Aspects of the Soviet Union' s Glonass Satellite Navigation System

Abstract

Global satellite navigation systems have been under development by the United States and the Soviet Union for many years. The US Navstar GPS system saw its first launch in 1978 and the USSR's Glonass system followed 4 years later. The US space shuttle, which was foreseen as the launch vehicle for Navstar spacecraft, received an enormous setback in 1986 as a result of the Challenger accident. In the meantime, Glonass launches, which carry three spacecraft at once into orbit, have proceeded without incident (until the failure on 24 April 1987). Both systems are currently still in test phase and can be expected to reach operational status in 3 or 4 years' time. In the meantime, the idea of combining Navstar and Glonass into a single civil programme has many attractions for all concerned. Some aspects of Glonass orbital characteristics and signal structure are discussed with this end in view. In addition, features of the data message content of Navstar and Glonass are also compared, to gain a better understanding of the feasibility of a dual satellite navigation system.