ICT - DEFENCE MANAGEMENT JOURNAL, Issue 41
Next generation GPS
Highlighting its fundamental importance in protecting today's battlefield, Defence Writer William Payne explores the developments in military GPS technology.
GPS permeates almost every aspect of modern weapons, military communications and control systems. The Task Force on the Future of the GPS, reporting to the US Department of Defense in 2005, noted that 'GPS is vital to the United States and to the DoD because, as a fundamental information system, it provides a common thread of precise position and time throughout our national security and economic infrastructures'. GPS can be considered, in a military context, as the 'fundamental information system' since it provides the synchronisation for all military command and communications systems, as well as precise navigation and targeting for both platforms and weapons systems globally.
The adoption of network centric and network enabled capabilities is accelerating the dependence on GPS. Such strategies, with their dependence on GPS synchronised data streams and precise GPS location and targeting, are raising GPS availability to mission-critical status.
GPS has helped transform risk on the battlefield. Tying GPS to weapons such as the joint direct attack munition (JDAM) – turning them into active systems – has cut down the number of attacks that have to be carried out on a single target. In today's battlefield – where the enemy employs more adaptive defence tactics – that saves lives, as pilots or other forces do not have to attack a target over and over again. GPS means one target, one weapon.
In the Vietnam War, allied forces attacking targets with unaided weapons were forced to revisit targets repeatedly. That allowed enemy forces to turn single targets into killing zones. Today, one GPS-aided active weapon would eliminate the target in a single strike.
GPS has also transformed legacy platforms and weapons systems, giving them startling new capabilities. In the Vietnam War, high altitude bombing was conducted in a way scarcely different from the Second World War. During the war in Afghanistan and in Operation Iraqi Freedom, high altitude strategic bombers have been used in a close air support role thanks to GPS, even being fitted to artillery shells to improve accuracy. The Excalibur Programme converts 155mm howitzer shells into active munitions in flight. Rounds carry a GPS system that can withstand 15g, activating and acquiring a GPS signal during their trajectory and completing programmed targeting, with accuracy better than 10 metres circular error probability.
Sometimes GPS is critical in subtle or hidden ways. Many military data communications and datalink systems use GPS for their timing synchronisation. Although such systems are separate from GPS, they could not function without it.
The US Military is developing a new concept called Joint Warfighting Space. This is designed as an agile programme to provide tailored theatre specific communications and navigation capabilities to enhance existing system capabilities. The concept calls for an adaptive satellite platform with a wide range of capabilities that can be customised and launched into orbit in just a matter of hours, and ready for use almost immediately. Such a system is planned to provide theatre commanders with battlefield navigation and communications specific to the needs of the terrain, coalition forces and likely enemy strategies.
As a close coalition partner of the US, GPS is increasingly widespread throughout British military units. British ships, submarines, aircraft and missiles all incorporate GPS navigational and synchronisation technologies. The replacement of inertial or laser guided munitions with GPS targeting – with a consequently greater improved circular error probability – has been a major factor in the RAF moving from a 1,000lb main munition to 500lb.
But the most prominent GPS related programme in the British military forces is Bowman, the British Army tactical radio system. Bowman is a key component of the Armed Forces' Network Enabled Capability and Future Integrated Soldier Technology strategies. In addition to tactical radio, it provides situational awareness and secured military intranet with protective measures such as frequency hopping spread spectrum. It can be seen as providing the bedrock of digitisation for the Army and the glue that will hold together the Command and Battlespace Management Strategy.
One of the key new features of Bowman is the Battlefield Information System Application (BISA), part of Bowman's associated framework architecture ComBAT Infrastructure and Platform (CIP). This will provide forces with a tactical data 'internet' on the battlefield. The BISA operates over the HCDR high-speed radio data backbone developed by ITT.
Bowman provides advanced situational awareness to battlefield commanders and troops via GPS. The Army states that access to such situational awareness is transforming the speed of action and decision-making on the ground.
Next generation GPS systems will incorporate advanced anti-spoofing technology, the Selective Availability Anti-Spoofing Module (Saasm). Anti-spoofing is seen as a critical element in Bowman, and a Saasm module is being provided to GDUK by Rockwell Collins.
Initial reports of the Bowman System were mixed, with some units testing the systems complaining of heavy power consumption, lack of ergonomics in the interface, and lack of application flexibility. More recent reports suggest that early problems are being ironed out and the potential of the system is beginning to become apparent.
Like many highly complex large IT projects, Bowman has been bedevilled by development issues and delivery delays. These have extended beyond the transfer of the programme to GDUK. Ultimately, they have led to a complete change in the way UK military technology is developed, tested and delivered, with implications for other MOD programmes.
Development and testing phases have been closely integrated, with feedback loops to allow development to expand on opportunities identified in the testing phases. This was achieved firstly at the module stage, and then expanded through a wide area network to cover all the individual collaborating contractors. Delivery of functionality has also been shifted from a 'Big Bang' to an incremental platform and module model, with new functionality delivered as module upgrades. The development of standardised 'synthetic environments' has allowed development and testing to become far more closely integrated and also interconnected between contractors. The adoption of capability releases, known as BCIPs, has allowed incremental roll-out of Bowman functionality.
Anti-Satellite Warfare and GPS
In January 2007, China shocked many by conducting an anti-satellite (Asat) test, using a ground-launched ballistic missile to conduct a kinetic kill against one of its high earth satellites. It was the first Asat test conducted by any nation since 1985. In an apparent parallel move, the Chinese deployed its latest Jian-10 fighters to airbases near to Taiwan. The aim of the Chinese exercise is widely considered to be to demonstrate its ability to deny the US and its allies – especially Taiwan and Japan – reconnaissance and GPS capabilities in the region in the event of a crisis.
In February 2008, the US used a modified tactical missile, the SM-3, to shoot down the malfunctioning USA 193 reconnaissance satellite. The SM-3 was fired from the USS Lake Erie, one the US Navy's newest Ticonderoga class guided missile cruisers in the Pacific Ocean west of Hawaii. The US test demonstrated that the US had the capability to deploy tactical force missiles against satellites and ballistic missiles, and a worldwide capability based on the US surface fleet.
The GPS constellation is seen as being a principal target of the Chinese Asat test. Official comments from the Japanese and Taiwanese Governments indicate their belief that the Chinese test was a demonstration that it could destroy US GPS and reconnaissance satellites during a period of crisis between China and Taiwan – the deployment of the Jian-10 fighters, at the same time, being interpreted as a clear Chinese signal. Some US analysts – although agreeing with the assessments – wonder if the Chinese would risk escalating a regional conflict with a strike against key US strategic assets, with the consequent risk of all-out war.
Anti-satellite warfare is hugely expensive and only available to a very few sophisticated nations. Since the 1990s, concern has mounted that battlefield GPS could be vulnerable to much simpler tactics – such as jamming. GPS jammers can be bought for under £100. That makes GPS jamming potentially available to any terrorist or insurgent group. Nations with greater technical capabilities – Iran or North Korea, for example – could devise far more powerful and sophisticated anti-GPS jamming technologies. In addition, non-nuclear radio frequency weapons could produce powerful electromagnetic pulse waves that would also threaten GPS-based command and control and weapons systems. Joint Vision 2020, the strategic planning document adopted by the US Joint Chiefs of Staff and Services in 2000, itemised both asymmetric low cost jamming and more sophisticated electronic anti-GPS threats as amongst the most serious dangers facing US forces in potential war theatres.
During the 2003 Iraq war, the Iraqi Military attempted to jam GPS with a network of six transmitters bought from the Russian company Aviaconversiya. All six were quickly discovered and destroyed – the last with a GPS guided bomb. One problem with the Russian transmitters was that they were very easy to detect and target.
China remains a more potent threat. In addition to its Asat activities, China appears, recently, to have deployed GPS jamming vans. In 1997, the RAND Corporation sounded the alarm in an internal report to the DoD – recently released under the Freedom of Information Act – over large-scale transfers of dual-use GPS know-how in joint ventures between US defence companies and Chinese firms owned by the Chinese Military.
A critical part of the GPS infrastructure is the Operational Control Segment (OCS), the software master control system based at Schriever Air Force Base. The 2005 Defense Sciences Board report into the GPS infrastructure expressed strong concerns about the state of the OCS system. According to the report, it is a patchwork of different pieces of software that has been neglected since the early 1990s. There are no common interfaces and the software comprises a 'combination of commercial off-the-shelf (COTS) and uniquely modified COTS products that are minimally adequate for maintaining system integrity'. Recent activity suggests that the OCS system would be subject to intensive cyber-warfare in the event of a future conflict.
In response to such threats, in 2000 the US Department of Defense initiated a testing programme; the Joint GPS Combat Effectiveness Joint Test and Evaluation programme (JGPSCE JT&E). Its remit was to study the potential impact of GPS degradation and loss on command and control, communications and weapons systems, and evaluate possible countermeasures.
Previous GPS loss studies had been limited and not very sophisticated. Most had simulated loss by either blocking or switching off GPS components within the systems, rather than emulating environmental GPS countermeasures such as Electronic Warfare (EW).
The JGPSCE exercise was far more extensive, studying the effects of a spectrum of GPS degradation from a range of countermeasures, including EW, Electromagnetic Interference (EMI) and Electromagnetic Pulse (EMP) on communications, command and weapons systems.
The JGPSCE study discovered that GPS degradation had widely varying effects on different systems. Since each system contained its own software – frequently both embedded and proprietary – its ability to tolerate degrees – or even a totality – of GPS loss was both unpredictable and peculiar to itself. The testing programme also discovered that frequently neither defence agencies nor the manufacturer had previously tested the systems for GPS degradation, despite their reliance upon it.
The US has developed a range of technologies and upgrades to GPS to counter-jamming efforts. A key vulnerability of GPS is the weakness of the signal, which could be drowned out by a jamming transmitter. To boost the GPS signal, the US has developed airborne pseudo satellites, or 'pseudolites', mounted on Global Hawk or Predator unmanned drones. Pseudolites capture the weak GPS satellite signal and boost it, relaying it at far higher power and closer range to local in-theatre forces. The pseudolites have special antennae and signal processors that allow them to capture the GPS signal accurately even with ongoing EMI or EW countermeasures.
Satellites within the GPS constellation are also being upgraded. While the GPS III system will carry advanced power and encryption technologies when it comes into service around 2013, current second generation GPS IIR satellites in the launch programme are being upgraded to the improved IIR-M standard. This includes flexible power, which can be increased to offset jamming attempts.
Anti-jamming is also being incorporated into receivers. This includes the GPS Antenna System-I (Gas-I) being produced by Raytheon Systems Ltd.
The GPS II constellation of satellites is ageing. Many are far past their mission lives of six years, and even their design lives of seven and a half years. Some are just one component failure away from shutdown.
From around 2013, these will begin to be replaced by an entirely new generation of GPS III satellites. GPS III will feature new navigational warfare capabilities to deprive opponents of GPS while safeguarding it for coalition forces. It will be far more powerful, and have advanced anti-jamming features as well as the ability to overwhelm anti-jamming broadcasts. It will also incorporate Blue Force Tracking (BFT), giving theatre and global commanders immediate views on the disposition of their forces.
GPS III will have about 500 times the transmission power of GPS II, and the ability to direct special capabilities and transmission power to specific areas through a high powered directional antenna system. The extra power and spot transmission mean that it will be able to overwhelm any local attempts at jamming, as well as proving unaugmented, real-time accuracy of one metre.
An alternative approach is to develop accurate GPS-free systems that can operate even if GPS is completely unavailable. The US Defense Advanced Research Projects Agency (DARPA) initiated two programmes that aim to do just that.
The Robust Surface Navigation programme (RSN) will exploit a landscape's existing radio characteristics. Signals from available civilian transmitters such as communications satellites, TV broadcast antennae and mobile phone masts will be assembled into a detailed radio map that should provide accurate positioning within three to seven metres – equal to enhanced GPS.
The Sub-Surface Navigation programme is designed to provide accurate positioning deep underground, within caves, tunnels or bunkers. Local radio transmissions from the RSN will be supplemented by natural phenomena such as lunar or solar gravity fields and geomagnetic noise, which can travel deep underground.
Both systems will utilise a software defined radio (SDR) system. The SDR will encapsulate all three modalities – GPS, RSN and SSN – switching or integrating each modality depending on signal and data availability. Together with GPS III, the SDR represents in all likelihood the shape of next generation military GPS technology.