Executive+Summary

=EXECUTIVE SUMMARY=

The objectives of the Astrodynamical Space Test of Relativity using Optical Devices (ASTROD) Mission are threefold. The first objective is to discover and explore fundamental physical laws governing matter, space and time via testing relativistic gravity with 3-6 orders of magnitude improvement. Relativistic gravity is an important cornerstone of physics, astronomy and cosmology. Its improved test is crucial to cosmology and modern theories of gravitation including superstring theories. Included in this objective is the precise determination of the relativistic parameters beta and gamma, the improved measurement of G and a precise determination of an anomalous, constant acceleration directed towards the Sun. The second objective of the ASTROD mission is the high-precision measurement of the solar-system parameters. This includes: (i) a measurement of solar angular momentum via Lense-Thirring effect and the detection of solar g-mode oscillations via their changing gravity field, thus, providing a new eye to see inside the Sun; (ii) precise determination of the planetary orbit elements and masses; (iii) better determination of the orbits and masses of major asteroids. These measurements give better solar dynamics and probe the origin of our solar system. The third objective is to detect and observe gravitational waves from massive black holes and galactic binary stars in the frequency range 50 uHz to 5 mHz. Background gravitational-waves will also be explored. A desirable implementation is to have two spacecraft in separate solar orbit carrying a payload of a proof mass, two telescopes, two 1-2 W lasers, a clock and a drag-free system, together with an Earth reference system. The Earth reference system could be ground stations, Earth satellites and/or spacecraft near Earth-Sun Lagrange points. The cost of this implementation is over the F2/F3 mission budget. International collaboration with US and the Orient will be pursued if this implementation is adopted. A simplified mission, mini-ASTROD, will fit into the F mission budget. For mini-ASTROD, one spacecraft ranging optically with ground stations will be implemented. The first objective will be largely achieved. The second objective will be partially achieved. For gravitational wave detection, the sensitivity will be better than the present-day sensitivity using Doppler tracking by radio waves.