GLONASS (Globalnaya Navigationnaya Sputnikovaya Sistema, Global Orbiting Navigation Satellite System) is a Soviet space-based navigation system comparable to the American GPS system, which consists of Uragan spacecraft. This was originally a military system, but now it's accessible to commercial GPS receivers. Newer satellites are called Uragan M, Uragan K1, and Uragan K2. The GLONASS-M version of the satellite featured improved antennas, extended lifetime and the introduction of a separate transmission frequency dedicated to civilian users, known as L2. Uragan-K1 spacecraft are the third generation of GLONASS navigation satellites. These satellites have an increased lifetime of 10 - 12 years, reduced weight of only 935 kg and offer an additional L-Band navigational signal.