A Time Transfer Experiment between Atomic Clocks on the Space Shuttle and on the Ground

From Oct. 30th to Nov. 6th 1985 a Shuttle Mission was performed with the European Spacelab and more than 70 scientific experiments on board. It was the first dedicated German Spacelab Mission, called D1. All experiments were controlled from the Satellite Operation Center near Munich in Germany. One of these experiments aimed at a high accurate time transfer between the Shuttle and the ground. A Cs-and a Rb-Clock onboard the Shuttle were compared with Cs-clocks on the ground with an RMS error of ot ≪ 10 nsec. The clock comparison was performed with pseudo random coded microwave signals in the L-Band. A two-way method was used and spread spectrum techniques were applied. A survey will be given on the progress of this experiment and on first raw data, which indicate a satisfactory operation of the used technique and a very accurate confirmation of the predicted relativistic clock effects.