Development Activities Aimed at Future Missions

Space missions of the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration (NASA) can be categorized into two major areas: deep-space exploration and Earth remote sensing. As scientists have learned from the previous missions, higher capabilities and more stringent system requirements are being placed on future missions, such as longer distance communications, higher data rate, and finer radar imaging resolution. Almost all these stringent requirements call for higher-gain and larger-aperture spacecraft antennas. At the same time, however, lower mass and smaller stowage volume for the spacecraft antenna are demanded in order to reduce payload weight and reduce required shroud space, and thus minimize overall launch cost. To meet these goals, several space-deployable antenna concepts [1] have been investigated over the past several decades. To name a few, there were the Harris Corporation's hoop-column umbrella type, Lockheed's wrapped-rib version, TRW's sunflower antenna, and the more recent Astro mesh. All these deployable antennas are of the parabolic reflector type with metalized mesh reflecting surfaces. Because they have been parabolic with a relatively small focal length, they lack wide-angle beam scanning ability—only a few beamwidths can be scanned. The mesh surface also limits the upper frequency of operation to Ku-band or lower. In addition, some of these concepts suffer from higher risk because of too many mechanical components. One good example of mechanical component failure is the Galileo spacecraft,