Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
J.R.P. Angel , J.M. Hill, P.A.
Strittmatter, P. Salinari and G. Weigelt:
Interferometry with the Large Binocular
Telescope
Proceedings of SPIE conference on Astronomical
Interferometry, 3350, p. 881-889 (1998)
Abstract.
The Large Binocular Telescope (LBT) has been designed for
optical/infrared interferometry that combines high sensitivity
and resolution. Key scientific projects will be deep, wide field
infrared images of the Hubble Deep Field, with nearly ten
times the resolution of the Hubble telescope, and the study of planets
and dust in extra-solar systems, from their formation
onward. A basic requirement for interferometry of faint objects is that
the aberrations across the two 8.4 m telescopes be
corrected for atmospheric phase errors. This will be done at the
telescopes' secondary mirrors, so as to preserve the very
low emissivity of the direct beam combination optics. Sodium lasers
projected co-axially from above each secondary will
allow wavefront sensing for correction of even the faintest objects.
The two telescopes are rigidly mounted close together
on a single alt-azimuth mount, to cover a large fraction of the u-v
plane in a single exposure, with baselines continuous
from 0 to 23 m. Field rotation during the night completes the cover, to
allow recovery of images with the full resolution of
a diffraction limited 23 m telescope. The beam combining optics will be
cryogenically cooled to maintain the very low
thermal background from only 3 warm reflections in total (primary,
adaptive secondary, tertiary). For wide field imaging,
the beams will be combined and stabilized so that in a long exposure
every source across a ~ 1 arcminute field is crossed by
interference fringes. From a set of such exposures the resultant deep
image will have a resolution 0.02 arcsec in the 2.2µm
K band. For high contrast studies of exo-planetary systems, a Bracewell
nulling system will be used with superposition by
division of amplitude, for 99.99% suppression of the stellar radiation.
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