required to capture the beam and the assumed efficiency of conversion of beam energy to electrical energy. (Efficiency estimates are available in existing literature.) 9) SPS size range of interest is 100 megawatts to 5 gigawatts delivered electric power to the power grid on Earth. H. SCOPE The scope of the work is to produce a design for the most practical, commercially viable solar power satellite built primarily out of lunar materials. A cost analysis is not required, but the design will be evaluated for simplicity, low technical risk, and minimized mass of Earth-required materials.