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Abstract: As the NASA Vision for Space Exploration takes shape, one of the key issues that will affect the lunar exploration is the ability to provide electric power to various surface locations. This power should be available through daylight times as well as night times. While nuclear reactors and radioisotope power sources are a choice for continuous power, it is the purpose of this paper to explore the advantages of an electric propulsion spacecraft plus laser power beaming to provide power to any location on the lunar surface. The starting point for the electric propulsion mission is a 500km altitude. Thrusting only occurs when the satellite is in sunlight. Radiation damage that occurs during transit of the Earth''s radiation belts is taken into account. The satellite is placed in a 30,000 by 500km orbit around the moon where it beams power to locations within 45° north or south of the equator. Laser power beaming only occurs when the satellite views the sun and the surface location is in the dark. Power delivered to the surface over a two year mission is presented along with the results of adding a second satellite. With two satellites, the maximum time when the site won’t receive power at night is about three days. This significantly reduces the need for a lunar storage system. [Copyright &y& Elsevier]

Abstract: The Cassini Mission to Saturn, a joint undertaking by NASA, the European Space Agency, and the Italian Space Agency, is now at about the mid-point of its planned four-year tour of the Saturnian system. Close encounters with Titan and the smaller icy satellites are occurring on schedule, and observations of these bodies along with Saturn''s atmosphere, its rings, and magnetosphere are being made and scientific data returned on a daily basis. The icy satellites are turning out to be more distinct and unique than had been anticipated, the dynamics of the ring particles have been shown to be even more extensive than expected, and Titan''s atmosphere had surprises for both the scientists as well as the engineers. A denser than expected upper atmosphere of Titan has led to the requirement to modify the planned orbital tour about Saturn to increase the flyby altitudes for about 20 of the Titan flybys to values above the originally planned 950km level in order to avoid the risk of atmospherically induced torques causing the spacecraft to be unable to maintain its commanded attitude. Navigation of the spacecraft on the tour continues to go exceptionally well, with optical navigation enabling delivery accuracies to some of the satellites down to the 1 or 2km level, and propellant consumption is running slightly below budget. Science observation sequence development and execution have been highly successful in acquiring virtually all of the originally designed observations. This paper summarizes the supporting engineering activities over the past year in support of operating the mission, as well as provides a high-level summary of the scientific results of the Cassini mission to date. [Copyright &y& Elsevier]