LISA Pathfinder, a space mission launched on Dec 3, 2015, is a test of one LISA laser interferometric arm.
The arm length is shrunk from one million kilometers to 40 centimeters length. The mission is currently testing the key technologies required for the LISA mission.
The concept and details of the optical system for LISA Pathfinder have been developed at the AEI in Hanover, Germany. Its director Karsten Danzmann is Co-Principal Investigator of the mission.