GRACE Follow-On will test a Laser Ranging Interferometer to measure intersatellite distance changes with unprecedented precision.
This new technology is a heritage of the LISA project, which proposed laser interferometry between satellites. While LISA would measure the effect of gravitational waves, GRACE Follow-On studies changes in the gravitational field of Earth. Those changes are mostly caused by the movement of water, vital to humankind. Processes related to climate change such as the decline of Greenland's ice sheet mass can be studied in great detail.
This video gives an introduction to test environments in which specific components of the Laser Ranging Interferometer have been investigated. It was produced by Daniel Schütze in the framework of his PhD thesis at the Albert Einstein Institute in Hanover, Germany.