During the Second German Spacelab Mission D-2, extensive onboard measurements of the residual acceleration have been performed. The payload was equipped with accelerometer packages distributed over the entire Spacelab module. The Microgravity Measurement Assembly (MMA) was the core system comprising fixed mounted as well as mobile sensor packages. On-board video has been taken as means to correlate the measured accelerations with mission events. The D-2 microgravity characterization program also included numerical calculations to predict low frequency effects which cause accelerations outside the sensor detection range. Results of characteristic quiet mission phases show that the microgravity level of D-2 was below the requirements of the Space Station. Data of active phases reveals what can be done to improve the microgravity quality of Spacelab missions by payload design and operation.