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GLONASS
ГЛОНАСС
GLONASS logo
Country/ies of origin Soviet Union
(now Russia)
Operator(s)Roscosmos
( Russia)
TypeMilitary, civilian
StatusOperational
CoverageGlobal
Accuracy2.8–7.38 metres
Constellation size
Nominal satellites24
Current usable satellites26
First launch12 October 1982; 43 years ago (1982-10-12)
Last launch2 March 2025
Orbital characteristics
Regime3 × MEO planes
Orbital height19,130 km
Orbital period8⁄17 sd, 11 hours and 16 minutes
Revisit period8 sidereal days
Websiteglonass-iac.ru/en

GLONASS (ГЛОНАСС, IPA: [ɡɫɐˈnas]; Russian: Глобальная навигационная спутниковая система, romanized: Global'naya Navigatsionnaya Sputnikovaya Sistema, lit. 'Global Navigation Satellite System') is a Russian satellite navigation system operating as part of a radionavigation-satellite service. It provides an alternative to Global Positioning System (GPS) and is the second navigational system in operation with global coverage and of comparable precision.

Satellite navigation devices supporting both GPS and GLONASS have more satellites available, meaning positions can be fixed more quickly and accurately, especially in built-up areas where buildings may obscure the view to some satellites.[1][2][3] Owing to its higher orbital inclination, GLONASS supplementation of GPS systems also improves positioning in high latitudes (near the poles).[4]

Development of GLONASS began in the Soviet Union in 1976. Beginning on 12 October 1982, numerous rocket launches added satellites to the system until the completion of the constellation in 1995. In 2001, after a decline in capacity during the late 1990s, the restoration of the system was made a government priority, and funding increased substantially. GLONASS is the most expensive program of Roscosmos, consuming a third of its budget in 2010.

By 2010, GLONASS had achieved full coverage of Russia's territory. In October 2011, the full orbital constellation of 24 satellites was restored, enabling full global coverage. The GLONASS satellites' designs have undergone several upgrades, with the latest version, GLONASS-K2, launched in 2023.[5]

System description

[edit]
Clickable image, highlighting medium altitude orbits around Earth,[a] from Low Earth to the lowest High Earth orbit (geostationary orbit and its graveyard orbit, at one ninth of the Moon's orbital distance),[b] with the Van Allen radiation belts and the Earth to scale

GLONASS is a global navigation satellite system, providing real time position and velocity determination for military and civilian users. The satellites are located in middle circular orbit at 19,100 km (11,900 mi) altitude with a 64.8° inclination and an orbital period of 11 hours and 16 minutes (every 17 revolutions, done in 8 sidereal days, a satellite passes over the same location[6]).[7][8] GLONASS's orbit makes it especially suited for usage in high latitudes (north or south), where getting a GPS signal can be problematic.[9][10]

The constellation operates in three orbital planes, with eight evenly spaced satellites on each.[8] A fully operational constellation with global coverage consists of 24 satellites, while 18 satellites are necessary for covering the territory of Russia. To get a position fix the receiver must be in the range of at least four satellites.[7]

Signal

[edit]

FDMA

[edit]
A combined GLONASS/GPS receiver, ruggedised for the Russian military, 2003
A combined GLONASS/GPS Personal Radio Beacon

GLONASS satellites transmit two types of signals: open standard-precision signal L1OF/L2OF, and obfuscated high-precision signal L1SF/L2SF.

The signals use similar DSSS encoding and binary phase-shift keying (BPSK) modulation as in GPS signals. All GLONASS satellites transmit the same code as their standard-precision signal; however each transmits on a different frequency using a 15-channel frequency-division multiple access (FDMA) technique spanning either side from 1602.0 MHz, known as the L1 band. The center frequency is 1602 MHz + n × 0.5625 MHz, where n is a satellite's frequency channel number (n=−6,...,0,...,6, previously n=0,...,13). Signals are transmitted in a 38° cone, using right-hand circular polarization, at an EIRP between 25 and 27 dBW (316 to 500 watts). Note that the 24-satellite constellation is accommodated with only 15 channels by using identical frequency channels to support antipodal (opposite side of planet in orbit) satellite pairs, as these satellites are never both in view of an Earth-based user at the same time.

The L2 band signals use the same FDMA as the L1 band signals, but transmit straddling 1246 MHz with the center frequency 1246 MHz + n × 0.4375 MHz, where n spans the same range as for L1.[11] In the original GLONASS design, only obfuscated high-precision signal was broadcast in the L2 band, but starting with GLONASS-M, an additional civil reference signal L2OF is broadcast with an identical standard-precision code to the L1OF signal.

The open standard-precision signal is generated with modulo-2 addition (XOR) of 511 kbit/s pseudo-random ranging code, 50 bit/s navigation message, and an auxiliary 100 Hz meander sequence (Manchester code), all generated using a single time/frequency oscillator. The pseudo-random code is generated with a 9-stage shift register operating with a period of 1 milliseconds.

The navigational message is modulated at 50 bits per second. The superframe of the open signal is 7500 bits long and consists of 5 frames of 30 seconds, taking 150 seconds (2.5 minutes) to transmit the continuous message. Each frame is 1500 bits long and consists of 15 strings of 100 bits (2 seconds for each string), with 85 bits (1.7 seconds) for data and check-sum bits, and 15 bits (0.3 seconds) for time mark. Strings 1-4 provide immediate data for the transmitting satellite, and are repeated every frame; the data include ephemeris, clock and frequency offsets, and satellite status. Strings 5-15 provide non-immediate data (i.e. almanac) for each satellite in the constellation, with frames I-IV each describing five satellites, and frame V describing remaining four satellites.

The ephemerides are updated every 30 minutes using data from the Ground Control segment; they use Earth Centred Earth Fixed (ECEF) Cartesian coordinates in position and velocity, and include lunisolar acceleration parameters. The almanac uses modified orbital elements (Keplerian elements) and is updated daily.

The more accurate high-precision signal is available for authorized users, such as the Russian military, yet unlike the United States P(Y) code, which is modulated by an encrypting W code, the GLONASS restricted-use codes are broadcast in the clear using only security through obscurity. The details of the high-precision signal have not been disclosed. The modulation (and therefore the tracking strategy) of the data bits on the L2SF code has recently changed from unmodulated to 250 bit/s burst at random intervals. The L1SF code is modulated by the navigation data at 50 bit/s without a Manchester meander code.

The high-precision signal is broadcast in phase quadrature with the standard-precision signal, effectively sharing the same carrier wave, but with a ten-times-higher bandwidth than the open signal. The message format of the high-precision signal remains unpublished, although attempts at reverse-engineering indicate that the superframe is composed of 72 frames, each containing 5 strings of 100 bits and taking 10 seconds to transmit, with total length of 36 000 bits or 720 seconds (12 minutes) for the whole navigational message. The additional data are seemingly allocated to critical Lunisolar acceleration parameters and clock correction terms.

Accuracy
[edit]

At peak efficiency, the standard-precision signal offers horizontal positioning accuracy within 5–10 metres, vertical positioning within 15 m (49 ft), a velocity vector measuring within 100 mm/s (3.9 in/s), and timing within 200 nanoseconds, all based on measurements from four first-generation satellites simultaneously;[12] newer satellites such as GLONASS-M improve on this.

GLONASS uses a coordinate datum named "PZ-90" (Earth Parameters 1990 – Parametry Zemli 1990), in which the precise location of the North Pole is given as an average of its position from 1990 to 1995. This is in contrast to the GPS's coordinate datum, WGS 84, which uses the location of the North Pole in 1984. As of 17 September 2007, the PZ-90 datum has been updated to version PZ-90.02 which differ from WGS 84 by less than 400 mm (16 in) in any given direction. Since 31 December 2013, version PZ-90.11 is being broadcast, which is aligned to the International Terrestrial Reference System and Frame 2008 at epoch 2011.0 at the centimetre level, but ideally a conversion to ITRF2008 should be done.[13][14]

CDMA

[edit]

Since 2008, new CDMA signals are being researched for use with GLONASS.[15][16][17][18][19][20][21][22][23]

The interface control documents for GLONASS CDMA signals was published in August 2016.[24]

According to GLONASS developers, there will be three open and two restricted CDMA signals. The open signal L3OC is centered at 1202.025 MHz and uses BPSK(10) modulation for both data and pilot channels; the ranging code transmits at 10.23 million chips per second, modulated onto the carrier frequency using QPSK with in-phase data and quadrature pilot. The data is error-coded with 5-bit Barker code and the pilot with 10-bit Neuman-Hoffman code.[25][26]

Open L1OC and restricted L1SC signals are centered at 1600.995 MHz, and open L2OC and restricted L2SC signals are centered at 1248.06 MHz, overlapping with GLONASS FDMA signals. Open signals L1OC and L2OC use time-division multiplexing to transmit pilot and data signals, with BPSK(1) modulation for data and BOC(1,1) modulation for pilot; wide-band restricted signals L1SC and L2SC use BOC (5, 2.5) modulation for both data and pilot, transmitted in quadrature phase to the open signals; this places peak signal strength away from the center frequency of narrow-band open signals.[21][27]

Binary phase-shift keying (BPSK) is used by standard GPS and GLONASS signals. Binary offset carrier (BOC) is the modulation used by Galileo, modernized GPS, and BeiDou-2.

The navigational message of CDMA signals is transmitted as a sequence of text strings. The message has variable size - each pseudo-frame usually includes six strings and contains ephemerides for the current satellite (string types 10, 11, and 12 in a sequence) and part of the almanac for three satellites (three strings of type 20). To transmit the full almanac for all current 24 satellites, a superframe of 8 pseudo-frames is required. In the future, the superframe will be expanded to 10 pseudo-frames of data to cover full 30 satellites.[28]

The message can also contain Earth's rotation parameters, ionosphere models, long-term orbit parameters for GLONASS satellites, and COSPAS-SARSAT messages. The system time marker is transmitted with each string; UTC leap second correction is achieved by shortening or lengthening (zero-padding) the final string of the day by one second, with abnormal strings being discarded by the receiver.[28]

The strings have a version tag to facilitate forward compatibility: future upgrades to the message format will not break older equipment, which will continue to work by ignoring new data (as long as the constellation still transmits old string types), but up-to-date equipment will be able to use additional information from newer satellites.[29]

The navigational message of the L3OC signal is transmitted at 100 bit/s, with each string of symbols taking 3 seconds (300 bits). A pseudo-frame of 6 strings takes 18 seconds (1800 bits) to transmit. A superframe of 8 pseudo-frames is 14,400 bits long and takes 144 seconds (2 minutes 24 seconds) to transmit the full almanac.

The navigational message of the L1OC signal is transmitted at 100 bit/s. The string is 250 bits long and takes 2.5 seconds to transmit. A pseudo-frame is 1500 bits (15 seconds) long, and a superframe is 12,000 bits or 120 seconds (2 minutes).

L2OC signal does not transmit any navigational message, only the pseudo-range codes:

Roadmap of GLONASS modernization
Satellite series Launches Current status Clock error FDMA signals CDMA signals Interoperability CDMA signals
1602 + n×0.5625 MHz 1246 + n×0.4375 MHz 1600.995 MHz 1248.06 MHz 1202.025 MHz 1575.42 MHz 1207.14 MHz 1176.45 MHz
GLONASS 1982–2005 Out of service 5×10−13 L1OF, L1SF L2SF
GLONASS-M 2003–2022 In service 1×10−13 L1OF, L1SF L2OF, L2SF - - L3OC ‡
GLONASS-K 2011– In service 5×10−14...1×10−13 L1OF, L1SF L2OF, L2SF - - L3OC
GLONASS-K2 2023– Testing 5×10−15...5×10−14 L1OF, L1SF L2OF, L2SF L1OC, L1SC L2OC, L2SC L3OC
GLONASS-V 2025– Design phase L1OF, L1SF L2OF, L2SF L1OC, L1SC L2OC, L2SC L3OC, L3SVI
GLONASS-KМ 2030– Research phase L1OF, L1SF L2OF, L2SF L1OC, L1SC L2OC, L2SC L3OC, L3SVI L1OCM L3OCM L5OCM
"O": open signal (standard precision), "S": obfuscated signal (high precision); "F":FDMA, "С":CDMA; n=−7,−6,−5,...,6

‡Glonass-M spacecraft produced since 2014 include L3OC signal

Glonass-K1 test satellite launched in 2011 introduced L3OC signal. Glonass-M satellites produced since 2014 (s/n 755+) will also transmit L3OC signal for testing purposes.

Enhanced Glonass-K1 and Glonass-K2 satellites, to be launched from 2023, will feature a full suite of modernized CDMA signals in the existing L1 and L2 bands, which includes L1SC, L1OC, L2SC, and L2OC, as well as the L3OC signal. Glonass-K2 series should gradually replace existing satellites starting from 2023, when Glonass-M launches will cease.[23][30]

Glonass-KM satellites will be launched by 2025. Additional open signals are being studied for these satellites, based on frequencies and formats used by existing GPS, Galileo, and Beidou/COMPASS signals:

  • open signal L1OCM using BOC(1,1) modulation centered at 1575.42 MHz, similar to modernized GPS signal L1C, Galileo signal E1, and Beidou/COMPASS signal B1C;
  • open signal L5OCM using BPSK(10) modulation centered at 1176.45 MHz, similar to the GPS "Safety of Life" (L5), Galileo signal E5a, and Beidou/COMPASS signal B2a;[31]
  • open signal L3OCM using BPSK(10) modulation centered at 1207.14 MHz, similar to Galileo signal E5b and Beidou/COMPASS signal B2b.[17]

Such an arrangement will allow easier and cheaper implementation of multi-standard GNSS receivers.

With the introduction of CDMA signals, the constellation will be expanded to 30 active satellites by 2025; this may require eventual deprecation of FDMA signals.[32] The new satellites will be deployed into three additional planes, bringing the total to six planes from the current three—aided by System for Differential Correction and Monitoring (SDCM), which is a GNSS augmentation system based on a network of ground-based control stations and communication satellites Luch 5A and Luch 5B.[33][34] GLONASS-KM satellites will also use new L3SVI open signal to broadcast Precise Point Positioning (PPP) to deliver GLONASS High Accuracy Services.[35]

Six additional Glonass-V satellites, using Tundra orbit in three orbital planes, will be launched starting in 2025;[5] this regional high-orbit segment will offer increased regional availability and 25% improvement in precision over Eastern Hemisphere, similar to Japanese QZSS system and Beidou-1.[36] The new satellites will form two ground traces with inclination of 64.8°, eccentricity of 0.072, period of 23.9 hours, and ascending node longitude of 60° and 120°. Glonass-V vehicles are based on Glonass-K platform and will broadcast new CDMA signals only.[36] Previously Molniya orbit, geosynchronous orbit, or inclined orbit were also under consideration for the regional segment.[17][28]

Roscosmos also plans to launch up to 240 small size satellites on the low Earth orbit (LEO) to improve signal availability and interfecence; LEO satellites will have a limited lifespan of 5 years to allow a faster pace of replenishment.[35]

[edit]

L1OC

[edit]
Full-length string for L1OC navigational message
Field Size, bits Description
Timecode СМВ 12 Constant bit sequence 0101 1111 0001 (5F1h)
String type Тип 6 Type of the navigational message
Satellite ID j 6 System ID number of the satellite (1 to 63; 0 is reserved until FDMA signal switch-off)
Satellite state Гj 1 This satellite is:
0 — healthy,
1 — in error state
Data reliability lj 1 Transmitted navigational messages are:
0 — valid,
1 — unreliable
Ground control callback П1 4 (Reserved for system use)
Orientation mode П2 1 Satellite orientation mode is:
0 — Sun sensor control,
1 — executing predictive thrust or mode transition
UTC correction КР 2 On the last day of the current quarter, at 00:00 (24:00), a UTC leap second is:
0 — not expected,
1 — expected with positive value,
2 — unknown,
3 — expected with negative value
Execute correction А 1 After the end of the current string, UTC correction is:
0 — not expected,
1 — expected
Satellite time ОМВ 16 Onboard time of the day in 2 seconds intervals (0 to 43199)
Information 184 Content of the information field is defined by string type
CRC ЦК 16 Cyclic redundancy code
Total 250

L3OC

[edit]
Full-length string for L3OC navigation message
Field Size, bits Description
Timecode СМВ 20 Constant bit sequence 0000 0100 1001 0100 1110 (0494Eh)
String type Тип 6 Type of the navigational message
Satellite time ОМВ 15 Onboard time of the day in 3 seconds intervals (0 to 28799)
Satellite ID j 6 The same as in L1OC signal
Satellite state Гj 1
Data reliability lj 1
Ground control callback П1 4
Orientation mode 222
UTC correction КР 2
Execute correction А 1
Information 219 Content of the information field is defined by string type
CRC ЦК 24 Cyclic redundancy code
Total 300

Common properties of open CDMA signals

[edit]
String types for navigational signals
Type Content of the information field
0 (Reserved for system use)
1 Short string for the negative leap second
2 Long string for the positive leap second
10, 11, 12 Real-time information (ephemerides and time-frequency offsets).
Transmitted as a packet of three strings in sequence
16 Satellite orientation parameters for the predictive thrust maneuver
20 Almanac
25 Earth rotation parameters, ionosphere models, and time scale model for the difference between UTC(SU) and TAI
31, 32 Parameters of long-term movement model
50 Cospas-Sarsat service message — L1OC signal only
60 Text message
Information field of a string type 20 (almanac) for the orbit type 0.[nb 1]
Field Size, bits Weight of the low bit Description
Orbit type ТО 2 1 0 — circular orbit with 19100 km altitude [nb 2]
Satellite number NS 6 1 Total number of satellites transmitting CDMA signals (1 to 63) which are referenced to in the almanac.
Almanac age EA 6 1 Number of full days passed since the last almanac update.
Current day NA 11 1 Day number (1 to 1461) within a four-year interval starting on 1 January of the last leap year [nb 3] according to Moscow decree time.
Signal status PCA 5 1 Bit field encoding types of CDMA signals transmitted by the satellite.
Three highest bits correspond to signals L1, L2 and L3:
0 — transmitted,
1 — not transmitted
Satellite type PCA 3 1 Satellite model and the set of transmitted CDMA signals:
0 — Glonass-M (L3 signal),
1 — Glonass-K1 (L3 signal),
2 — Glonass-K1 (L2 and L3 signals),
3 — Glonass-K2 (L1, L2, and L3 signals)
Time correction τA 14 2−20 Rough correction from onboard time scale to the GLONASS time scale (±7.8×10−3 с).
Ascension λA 21 2−20 Longitude of the satellite's first orbital node (±1 half-cycles).
Ascension time tλA 21 2−5 Time of the day when the satellite is crossing its first orbital node (0 to 44100 s).
Inclination ΔiA 15 2−20 Adjustments to nominal inclination (64,8°) of the satellite orbit at the moment of ascension (±0.0156 half-cycles).
Eccentricity εA 15 2−20 Eccentricity of the satellite orbit at the ascension time (0 to 0.03).
Perigee ωA 16 2−15 Argument to satellite's perigee at the ascension time (±1 half-cycles).
Period ΔTA 19 2−9 Adjustments to the satellite's nominal draconic orbital period (40544 s) at the moment of ascension (±512 s).
Period change ΔṪA 7 2−14 Speed of change of the draconic orbital period at the moment of ascension (±3.9×10−3 s/orbit).
(Reserved) L1OC: 23 -
L3OC: 58
  1. ^ Navigational message field j (satellite ID) references the satellite for the transmitted almanac (jA)
  2. ^ The set of almanac parameters depends on the orbit type. Satellites with geosynchronous, medium-Earth, and high-elliptical orbits could be employed in the future.
  3. ^ In a departure from the Gregorian calendar, all years exactly divisible by 100 (i.e. 2100 and so on) are treated as leap years

Satellites

[edit]
See also: List of GLONASS satellites
The Glonass-K spacecraft model

The main contractor of the GLONASS program is Joint Stock Company Information Satellite Systems Reshetnev (ISS Reshetnev, formerly called NPO-PM). The company, located in Zheleznogorsk, is the designer of all GLONASS satellites, in cooperation with the Institute for Space Device Engineering (ru:РНИИ КП) and the Russian Institute of Radio Navigation and Time. Serial production of the satellites is accomplished by the company Production Corporation Polyot in Omsk.

Over the three decades of development, the satellite designs have gone through numerous improvements, and can be divided into three generations: the original GLONASS (since 1982), GLONASS-M (since 2003) and GLONASS-K (since 2011). Each GLONASS satellite has a GRAU designation 11F654, and each of them also has the military "Cosmos-NNNN" designation.[37]

First generation

[edit]
Main article: GLONASS (satellite)

The true first generation of GLONASS (also called Uragan) satellites were all three-axis stabilized vehicles, generally weighing 1,250 kg (2,760 lb) and were equipped with a modest propulsion system to permit relocation within the constellation. Over time they were upgraded to Block IIa, IIb, and IIv vehicles, with each block containing evolutionary improvements.

Six Block IIa satellites were launched in 1985–1986 with improved time and frequency standards over the prototypes, and increased frequency stability. These spacecraft also demonstrated a 16-month average operational lifetime. Block IIb spacecraft, with a two-year design lifetimes, appeared in 1987, of which a total of 12 were launched, but half were lost in launch vehicle accidents. The six spacecraft that made it to orbit worked well, operating for an average of nearly 22 months.

Block IIv was the most prolific of the first generation. Used exclusively from 1988 to 2000, and continued to be included in launches through 2005, a total of 56 satellites were launched. The design life was three years, however numerous spacecraft exceeded this, with one late model lasting 68 months, nearly double.[38]

Block II satellites were typically launched three at a time from the Baikonur Cosmodrome using Proton-K Blok-DM2 or Proton-K Briz-M boosters. The only exception was when, on two launches, an Etalon geodetic reflector satellite was substituted for a GLONASS satellite.

Second generation

[edit]
Main article: GLONASS-M

The second generation of satellites, known as Glonass-M, were developed beginning in 1990 and first launched in 2003. These satellites possess a substantially increased lifetime of seven years and weigh slightly more at 1,480 kg (3,260 lb). They are approximately 2.4 m (7 ft 10 in) in diameter and 3.7 m (12 ft) high, with a solar array span of 7.2 m (24 ft) for an electrical power generation capability of 1600 watts at launch. The aft payload structure houses 12 primary antennas for L-band transmissions. Laser corner-cube reflectors are also carried to aid in precise orbit determination and geodetic research. On-board cesium clocks provide the local clock source. 52 Glonass-M have been produced and launched.

A total of 41 second generation satellites were launched through the end of 2013. As with the previous generation, the second generation spacecraft were launched three at a time using Proton-K Blok-DM2 or Proton-K Briz-M boosters. Some were launched alone with Soyuz-2-1b/Fregat.

In July 2015, ISS Reshetnev announced that it had completed the last GLONASS-M (No. 61) spacecraft and it was putting it in storage waiting for launch, along with eight previously built satellites.[39][40]

As on 22 September 2017, GLONASS-M No.52 satellite went into operation and the orbital grouping has again increased to 24 space vehicles.[41]

Third generation

[edit]
Main articles: GLONASS-K and GLONASS-K2

GLONASS-K is a substantial improvement of the previous generation: it is the first unpressurised GLONASS satellite with a much reduced mass of 750 kg (1,650 lb) versus the 1,450 kg (3,200 lb) of GLONASS-M. It has an operational lifetime of 10 years, compared to the 7-year lifetime of the second generation GLONASS-M. It will transmit more navigation signals to improve the system's accuracy — including new CDMA signals in the L3 and L5 bands, which will use modulation similar to modernized GPS, Galileo, and BeiDou. Glonass-K consist of 26 satellites having satellite index 65-98 and widely used in Russian Military space.[42][43]

The new satellite's advanced equipment—made solely from Russian components — will allow the doubling of GLONASS' accuracy.[7] As with the previous satellites, these are 3-axis stabilized, nadir pointing with dual solar arrays.[citation needed] The first GLONASS-K satellite was successfully launched on 26 February 2011.[42][44]

Due to their weight reduction, GLONASS-K spacecraft can be launched in pairs from the Plesetsk Cosmodrome launch site using the substantially lower cost Soyuz-2.1b boosters or in six-at-once from the Baikonur Cosmodrome using Proton-K Briz-M launch vehicles.[7][8]

Ground control

[edit]
A map depicting ground control stations

The ground control segment of GLONASS is almost entirely located within former Soviet Union territory, except for several in Brazil and one in Nicaragua.[45][46][47][48]

The GLONASS ground segment consists of:[49]

  • a system control centre;
  • five Telemetry, Tracking and Command centers;
  • two Laser Ranging Stations;[50] and
  • ten Monitoring and Measuring Stations.[51]
Location System control Telemetry, Tracking and Command Central clock Upload stations Laser Ranging Monitoring and Measuring
Krasnoznamensk Yes - - - - Yes
Schelkovo - Yes Yes Yes Yes Yes
Komsomolsk - Yes - Yes Yes Yes
Saint Petersburg - Yes - - - -
Ussuriysk - Yes - - - -
Yeniseysk - Yes - Yes - Yes
Yakutsk - - - - - Yes
Ulan-Ude - - - - - Yes
Nurek - - - - - Yes
Vorkuta - - - - - Yes
Murmansk - - - - - Yes
Zelenchuk - - - - - Yes

Receivers

[edit]
A Russian stamp with a GLONASS satellite, 2016
A GLONASS receiver module 1K-181

Companies producing GNSS receivers making use of GLONASS:

NPO Progress describes a receiver called GALS-A1, which combines GPS and GLONASS reception.

SkyWave Mobile Communications manufactures an Inmarsat-based satellite communications terminal that uses both GLONASS and GPS.[52]

As of 2011, some of the latest receivers in the Garmin eTrex line also support GLONASS (along with GPS).[53] Garmin also produce a standalone Bluetooth receiver, the GLO for Aviation, which combines GPS, WAAS and GLONASS.[54]

Various smartphones from 2011 onwards have integrated GLONASS capability in addition to their pre-existing GPS receivers, with the intention of reducing signal acquisition periods by allowing the device to pick up more satellites than with a single-network receiver, including devices from:

Status

[edit]

Availability

[edit]
Screenshot of GPSTest application showing GLONASS satellites usage in South Tangerang, Indonesia (2025)

As of 17 February 2024, the GLONASS constellation status is:[62]

Total 26 SC
Operational 24 SC (Glonass-M/K)
In commissioning 0 SC
In maintenance 0 SC
Under check by the Satellite Prime Contractor 0 SC
Spares 0 SC
In flight tests phase 2 SC

The system requires 18 satellites for continuous navigation services covering all of Russia, and 24 satellites to provide services worldwide.[63] The GLONASS system covers 100% of worldwide territory.

On 2 April 2014, the system experienced a technical failure that resulted in practical unavailability of the navigation signal for around 12 hours.[64]

On 14–15 April 2014, nine GLONASS satellites experienced a technical failure due to software problems.[65]

On 19 February 2016, three GLONASS satellites experienced a technical failure: the batteries of GLONASS-738 exploded, the batteries of GLONASS-737 were depleted, and GLONASS-736 experienced a stationkeeping failure due to human error during maneuvering. GLONASS-737 and GLONASS-736 were expected to be operational again after maintenance, and one new satellite (GLONASS-751) to replace GLONASS-738 was expected to complete commissioning in early March 2016. The full capacity of the satellite group was expected to be restored in the middle of March 2016.[66]

After the launching of two new satellites and maintenance of two others, the full capacity of the satellite group was restored.

Accuracy

[edit]

According to Russian System of Differentional Correction and Monitoring's data, as of 2010, precision of GLONASS navigation definitions (for p=0.95) for latitude and longitude were 4.46–7.38 m (14.6–24.2 ft) with mean number of navigation space vehicles (NSV) equals 7—8 (depending on station). In comparison, the same time precision of GPS navigation definitions were 2.00–8.76 m (6 ft 7 in – 28 ft 9 in) with mean number of NSV equals 6—11 (depending on station).

Some modern receivers are able to use both GLONASS and GPS satellites together, providing greatly improved coverage in urban canyons and giving a very fast time to fix due to over 50 satellites being available. In indoor, urban canyon or mountainous areas, accuracy can be greatly improved over using GPS alone. For using both navigation systems simultaneously, precision of GLONASS/GPS navigation definitions were 2.37–4.65 m (7 ft 9 in – 15 ft 3 in) with mean number of NSV equals 14—19 (depends on station).

In May 2009, Anatoly Perminov, then director of the Roscosmos, stated that actions were undertaken to expand GLONASS's constellation and to improve the ground segment to increase the navigation definition of GLONASS to an accuracy of 2.8 m (9 ft 2 in) by 2011.[67] In particular, the latest satellite design, GLONASS-K has the ability to double the system's accuracy once introduced. The system's ground segment is also to undergo improvements. As of early 2012, sixteen positioning ground stations are under construction in Russia and in the Antarctic at the Bellingshausen and Novolazarevskaya bases. New stations will be built around the southern hemisphere from Brazil to Indonesia. Together, these improvements are expected to bring GLONASS' accuracy to 0.6 m or better by 2020.[68] The setup of a GLONASS receiving station in the Philippines is also now under negotiation.[69]

History

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Main article: History of GLONASS

See also

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Other systems

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Main article: Satellite navigation

Notes

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References

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Standards

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Bibliography

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

GLONASS

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GLONASS (ГЛОНАСС; Global'naya Navigatsionnaya Sput'nikovaia Sistema, meaning Global Navigation Satellite System) is a Russian space-based satellite navigation system that delivers positioning, navigation, and timing services to military and civilian users worldwide, independent of weather conditions. The system comprises 24 satellites distributed across three orbital planes, each containing eight satellites, positioned in medium Earth orbit at an altitude of 19,100 kilometers with a 64.8-degree inclination optimized for high-latitude coverage. Development originated in the Soviet Union during the 1970s as a counterpart to the American GPS, with flight testing commencing via the Kosmos-1413 satellite in 1982 and initial operational status declared in 1993. Following the Soviet dissolution, funding shortfalls reduced the constellation to as few as seven satellites by the early 2000s, but revitalized investment under Roscosmos restored full operational capability with 24 satellites by 2011, incorporating modernized GLONASS-M and GLONASS-K models for improved accuracy and CDMA signaling. Today, managed by Roscosmos, GLONASS supports applications including search-and-rescue via integration with Cospas-Sarsat and achieves signal-in-space range errors of 1-2 meters, with ongoing upgrades toward GLONASS-K2 for further precision enhancements.

Overview

Purpose and Strategic Objectives

The GLONASS (Global Navigation Satellite System) was established pursuant to a decree issued by the Central Committee of the Communist Party of the Soviet Union and the Council of Ministers on December 17, 1976 (No. 1043-361), with the primary purpose of developing a space-based radio navigation system to deliver precise positioning, navigation, velocity determination, and time transfer services on a global scale. This initiative responded to the Soviet Union's recognition in the late 1960s and early 1970s of the strategic necessity for an independent satellite navigation capability, mirroring but distinct from the U.S. NAVSTAR GPS program. Initially focused on military requirements, GLONASS aimed to support ballistic missile guidance, targeting, and troop navigation, ensuring operational autonomy in potential conflict scenarios where foreign systems might be unavailable or compromised. Strategically, GLONASS sought to achieve full global coverage through a nominal constellation of 24 satellites in , enabling uninterrupted service regardless of weather conditions or geographic location, thereby prioritizing national defense self-sufficiency and reducing dependence on adversarial infrastructure. The system's dual-use was designed to extend beyond applications to sectors, including air, sea, and ground safety, search-and-rescue operations via integration with Cospas-Sarsat, and high-precision tasks for and . commenced in 1982 with the launch of Kosmos-1413, leading to operational status by 1993 and a complete 24-satellite deployment in 1995, though early post-Soviet economic constraints necessitated subsequent federal programs (e.g., 2002–2011 and 2012–2020) to restore and modernize the constellation for sustained reliability. In the broader geopolitical context, GLONASS's objectives emphasized technological sovereignty for , particularly in military domains where GPS access could be selectively denied or jammed, as evidenced by efforts to attain parity in accuracy (targeting decimeter to centimeter levels) and to foster international cooperation while safeguarding encrypted military signals. This independence was reinforced through ongoing investments to counter vulnerabilities, supporting both defense readiness and socio-economic applications like and emergency response.

Key Features and Distinctions from GPS

GLONASS operates as a (MEO) constellation comprising 24 satellites distributed across three orbital planes, delivering positioning, navigation, and timing (PNT) services with global coverage comparable to GPS. The system's satellites transmit signals in the L-band, primarily on L1 (centered at MHz) and L2 (centered at 1246 MHz) frequencies, enabling receivers to compute positions with accuracies typically ranging from 5 to 10 meters under . Unlike earlier generations limited to 3-4 year lifespans, modern GLONASS satellites achieve extended operational durations through improved design and federal modernization programs. A primary distinction lies in the multiple access technique: GLONASS traditionally utilizes (FDMA), where each satellite broadcasts on a unique carrier within the L1 and L2 bands, contrasting with GPS's (CDMA) that employs identical differentiated by unique (PRN) codes. This FDMA approach enhances resistance to certain jamming scenarios by requiring interference across multiple but demands wider bandwidth allocation and precise Doppler compensation in receivers due to frequency offsets. Newer GLONASS satellites, such as those from the GLONASS-K series, introduce CDMA signals on L1 and L2 alongside legacy FDMA, improving with GPS and achieving up to 31% better performance on L2 compared to FDMA alone. Orbitally, GLONASS satellites maintain a semi-major axis of approximately 25,512 km and an inclination of 64.8°, higher than GPS's 26,561 km and 55° inclination, providing superior visibility and coverage at high latitudes, particularly beneficial for polar regions. GLONASS also references the PZ-90 geocentric coordinate system, which differs slightly from GPS's WGS-84 datum, necessitating datum transformations for integrated use. While GPS generally offers marginally higher standalone positional accuracy (3.5-7.8 meters), GLONASS's orbital geometry yields better performance in northern hemispheres, and combined GPS-GLONASS solutions enhance overall reliability and dilution of precision (DOP) metrics.
FeatureGLONASSGPS
Multiple AccessPrimarily FDMA; CDMA on newer satellitesCDMA
Orbital Inclination64.8°55°
L1 Center Frequency1602 MHz1575.42 MHz
Standalone Accuracy5-10 meters3.5-7.8 meters
High-Latitude PerformanceSuperior due to higher inclinationStandard global coverage

Technical Specifications

Orbital Configuration and Space Segment

The GLONASS space segment comprises a constellation of satellites in (MEO), nominally consisting of 24 satellites to ensure global navigation coverage. These satellites are distributed across three orbital planes, with eight satellites per plane, separated by 120 degrees in of the ascending node. Within each plane, satellites are equally spaced at 45-degree intervals along the orbit. The orbits are circular with an altitude of 19,100 kilometers above Earth's surface and an inclination of 64.8 degrees relative to the equator. This configuration yields an orbital period of approximately 11 hours and 15 minutes, allowing each satellite to complete about 17 orbits per day. The higher inclination compared to systems like GPS enhances coverage in high-latitude regions, particularly beneficial for operations in Russia and polar areas. As of October 2025, the operational constellation includes 23 satellites in active service, supported by additional units in maintenance, testing, or reserve slots to maintain against failures. The segment satellites transmit navigation signals on L-band frequencies, enabling position, velocity, and time determination for users worldwide, with the constellation designed for four-dimensional positioning accuracy. Orbital perturbations, such as atmospheric drag and gravitational influences, necessitate periodic station-keeping maneuvers by the satellites to preserve the configuration.

Signal Structure and Modulation

The GLONASS navigation signals in the L1 and L2 bands traditionally employ (FDMA), with each satellite transmitting on a distinct carrier frequency to enable , unlike the (CDMA) used in GPS. The L1 carrier frequencies range from 1592.9525 MHz to 1610.485 MHz, calculated as fL1=(1602+k)f_{L1} = (1602 + k) MHz where the channel number kk varies from -7 to +6 across 14 channels with 0.5625 MHz spacing. Similarly, L2 frequencies span 1246 MHz to 1256.5 MHz, given by fL2=1246+k×0.4375f_{L2} = 1246 + k \times 0.4375 MHz using the same kk values and maintaining a fixed fL2/fL1=7/9f_{L2}/f_{L1} = 7/9. These signals utilize binary phase-shift keying (BPSK) modulation, applying a π-radian phase shift to the . The L1 signal combines a standard precision (SP) component—modulated by a coarse/acquisition pseudo-random noise (PRN) known as the ST code (511 chips at 0.511 Mcps, repeating every 1 ms, generated from an M-sequence g(x)=x9+x5+1g(x) = x^9 + x^5 + 1)—with navigation data at 50 bits per second and a high precision (HP) component using the encrypted VT (33,554,432 chips at 5.11 Mcps, period 1 second). The L2 signal transmits only the HP VT without navigation data in the legacy configuration. All satellites broadcast identical PRN codes, relying on FDMA for , with the modulated signal formed by modulo-2 summation of the codes, data, and a 100 Hz meander subcarrier for polarization . Modernized GLONASS satellites, starting with GLONASS-K and advancing in the GLONASS-K2 series (e.g., satellite R803 launched in August 2023), introduce CDMA signals on L1 and L2 alongside or replacing FDMA, using unique spreading codes for satellite separation at shared center frequencies of 1600.995 MHz (L1) and 1248.06 MHz (L2). These employ quadrature phase-shift keying (QPSK) to multiplex open (OC) and secure (SC) components, with L1 featuring binary offset carrier (BOC) modulation for SC side lobes at offsets like ±5 MHz, and L2 including pilot (OCp), service information (CSI), and SC signals; chipping rates remain around 0.5115 Mcps for OC components, offering improved multipath resistance and interoperability compared to FDMA. The legacy FDMA persists on many operational satellites, but CDMA deployment enhances overall system capacity and precision. The GLONASS navigation messages are transmitted continuously by each on the L1 and L2 carrier frequencies to deliver , , clock correction, and auxiliary data essential for user receivers to compute position, , and time. These messages are modulated using bi-phase shift keying (BPSK) at a rate of 50 bits per second, superimposed on the pseudorandom ranging codes (standard precision SP code for civilian use and high-precision HP code for authorized users) via (FDMA), with each assigned a unique channel number offset from the base frequencies of approximately 1602 MHz (L1) and 1246 MHz (L2). The message structure follows a hierarchical format of superframes, , and strings, repeating indefinitely without subcommutation to ensure predictable access to . A superframe spans 150 seconds and comprises five 30-second , each containing fifteen 2-second strings of 100 bits total, where 85 bits convey navigation over 1.7 seconds and the remaining 0.3 seconds provide a 30-chip time mark for . The bits employ Hamming (15,11) coding within each 15-bit codeword, with an additional bi-binary offset modulation using a 100 Hz sequence to mitigate -code interference, achieving single-error correction capability across the string. Content within frames prioritizes immediate satellite-specific parameters in strings 1–4, including Earth-centered Earth-fixed (ECEF) position and velocity vectors (ΔX, ΔY, ΔZ; Vx, Vy, Vz), axial accelerations due to lunisolar perturbations, satellite clock bias relative to GLONASS time (τ), relative frequency bias (γ), information age (Δt), and a health flag indicating operational status or signal degradation. Strings 5–14 disseminate almanac data—modified Keplerian orbital elements (eccentricity, inclination, etc.) for up to 24 satellites—cycling across frames to cover the full constellation (frames I–IV for five satellites each, frame V for four), while string 15 includes GLONASS-UTC time offsets (ΔT_UT), coefficients for ionospheric delay models (X, Y, Z for ionospheric height), and almanac health flags. Ephemeris parameters update every 30 minutes, almanac approximately daily, and all data synchronize across satellites within 2 milliseconds of system time. For the high-precision (HP) service on the L2 band, the structure diverges with 72 ten-second frames per 12-minute superframe, each holding five strings focused on detailed ephemeris for the transmitting satellite in frames 1–3, enabling differential corrections for authorized users. GLONASS-M satellites maintain this legacy format, while newer GLONASS-K series introduce CDMA signals on L3 (around 1200 MHz) with a flexible row-based structure—300-bit rows transmitted every 3 seconds—allowing variable content types (e.g., ephemeris every 24 seconds, almanac periodically) for enhanced interoperability and upgradability without fixed paging, though FDMA remains primary for the operational constellation as of 2025.

Satellite Constellations and Infrastructure

Generations of GLONASS Satellites

The GLONASS satellite constellation has evolved through three primary generations, with each introducing enhancements in design life, mass efficiency, signal capabilities, and reliability to address limitations in earlier models. The first generation comprised the baseline Uragan (GLONASS) satellites, launched from 1982 to 2005, which established the system's (MEO) architecture but suffered from short operational lifespans and frequent replacements due to early failures. Subsequent generations, GLONASS-M and GLONASS-K, extended service life and incorporated civilian signals, transitioning toward (CDMA) modulation for improved interoperability with systems like GPS. As of 2025, the operational fleet mixes second- and third-generation satellites, with over 50 GLONASS-M units launched and a growing number of GLONASS-K vehicles. First-generation satellites, designated as Uragan or GLONASS blocks (including prototypes, IIa, IIb, and IIv variants), totaled approximately 80 launches between October 1982 and the early , with a design life of 2–4 years but actual often limited to 3.5 years on average due to cesium clock degradation and issues. These satellites, manufactured by NPO PM in Zheleznogorsk, weighed about 1,415–1,500 kg, featured (FDMA) signals on L1 (1,602 MHz) and L2 (1,246 MHz) bands for civil (L1OF, L2OF) and (L1SF, L2SF) use, and relied on Proton for deployment into 19,100 km orbits at 64.8° inclination. Improvements in later blocks included better time-frequency standards and orbit relocation capabilities, yet the generation's high failure rate—exacerbated by post-Soviet funding shortfalls—necessitated over 130 total launches to maintain partial coverage. The second generation, GLONASS-M (Uragan-M), marked a significant with 52 satellites produced and launched from December 2003 to 2022, achieving a 7-year design life through refined cesium atomic clocks (stability of 5×10^{-14}) and added retroreflectors for ground calibration. Weighing 1,415–1,570 kg, these satellites introduced a dedicated civilian L2OF signal for dual-frequency positioning, reducing ionospheric errors, and experimental L3 CDMA on select units (e.g., satellites 755–761); they maintained FDMA compatibility while spanning 2.4 m in diameter with 7.2 m solar arrays for sustained power. Deployed via /Breeze-M or /, GLONASS-M vehicles restored full constellation operability by 2011, though some exceeded design life into the 2020s. Third-generation GLONASS-K satellites, first launched on February 26, 2011, represent a shift to lighter, unpressurized designs on the Ekspress-1000 platform, with a mass of 935 kg and 10-year enabled by advanced clocks (stability approaching 5×10^{-14}) and integrated search-and-rescue transponders. These vehicles support both FDMA legacy signals and full CDMA on L1OF, L2OF, L3OC (1,202 MHz), and L2OC bands, enhancing global accuracy to 2.8–5 meters and compatibility with international standards; they are launched in pairs via Soyuz-2.1b/ for cost efficiency. By 2018, initial maturation issues were resolved, with ongoing deployments aiming to phase out older generations; future variants, in development since 2017, will add inter-satellite links and higher power (up to 3,000 W) for 10–12 year lifespans.
GenerationLaunch PeriodDesign Life (years)Mass (kg)Key SignalsClock Stability
GLONASS (1st)1982–20053.51,415–1,500FDMA (L1OF, L1SF, L2SF)1×10^{-13}
GLONASS-M (2nd)2003–202271,415–1,570FDMA + L2OF civilian; partial CDMA L35×10^{-14}
GLONASS-K (3rd)2011–present10935FDMA + CDMA (L1, L2, L3OC)5×10^{-14}

Launch and Deployment History

The initial launches of GLONASS satellites occurred on October 12, 1982, when three first-generation Uragan vehicles—designated Kosmos-1413, Kosmos-1414, and Kosmos-1415—were deployed into via a Proton-K rocket from , initiating of the system. Subsequent missions throughout the and early added satellites incrementally, with the conducting a total of 43 GLONASS-related launches by April 1991, supplemented by five test satellites, though orbital failures and limited funding constrained full constellation buildup. Limited operational capability was achieved in 1993 with a partial network, followed by the completion of the 24-satellite constellation across three orbital planes in 1995; the system was declared fully operational on January 18, 1996. Post-Soviet economic challenges halted regular deployments, reducing operational satellites to six by 2001 as aging Uragan units failed without replacements. Revival efforts commenced under the 2002–2011 Federal Targeted Program "Global Navigation System," which prioritized restoration and modernization, enabling the debut of second-generation GLONASS-M satellites with the launch of Kosmos-2404 on December 10, 2003, via Proton-K/Briz-M. A notable early recovery launch on December 26, 2004, inserted three satellites (two Uragan-M and one Uragan) into orbit. Increased funding from 2007 targeted 18 operational satellites by year's end, culminating in the restoration of the full 24-satellite constellation in 2011 through Soyuz and Proton missions from Plesetsk and . Deployment setbacks included the December 5, 2010, failure, which destroyed three GLONASS-M satellites shortly after liftoff, and a July 2, 2013, crash that eliminated another trio of GLONASS-M units due to a manufacturing defect in the rocket's boosters. The third-generation GLONASS-K series, featuring improved and signals, entered service with its inaugural launch in November 2011 via Soyuz-2.1b from Plesetsk. A successor federal program for 2012–2020 emphasized GLONASS-K integration for enhanced accuracy and redundancy, supporting ongoing launches such as the September 12, 2025, Soyuz-2.1b mission deploying GLONASS-K1 No. 18 alongside an experimental payload. Plans aim for a 27-satellite configuration by late 2025 to bolster global coverage.

Ground Control Segment

The GLONASS ground control segment oversees satellite constellation monitoring, orbit and clock determination, navigation data upload, and system maintenance to ensure operational integrity and accuracy. It includes the System Control Centre (SCC), telemetry, tracking, and command (TT&C) stations, upload stations, monitoring stations, laser ranging facilities, and a central clock. All components are located within Russian territory, emphasizing national sovereignty over the system's control functions. The SCC, situated in Krasnoznamensk near , functions as the primary processing hub, aggregating data from peripheral stations to compute precise ephemerides, time corrections, and information before disseminating commands and navigation uploads to . It coordinates overall system performance, including failure detection and contingency responses. The TT&C network comprises five key stations—Schelkovo (near ), Komsomolsk-on-Amur, , Ussuriysk (near ), and Yeniseysk (near )—equipped for pseudorange measurements, Doppler tracking, and reception to assess satellite health, positions, and velocities in real time. Three dedicated upload stations, co-located at Yeniseysk, Komsomolsk-on-Amur, and , transmit updated navigation messages to the space segment via S-band links. Ten monitoring stations across evaluate signal integrity, ionospheric delays, and multipath effects, feeding data back to the SCC for error modeling and correction. Two stations deliver sub-centimeter precision for orbit validation, complementing radio-based tracking. A central clock in provides UTC synchronization, maintaining system time standards within nanoseconds of international references. Modernization since the early has integrated digital processing, automated algorithms, and expanded coverage at these facilities, enabling support for advanced GLONASS-K satellites and achieving positioning accuracies comparable to GPS through enhanced ground .

Operational Status and Performance

Current Constellation and Availability

As of October 2025, the GLONASS constellation maintains 24 operational satellites in , supplemented by spares and satellites in testing or maintenance phases, enabling full global coverage for positioning, navigation, and timing services. The system operates with satellites distributed across three orbital planes inclined at 64.8 degrees, at an altitude of approximately 19,100 km, ensuring at least four satellites visible from any point on under nominal conditions. Recent additions include the launch of GLONASS-K No. 18 on September 13, 2025, from aboard a Soyuz-2.1b rocket, which entered commissioning to replace aging units and bolster redundancy. Availability exceeds 95% for the L1 and L2 frequency bands worldwide, with minimal outages attributable to satellite failures or ground segment issues, though regional jamming risks—particularly in conflict zones—can intermittently degrade signal reception. The constellation's design incorporates frequency-division multiple access (FDMA), allowing simultaneous signals from all visible satellites without code-division conflicts, which supports robust availability even with partial degradation. Roscosmos monitors and controls the fleet via the ground segment, including command centers in Moscow and Krasnoznamensk, ensuring rapid anomaly resolution and orbital adjustments to sustain service continuity. Civilian and users access GLONASS signals openly, with open service providing standalone accuracy of 5–10 meters horizontally under good conditions, though integration with GPS or other GNSS enhances reliability. Export variants and international cooperation, such as with India's IRNSS, extend availability to partner nations, but U.S. and sanctions since have constrained component sourcing, prompting reliance on domestic Uragan-M and GLONASS-K blocks for sustainment. Full operational capacity requires 18–24 satellites, a threshold consistently met since 2011, barring isolated deorbiting events.

Accuracy Metrics and Influencing Factors

The standard positioning accuracy for GLONASS open service signals, as specified in the Open Service Performance Standard, provides a global average of ≤5 meters horizontal and ≤9 meters vertical error at the 95% confidence level over 24-hour periods, with worst-site values of ≤12 meters horizontal and ≤25 meters vertical. Independent assessments confirm horizontal accuracies of 4-7 meters and vertical accuracies of 10-15 meters under typical conditions with a full constellation. These metrics represent user range errors (URE) after accounting for signal-in-space contributions, with single-frequency L1/L2 URE ≤11.7 meters (95% global average) and dual-frequency ≤7.8 meters over daily periods. Velocity determination achieves ≤0.014 m/s (95% global average), while timing synchronization reaches ≤40 nanoseconds relative to UTC. Accuracy is influenced by satellite geometry, quantified by dilution of precision (DOP) metrics such as PDOP, which degrades with fewer visible satellites or poor sky visibility; GLONASS typically offers 8-10 satellites in view globally, fewer than GPS's 10-12, exacerbating DOP in obstructed environments. Atmospheric delays, including ionospheric refraction (more variable in GLONASS due to across channels, spanning 8 MHz) and tropospheric effects, introduce errors of several meters unless mitigated by dual-frequency processing or models. Multipath reflections from urban or forested surfaces, receiver hardware noise, and cycle slips in carrier-phase tracking further reduce precision, with standalone GLONASS performing worse in low-latitude regions due to orbital inclination favoring higher latitudes. Ephemeris and clock errors from broadcast data, historically higher in GLONASS (e.g., 3 cm accuracy versus GPS's 2.5 cm), contribute to URE but have improved with GLONASS-M and GLONASS-K satellites featuring better atomic standards and CDMA signals in newer blocks. Constellation completeness—requiring 24 operational satellites in three orbital planes—directly impacts and ; partial outages, as occurred in the 1990s-2000s, historically inflated errors to 35 meters or more, though post-2011 full deployment stabilized performance below 5 meters horizontally. High-precision applications, using restricted signals or differential corrections, achieve decimeter to centimeter levels but remain subject to these factors without augmentation.

Global Coverage and Regional Variations

GLONASS achieves global coverage with a full operational constellation of 24 s in , enabling positioning, navigation, and timing services worldwide once sufficient satellites are visible above the horizon. The system reached full operational capability in , with satellites distributed across three orbital planes to ensure at least four to eight visible satellites for most users under nominal conditions. This configuration supports horizontal positioning accuracy of approximately 5–10 meters and vertical accuracy of 10–15 meters under open-sky conditions, though performance depends on factors such as , signal multipath, and atmospheric interference. Regional variations in coverage and accuracy stem primarily from the constellation's 64.8° orbital inclination, which optimizes satellite visibility in mid-to-high latitudes, particularly in the Northern Hemisphere where Russia is located. In high-latitude regions (above 55° N), GLONASS provides superior elevation angles and more uniform satellite distribution overhead compared to GPS, reducing dilution of precision (DOP) values and enhancing positioning reliability near the poles. Studies of precise point positioning confirm that GLONASS alone yields the highest accuracy in high-latitude networks, with root-mean-square errors often below 2 cm in static modes when combined with GPS. This makes it particularly effective for applications in Arctic or sub-Arctic environments, where fewer GPS satellites may be visible. In contrast, GLONASS exhibits reduced accuracy in low-latitude (equatorial) regions due to poorer satellite visibility and higher DOP from the inclined orbits, which limit overhead passes. Here, standalone GLONASS performance lags behind GPS, with positioning errors potentially exceeding 10–20 meters in dynamic scenarios, though augmentation via multi-constellation receivers (e.g., GPS+GLONASS) mitigates this by improving overall . These variations underscore GLONASS's design prioritization for Russian territorial needs, where high-latitude efficacy compensates for global equatorial trade-offs.

Historical Evolution

Soviet-Era Foundations (1970s–1991)

The Soviet Union began development of the GLONASS (Global Navigation Satellite System) in 1976 as a military initiative primarily aimed at providing precise navigation for ballistic missiles and targeting capabilities. This effort paralleled the United States' GPS program, reflecting Cold War competition in space-based navigation technologies, though Soviet planners sought independent global positioning independent of Western systems. The system was designed to achieve worldwide coverage using a constellation of satellites in medium Earth orbit, with an initial goal of full operational capability by 1991. Flight testing commenced on October 12, 1982, with the launch of the first GLONASS prototype satellite, designated Kosmos-1413, aboard a Proton rocket from the . This marked the start of experimental operations, focusing on verifying orbital parameters, signal transmission, and navigation accuracy using techniques distinct from GPS's code-division approach. Subsequent launches between 1982 and 1985 deployed up to 18 early Uragan-series satellites, which served as prototypes to refine the system's architecture despite challenges like limited battery life and orbital stability issues. By April 1991, the Soviet Union had successfully orbited 43 GLONASS-related satellites, including five dedicated test vehicles, through repeated Proton launches. These efforts established the foundational constellation, with satellites operating in three orbital planes at approximately 19,100 kilometers altitude, enabling preliminary navigation services over Soviet territory and select military applications. However, the system remained incomplete at the USSR's dissolution in December 1991, with only partial global coverage achieved due to ongoing technical hurdles and resource constraints.

Post-Soviet Challenges and Near-Collapse (1990s–Early 2000s)

Following the in December 1991, inherited the GLONASS program amid severe economic turmoil, including and a sharp contraction in GDP, which led to drastic reductions in space sector funding. Between 1989 and 1999, overall space program expenditures were slashed by approximately 80%, severely limiting the ability to launch replacement satellites and maintain the constellation. This funding crisis halted regular launches after the mid-1990s, as the aging first-generation Uragan satellites—designed for 2-3 year lifespans—began failing without successors, causing orbital slots to go vacant. The GLONASS constellation, which had achieved full operational deployment of 24 satellites across three orbital planes by 1995 and was declared globally operational on January 18, 1996, rapidly degraded thereafter. By the late , the number of functional satellites had fallen below 18—the minimum required for partial global coverage—exacerbating reliability issues for both precision-guided munitions and emerging applications. Technical shortcomings compounded the problem, including proton radiation-induced failures in and inconsistent allocations due to incomplete FDMA , further eroding positional accuracy to levels often exceeding 100 meters. Into the early 2000s, the system approached collapse, with only 7-9 operational satellites by 2002, rendering GLONASS effectively unusable for continuous navigation services outside limited Russian territories. This forced temporary reliance on degraded U.S. for some Russian forces, despite geopolitical tensions, while domestic ground segment maintenance lagged due to underfunding and brain drain in the . Efforts to sustain the system through sporadic Proton launches yielded mixed results, as second-generation Glonass-M prototypes faced delays until 2003, underscoring the program's vulnerability to fiscal instability rather than inherent design flaws.

Revival and Expansion (2000s–Present)

In the early 2000s, following a decade of decline, the Russian government under President Vladimir Putin elevated the restoration of GLONASS to a national priority, substantially increasing funding to rebuild the constellation. This policy shift addressed the system's degradation, where operational satellites had fallen below critical thresholds for reliable service. By 2008, Prime Minister Putin approved an additional 67 billion rubles (approximately US$2.62 billion) to the GLONASS budget, supporting accelerated satellite production and launches. A series of rocket launches from 2001 onward replenished the orbital segment, transitioning from aging first-generation satellites to the improved GLONASS-M series, which offered extended service life of up to seven years and enhanced signal stability. All satellites launched after December 2005 were GLONASS-M models until the introduction of newer variants. These efforts restored full coverage over Russian territory by 2010 and achieved global operational capability in 2011 with a complete constellation of 24 satellites. The revival extended into satellite modernization with the debut of the third-generation GLONASS-K1 on February 26, 2011, featuring reduced mass, higher power efficiency, and initial (CDMA) signals for better compatibility with other GNSS systems. Subsequent launches, including a second GLONASS-K1 in November 2014, paved the way for broader deployment. pursued constellation expansion beyond 24 satellites, targeting 29–30 by the early 2010s to enhance redundancy and accuracy, alongside ground segment upgrades such as a new control center in Korolev commissioned in 2013. Ongoing efforts through the and focused on transitioning to full CDMA signaling and deploying advanced satellites, with plans for multiple launches to sustain and improve performance amid challenges like aging hardware reliance. By 2022, reported progress in signal-in-space user range error reductions, underscoring commitments to long-term development for and military applications.

Geopolitical and Strategic Dimensions

Military Applications and National Security Role

GLONASS, developed under the Soviet Ministry of Defense in the late 1970s, serves as a cornerstone of , providing positioning, navigation, and timing (PNT) capabilities essential for operational effectiveness. The system supports the in guiding precision-guided munitions, including cruise missiles and artillery projectiles, with encrypted military signals offering accuracy superior to civilian channels—typically under 10 meters for authorized users. For example, during Russian military interventions in beginning in 2015, GLONASS satellites facilitated the precise targeting of high-explosive aviation bombs and other munitions, demonstrating its integration into combat scenarios. The Russian Military Space Forces, now part of the Aerospace Forces, maintain operational control over GLONASS, embedding it in strategic platforms such as intercontinental ballistic missiles (ICBMs), , and tactical for real-time and control. This includes compatibility with systems like the Iskander and Kalibr cruise missiles, where GLONASS augments inertial guidance to correct for drift and enhance terminal accuracy. Military-grade receivers employ (FDMA) with anti-jamming features, contrasting with the (CDMA) of GPS, to ensure resilience in contested electromagnetic environments. In terms of , GLONASS underpins Russia's by reducing dependence on foreign GNSS like GPS, which could be selectively degraded or denied by the in wartime per its operational policies. The system's dual-use architecture, with restricted high-precision channels reserved for defense purposes, bolsters deterrence and , as evidenced by its role in exercises simulating conflicts where signal independence is critical. Recent upgrades, including search-and-rescue payloads on GLONASS-K satellites capable of for locating distressed personnel, further extend its utility in expeditionary operations. However, reliability issues, such as incomplete constellation coverage in the early , have occasionally compelled reliance on hybrid GPS-GLONASS solutions in munitions, highlighting ongoing vulnerabilities despite modernization efforts.

Civilian Adoption and Economic Impact

The Russian government opened GLONASS to applications through Presidential Decree No. 638 on May 17, 2007, aiming to leverage the system for social and across sectors including transportation, , and . This policy shift facilitated integration into consumer devices such as smartphones supporting dual GPS-GLONASS functionality for enhanced positioning accuracy, particularly in high-latitude regions where GLONASS performs reliably. In transportation, the ERA-GLONASS emergency response system, operational since 2016 and mandatory for new vehicles from , 2017, combines GLONASS and to automatically detect accidents and transmit location data to rescuers, processing over 347,000 calls in its early years and connecting more than 12.9 million vehicles by September 2025. Adoption has been particularly strong in Russia's automotive and sectors, with approximately 2.1 million cars equipped with GNSS terminals as of the mid-2010s, expanding to broader fleet integration. In , GLONASS enables precision farming on around 3,000 machines for decimeter- to centimeter-level accuracy in real-time operations, optimizing resource use and yields. benefits from ground-based augmentation systems (GBAS) at 94 civil airports, improving precision and safety. Maritime and rail applications further support logistics efficiency, while systems like , a GLONASS-enabled toll collection for heavy trucks operational since 2015, cover 50,774 km of and generated 32.9 billion rubles in revenue for infrastructure by 2017. Economically, GLONASS contributes to cost reductions and productivity gains; ERA-GLONASS is projected to save over 4,000 lives annually at full vehicle fleet coverage (estimated at 42 million terminals), lowering societal costs from road accidents. Precision applications in and minimize and input , while mandatory integrations drive domestic receiver production and innovation, though global market share remains limited outside due to reliance on multi-constellation GNSS devices. The system's role in emergency and toll systems underscores its fiscal impact, with ERA-GLONASS infrastructure enabling service expansion and Platon funding road maintenance directly.

International Relations and Export Efforts

Russia has engaged in bilateral agreements to establish GLONASS ground monitoring stations abroad, aiming to improve system accuracy, expand coverage, and foster technological partnerships. As of 2021, planned deployments in , , , , and , building on existing stations in (Brasília) and (Bellingshausen, Novolazarevskaya, and sites). These efforts, initiated in the early , targeted up to 36 countries by 2014 to enhance and user access, with additional sites proposed in ( and Colorado do Oeste), , , , , and . Early cooperation included a 2004 U.S.-Russia joint statement promoting between GLONASS and GPS for applications, though signals remained separate. ratified cooperation pacts with and in May 2014, incorporating GLONASS differential correction stations to support regional navigation services. Similar arrangements with focused on joint use of infrastructure, including GLONASS integration. These initiatives often align with broader geopolitical ties, such as partnerships, where ground stations enable reciprocal benefits like data sharing while advancing Russia's global positioning influence. Export efforts emphasize promoting GLONASS-compatible receivers and multi-constellation devices internationally, particularly in allied markets. Russia-India discussions in the explored joint marketing of GLONASS services and receivers for and maritime applications. Civilian access to GLONASS signals has been offered freely since the , with mandates for compatibility in Russian exports of vehicles and equipment to ensure in partner nations like those in and . However, Western sanctions following the 2014 Crimea annexation and 2022 invasion have constrained hardware exports, shifting focus to software integration and indigenous production in cooperating countries. Despite these hurdles, GLONASS receivers remain integrated into dual-use systems exported to nations like , supporting hybrid GNSS navigation in missiles and drones.

Criticisms and Limitations

Technical Reliability and Shortcomings

GLONASS has experienced recurrent satellite outages and system-wide failures, undermining its operational reliability. In April 2014, all GLONASS satellites transmitted erroneous broadcast messages starting at 21:15 UTC on , leading to a half-day outage that affected global users of combined GPS/GLONASS receivers. This incident, traced to faulty software containing mathematical errors, caused widespread tracking disruptions, with over 40% of monitored sites in networks like New Zealand's GeoNet experiencing total GLONASS signal loss. Similar disruptions occurred earlier, including triple-satellite failures in July 2013 and multiple outages in April 2014 that persisted for over 10 hours, marking the system as prone to cascading technical faults. Post-1996, after achieving a full constellation, GLONASS provided uninterrupted global coverage for fewer than 40 days due to frequent satellite malfunctions and challenges with GPS receivers. Ground-based tracking limitations have exacerbated these issues, contributing to inconsistent and compared to GPS. As of 2023, the system's outdated hardware has led to persistent inaccuracies, particularly in precision-guided applications, where GLONASS deficiencies have been cited as factors in reduced weapon effectiveness. In terms of positioning accuracy, GLONASS typically achieves 5–10 meters horizontally, inferior to GPS's 3.5–7.8 meters under similar conditions, owing to differences in modulation (FDMA versus GPS's CDMA) and less precise onboard atomic clocks. Empirical studies confirm GLONASS orbits exhibit higher errors in precise than GPS, limiting its utility in high-precision tasks despite advantages in high-latitude coverage. Clock stability remains a weakness, with GLONASS products showing greater variability than GPS equivalents, further degrading long-term signal reliability. These technical gaps persist despite upgrades, highlighting inherent design constraints in frequency management and error correction.

Funding Dependencies and Political Hurdles

The GLONASS program's funding has historically been heavily dependent on the Russian federal budget, rendering it vulnerable to economic fluctuations and shifting governmental priorities. In the 1990s, following the Soviet Union's dissolution, severe budget cuts amid Russia's financial crisis led to the program's near-collapse, with operational satellites dropping to as few as nine by the late decade due to insufficient maintenance and replacement funding. Restoration efforts began in 2001 under President Vladimir Putin, who prioritized the system and doubled its funding, including an additional 67 billion rubles (approximately $2.62 billion) approved in 2008 to accelerate satellite deployments. Despite these infusions—such as the 346.5 billion rubles (nearly $12 billion) allocated for 2012–2020—GLONASS has consistently consumed a significant portion of Roscosmos's budget, up to one-third in peak years, tying its sustainability to volatile oil revenues and state allocations that compete with military and other space initiatives. Political hurdles have compounded these fiscal dependencies, particularly through that restrict access to critical technologies. U.S. and Western sanctions, intensified after Russia's 2014 annexation of and escalated following the 2022 invasion of , have blocked procurement of advanced components for modernization, delaying upgrades and contributing to the constellation's deterioration. This has forced reliance on domestic or alternative suppliers, including Chinese-made parts, which compromise long-term reliability and precision goals for the 2021–2030 program budgeted at 484 billion rubles. Pre-2022, foreign commercial launches accounted for 10–20% of 's revenue, a stream now curtailed by geopolitical isolation, exacerbating funding shortfalls and hindering full operational capability. Domestically, bureaucratic inefficiencies and leadership instability, such as the 2025 dismissal of Roscosmos head Yuri Borisov amid performance shortfalls, further politicize resource allocation, prioritizing military applications over comprehensive civilian enhancements.

Comparative Deficiencies Versus Western Systems

GLONASS employs (FDMA) for its legacy signals on L1 and L2 bands, assigning unique carrier frequencies to each , in contrast to the (CDMA) used by GPS and Galileo, which broadcasts all satellites on the same frequency but distinguishes them via unique (PRN) codes. This FDMA approach introduces inter-frequency biases and complicates carrier-phase ambiguity resolution in receivers, requiring additional modeling of hardware-induced channel biases that are absent in CDMA systems, thereby increasing processing complexity and potential error sources in precise positioning applications. In terms of global positional accuracy, GPS typically achieves slightly superior performance to standalone GLONASS under standard conditions, with root-mean-square errors for horizontal positioning around 1-2 meters for GPS compared to marginally higher values for GLONASS due to frequency-dependent signal effects and less mature error correction models. While GLONASS's higher of 64.8 degrees provides better visibility in high-latitude regions, its equatorial coverage remains inferior to GPS's 55-degree inclination optimized for global uniformity, historically resulting in larger position dilution of precision (PDOP) values in tropical zones during periods of incomplete constellations. Reliability challenges stem from GLONASS's legacy FDMA structure, which exhibits poorer with Western systems; for instance, combined GPS/GLONASS processing demands explicit handling of differential code biases absent in pure CDMA environments, leading to longer convergence times in real-time kinematic (RTK) applications—often 20-50% extended compared to GPS-only modes. Moreover, GLONASS receivers consume more power when tracking FDMA signals due to the need for wider bandwidth filtering per channel, exacerbating battery drain in multi-constellation devices versus GPS-centric operations. Signal-in-space (SIS) anomalies occur sporadically in GLONASS, with user range errors occasionally exceeding tens of meters, compounded by the system's reliance on older satellites still transmitting FDMA signals despite ongoing transitions to CDMA on new GLONASS-K and GLONASS-M variants, which limits seamless integration with Galileo’s advanced and high-accuracy services. These factors collectively hinder GLONASS's standalone efficacy against GPS's mature ecosystem and Galileo's forthcoming open-service enhancements, necessitating hybrid use for optimal performance in demanding scenarios.

Future Developments

Upcoming Satellite Upgrades and Launches

intends to expand the GLONASS constellation through launches of modernized satellites, which incorporate import-substitution to eliminate reliance on foreign components and enable multifunctional operations including enhanced . Launches of these upgraded satellites commenced in 2025, with the configuration featuring both traditional FDMA signals and additional CDMA signals for improved global compatibility and positioning accuracy. The agency projects deploying more than ten satellites into orbit by the end of the decade, aiming for full constellation renewal by to sustain 24 operational satellites with superior longevity—up to 10 years compared to 7-10 years for prior Glonass-K models—and reduced mass for more efficient launches. This upgrade addresses historical reliability issues by integrating advanced atomic frequency standards and inter-satellite links, potentially boosting system availability amid ongoing replacements of aging satellites. A planned high-orbital GLONASS cluster, designed to augment medium-Earth coverage with geostationary satellites for polar region improvements, has been postponed to 2028 from an initial 2025 target due to development delays. Supporting includes the launch of four spherical satellites in 2025 to refine optics and enhance overall precision. These efforts align with the federal GLONASS program through 2030, prioritizing domestic production amid geopolitical constraints on international .

Technological Enhancements and Multi-System Integration

The modernization of GLONASS has focused on transitioning from (FDMA) to (CDMA) signals to enhance compatibility and performance, with the first GLONASS-K2 satellite, launched in November 2022, introducing CDMA transmissions on L1 and L2 bands alongside legacy FDMA. Subsequent launches, including additional GLONASS-K2 vehicles in 2023 and planned for 2024-2025, aim to equip at least 12 satellites with full CDMA capabilities across L1, L2, and L3 bands, improving signal-in-space accuracy by up to 18% on L1 and 31% on L2 compared to FDMA equivalents. These upgrades also incorporate new open signals such as L1OC, L2OC, and L3OC, designed for use with better resistance to interference and multipath effects. Future enhancements include the GLONASS-KM variant, slated for launches post-2025, which will add L5 band transmission at 1176.45 MHz to align with GPS and Galileo modernization, enabling dual-frequency operations for higher precision in challenging environments like urban canyons. Ground segment improvements, such as upgraded monitoring stations and inter-satellite links in newer satellites, further support these signal evolutions by providing real-time orbit and clock corrections. Multi-system integration has advanced through CDMA adoption, which standardizes signal structures for seamless interoperability with GPS, Galileo, and BeiDou in multi-constellation receivers, yielding up to 20-30% gains in positioning accuracy and satellite availability in global navigation satellite systems (GNSS) fusion modes. Commercial modules like the LC76G and high-precision antennas now routinely combine GLONASS CDMA signals with those from other constellations, supporting applications in aviation, agriculture, and autonomous vehicles across regions with partial sky visibility. Initiatives such as the International GNSS Service's Multi-GNSS Experiment (MGEX) validate this integration by tracking and analyzing GLONASS-K2 signals alongside international peers, facilitating standardized precise point positioning (PPP) and real-time kinematic (RTK) services. As of 2025, over 70% of new GNSS receivers incorporate multi-constellation support, with GLONASS contributing to enhanced coverage in high-latitude regions where GPS alone may underperform.

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