Max Planck Institute for Astronomy - Annual Report 2005

Darwin will consist of three to six independent, freeflying
spacecrafts of two different types: several telescope
receiver satellites and a single beam combiner. Industrial
and academic design studies are currently running to determine
the optimum number, size, and flight configuration of
the individual spacecraft.
Darwin is being proposed as a large mission within
the Esa Cosmic Vision program. With sufficient technological
development, the interferometer will be ready to
fly in 2020. The road to a successful Darwin mission is
long and difficult, but researchers at the MPIA are already
attacking a number of core issues. In particular, the institute
is working on a novel technique for achieving the necessary
180 ° phase shift that will cancel out the star light. A
German-French collaboration, of which this effort is a part,
will demonstrate a number of such techniques to Esa in
late 2006.
Finally, MPIA scientists are deeply involved in planning
for and executing Darwin. Tom Herbst was on the original
Darwin Scientific Advisory Group (SAG) from 1997
through the end of an initial industrial study early in the
new decade. Esa reconstituted this advisory board as the
Terrestrial Exoplanet Scientific Advisory Team (TE-SAT),
with both Herbst and Thomas Henning as members. The
TE-SAT is currently writing the formal Darwin proposal,
and will guide a pair of industrial system studies through
to their completion at the end of 2006. With a successful
proposal outcome in early 2007, the MPIA will be ramping
up its involvement and support of this most fundamental
and important scientific space mission.
(Tom Herbst, Thomas Henning
and the Darwin APS group)
IV.4 Progress with Linc-nirvana for the LBT 99
IV.4 Progress with Linc-nirvana for the LBT
Linc-nirvana is an innovative imaging interferometer
fed by dedicated multi-conjugated adaptive optics systems.
The instrument combines the light of the two 8.4
meter primary mirrors of the Large Binocular Telescope
(LBT) on a single focal plane, providing panoramic
imagery with the spatial resolution of a single 23 meter
telescope. Linc-nirvana is being built by a consortium
of four institutes led by the MPIA. Our other partners
include the Istituto Nazionale di Astrofisica (Italy), the
University of Cologne, and the Max Planck Institute for
Radioastronomy (MPIfR) in Bonn.
Linc-nirvana will occupy one of the shared focal
stations on the central platform of the Large Binocular
Telescope (see Fig. V.1.4). At this location, the instrument
receives light from both optical trains of the LBT.
By creating a scaled-down version of the telescope
entrance pupil, Linc-nirvana permits Fizeau-type interferometry
over a wide field of view. The resulting images
contain information at spatial frequencies up to that corresponding
to the maximum dimension of the telescope
(22.8 meters) along the direction connecting the primary
mirrors, and up to 8.4 m spatial frequencies along the
perpendicular direction. The Large Binocular Telescope
has an alt-azimuth mount configuration, which means
that the projected telescope pupil rotates with respect to
the sky – so-called »earth rotation synthesis«. Combining
multiple exposures taken at different projection angles
Fig. IV.4.1: The Linc-nirvana optical bench in the MPIA assembly
hall.