Modular Gravitational Reference Sensor: Simplified Architecture to future LISA and BBO

We present the Modular GRS (previously named as Stand-Alone GRS), in which the laser light from the remote spacecraft does not illuminate the proof mass. The modular GRS uses only a single spherical proof mass on each spacecraft and optical, as opposed to capacitive, position sensing. The use of a single sphere as the test mass avoids the issue of cross coupling that is inherent for the cubic proof mass, and allows true drag free flight with no forcing. Together, the modular design, optical sensing and a single spherical proof mass reduce the disturbances and the number of degrees of freedom that must be managed for future LISA and BBO.