GRACE, for Gravity Recovery and Climate Experiment, is a joint American-German project that has been an incredibly successful satellite mission. In the GRACE mission, the distance between two spacecraft is measured using a microwave ranging system. Temporal estimates of the Earth's gravity field are inferred from changes in this distance and it has provided new and unexpected insights into the natural processes of the Earth. This mission will not extend beyond 2013 and a GRACE Follow-on mission is scheduled to launch in 2017.
GRACE Follow-on mission would refly the identical GRACE spacecraft and instruments, but supplement the micrometre-level accuracy microwave measurement with a laser interferometer with nanometre-level accuracy. The laser demonstration on GRACE Follow-On will be a partnership between NASA, which will provide the laser, cavity assembly, and ranging processor, and the German Space Program, which will provide the measurement optics and steering mirror assembly along with instrument integration and testing.
Under this project a consortium of U.S., German and Australian institutions will produce prototype hardware for the laser ranging system to be flown on the GRACE Follow-on mission. This system will improve the sensitivity by a factor of 25 over the original GRACE mission. This project will also build Australia's analysis capacity to exploit the mission's current and future scientific data.
The project consortium is made up of the Australian National University, Jet Propulsion Laboratory, Max Planck Institute for Gravitational Physics, EOS Space Systems, CSIRO Australia Centre for Precision Optics and National Measurement Institute. At ANU, Research School of Physics and Engineering (RSPE) and Research School of Earth Science (RSES) are involved for the development of laser ranging system and space gravity data analysis respectively.
GRACE Follow-on Mission project is supported under the Australian Government's Australian Space Research Program. 'GRACE Follow-on Mission', an Australian Government initiative.
 Laser System on GRACE Follow-On to Measure Earth's Gravity as Never Before. Available from http://esto.nasa.gov/news/news_GraceFollowOn.html