Also known as: GLONASS
GLONASS (from the Russian Globalnaya Navigatsionnaya Sputnikovaya Sistema, “Global Navigation Satellite System”) is Russia’s satellite navigation system and one of the four global members of the GNSS family.1 Its defining technical feature is historical: where GPS separates satellites by unique codes on one frequency, legacy GLONASS gives each satellite its own frequency — a textbook use of FDMA in space.
Overview
GLONASS is a constellation of 24 satellites in medium Earth orbit, in three orbital planes at about 19,100 km — slightly lower than GPS. Its high orbital inclination (about 64.8°) was chosen for good coverage at high latitudes, making it particularly effective across Russia’s northern territory. Like every GNSS, it works by one-way ranging: satellites broadcast time and orbit data, and a receiver measures pseudoranges to four or more of them and multilaterates its position and clock error.
Technical characteristics
| Property | Value |
|---|---|
| Access (legacy) | FDMA: channel spacing 562.5 kHz on L1 |
| Access (modern) | CDMA on new L3/L1OC signals |
| Carrier | L1 ≈ 1602 MHz, L2 ≈ 1246 MHz |
| Satellites | 24 in three MEO planes, ~19,100 km |
| Inclination | 64.8° (high-latitude coverage) |
| Modulation | BPSK direct-sequence spread spectrum |
The FDMA scheme means antipodal satellites (never simultaneously visible) can reuse the same channel number, so a modest set of frequencies covers the whole constellation. The trade-off is that a receiver’s front end must span a wider band and handle per-channel Doppler shift offsets, which is one reason modern GLONASS signals are migrating toward CDMA for easier interoperability with GPS, Galileo, and BeiDou.
History
The Soviet Union began launching GLONASS satellites in 1982 and declared the system operational in 1993, but the constellation decayed after the Soviet collapse and did not return to full global coverage until 2011 following a sustained modernization program. Newer GLONASS-K satellites add CDMA signals alongside the legacy FDMA ones.
Deployment
GLONASS is used worldwide, almost always in combination with other constellations: most modern smartphone and survey receivers track GPS, GLONASS, Galileo, and BeiDou together for faster, more robust fixes. Adding GLONASS to a multi-constellation receiver noticeably improves availability in urban canyons and at high latitudes.
Decoding it with GopherTrunk
GopherTrunk does not decode GLONASS. As a VHF/UHF land-mobile trunking scanner it has no L-band satellite navigation path. GLONASS is receivable with a general-purpose software-defined radio and an active L-band antenna — its FDMA structure actually makes the individual carriers easier to see on a spectrum display than code-multiplexed GPS — but recovering a position fix still requires wideband capture and dedicated correlation software. For GopherTrunk it is out of scope; any GNSS involvement is limited to external timing hardware.