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Session 64 - Telescopes for the Next Millennium.
Oral session, Thursday, January 08
Jefferson,
As part of our Mission Architecture Study, Ball Aerospace has developed concepts for NGST which address the scientific goals developed by the Science Working Group and described in the Design Reference Mission. The core objectives are to obtain wide-field multi-spectral imaging and moderate resolution spectroscopy of exceedingly faint sources in the near infrared wavelength region, 1 - 5 \mu m. Our approach allows a telescope with an aperture of 6 to 8 meters to be placed into a heliocentric orbit which will permit passive cooling to low temperature but still allow relatively simple solutions to issues such as power, communications and operations. All aspects of the design are subject to detailed trade studies which evaluate their value to the mission with reference to technological feasibility, mass and volume, cost and contribution to scientific productivity. The efficiency with which a candidate system architecture carries out the DRM is an important figure of merit. The approach favored by Ball includes an 8m diameter primary mirror fabricated from Berylium panels, and folded in an efficient manner to accomodate existing launch vehicles. An integrated science instruments module provides the required imaging and spectroscopic instrumentation. Radiometric analysis shows that the foreground Zodiacal Light influences the ability to image faint sources, while spectroscopic observations are much more sensitive to the telescope aperture and detector noise. These dependencies are crucial to the mission architecture analysis, since the aperture drives the overall size and mass, and the ability of a launch vehicle to deliver NGST to a preferred orbit. The scientific requirements on the imaging and spectroscopy, and the mix of such exposures in the DRM will the the ultimate referee of the options available for the NGST mission.
