A Russian space-based navigational system initially developed for experimental military purposes during the 1970s but applied to commercial applications after the end of the Cold War. The first GLONASS satellite launched in 1982 and the system became fully operational in 1993; in 2005 this satellite was decommissioned and, since 2003, had gradually been replaced with the more evolved GLONASS-M class satellite. Currently the system is comprised of a constellation of 24 satellites (plus three spares) in three orbital planes (eight satellites per plane). The satellites circle the Earth at an altitude of 19 140 km, about 1 060 km lower than GPS satellites; the GLONASS-M satellites will be replaced with an even more evolved GLONASS-K class satellite (launched in 2011 and now undergoing design maturation and validation testing).