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Session 64 - Telescopes for the Next Millennium.
Oral session, Thursday, January 08
Jefferson,
Interferometry from space and ground-based telescope has a central role to play in the Origins program. Interferometers complement the NGST by yielding sharper infrared images, and a nulling capability to explore extra-solar planetary system s. Because of its unique geometry the LBT is strongly differentiated from other interferometers in its scientific capabilities. Its two 8.4 m mirrors are side by side in a single alt-az mount, and adaptive optics correction of wavefront errors, essential for large ground based interferometers, will be accomplished at the secondary mirrors. So, the optical path to the interferometric focus is extremely direct, with only three warm reflecting surfaces before the beam combining dewar. This results in low thermal background, and uniquely high sensitivity to thermal emission from dust clouds.
The lowest surface brightness objects observable with an interferometer depend not only on background, but also as the square of the ratio of mirror separation to mirror diameter. Because this ratio is very low for the LBT, it will be able to see galaxies. An integration of several hundred hours will enable it to image galaxies in the Hubble deep field with 10 times the Hubble resolution. The fact that the mirrors are rigidly co-mounted and always perpendicular to the line of sight means that a beam combiner can be built that respects the sine condition, yielding a wide field of view of several arc minutes for interferometric imaging. This will be exploited with a 2000x6000 pixel infrared array detectors.
A second beam combiner will be built for nulling interferometry. In this mode, the LBT will be uniquely capable of detecting the 10 micron emission at 1 AU from extra-solar zodiacal clouds no stronger than our own. An understanding of this emission is crucial for planning the Planet Finder mission.
