Design issues for a mission to exploit the gravitational lensing effect at550 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 fo r electromagnetic waves grazing the Sun's disk. With regard to scientific p romise, these results, reported at about the halfway point of the study, su bstantiate 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 t he telescope's usefulness as a general purpose astrophysical research tool. These limitations are seen to arise, primarily, from the geometry and scal e of the "virtual" telescope which must be achieved and maintained to utili ze the lensing effect and the turbulence effects of the Sun's plasma on the observed target's signal. With regard to technological viability, the prel iminary results suggest a very aggressive use of unproven, as-yet-unflown n ew technology will be required to enable the desired science observations a nd mission durations approaching the short (3-10 year) NASA-targeted missio n duration goal. Key needed new technologies are advanced propulsion, light weight telescopes, membrane mirrors, inflatable/rigidizeable structures, an d novel coronagraphic techniques. (C) 1999 Published by Elsevier Science Lt d. All rights reserved.