The Global Navigation Satellite System (in Russian: Global'naya Navigatsionnaya Sputnikovaya Sistema) is a Russian space-based radionavagiation system capable of providing three-dimensional position and velocity determination as well as time dissemination. The system is similar to the Global Positioning System. GLONASS was started in the mid 1970s at the Scientific Production Association of Applied Mechanics (NPO PM). Originally, the Soviet Navy requested development of the system. At a meeting of the Special Committee on Future Air Navigation Systems (FANS) of the International civil Aviation Organization (ICAO) in 1988, the USSR allowed the world community free use of the GLONASS navigation signals.
The system consists of 21 satellites with 3 on-orbit spares. The 24 satellites are located in three orbital planes 120 degrees apart in right ascesion. Only 21 satellites are active at any given time. Each satellite is in a 19,100 km circular orbit (referenced to the Earth's surface) with an inclination of 64.8 degrees and an orbital period of 11 hours and 15 minutes. The GLONASS satellites have a service life of 1-3 years. The first launch occurred on October 12, 1982 which carried three satellites launched by a Proton rocket. The system was announced to be operational on September 24, 1993 but the constellation was not completed until December 1995.
The Russian Ministry of Defense is the principle user and owner of GLONASS yet the Military Space Forces are responsible for the policy and operation. Similar to the GPS, GLONASS provides two levels of accuracy; high accuracy is restricted to Russian military use while low accuracy is for civil use. The high-accuracy (according to observations by universities and corporations) has approximately 20m (2 drms, 95% probability) in the horizontal plane and 34m (2-sigma) in the vertical dimension. The low accuracy (civil use) is 100m (2 drms, 95% probability) in the horizontal plane, 150m (2-sigma) in the vertical dimension and 15cm/s (2-sigma) in velocity.
On December 25, 2002, three satellites were launched from Russia's Baikonur cosmodrome on board a Proton booster and were successfully put into orbit. However, a new class of satellites titled "GLONASS-M" will replace the GLONASS class and will have a service life of seven years. The first of the GLONASS-M will be launched into orbit in the second quarter of 2003.
Sources:
http://english.pravda.ru/region/2002/12/25/41321.html
http://www.fas.org/spp/guide/russia/nav/glonass.htm
www.glonass-center.ru/
http://www.spaceandtech.com/spacedata/constellations/glonass_consum.shtml