  ASTROD I is a planned interplanetary space mission with multiple goals. The
primary aims are: to test General Relativity with an improvement in sensitivity
of over 3 orders of magnitude, improving our understanding of gravity and
aiding the development of a new quantum gravity theory; to measure key solar
system parameters with increased accuracy, advancing solar physics and our
knowledge of the solar system and to measure the time rate of change of the
gravitational constant with an order of magnitude improvement and the anomalous
Pioneer acceleration, thereby probing dark matter and dark energy
gravitationally. It is an international project, with major contributions from
Europe and China and is envisaged as the first in a series of ASTROD missions.
ASTROD I will consist of one spacecraft carrying a telescope, four lasers, two
event timers and a clock. Two-way, two-wavelength laser pulse ranging will be
used between the spacecraft in a solar orbit and deep space laser stations on
Earth, to achieve the ASTROD I goals. A second mission, ASTROD II is envisaged
as a three-spacecraft mission which would test General Relativity to one part
per billion, enable detection of solar g-modes, measure the solar
Lense-Thirring effect to 10 parts per million, and probe gravitational waves at
frequencies below the LISA bandwidth. In the third phase (ASTROD III or
Super-ASTROD), larger orbits could be implemented to map the outer solar system
and to probe primordial gravitational-waves at frequencies below the ASTROD II
bandwidth.
