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Recent years have witnessed an increasingly use of GNSS technologies in diverse areas of human endeavours. Governments, organisations, individuals etc. are beginning to rely upon GNSS technology in finding solutions to problems in different fields of life (Spirent, 2002: 17). One obvious area where GNSS technology has been deployed successfully since the launching of satellite navigation is in military applications. Military applications of GNSS date back in 1978 when the first Global Positioning System was launched by US Department of Defence. Since then, many GNSS and associated navigation systems are being used in military mission fields. This report examines past and present military applications of GNSS; it also attempts to look into future of military applications in the context of emerging trends and developments in GNSS world.
1.2 Global Navigation Satellite Systems (GNSS)
Global Navigation Satellite Systems (GNSS) is generic term encompassing all satellite navigation systems that allows users to determine their locations by observing radio signals transmitted by GNSS satellites. First among them is the US Navigation by Satellite Ranging and Timing (NAVSTAR) Global Positioning System (GPS). Russian Global Navigation Satellites System (GLONASS) is the second generation of GNSS, conceived also as a military system.. The next generation of GNSS is the European Union’s Galileo which is expected to be in full operation by early 2014. GNSS market is poised for revolution with the full deployment of Galileo constellation of satellites. Other Regional GNSS include Beidou operated by China, although through its Compass, China has planned to launch satellite navigation system with global coverage. Indian Regional Navigation Satellite System (IRNSS) is another GNSS in the development. Uncertainty still trail IRNSS project since India entered into partnership with Russian GLONASS. QZSS is another regional navigation system operated by Japan. It is developed to supplement GPS signals in Japan and neighbouring areas.
Besides these, there are other regional GNSS space-based augmentation systems aim to improve the performance of GPS/GLONASS. The major regional augmentation systems are WAAS, EGNOS (European Geostationary National Overlay Service), MTSAT-Based Satellite Augmentation System (MSAS) in Japan and Indian GPS Aided Geo Augmented Navigation (GAGAN)
GPS and GLONASS stand out among the list when it comes to military applications. GPS and GLONASS have been used in many military operations.
1.3 Global Positioning Systems (GPS)
US Global Positioning System (GPS) was designed as a dual-use technology (civilian and military use). The positioning service available to civil users is called – Standard Positioning Service, while that of the military is called Precise Positioning Service. GPS’s Precise Positioning Service (PPS) is used for most military applications. Precise Positioning Service is restricted to only US military, NATO forces, and other users licensed by US Government. The encrypted precise code signals – P(Y) and M-code are used for military applications. M- Code is a new signal being to realise the fundamental aim of achieving precise and accurate navigation services for military applications. These signals are broadcasted in link 1 (L1) and link 2 (L2) bands. L1C-d and L1C-p signals will be added to the PPS users under the GPS phased modernisation programme (Groves, 2008: 12). In times of navigation data messages, MNAV message broadcasts are broadcast on M-code signals. GPS is presently undergoing phased restructuring and modernisation and it is expected that new programme will ensure that existing users are transmitted P(Y) code while the new users are transmitted new M code (Kaplan and Hegarty (2006: 654).
Like GPS, GLONASS was conceived as a military system but designed to offer both military and civil positioning service (Groves 2008: 17). GLONASS P code signals are used for military applications and transmitted in both bands LI and L2 with frequencies 1592.95MHz – 1613.86MHz and 1237.83 MHz – 1256MHz respectively (Groves, 2008: 19). GLONASS – K, fully modernised satellites are set to broadcast new signals that will improve the accuracy of military operations.
2.0 GNSS Positioning Requirements:
The positioning principles are basically the same for GNSS systems. Generally, a GNSS receiver records three or more satellites signals to determine a 2 – dimensional coordinates, while four or more signals are needed for 3 – dimensional coordinates. The accuracy of GNSS position solution depends on the type of GNSS device used and application under consideration.
Accuracy is a critical factor in military applications. GPS was launched because of the military requirements for high accurate global navigation (Len, 2007:185). In case of timing service, military operations require precise time transfer for synchronization of equipment and various operations (Len 2007: 184). The GPS PPS offers horizontal accuracy of 1.2m and vertical accuracy of 1.9m based on 24 – satellite constellations (Groves, 2008). With its modernisation program, GLONASS is set to compete with GPS as it planned to achieve the same positioning accuracy with GPS. The Galileo Public-Regulated Service (PRS) has a lower accuracy when compared to that of GPS PPS; it has horizontal accuracy of 3m and vertical accuracy of 6m, much more lower to its Open Service (Groves, 2008: 20)
Availability is also of the important characteristics of GNSS performance. Availability of navigation system is defined by US Federal Radionavigation Plan (FRP) as “the percentage of time that the services of the system are within the required performance limits” (Wang et al 2006: 1). Global availability of GNSS for military applications is expected to increase with the ongoing modernisation of GLONASS. GLONASS – K satellites when fully launched will improve the accuracy of P code for military applications. India has partnered with Russia in the GLONASS project, and it is expected that India and other countries will have access GLONASS military signals for their mission operations and equipment testing. Aside from GPS military signals, more countries are today using civil signals in many military missions and equipment testing.
GPS will have full integrity monitoring and alert system as the fourth segment when the modernisation programme is completed. GLONASS – K satellites will broadcast integrity information and differential corrections in L3 band. Similarly, Galileo will broadcast integrity alerts and some differential corrections.
2.1 GNSS Markets
GNSS technology is naturally divided into two broad markets/applications – civil / commercial markets and military markets. The user equipment used in military applications can be classified into two types:
(i) GNSS receivers operated by human beings such as handheld type, human operated receivers on ships, aircrafts and vehicles (Len, 2007: 184 -185)
(ii) Autonomous receivers – these are not dependent of any human operation and usually integrated with inertial sensors. They are used in guided missile programs and newer military applications.
Comparison between Military and Civil Receivers
L1 and /or L1, L2 (L5 on 11F satellites
P(Y), M, C/A, C
C/A and C (on modernised satellites
Card, handheld, receiver unit
Chips, handheld, receiver unit
1m to 5m
5m to 10m
Anti – interference
Greater than 54 dB
Usually not more than 24 dB
A/J antennas, communications, inertial sensors
Speed/heading sensors, communications, GIS, inertial sensors
Adapted from (Len 2007: 183)
3.0 Military Applications of GNSS
Of all GNSS, GPS has been most widely used in military applications. Essentially, GPS was developed to satisfy military requirements for a global positioning, navigation and timing service. (Kaplan, and Hegarty, 2006: 654). Military application of GPS started in late 1970s when GPS was used for weapon testing in the then US Navy Submarine Launched Ballistic Program (SLBM). GPS was used to track the Submarine Launched Ballistic Missiles from a ship as the missile travelled down the Atlantic (Len, 2007: 174). The GPS military equipment used for the missile testing then made use of translator. Subsequently, other weapon testing was conducted in the air and ground vehicles (Len, 2007: 177). Today, GPS can be deployed to variety of military applications. Some of these include: target acquisition; missile guidance, search and rescue; coordinate bombing; precision survey, instrument approach; antisubmarine warfare; range instrumentation; remotely piloted vehicle operations; barebase operations; close air support; en – route navigation; command and control; field artillery and shore bombardment; rendezvous, sensor emplacement etc. (Len, 2007: 177 -178). Other military applications of GNSS include mine location, enemy radar location, Special Forces intelligence gathering etc (Dye and Baylin, 1997: 82).
3.1 GNSS/ Inertial Integration Systems:
GNSS such as GPS has been proved to be weak in term of providing high quality and reliable position solution (Spirent, 2010). Thus inertial sensors are being used in many applications to complement GNSS. Inertial navigation system is a small, self – contained device that uses inertial sensors (accelerometers and gyroscopes) to calculate position and velocity solution of a moving object (Logsdon, 1995: 39). It makes use of dead reckoning navigation system (Groves 2008: 7). Using GPS measurements, INS navigation solution is calibrated and corrected via integration algorithm (Groves and Long, 2005: 2). GPS/INS integration is popular in the guided weapons and unmanned air vehicles (UAVs) where low cost sensors are used (Groves and Long, 2005: 2). INS function independently of GNSS signals susceptible to jamming, interference, enemy manipulation and other distortions and are therefore used in many military applications (Dye and Baylin, 1997: 13). Examples of practical applications of GNSS/INS based solutions are given in the report.
Advantages of GNSS/INS based solution:
“INS offers continuous navigation operations; it provides high-bandwidth output (50 Hz) and low short-term noise; it also provides attitude, angular rate, and acceleration measurements as well as position and velocity” (Groves and Long 2005: 419) (Groves 2008: 8). “GPS provides a high accuracy which does not drift with time”(Groves and Long, 2005: 419)
Disadvantages of GNSS/INS based solution: The accuracy of INS output is degraded with time thus necessitating the need to calibrate the errors (Groves 2008: 8). Unlike INS, “GNSS has lower bandwidth (1Hz), more noisier than that INS and does not usually include altitude” (Groves and Long 2005: 419, 420)
One obvious challenge in the military use of GNSS is issue of deliberate jamming and interference by the enemies. GPS receivers have been found to be susceptible to jamming due to low signal power of GPS signal. This trend has raised a concern to US Department of Defence in the recent years thus signalling the programme of developing various anti-jamming techniques to mitigate these effects. Recent anti – jamming technologies include nulling of antennas and ultra tight coupling of the GPS and the inertial sensors (Kaplan, and Hegarty (2006: 656).
3.2 Practical Applications of GPS in Precision Guidance
In 1991, US army and its allies successfully deployed GPS in the attack to rescue oil rich Kuwait after its invasion by Iraq in an operation tagged “Operation Desert Storm”. GPS receivers were fitted in the military aircrafts and helicopters, bombs were dropped from these aircrafts as targeted thus eliminating unwanted casualties. GPS receivers were used to know the coordinates of the targets so that the weapons can be delivered accurately.
In 1995, GPS was also deployed during the Bosnia war by the combined US and NATO forces in a campaign tagged “Operation Deliberate Force”. Military aircrafts operating from their base in Italy were fully equipped with GPS equipment in the strike against the Bosnia Serb forces.
Perhaps, the Joint Direct Attack Munition (JDAM) is the most impressive breakthrough GPS has achieved in area of precision guidance. JDAM is an independent, tail kit with gravity bomb; it is usually mounted on the military fighter jets and uses GPS/INS guidance to deliver the target (Cozzens, 2006). JDAM has the capability of working in all weather conditions and its accuracy is not dependent on the altitude (Cozzens, 2006). JDAM recorded 9.6m accuracy during their testing. JDAM have been successfully deployed in many operations. For example, in June 2006, US Air Force successfully used GBU-38 Joint Direct Attack Munition equipped with GPS precision guidance to kill former Iraq terrorist leader – Abu Musab al – Zarqawi in his house (Cozzens, 2006). Once on the air, GPS/INS guidance enables the gravity bomb to be delivered accurately at the targets (Cozzens, 2006).
In case of GLONASS, Russian military has deployed GLONASS military signals in many missions (Len, 2007: 189). Russian Federation Airforce recently developed latest KAB family of weapons called KAB – 500S. KAB – 500S is a guided bomb similar to that of US JDAM. “KAB – 500S can be dropped from aircraft at altitudes of 500 to 10,000 metres and airspeeds of 550 to 1,100 kilometres per hour” (Deagel, 2007). It uses GLONASS Military code and INS to strike the targets (Len, 2007: 189). The third generation GNSS, Galileo has encrypted signal – Public Regulated Service that may be used for military applications in the near future.
4.0 GNSS Future and Military Applications:
The GNSS have made giant strides in military applications particularly in area of guided weaponry and smart bombs. GPS-aided munitions, ranging from artillery shells to smart shells have proved to be a reliable technology in recent time in times of accuracy (Lucio, (2002), (Wells, (2001). Countries all over the world will continue to embrace these technologies as cheaper GPS/INS coupled munitions are being produced to meet the requirements for accurate, precise timing and navigation solutions in the land, air and sea in near future.
Current developments in GNSS industry like new signals and constellations acquisition will usher new era of high accurate military based satellite navigation. The separation of GPS signals for military and civilian use will lessen the effects of jamming and interference in military operations coupled with high signal power of new M – code. GPS new military code will improve the anti-jamming capability of the system as current modernisation programme will make it autonomous. Non coherence integration of the acquisition circuit of the new military code will enhance the performance of the system in the presence of noise and jamming (Betz et al, 2005: 45, 46). In the area of system integrity, modernization programme of GPS and GLONASS will offer users more reliable measurements as they will have options to validate GNSS measurements.
Presently, only GPS and GLONASS are used for military applications. I look at future where GNSS will be more available for military applications. More countries will be authorised to have access to GPS P(Y) code in near future and others will want develop their own SBASs. For example, Nigeria has developed its own SBAS called NIGCOMSAT with coverage only in Nigeria for now. Modernised GPS civil signals will continue to be used by countries not authorised to use P(Y) code. Only, recently, Russian Government announced that GLONASS military signals will be freely made available to any country that want to use them. Already, India and Russian have agreed to collaborate on GLONASS project (Len, 2007: 190). It is expected that more Countries will enter into agreements with Russian when GLONASS constellation of satellites are fully deployed in the orbit. China is making steady progress on its Compass project and is poised to use the system to strengthen its national security.
Finally, GNSS industry is geared for revolution when Galileo is fully operationalised in next few years. Galileo has an encrypted signal – PRS which has potentials for military applications. It is already been speculated that this may be used for military applications in the near future, although Galileo is purely conceived as a civilian system.
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