Polar Motion: A Historical Overview on the Occasion of the Centennial of the International Latitude Service

Abstract

AbstractThe study of polar motion, termed “variation of latitude” at the time of its discovery in the late 19th century by F. Küstner and S. Chandler, is of historical interest for many reasons. From a scientific viewpoint, its discovery must be seen in the context of positional astronomy, geodesy and Earth rotation studies. From an institutional viewpoint, the founding of the International Latitude Service (ILS) in 1899 represents an early case of international cooperation in astronomy, preceding the International Astronomical Union by two decades. In addition to discussing these themes in this review, we analyze in some detail the Gaithersburg (USA) station of the ILS as a case study of the early problems and promise of polar motion studies. With milliarcsecond accuracies, polar motion studies are important today not only for astronomy and geophysics, but also for practical problems like spacecraft navigation and positioning.