IN-STEP INFLATABLE ANTENNA EXPERIMENT

Large deployable space antennas are needed to accommodate a number of applications that include mobile communications, earth observation rad iometry, active microwave sensing, space-orbiting very long baseline i nterferometry, and Department of Defense (DoD) space-based radar. The criteria for evaluating candidate structural concepts for essentially all the applications is the same; high deployment reliability, low cos t, low weight, low launch volume, and high aperture precision. A new c lass of space structures, called inflatable deployable structures, hav e tremendous potential for completely satisfying the first four criter ia and good potential for accommodating the longer wavelength applicat ions. An inflatable deployable antenna under development by L'Garde In c. of Tustin, California, represents such a concept. Its level of tech nology is mature enough to support a meaningful orbital technology exp eriment. The NASA Office of Aeronautics and Space Technology initiated the In-Space Technology Experiments Program (IN-STEP) specifically to sponsor the verification and/or validation of unique and innovative s pace technologies in the space environment. The potential of the L'Gar de concept has been recognized and resulted in its selection for an IN -STEP experiment. The objective of the experiment is to (a) validate t he deployment of a 14-meter, inflatable parabolic reflector structure, (b) measure the reflector surface accuracy, and (c) investigate struc tural damping characteristics under operational conditions. The experi ment approach will be to use the NASA Spartan Spacecraft to carry the experiment on orbit. Reflector deployment will be monitored by two hig h-resolution video cameras. Reflector surface quality will be measured with a digital imaging radiometer. Structural damping will be based o n measuring the decay of reflector structure amplitude. The experiment is being managed by the Jet Propulsion Laboratory. The experiment def inition phase (Phase B) will be completed by the end of fiscal year (F Y) 1992; hardware development (Phase C/D) is expected to start by earl y FY 1993; and launch is scheduled for 1995. The paper describes the a ccomplishments to date and the approach for the remainder of the exper iment.