GLONASS is a global positioning, navigation and timing system. Its basic ranging problem resembles GPS, but its legacy radio interface uses different frequencies to separate satellite signals. This difference matters when designing receiver tracking channels and precise carrier-phase processing.
Related: GPS constellation and GPS receiver principles. Reviewed October 30, 2026. Baseline designs below are not live satellite inventories.
Executive Summary
Item | Meaning |
|---|---|
System scope | Global; Russia |
Design baseline | 24 satellites: three planes with eight slots each |
Nominal orbit | Approximately 19,100 km altitude; 64.8 degrees inclination |
Legacy access | FDMA; frequency channel number identifies the carrier |
Constellation and Coverage
Orbit design
The GLONASS baseline distributes 24 satellites across three orbital planes. Adjacent planes differ by 120 degrees in longitude of ascending node. Within a plane, nominal satellites are separated by 45 degrees in argument of latitude. These describe orbital geometry, not permanent positions above particular cities. [1]
Figure 1 groups the main design elements. Read the rows as categories, not as a map of the sky. Satellites within one orbital plane travel around Earth; they do not remain above fixed user locations unless the orbit is geostationary.
Figure 1. The design groups explain the constellation architecture; operational inventory can differ.
What does the geometry mean ?
The satellites orbit at approximately 19,100 km, with a 64.8-degree inclination and an orbital period near 11 hours 15 minutes. The relatively high inclination supports useful viewing geometry at high latitudes. Actual reception still depends on local obstructions and the satellites available to the receiver. [1]
Signals and Receiver Operation
Spectrum / RF details
The legacy FDMA plan uses channel numbers k from -7 to +6. Satellites on opposite sides of an orbital plane can reuse a channel because a ground receiver does not normally see both simultaneously. Modernization introduces CDMA signals, so legacy FDMA does not describe every GLONASS signal. [2]
Signal / parameter | Carrier centre (MHz unless stated) | Receiver implication |
|---|---|---|
Legacy L1 | 1602 + k × 0.5625 MHz | FDMA channel k selects the carrier |
Legacy L2 | 1246 + k × 0.4375 MHz | Same channel number; different spacing |
Example k = -7 | L1: 1598.0625 MHz | Calculated from the L1 expression |
Example k = +6 | L1: 1605.375 MHz | Calculated from the L1 expression |
Carrier centres do not describe occupied bandwidth. Two services at the same centre can use different codes, modulation and navigation data. The RF front end must pass the required bandwidth, and the baseband must implement the particular signal.
Why does FDMA matter to a receiver ?
The receiver must search the correct frequency channel as well as code delay and Doppler. Different RF frequencies can produce different receiver hardware delays. For precise processing, these inter-frequency biases must be handled rather than assuming that every tracking channel has identical delay. The examples in the table are nominal carrier centres; motion adds Doppler to the actual received frequency. A channel number is also different from a satellite slot number.
Combining constellations
A multi-GNSS receiver combines pseudoranges after accounting for each system's timing and measurement conventions. More satellites can help geometry and availability, but they do not automatically eliminate interference, multipath or clock biases. If an extra system-time offset is unknown, the estimator needs an additional bias parameter or external timing information. Four arbitrary satellites from mixed systems are therefore not always sufficient for an unconstrained solution.