  The Laser Astrometric Test Of Relativity (LATOR) is a Michelson-Morley-type
experiment designed to achieve a major improvement in the accuracy of the tests
of relativistic gravity in the solar system. By using a combination of
independent time-series of gravitational deflection of light in the immediate
proximity to the Sun, along with measurements of the relativistic time delay on
interplanetary scales (to a precision respectively better than 0.1 picoradians
and 1 cm), LATOR will measure the key post-Newtonian Eddington parameter \gamma
with accuracy of one part in a billion - a factor of 30,000 improvement
compared to the present best result, Cassini's 2003 test. LATOR's primary
measurement pushes to unprecedented accuracy the search for cosmologically
relevant scalar-tensor modifications of gravity by looking for a remnant scalar
field in today's solar system. We present a comprehensive discussion of the
science objectives, proposed technology, mission and optical designs, as well
as the expected performance of this fundamental physics experiment in space.
