The principal types of systems tested with associated performance measures are summarized in Figure 5. Typical performance effects for SPS power densities within 100 km of the rectenna edge (~1 mw/cm2) for microwave FDM communications, instrumentation radar, and high resolution plumbicon cameras are presented in Figure 6. These data were derived as part of an examination of the utility of a candidate rectenna site in the Mojave Desert. Performance scores for all systems evaluated included fundamental power densities over the range of 0.1- 1 mw/cm2, and 10"7 - 10"* mw/cm for harmonics. These ranges are typical of sets of scores that provide a continuum of performance measure-SPS interference ratio responses which guide the priorities for functional mitigation. Sensors employed for satellites include high resolution vidicons, image dissectors, charge coupled devices, and IR scanners. These are utilized for mapping, speedrometry, attitude control, and transient event detection as required for LANDSAT, NAVSTAR and surveillance operations. Performance criteria affected by passage through the SPS power beam include video noise, spatial resolution, and video dynamic range. Guidelines for future satellite developments address mitigation methods for optical sensors, communications, and special purpose RF sensors (monostatic and bi static holographic radar, synthetic aperture radar). GEO satellite interference areas include communication relays (COMSTAR, INTELSAT, DSCS), future switching and processing satellites (computer controlled spotbeam operations), and satellite-satellite spotbeam modes. The latter includes the interference caused by SPS reflective multipath; identifying the necessity for a frequency offset transponder on the SPS vehicle to eliminate the effects of the SPS reflection component. Mitigation techniques include antenna pattern control, cable and module shielding, single point grounding methods with low resistance connections, and modification of module interface circuitry and transient protector circuits. For terrestrial and aircraft communications, radars, sensors, and computer/proces- sors, these methods restore capabilities to the 96-100% range. More specialized shielding and procedural modifications are required for LEO and GEO satellites. Mitigation techniques being investigated for radio astronorny equipment include cryogenic rejection filters, and interference cancellation in the preamplifier waveguide or coaxial cable. Rectenna site-susceptible system separation distance categories for positive and potential exclusions have been specified where dictated by safety and sensitivity considerations; 150 km for military OT&E and radio astronomy sites, 100 km for air and missile defense sites and radar astronomy facilities, 60 km for military development test ranges and ATC sites, and 50 km for nuclear and optical astronomy facilities. An evaluation of possible alternative frequency ranges for the SPS covers the range of 2.45-30 GHz. Parametric displays of spacetenna and rectenna area, attenuation, and refraction and scatter losses are being developed. Spacetenna far field criteria varying from a maximum distance of 2D2/X are played into the sizing exercises to determine a range of minimum rectenna areas.
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