Design issues for a mission to exploit the gravitational lensing effect at 550 AU

Reported herein are the first results of a NASA-sponsored study at the Jet Propulsion Laboratory (JPL), California Institute of Technology, exploring the scientific promise and technological viability of a mission to exploit the gravitational lensing effect of the Sun to obtain huge antenna gains for electromagnetic waves grazing the Sun's disk. With regard to scientific promise, these results, reported at about the halfway point of the study, substantiate the huge antenna gains offered by, as it will be called here, a Solar Gravitational Telescope (SGT) and point to the instrument's potential promise as a ``discovery machine'' but suggest considerable limitations to the telescope's usefulness as a general purpose astrophysical research tool. These limitations are seen to arise, primarily, from the geometry and scale of the ``virtual'' telescope which must be achieved and maintained to utilize the lensing effect and the turbulence effects of the Sun's plasma on the observed target's signal. With regard to technological viability, the preliminary results suggest a very aggressive use of unproven, as-yet-unflown new technology will be required to enable the desired science observations and mission durations approaching the short (3-10 year) NASA-targeted mission duration goal. Key needed new technologies are advanced propulsion, lightweight telescopes, membrane mirrors, inflatable/rigidizeable structures, and novel coronagraphic techniques. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.