Since 1581 a JMR-4A Doppler eceiver is used mostly for stationary observations at the Potsdam observatory. The research activities have three main directions: 1. Methodical investigations of satellite interferometry using Doppler receivers and receiver calibration, 2. Computation of regional networks using the orbital program POTSDAM-5, 3. Computation of long global arcs for determination of polar motion and station coordinates.