Dedication: Professor Henry J. Kelley

Professor Henry J. Kelley (February 8, 1926 - February 9, 1988). It is with deep regret that we record the sudden passing of Professor Henry J. Kelley on February 9, 1988. He will be missed by many in the optimal controls community as a researcher, teacher, mentor and friend. Professor Kelley started his career at Grumman Aircraft Engineering Corporation, Bethpage, NY, where he worked from 1948 to 1963. Subsequently, he was with The Analytical Mechanics Associates, Incorporated, as a vice president. Since 1978, he has been a professor at Virginia Polytechnic and State University and was awarded the Christopher C. Kraft Chair of Aerospace Engineering there i.n 1984. Professor Kelley´s research was focused on optimal control theory, beginning with his doctoral dissertation at New York University in 1958. He was the recipient of the 1959 New York University Founder´s Day Award. He was awarded the IAS New York Section Research Award in 1959. His research has been a harmonious blend of theory and applications of optimal control in aerospace vehicle trajectory analysis. His research in singular control following Lawden´s work on the spiral led to the now-famous Kelley-Contensou Test, a necessary condition that must be satisfied along a minimizing s-ingular arc. The investigations he carried out on guidance theory have contributed to the development o-f flight vehicle guidance schemes. His early research on steepest descent and quadratic penalty functions remains a classic contribution in the numerical optimization area. Professor Kelley was one of the early researchers to examine the applications of second order necessary conditions in the Calculus of Variations for guidance law development. He was one of the first researchers to revive the energy management concept in flight mechanics, pioneered by Kaiser in 1945, and to apply it to aircraft guidance. For his contributions to flight mechanics and control, he was awarded the AlM Mechanics and Control of Flight Award i- 1972, and the Pendray Aerospace Literature Award in 1980. In 1980, he was elected a Fellow of the AIAA. His early work on singular perturbation theory laid the foundations for the development of mechanizable optimal guidance schemes. Among Professor Kelley´s keen technical interests was the differential game theory and its applications to aerial combat problems. His research is being used today in efforts to automate the cockpits of future aircraft. He was a strong proponent of the ACC and IFAC and was the founder and first chairman of IFAC Mathematics of Control Conmittee. He was one of the founders and an editor-at-large of the Journal of Guidances Control.and Dynamics. We appreciated Professor Kelley´s writing style and sense of humor. He was to participate in the 1988 ACC where he had submitted two papers.