A geosynchronous synthetic aperture radar (SAR) with an orbit inclination of 50-65° can provide daily coverage of all of North and South America. Longitudinally, the width of the mapped area would be on the order of ±50° at the Equator, somewhat more at the most northern/southern latitudes. Within the area mapped, very good temporal coverage can be obtained -up to several mappings during the 12 hours per day where the satellite is in the "right" hemisphere. This would be a key capability in relation to disaster management, tectonic mapping and modeling, vegetation and soil moisture mapping, and for operational and semi-operational requirements. A constellation of geosynchronous satellites could provide global coverage.

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Ab3tmct-A new technique for full duplex digital communications using adaptive phase conjugation is presented. The technique is based on mixing the RF signal to an intermediate frequency where it can be easily processed, and filtering the phase of the IF signal to separate the geometry phase and the message phase. A 6 GHz microstrip retrodirective antenna array w a s built, together with the signal IF processing needed for full duplex operation. The measured RCS values of a circular array are much flatter and are 0 to -5 dB up to f80°. Two way digital communications at a baud rate of 78 KBits/sec was also demonstrated with BER < for SNRs around 10 dB. The application areas are in highperformance digital mobile telecommunications for commercial and military applications.Kevwods-Phase Conjugation, phase filtering, adaptive beam forming, digital communications.

Quantum entanglement has the potential to revolutionize the entire field of interferometric sensing by providing many orders of magnitude improvement in interferometer sensitivity. The quantum-entangled particle interferometer approach is very general and applies to many types of interferometers. In particular, without nonlocal entanglement, a generic classical interferometer has a statistical-sampling shot-noise limited sensitivity that scales like 1/ √ N , where N is the number of particles passing through the interferometer per unit time. However, if carefully prepared quantum correlations are engineered between the particles, then the interferometer sensitivity improves by a factor of √ N to scale like 1/N , which is the limit imposed by the Heisenberg Uncertainty Principle. For optical interferometers operating at milliwatts of optical power, this quantum sensitivity boost corresponds to an eight-order-of-magnitude improvement of signal to noise. This effect can translate into a tremendous science pay-off for space missions. For example, one application of this new effect is to fiber optical gyroscopes for deep-space inertial guidance and tests of General Relativity (Gravity Probe B). Another application is to ground and orbiting optical interferometers for gravity wave detection, Laser Interferometer Gravity

Abstract. The microwave thermal thruster heats propellant via a heat-exchanger then expands it through a rocket nozzle to produce thrust. The heat-exchanger is simply a microwave-absorbent structure through which propellant flows in small channels. Nuclear thermal thrusters are based on an analogous principle, using neutrons rather than microwaves, and have experimentally demonstrated specific impulses exceeding 850 seconds. A microwave equivalent will likely have a similar specific impulse, since both nuclear and microwave thermal thrusters are ultimately constrained by material thermal limits, rather than the energy-density limits of chemical propellants. We present the microwave thermal thruster concept by characterizing a novel variation for beamedenergy launch. In reducing the thruster concept to practice, the enabling physical process is microwave absorption by refractory materials, and we examine semiconductor and susceptor-based approaches to achieving this absorption within the heat-exchanger structure.