Next Generation Space Telescope-inflatable sunshield development

The Next Generation Space Telescope (NGST) is a NASA Origins program whose goal is to observe the first stars and galaxies in the Universe. The NGST will detect 0.6 to 20 /spl mu/m radiation, seeing objects 400 times fainter than those currently studied with ground or space-based infrared telescopes, all with a spatial resolution comparable to the Hubble Space Telescope. The Next Generation Space Telescope will be constructed using deployable structures since the maximum size of the rocket shrouds likely to be available will not accommodate the full mirror or sunshield. Current designs of NGST have a large deployable sunshield (on the order of 200 m/sup 2/) thermally insulating a large telescope, keeping vital detector temperatures to below 60 K. As a precursor to the flight telescope, NASA has begun a technology validation program to prove the merits of a large deployable structure. The Inflatable Sunshield In Space (ISIS) Experiment is currently under development and planned to be flown on a Space Shuttle Mission in mid-year 2001. ISIS will demonstrate a controlled deployment of a large sunshield enabling it to stay out of NGST's "zone of exclusion" which guarantees that the sunshield will not disturb the optics or systems of NGST. In addition, ISIS will demonstrate in-situ rigidization of a thermoset composite structural frame utilizing a resistive heating circuit. This paper describes the status of the ISIS sunshield development. Objectives for the flight experiment are discussed in detail and developments in in-situ rigidization methods and controlled deployment in relation to the telescope are also presented.