GLONASS or Global Navigation Satellite System is the satellite navigation system developed by Russia that consists of 24 satellites, in three orbital planes, with eight satellites per plane. Russia started developing GLONASS in 1976 as an experimental military communications system. They launched the first GLONASS satellite in 1982 and the constellation became fully operational in 1995. 

The satellites are placed into nominally circular orbits with target inclinations of 64.8 degrees and an orbital radius of 19,140 km, about 1,060 km lower than GPS satellites, with an orbit period of 11 hrs and 15 minutes.

Versions of GLONASS:

• GLONASS - These satellites were launched in 1982 for the military and official organizations. They were intended to for weather, positioning, timing and velocity measurements. 
• GLONASS-M - These satellites were launched in 2003 to add second civil code, which is important for GIS mapping receivers.
• GLONASS-K - These satellites were launched in 2011 to add third civil frequency. These are of 3 types - K1, K2 and KM.
• GLONASS-K2 - These satellites will be launched after 2015 (currently in design phase).
• GLONASS-KM - These satellites will be launched after 2025 (currently in research phase).

Currently, second generation GLONASS-M satellites as well as GLONASS-K1 satellites are in service while the GLONASS-K2 and KM satellites are under development. GLONASS signals have the same polarization (orientation of the electromagnetic waves) as GPS signals, and have comparable signal strength.

Each GLONASS satellite transmits a C/A-code for standard positioning on frequency L1, and a P-code for precise positioning on L1 and L2. The P-code is only available for military purposes. Unlike GPS and Galileo, GLONASS uses a different frequency for each satellite.

Click here to see GLONASS Frequency Bands.