Rubidium locked oscillator life testing

Space programs increasingly use atomic frequency standards (commonly known as atomic clocks) for precision time-keeping and stable frequency generation. A new generation of military communication satellites (Milstar) will carry multiple redundant rubidium atomic frequency standards to meet two requirements-autonomous operation and reduced sensitivity to radiation. A test was developed to monitor the performance of two space qualified rubidium locked crystal oscillators for one year. To date, this represents one of the most extensive long term tests of atomic frequency standards in a space environment. There were several operational, logistic and contractual problems that developed over the test period that were overcome. The test, the test equipment, the test philosophy and some of the problems encountered are described in this paper