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Optical interferometry will open new vistas for astronomy over the next decade. The Space Interferometry Mission
(SIM-PlanetQuest), operating unfettered by the Earth's atmosphere, will offer unprecedented astrometric precision that
promises the discovery of Earth-analog extra-solar planets as well as a wealth of important astrophysics. Results from
SIM will permit the determination of stellar masses to accuracies of 2% or better for objects ranging from brown dwarfs
through main sequence stars to evolved white dwarfs, neutron stars, and black holes. Studies of star clusters will yield
age determinations and internal dynamics. Microlensing measurements will present the mass spectrum of the Milky
Way internal to the Sun while proper motion surveys will show the Sun's orbital radius and speed. Studies of the
Galaxy's halo component and companion dwarf galaxies permit the determination of the Milky Way's mass distribution,
including its Dark Matter component and the mass distribution and Dark Matter component of the Local Group.
Cosmology benefits from precision (1-2%) determination of distances to Cepheid and RR Lyrae standard candles. The
emission mechanism of supermassive black holes will be investigated. Finally, radio and optical celestial reference frames will be tied together by an improvement of two orders of magnitude.
Optical interferometers present severe technological
challenges. The Jet Propulsion Laboratory, with the support of
Lockheed Martin Advanced Technology Center (LM ATC)
and Northrop Grumman Space Technology (NGST), has
addressed these challenges with a technology development
program that is now complete. The requirements for SIM have
been satisfied, based on outside peer review, using a series of
laboratory tests and appropriate computer simulations: laser
metrology systems perform with 10 picometer precision;
mechanical vibrations have been controlled to nanometers,
demonstrating orders of magnitude disturbance rejection; and
knowledge of component positions throughout the whole test
assembly has been demonstrated to the required picometer
level. Technology transfer to the SIM flight team is now well
along.
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