The European LISA test package (LTP) and US Disturbance Reduction System (DRS) will fly on the upcoming ESA SMART-2 mission in scheduled in 2006. The DRS system will contain two isolated proof masses which will be used as references for the drag-free/attitude control system. The proof masses will also serve as reference mirrors for the laser interferometer package. The interferometer will provide an independent measurement of relative displacement between the masses, allowing a direct assessment of the relative acceleration between the masses.
The relative motions of the two masses will be compared to determine the disturbance level. The purpose is to validate the inertial sensors and micro-newton thrusters.