By invitation of Edoardo Proverbio, the President of Commission 31 (Time), this report attempts to summarize “new possibilities in time-frequency standards”. Especially because recent work in this highly specialized field is so diverse and so complex, I appreciate the support of our colleague, Dr. G. Busca, who will survey the extensive progress being made east of the Atlantic. I confine this paper to work that has appeared in the open literature from the United States and Canada.

Since much of this work is proprietary, and since it is difficult to assign credit fairly, I will not attempt to give either a comprehensive or selected bibliography of references in this paper. There are three primary symposia where such work is published: (1) the annual IEEE International Frequency Control Symposia; (2) the more recently organized annual European Frequency and Time Forums; and (3) the (United States) Annual Precise Time and Time Interval (PTTI) Applications and Planning Meetings, organized jointly by the Department of Defense and NASA. The best general review of recent work on frequency standards, which appeared just before our last IAU General Assembly and is not yet outdated, is the special issue of the Proceedings of the IEEE, volume 79, no 7 (July 1991), and especially the papers “An Introduction to Frequency Standards” by Lindon L. Lewis, “Atomic Ion Frequency Standards” by Wayne M. Itano, and “Laser- Cooled Neutral Atom Frequency Standards” by Steven L. Rolston and William D. Phillips.