GLONASS (, ) is a radio-based satellite navigation system operated for the Russian government by the Russian Space Forces. It is an alternative and complement to the United States' Global Positioning System (GPS), the Chinese Compass navigation system, and the planned Galileo positioning system of the European Union (EU) and Indian Regional Navigational Satellite System of India.

Development on the GLONASS began in the Soviet Union in 1976. Beginning on 12 October 1982, numerous rocket launches added satellites to the system until the constellation was completed in 1995. Following completion, the system fell into disrepair with the collapse of the Russian economy. In the early 2000s, under Vladimir Putin's presidency, the restoration of the system was made a top government priority and funding was substantially increased. GLONASS is currently the most expensive program of the Russian Federal Space Agency, consuming a third of its budget in 2010.

By 2010, GLONASS had achieved 100% coverage of Russia's territory. As of February 2011, the constellation consists of 22 operational satellites, short of the 24 satellites needed to provide continuous global coverage, and is expected to be completed during 2011. The GLONASS satellites designs have undergone several upgrades, with the latest version being GLONASS-K.

History

Inception and design

The first satellite-based radio navigation system developed in the Soviet Union was Tsiklon, which had the purpose of providing ballistic missile submarines a method for accurate positioning. 31 Tsiklon satellites were launched between 1967 and 1978. The main problem with the system was that, although highly accurate for stationary or slow-moving ships, it required several hours of observation by the receiving station to fix a position, making it unusable for many navigation purposes and for the guidance of the new generation of ballistic missiles. In 1968–1969, a new navigation system, which would support not only the navy, but also the air, land and space forces, was conceived. Formal requirements were completed in 1970; in 1976, the government made a decision to launch development of the "Unified Space Navigation System GLONASS".

The task of designing GLONASS was given to a group of young specialists at NPO PM in the city of Krasnoyarsk-26 (today called Zheleznogorsk). Under the leadership of Vladimir Cheremisin, they developed different proposals, from which the institute's director Grigory Chernyavsky selected the final one. The work was completed in the late 1970s; the system would consist of 24 satellites operating at an altitude of 20,000 km in medium circular orbit. It would be able to promptly fix the receiving station's position based on signals from 4 satellites, and also reveal the object's speed and direction. The satellites would be launched 3 at a time on the heavy-lift Proton rocket. Due to the large number of satellites needed for the program, NPO PM delegated the manufacturing of the satellites to PO Polyot in Omsk, which had better production capabilities.

Originally, GLONASS was designed to have an accuracy of 65 m, but in reality it had an accuracy of 20 m in the civilian signal and 10 m in the military signal. The first generation GLONASS satellites were 7.8 m tall, had a width of 7.2 m, measured across their solar panels, and a mass of 1,260 kg.

Achieving full orbital constellation

In the early 1980s, NPO PM received the first prototype satellites from PO Polyot for ground tests. Many of the produced parts were of low quality and NPO PM engineers had to perform substantial redesigning, leading to a delay. On 12 October 1982, three satellites, designated Kosmos-1413, Kosmos-1414, and Kosmos-1415 were launched aboard a Proton rocket. As only one GLONASS satellite was ready in time for the launch instead of the expected three, it was decided to launch it along with two mock-ups. The American media reported the event as a launch of one satellite and "two secret objects." For a long time, the Americans could not find out the nature of those "objects". The Telegraph Agency of the Soviet Union (TASS) covered the launch, describing GLONASS as a system "created to determine positioning of civil aviation aircraft, navy transport and fishing-boats of the Soviet Union".

From 1982 through April 1991, the Soviet Union successfully launched a total of 43 GLONASS-related satellites plus five test satellites. When the Soviet Union disintegrated in 1991, twelve functional GLONASS satellites in two planes were operational; enough to allow limited usage of the system (to cover the entire territory of the country, 18 satellites would have been necessary.) The Russian Federation took over control of the constellation and continued its development. In 1993, the system, now consisting of 12 satellites, was formally declared operational and in December 1995, the constellation was finally brought to its optimal status of 24 operational satellites. This brought the precision of GLONASS on-par with the American GPS system, which had achieved full operational capability two years earlier.

Economic crisis and fall into disrepair

Since the first generation satellites operated for 3 years each, to keep the system at full capacity, two launches per year would have been necessary to maintain the full network of 24 satellites. However, in the financially difficult period of 1989–1999, the space program's funding was cut by 80% and Russia consequently found itself unable to afford this launch rate. After the full complement was achieved in December 1995, there were no further launches until December 1999. As a result, the constellation reached its lowest point of just 6 operational satellites in 2001. As a prelude to demilitarisation, responsibility of the program was transferred from the Ministry of Defence to Russia's civilian space agency Roscosmos.

Renewed efforts and modernization

In the early 2000s, under Vladimir Putin's presidency, the Russian economy recovered and state finances improved considerably. Putin himself took special interest in GLONASS and the system's restoration was made one of the government's top priorities. For this purpose, on August 2001, the Federal Targeted Program "Global Navigation System" 2002–2011 (Government Decision No. 587) was launched. The program was given a budget of $420 million and aimed at restoring the full constellation by 2009.

On 10 December 2003, the second generation satellite design, GLONASS-M, was launched for the first time. It had a slightly larger mass than the baseline GLONASS, standing at 1,415 kg, but it had double the original's lifetime, decreasing the required replacement rate by 50%. The new satellite also had better accuracy and ability to broadcast two extra civilian signals.

In 2006, Defence Minister Sergey Ivanov ordered one of the signals (with an accuracy of 30 m) to be made available to civilian users. Putin, however, was not satisfied with this, and demanded that the whole system should be made fully available to everyone. Consequently, on 18 May 2007, all restrictions were lifted. The accurate, formerly military-only signal with a precision of 10 m, has since then been freely available to civilian users.

During the middle of the first decade of the 2000s, the Russian economy boomed, resulting in substantial increases in the country's space budget. In 2007, the financing of the GLONASS program was increased considerably; its budget was more than doubled. While in 2006 the GLONASS had received $181 million from the federal budget, in 2007 the amount was increased to $380 million.

In the end, 140.1 billion rubles ($4.7 billion) were spent on the program 2001–2011, making it Roscosmos' largest project and consuming a third of its 2010 budget of 84.5 billion rubles.

Restoring full capacity

In June 2008, the system consisted of 16 satellites, 12 of which were fully operational at the time. At this point, Roscosmos aimed at having a full constellation of 24 satellites in orbit by 2010, one year later than previously planned.

The military importance of having a domestic, independent satellite navigation system was highlighted by the 2008 South Ossetia war in August 2008: during the hostilities, the American GPS system was completely blacked out in the region. In September 2008, Prime Minister Vladimir Putin signed a decree allocating additional 67 billion rubles (2.6 billion USD) to GLONASS from the federal budget.

Promoting commercial use

Although the GLONASS constellation is nearing global coverage, its commercialisation, especially development of the user segment, has been lacking compared to the American GPS system. For example, the first commercial Russian-made GLONASS navigation device for cars, Glospace SGK-70, was introduced in 2007, but it was much bigger and more costly than similar GPS receivers. In late 2010, there were only a handful of GLONASS receivers on the market, and few of them were meant for ordinary consumers. To improve the situation, the Russian government has been actively promoting GLONASS for civilian use.

To improve development of the user segment, on August 11, 2010, Sergei Ivanov announced a plan to introduce a 25% import duty on all GPS-capable devices, including mobile phones, unless they are compatible with GLONASS. As well, the government is planning to force all car manufacturers in Russia to make cars with GLONASS starting from 2011. This will affect all car makers, including foreign brands like Ford and Toyota, which have car assembly facilities in Russia.

Current GPS and phone baseband chips from major vendors ST-Ericsson, Broadcom and Qualcomm all support GLONASS in combination with GPS. Any import restriction is likely to have little change as most devices shipping worldwide will soon support GLONASS.

In April 2011 Sweden's Swepos, a national network of satellite reference stations which provides data for real-time positioning with meter accuracy, become the first known foreign company to use GLONASS.

Finishing the constellation

Russia's aim of finishing the constellation in 2010 suffered a setback when a December 2010 launch of three GLONASS-M satellites failed. The Proton-M rocket itself performed flawlessly, but the upper stage Blok DM3 (a new version which was to make its maiden flight) was loaded with too much fuel due to a sensor failure. As a result, the upper stage and the three satellites crashed into the Pacific Ocean. Kommersant estimated that the launch failure cost up to $160 million. Russian President Dmitry Medvedev ordered a full audit of the entire program and an investigation into the failure.

Following the mishap, Roscosmos activated two reserve satellites and decided to make the first improved GLONASS-K satellite, to be launched in February 2011, part of the operational constellation instead of mainly for testing as was originally planned. This would bring the total number of satellites to 23, obtaining almost complete worldwide coverage. The second GLONASS-K will be ready within three to four months.

In 2010, President Dmitry Medvedev ordered the government to prepare a new federal targeted program for GLONASS, covering the years 2012–2020. The original 2001 program is scheduled to end in 2011. On 22 June 2011, Roscosmos revealed that the agency was looking for a funding of 402 billion rubles ($14.35 billion) for the program. The funds would be spent on maintaining the satellite constellation, on developing and maintaining navigational maps as well as on sponsoring supplemental technologies to make GLONASS more attractive to users.

System description

GLONASS is a global satellite navigation 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 altitude with a 64.8 degree inclination and a period of 11 hours and 15 minutes. GLONASS' orbit makes it especially suited for usage in northern latitudes, where getting a GPS signal can be problematic. The constellation operates in three orbital planes, with 8 evenly spaced satellites on each. 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, three of which will be used to determine the user's location and the fourth to synchronise clocks of the receiver and the three other spacecraft.

Signals

GLONASS satellites transmit two types of signal: a standard precision (SP) signal and an obfuscated high precision (HP) signal.

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 SP 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''=−7,−6,−5,...0,...,6, previously ''n''=0,...,13). Signals are transmitted in a 38° cone, using right-hand circular polarization, at an EIRP between 25 to 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 will never be in view of an earth based user at the same time.

The HP signal is broadcast in phase quadrature with the SP signal, effectively sharing the same carrier wave as the SP signal, but with a ten times higher bandwidth than the SP signal.

The L2 signals use the same FDMA as the L1 band signals, but transmit straddling 1246 MHz with the center frequency determined by the equation 1246 MHz + ''n''×0.4375 MHz, where ''n'' spans the same range as for L1. Other details of the HP signal have not been disclosed.

At peak efficiency, the SP signal offers horizontal positioning accuracy within 5–10 meters, vertical positioning within 15 meters, a velocity vector measuring within 10 cm/s, and timing within 200 ns, all based on measurements from four first-generation satellites simultaneously; newer satellites such as GLONASS-M improve on this. The more accurate HP signal is available for authorized users, such as the Russian Military, yet unlike the US P(Y) code which is modulated by an encrypting W code, the GLONASS P codes are broadcast in the clear using only 'security through obscurity'. Use of this signal bears risk however as the modulation (and therefore the tracking strategy) of the data bits on the L2P code has recently changed from unmodulated to 250 bit/s burst at random intervals. The GLONASS L1P code is modulated at 50 bit/s without a manchester meander code, and while it carries the same orbital elements as the CA code, it allocates more bits to critical Luni-Solar acceleration parameters and clock correction terms.

Currently, an additional civil reference signal is broadcast in the L2 band with an identical SP code to the L1 band signal. This is available from all satellites in the current constellation, except satellite number 795 which is the last of the inferior original GLONASS design, and one partially inoperable GLONASS-M satellite which is broadcasting only in the L1 band. (see www.glonass-ianc.rsa.ru for daily updates on constellation status.)

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 1900 to 1905. This is in contrast to the GPS's coordinate datum, WGS 84, which uses the location of the North Pole in 1984. As of September 17, 2007 the PZ-90 datum has been updated to differ from WGS 84 by less than in any given direction.

CDMA signals

Since 2008, new CDMA signals are being researched for use with GLONASS.

The latest Glonass-K1 satellites to be launched in 2011–2012 will introduce an additional open CDMA signal for testing purposes, located in the L3 band at 1202.025 MHz. Glonass-K2 satellites, to be launched in 2013–2015, will relocate the L3 signal to 1207.14 MHz and add an additional open CDMA signal located at 1575.42 MHz in the L1 band; subsequent Glonass-KM satellites to be launched after 2015 will feature additional open CDMA signals - one on existing L1 frequency, one at 1242 MHz in the L2 band, and one at 1176.45 MHz in the L5 band. Glonass-KM will probably broadcast obfuscated CDMA signals in existing L1, L2 and L3 bands.

Although the format and modulation of GLONASS CDMA signals are not finalized, preliminary statements from developers indicate that the new signals are essentially GPS/Galileo/COMPASS format signals placed at the same frequencies. The open signal in the L1 band will use BOC(1,1) modulation centered at 1575.42 MHz, similarly to corresponding modernized GPS signals in L1 band and Galileo/COMPASS signal E1. The open signal in the L5 band will use BOC(4,4) modulation centered at 1176.45 MHz, the same as the modernized GPS signal "Safety of Life" (L5) and Galileo signal E5a; the open signal in the L3 band will use QPSK(10) modulation centered at 1207.14 MHz, the same frequency as Galileo/COMPASS signal E5b, and will contain information and pilot components. Such an arrangement will allow easier and cheaper implementation of multi-standard GNSS receivers.

Binary phase-shift keying (BPSK) is used by standard GPS and GLONASS signals, however both BPSK and quadrature phase-shift keying (QPSK) can be considered as variations of quadrature amplitude modulation (QAM), specifically QAM-2 and QAM-4. Binary offset carrier (BOC) is the modulation used by Galileo, modernized GPS, and COMPASS.

With the introduction of CDMA signals, the constellation will be expanded to 30 active satellites by 2020; this may require eventual deprecation of FDMA signals. Additional satellites may use Molniya orbit or Tundra orbit for increased regional availability, similar to Japanese QZSS system.

Satellites

The main contractor of the GLONASS program is Joint Stock Company Reshetnev Information Satellite Systems (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 PC 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.

First generation

The true first generation of GLONASS (also called Uragan) satellites were all 3-axis stabilized vehicles, generally weighing 1,250 kg 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 2-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 25 satellites were launched. The design life was three years, however numerous spacecraft exceeded this, with one late model lasting 68 months.

Block II satellites were typically launched three at a time from the Baikonur Cosmodrome using Proton-K Blok-DM-2 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

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. They are approximately in diameter and high, with a solar array span of 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.

A total of fourteen second generation satellites were launched through the end of 2007. As with the previous generation, the second generation spacecraft were launched in triplets using Proton-K Blok-DM-2 or Proton-K Briz-M boosters.

Third generation

GLONASS-K is a substantial improvement of the previous generation: it is the first unpressurised GLONASS satellite with a much reduced mass (750 kg versus 1,450 kg 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 Compass. The new satellite's advanced equipment—made solely from Russian components—will allow the doubling of GLONASS' accuracy. As with the previous satellites, these are 3-axis stabilized, nadir pointing with dual solar arrays. The first GLONASS-K satellite was successfully launched on 26 February 2011.

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.

Ground control

The ground control segment of GLONASS is entirely located within former Soviet Union territory. The Ground Control Center and Time Standards is located in Moscow and the telemetry and tracking stations are in Saint Petersburg, Ternopol, Eniseisk, and Komsomolsk-na-Amure.

Receivers

Septentrio, Topcon, JAVAD, Magellan Navigation, Novatel, Leica Geosystems and Trimble Inc produce 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.

Current status

Availability

, the GLONASS constellation status is:

! Total satellites in constellation	27 SC
Operational	23 SC
In commissioning phase	1 SC
In maintenance	3 SC
Spares	–
In decommissioning phase	–

The system requires 18 satellites for continuous navigation services covering the entire territory of the Russian Federation, and 24 satellites to provide services worldwide. The GLONASS system currently covers 100% of Russian territory.

Accuracy

[[File:GLONASS integral availability.gif|thumb|right|350px| Integral navigation availability for GLONASS customer (PDOP≤6) on the diurnal range for elevation not less than 5 degrees on ]] According Russian System of Differentional Correction and Monitoring's data, , precisions of GLONASS navigation definitions (for p=0.95) for latitude and longitude were 4.46—7.38 m with mean number of NSV equals 7—8 (depending on station). In comparison, the same time precisions of GPS navigation definitions were 2.00—8.76 m with mean number of NSV equals 6—11 (depending on station). Civilian GLONASS used alone is therefore very slightly less accurate than GPS. On northern latitudes, GLONASS' accuracy is better than that of GPS due to the orbital position of the satellites.

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 precisions of GLONASS/GPS navigation definitions were 2.37—4.65 m with mean number of NSV equals 14—19 (depends on station).

In May 2009, Anatoly Perminov the then director of the Russian Federal Space Agency stated that actions were undertaken to expand GLONASS's constellation and to improve the ground segment in order to increase the navigation definition of GLONASS to an accuracy of 2.8 m by 2011. In particular, the latest satellite design, GLONASS-K has the ability to double the system's accuracy once introduced.

See also

Global Navigation Satellite System – the generic term for a global satellite positioning system

Multilateration – the mathematical technique used for positioning

References

Bibliography

''GLONASS Interface Control Document'' Edition 5.1, 2008

''GLONASS Interface Control Document'' Version 4.0, 1998

External links

Official GLONASS web page

GNSS web page including GLONASS

Description of GLONASS on the web page of the International Laser Ranging Service (ILRS)

GLONASS: present, future and past Presented on the ILRS Technical Workshop, September 14–19, 2009, Metsovo, Greece

A homemade receiver for GPS & GLONASS satellites

Category:Soviet Earth satellites Category:Russian Earth satellites Category:Satellite navigation systems Category:Wireless locating Category:Soviet inventions Category:Russian inventions Category:GLONASS

af:GLONASS bg:ГЛОНАСС ca:GLONASS cv:ГЛОНАСС cs:GLONASS de:GLONASS et:GLONASS es:GLONASS eu:GLONASS fr:GLONASS ko:글로나스 hi:ग्लोनास (GLONASS) hr:GLONASS it:GLONASS he:GLONASS kn:ಗ್ಲೋನಾಸ್ lv:GLONASS nl:GLONASS ja:GLONASS no:GLONASS pl:GLONASS pt:GLONASS ro:GLONASS ru:ГЛОНАСС sk:GLONASS sl:GLONASS sr:GLONASS sh:GLONASS fi:GLONASS sv:GLONASS uk:ГЛОНАСС vi:GLONASS zh:格洛纳斯系统