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GLONASS is a Russian GNSS, which – like GPS – originally was intended for military applications. It has now for a long time also been used by civilian users, mainly in combination with GPS.
Russian satellite system
The establishment of GLONASS (Globalnaya Navigatsionnaya Sputnikovaya Sistema) started in 1976 and the first satellite was launched in 1982. The system is owned and managed by the Russian armed forces and was developed as an alternative to GPS with respect to global coverage and position uncertainty. Since 1999, the system has full civilian use and consists of 24 satellites, which was achieved in December 2011 (except for a short period in 1996).
GLONASS differs slightly from GPS with regard to, among others, the satellite constellation. The usually 24 active satellites are distributed over three orbital planes at an altitude of approximately 19,140 kilometres above the earth's surface. The satellite orbits have a greater inclination than what the GPS satellites have, namely 64.8 degrees, which means slightly better coverage at northern latitudes (for example in Sweden).
Satellite signals and modernisation
The GLONASS satellites transmit two signals, L1 and L2, which both contain a civilian and a military code, similar to GPS. Unlike GPS, the satellites are identified by frequency-division multiple access (FDMA). The generation of satellites launched 2003–2022 is called GLONASS‑M, with significant improvements and modernisation of the satellites. The subsequent generation is called GLONASS‑K and here the satellites also transmit a third signal called L3. With an improved version of the GLONASS‑K satellites, access to all signals is also provided through code-division multiple access (CDMA).
The satellites are controlled and adjusted through a number of control stations that were initially mainly deployed in Russia. Nowadays there are also some globally localised stations. GLONASS uses the geodetic reference frame PZ‑90. Several improved versions of PZ‑90 have been released and the version from 2011 is called the PZ‑90.11.
More information
The Russian space agency Roskosmos (new window) reports official information about GLoNASS and current status of the system (new window)