The Explanatory Supplement to the Astronomical Almanac offers explanatory material, supplemental information, and detailed descriptions of the computational models and algorithms used to produce The Astronomical Almanac, which is an annual publication prepared jointly by the US Naval Observatory and Her Majesty's Nautical Almanac Office in the UK. Like The Astronomical Almanac, The Explanatory Supplement provides detailed coverage of modern positional astronomy. Chapters are devoted to the celestial and terrestrial reference frames, orbital ephemerides, precession, nutation, Earth rotation, and coordinate transformations. These topics have undergone substantial revisions since the last edition was published in 1992. Astronomical positions are intertwined with timescales and relativity in The Astronomical Almanac, so related chapters are provided in The Explanatory Supplement. The Astronomical Almanac also includes information on lunar and solar eclipses, physical ephemerides of solar system bodies, and calendars, so The Explanatory Supplement expounds upon each of these topics as well. The book is written at a technical, but non-expert level. As such, it provides an important reference for a full range of users including astronomers, engineers, navigators, surveyors, space scientists, and educators.
Seidelmann, P. Kenneth: - P. Kenneth Seidelmann received an Electrical Engineering degree from the University of Cincinnati in 1960, a Master of Science degree in 1962, and a Doctor of Philosophy degree in Dynamical Astronomy in 1968. He joined the Nautical Almanac Office of the U. S. Naval Observatory in 1965, where he was subsequently named Director of the Nautical Almanac Office, Director of the Orbital Mechanics Department, and Director of the Directorate of Astrometry. In 2000 he retired from the U S Naval Observatory and became a research professor in the Astronomy Department of the University of Virginia. Seidelmann is coauthor of two books, Fundamentals of Astrometry and TIME, From Earth Rotation to Atomic Physics.
Urban, Sean E.: - Sean E. Urban graduated from the University of Maryland with a degree in astronomy in 1984. In 1985, he was hired as a staff astronomer in the Astrometry Department of the US Naval Observatory, where he eventually rose to Chief of the Cataloging and Requirements Division. In 2004, he became Chief of the Nautical Almanac Office of the US Naval Observatory, a position that he holds today. He has authored or co-authored more than 50 articles, most on positional astronomy. He is a member of the American Astronomical Society, the Division of Dynamical Astronomy, and the International Astronomical Union's Division I (Fundamental Astronomy), Commission 4 (Ephemerides), and Commission 8 (Astrometry).
