Abstract
The most stringent requirements for high-stability oscillators will be in space appleations involving the generation and propagation of microwave signals for distance and angle measurement and for time and frequency comparison. This paper describes systems for cancelling the effects of the ionosphere and troposphere on signal propagation so as to make full use of the stability currently available from atomic clocks.
An advanced form of Doppler tracking system for gravitational and relativistic tests is described and its use in the search for low-frequency (10-3 Hz) gravitational pulsed radiation is discussed. The current status and future trends of clocks for space use are also reviewed.