The Global Orbiting Navigation System (GLONASS) is a radio-based satellite navigation system, developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces. It is the Russian counterpart of the US Global Positioning System (GPS) system and the European GALILEO system. GLONASS comprises a constellation of 21 satellites plus three spares. These satellites operate in an 11 hour and 15 minute orbit at an altitude of 19,100 km and each satellite transmits on a unique frequency using the same pseudo noise code. The level of accuracy for GLONASS is similar to GPS operating in the C/A mode.
Development on the GLONASS began in 1976, with a goal of global coverage by 1991. Beginning in 1982, numerous satellite launches progressed the system forward until the constellation was completed in 1995. Following completion, the system rapidly fell into disrepair with the collapse of the Russian economy. Beginning in 2001, Russia committed to restoring the system by 2011.
By 2010, GLONASS had achieved 100% coverage of Russia's territory and in October 2011, the full orbital constellation of 24 satellites was restored, enabling full global coverage. The GLONASS satellites' designs have undergone several upgrades, with the latest version being GLONASS-K.