By William W. Kellogg and Charles A. Barth

Joseph Kaplan's research was largely concerned with the spectra of diatomic molecules and, more specifically, in afterglows of nitrogen and oxygen and their mixtures. These spectra are important in understanding the photochemistry of the upper atmosphere of the Earth and other planets.

Kaplan will be more widely remembered, however, for his leadership in the geophysics community. He was one of the creators of the new science of aeronomy. For ten years he served as chairman of the U.S. National Committee for the International Geophysical year and for five years he was a member of the Executive Committee of the International Committee of Scientific Unions. He played a leading role in establishing such significant programs as the International Hydrological Decade and the Global Atmospheric Research Program.

In spite of his involvement in such public arenas, he remained a popular and inspiring teacher at the University of California at Los Angeles, not only of many science graduate students, but also of undergraduates. Because of his warmth and charm, he was in constant demand by the public and the media as well as the scientific community, and he always seemed to welcome the opportunity to explain the scientific enterprise to non-scientists.