GRACE-Follow On Laser Ranging Interferometer: German contribution

The Gravity Recovery and Climate Experiment (GRACE) is a joint US/German mission that has been mapping the Earth's gravity field since 2002 by measuring the distance variations between two spacecraft using a micro-wave link. GRACE is reaching the end of its lifetime. For this reason and in order to minimize data gaps, an almost identical mission will be launched in 2017. This mission is called GRACE-Follow On (GRACE-FO) and it will include an additional instrument as a technological demonstrator to monitor distance changes between the spacecraft. This instrument is the Laser Ranging Interferometer (LRI), which is based on heterodyne laser interferometry at 1064 nm and takes advantage of many technologies developed for LISA. In this paper a short overview of the current status of the German contribution is presented.