Global positioning system means more than location

By Loring Wirbel
EE Times
September 20, 2004 (9:08 AM EDT)

The global-positioning system has become a Swiss army knife of space-based navigational services, used for everything from pinpointing location for emergency response to synchronizing third-generation (3G) cellular basestations.

The wealth of civilian and military applications already found for the 29-satellite constellation of navigational units will be enriched even further when satellites with a new suite of signals are launched beginning in 2005, improving the system’s accuracy. And when enhancements now slated for 2012 are made, the system, which is managed out of Schriever Air Force Base near Colorado Springs, Colo., promises to increase in accuracy from the current 10 meters down to 30 to 50 centimeters.

The current global market of applications and services, in excess of $3 billion, could grow to $10 billion by 2010, according to Frost & Sullivan.

The mainstream location-based services of GPS have become all but mundane. More than 5 million GPS consumer recreational units were shipped in 2003, according to ABI Research (formerly Allied Business Intelligence), up from 3.2 million units in 2002. New applications that are making everyday use of GPS signals range from the OnStar automobile service to Microsoft Corp.’s Streets and Trips 2005. The latter includes a GPS receiver for laptops, using a USB port to link Microsoft’s previous mapping application to a position finder.

Industry applications range even wider, from geodetic surveys to the accurate basestation synchronization described by Symmetricom Inc. in this In Focus section. Some uses span military and civilian applications, such as GPS transceivers used in tracking other satellites in space, as Peregrine Semiconductor Corp. points out here.

The application base now extends beyond hiking-and-fishing consumer aids, partly because military GPS signals were unblocked by the Clinton administration in May 2000. The accuracy of a sub-$100 consumer receiver increased from 100 meters to about 10 meters. At that time civilian corporations that were gaining better industrial accuracy through differential comparison of GPS signals from the ground found they could achieve sub-10-meter position accuracy far more cheaply than before.

Upgrades to GPS will be coming in three waves. By the end of September, with the launch of GPS-IIR-13, there will be an all-time high of 30 GPS satellites in space, consisting of 24 active birds and six on-orbit spares. They reside in six orbital planes. Receivers obtain coordinates in three dimensions plus time stamps by “trilaterating,” or triangulating, distances from at least four GPS satellites, which actively broadcast signals in orbit.

Major upgrade
Beginning next March, the Lockheed Martin Corp. GPS IIR-M, for “modernized,” will add a new military code to the GPS transmissions, while the Boeing GPS-IIF (“follow-on”) will begin launches in 2006, with additional signals in both military and commercial frequencies. The most significant evolution in GPS architecture will come with GPS III (not to be confused with a consumer receiver of the same name), which will add major security, accuracy and availability features when the first satellite is launched in 2012.

The current generation of IIA/IIR satellites utilizes two microwave frequencies, the civil L1 and military L2. Since May 2000, civilian users have had access to the L2 frequency, albeit without knowing the L2 pseudorandom codes, and the military has always used both frequencies. When IIR-M launches next March, a second civil signal will be added in the L2 band, while two new military codes will be added to both L1 and L2. The IIF satellite will add a third civil signal on a band called L5, since bands L3 and L4 will be reserved for military uses outside traditional navigational duties.

The addition of the new bands will make dual-band navigation on civil frequencies more robust and less costly, since current use of L1 and L2 for commercial applications involves costly DSP resources to calculate L2 signals when pseudorandom noise codes are not known. The users of differential GPS (D-GPS) rely on a stationary reference receiver and a roving receiver to make ground-based corrections on satellite triangulation. Before the May 2000 unblocking of L2, D-GPS was the only means of commercial resolution of location in areas under 10 meters.

When IIR-M and IIF satellite frequencies are added, D-GPS will offer a position accuracy of 30 to 50 centimeters.

New services
Such accuracy will be of most interest to demanding commercial users in aviation, farming, public services, geodetic surveys and small-scale mapping. But it also will enable a variety of new services, including location-based advertising to augment existing 2.5G and 3G services, and even sophisticated personal surveillance tools.

The availability of such precise locators may have social implications as well. In early September, a southern California man earned the dubious distinction of being the first person to be arrested for “stalking” using GPS, a capability that will be enhanced significantly with the more accurate civil frequencies on the horizon.

The military implications for the evolution of GPS, meanwhile, are inescapable. The Pentagon made very clear during the early days of the Iraq war that it sees GPS as a war-fighting weapon system, to be used to guide everything from ships and jet fighters to individual precision-guided munitions like the Joint Direct Attack Munition.

The speed with which airborne raids took out a rudimentary Iraqi anti-GPS jammer, and the degree to which the Pentagon touted such jamming as an offensive action, show both how seriously space warfare advocates consider measure/countermeasure battles using GPS, and also how utterly U.S. forces dominate air and space. Indeed, GPS III plans often are referred to as “NavWar” within the Air Force Space Command.

The Defense Department is looking to GPS III as an enabler for maintaining navigational dominance over emerging systems like the European Space Agency’s Galileo network, while still keeping the GPS system as open as possible.

In some senses, however, GPS migration to II and III resembles the migration to new generations of the Milstar VHF/EHF communications satellite: There’s a lot of talk about maneuverability and survivability, but not a lot of detail in the plans, even for those with the proper security clearance.

GPS III is a going concern, in that competing teams led by Lockheed Martin and Boeing have submitted data for Phase A of the design effort, leading to a system requirement review slated for next spring, and a decision on system go-ahead in November 2005. Assuming a positive review is issued next November, the Air Force will request proposals for Phase B in early 2006.

Networked warrior
But GPS III barely survived some tough budget juggling between the Afghanistan and Iraq wars, as Congress tried to balance demands between future weapon systems and current troop deployments. Air Force Undersecretary of Space Peter Teets originally agreed with Congress that no funding would be allocated to GPS III in fiscal 2004, because the Air Force was more interested in gaining initial funding for two new programs promoted by the National Reconnaissance Office: Space-Based Radar and Transformational Communications Satellite, or TSAT.

Then along came the war in Iraq: GPS capabilities were cited constantly as the way to provide the backbone for the “networked warrior,” and to enable precision bombing over Baghdad and Tikrit. During the fiscal 2005 budget process, the Air Force received its full request of $40.5 million for GPS III. By contrast, Space-Based Radar and TSAT have been put on hold by a skeptical Congress, worried that the two new programs are so revolutionary, they will fall victim to the same massive cost overruns that plagued the Space-Based Infrared System, known as SBIRS-High.

If the past is any guide, the capabilities provided to the military in initial launches will be translated to broad and unanticipated civilian applications 10 to 20 years later.

But the Pentagon’s wish list for GPS III is still far from formulated. Even if the first GPS III satellite meets its 2012 target, the gap between the first GPS I launch in 1978 and the early civilian applications around 1990 would suggest that the radical upgrade in civilian position-location service resulting from GPS III might not show up until 2025.

http://www.eet.com/in_focus/communications/showArticle.jhtml?articleID=47212329

Arun posted this article in BR
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from the chart many wud be indeed surprised that the Russians are still sending comparatively large amounts of satellites, but as usual their marketing is poor, else, they shus by now have made good sums with their GLONASS ……. I wud say Indian sud conver all their guidance to the GlONASS from the GPS and later on with a dual GLONASS and GALILEO …… and that said I’d prefer India to invest in a joint venture and expanding the current Russian ones so as for use of both nations exclusively

enlarge the figure and it wud be much clear to distinguish ..

here is small article abt the various missile guidance …..

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THE GLOBAL POSITIONING SYSTEM (GPS)

Satellite navigation systems provide a highly accurate means of determining the precise position of an object on or over the earth’s surface. Accurate satellite data allows a cruise missile to receive regular mid-course updates which counteract the drift inherent in traditional gyroscope-based inertial navigation systems (‘INS’). Packaged with even a simple INS, satellite navigation systems give a cruise missile accuracies of between 10 and 100 metres.

Two satellite navigation systems are currently being established. The United States has recently completed its Global Positioning System (‘GPS’); its Russian equivalent is the Global Navigation Satellite System (‘GLONASS’).

The US GPS consists of twenty four NAVSTAR satellites in polar orbit (three of which are back-ups), a network of ground stations which constantly check and maintain the accuracy of the satellite data, and the necessary receiver units which translate the satellite data into precise positional information. The system can be used to obtain both horizontal (latitude and longitude) and vertical (altitude) fixes. Signals from three satellites are needed to obtain horizontal fixes, the signal from a fourth to obtain the vertical fix and give a complete three-dimensional position. If the receiver picks up data from more than four satellites, the accuracy of the fix is increased.

Although the GPS was originally intended to be used for purely military applications, the shooting down of an off-course Korean commercial airliner by Soviet fighters in 1983 led President Reagan to direct that it be made available for commercial users.

The commercial Course/Acquisition (‘C/A’) Code is openly available, and was intended to give accuracies of between 30 and 100 metres. However, when it became clear that in practice the C/A code was accurate to nearer 10 metres, the US Department of Defense introduced Selective Availability (‘S/A’), which deliberately reduces the accuracy of the signal (‘degrades’ it) to some 100 metres in the horizontal plane and 140 metres in the vertical. It is claimed that S/A fixes will be accurate 95% of the time, yet in circumstances when an optimal configuration of four or five satellites is not ‘visible’ to the receiver it is possible that this accuracy may fall to around 300 metres.

GPS accuracies are expressed in terms of dRAMS, one dRAM being a 2.5% probability of inaccuracy. The accuracy of the S/A code is defined as 100 metres with a 2 dRAMS confidence. This means that 95% of fixes will be accurate to within 100 metres of the actual position. It does not, however, follow that a missile guided by S/A code would achieve a Circular Area Probable (‘CEP’) of 100 metres: dRAM has a 95% confidence level and CEP a 50% confidence level, therefore the two figures cannot be interchanged. As the 2 dRAM S/A GPS fix equates to a CEP four tenths as large, the CEP of a cruise missile utilising the S/A code would be approximately 40 metres (i.e. 50% of missiles fired would arrive within 40 metres of the target).

Although the full implementation of the Russian GLONASS has slowed since the break up of the Soviet Union, it should offer a very similar service to its US counterpart. Like the GPS, GLONASS consists of twenty four satellites which transmit both military and civilian signals of comparable accuracies to the GPS P and C/A codes. Whilst the two systems operate slightly differently, integrated receivers accessing signals from both networks will reportedly give accuracies of some 20 metres, effectively circumventing US efforts to degrade the S/A code.

DIFFERENTIAL GPS

The data transmitted by GPS can, however, be significantly upgraded by a process known as Differential GPS (‘DGPS’). This relies on a second receiver, known as the reference receiver, located in a precisely-determined spot, broadcasting a correction signal on a different frequency to the other GPS receiver. This can be effective even if the two receivers are more than 1,000 km apart, and makes it possible for users of the military P-code to attain fixes accurate to between 75 cm and 5 metres. S/A code can be improved by a factor of ten, to between 2 and 5 metres.

Although this technology is only just beginning to emerge, it is already utilised for surveying, maritime safety and civilian aviation applications. The integration of DGPS into cruise missile guidance systems is certainly feasible, although this would require that reference updates be transmitted through a data link to the missile in flight via a mother plane or ground station. However, given that DGPS reference stations are being constructed along the coast of the United States and their signals broadcast by way of other satellites, it appears likely that its accessibility will grow.

Integrated into a cruise missile, these navigation systems will enable developing nations to perform a technological leap-frog. Israel already claims that its GPS-equipped Delilah RPV can reportedly attain accuracies of less than 100 metres, and India is working to adapt GPS for both its cruise and ballistic missile programmes. Pakistan, China and Iran are also reported to be seeking means of integrating GPS into RPVs and missiles. Although the degrading of codes from GPS and GLONASS should, in theory, prevent developing nations from developing cruise missiles with accuracies better than 100 metres, this is likely to be circumvented by further advances in technology. Likewise, whilst GPS signals can be jammed using electronic countermeasures, this may not prove practical in all circumstances. However, the GPS S/A code can, if necessary, be switched off, as was the case during operation Desert Storm and during the US invasion of Haiti.

INERTIAL GUIDANCE

Inertial Guidance or Inertial Navigation Systems (‘INS’) use gyroscopes and accelerometers (which detect motion) to calculate changes in relative positions. Wholly independent of any external signals or support, they cannot be jammed or affected by electronic countermeasures.

The disadvantage of INS is its inherent inaccuracy, making it unsuitable for use as the sole guidance system in a cruise missile. Gyro-scopes are subject to errors which accumulate over time – the longer the flight time, the greater the error. The INS fitted to the US Tomahawk drifts by 900 metres per hour. At its cruising speed of 800 km/hr and a distance of 1,600 km, this inertial drift equates to an error of 1,800 metres, necessitating the use of supplementary guidance systems such as Terrain Contour Matching (TERCOM) or GPS.

Whilst gyroscopes used to be sensitive mechanical devices, Ring Laser and Fibre Optic Gyroscopes are becoming increasingly common; the US company Northrop has developed a micro-optic gyro which places an entire INS on a computer chip. Nonetheless, the 10 degree per hour drift claimed for this system is still too high for cruise missile guidance, and any system so equipped would require regular positional updates from external sources such as GPS in order to achieve the accuracy necessary for a precision strike.

TERCOM GUIDANCE

Terrain Contour Matching (‘TERCOM’) was first patented in 1958, but it was not until the development of micro-electronics in the 1970s that practical TERCOM systems first appeared.

A pre-requisite for TERCOM is the ability to generate electronic maps from high-resolution satellite images. These are digitised and stored in the system’s memory across a matrix of cells. Each cell covers a set area of ground and is allotted an average elevation. A radar-altimeter is used to compare the elevation of the terrain over which the missile is flying with the elevation data in the on-board maps. This establishes the position of the missile and makes any necessary corrections to its inertial navigation system. Using this technique, TERCOM can achieve accuracies of 30-100 metres.

During the missile’s flight, TERCOM readings are not taken constantly. Rather the INS flies it from one area of distinctive topography to another, where more readings are taken and the missile’s heading is corrected if necessary. These are known as ‘waypoint fixes,’ and can also be used to introduce unpredictable changes in the missile’s flight path, allowing it to avoid enemy radar and air defences. But because TERCOM relies on elevation data for its waypoint fixes, over largely flat terrain the missile may have to fly a circuitous route from feature to feature, reducing its overall mission range.

Each waypoint fix utilises a different map, and whilst each contains the same number of cells, the first maps used cover a larger overall area – and thus contain less detail in each cell – than each subsequent map, giving an ‘accuracy funnelling’ effect as the target is approached.

The real technical difficulty with TERCOM lies not with the guidance system itself, but in the technical infrastructure needed to create the digitised maps. For TERCOM-guided cruise missiles to be effective, databases must be built up of every part of the world in which they might potentially be used. The cost of this exercise to the US is estimated to approach the total investment made in TERCOM-equipped cruise missile hardware. Even so, it is reported that following the Iraqi invasion of Kuwait in 1990, the US military had to embark upon a crash programme to prepare data for the TERCOM guidance systems of its Tomahawk TLAMs.

This reliance on space technology to support TERCOM has hitherto ensured that only the US and Russia have deployed TERCOM-guided cruise missiles. However, the increasing availability of commercial satellite imagery from SPOT and Landsat, together with the growing sophistication of computer aided design (CAD) software means that the ability to produce digitised maps may no longer be beyond the reach of potential proliferators.

STEALTH TECHNOLOGY

‘Low Observable Technologies’, popularly known as ‘Stealth’ technologies, are a range of related technologies whose intent is to avoid or minimise an object’s radar reflectivity.

Perhaps the best known application of Stealth technology is in the US F-117 ‘Stealth’ fighter, which was able to bomb targets in Iraq during the 1991 Gulf War without being detected by the air defence system.

The peculiar shape of stealthy bodies such as the F-117 and B-2B is a result of the advanced geometric design techniques necessary to minimise their radar cross section (‘RCS’). Curving surfaces on conventional aerodynamic bodies act as isotropic scatterers, reflecting radar waves from any angle and giving the radar operator a clear signal. The right-angled surfaces at the wing and tail roots also reflect radar signals straight back to their source.

A stealthy airframe, however, is composed of a series of flat plates, or facets, none of which lies in the same plane or has the same orientation. This prismatic shape means that if the body is illuminated by radar, only the surface segment that is directly perpendicular to the beam reflects back to the radar. The other facets split the radar waves and direct them away from the radar emitter. As only the reflection of a single faceted surface is returned to the radar receiver, the RCS of the body appears far smaller than its actual physical size.

In addition to these design techniques, a host of materials technologies can further reduce detectability. Known as Radar Absorbing Materials (‘RAM’), these utilise carbon, ferrites, graphite and particularly carbon-fibre composites to absorb radar waves.

Lightweight nonmetallic composites or re-inforced polymers that allow radar waves to pass through them with minimal reflection can be used in airframes. Flight-control surface can be made from honeycombed materials which reflect incoming radar waves internally rather than back to the radar. Metal components such as the engine, which produce significant radar reflections, can be shielded using a metal and plastic sandwich whose layers are spaced in such a way as to create a standing wave, cancelling out any radar reflections. Radar-absorbing coatings can be applied to the surface of the body which effectively drain the energy of the radar signal, and the heat signature generated from the engine can be ‘cloaked’ by an infrared-suppression system which mixes cool air with the hot engine-exhaust gases.

The effect of these techniques can be dramatic. A conventional fighter aircraft has an Radar Cross Section (RCS) in the region of 6 square metres. The much larger B-2B bomber, using the latest stealth technology, displays an RCS of only 0.75 square metres. Incorporating stealth technology into an object that is already as small as a cruise missile can render it all but invisible to conventional radar. The Tomahawk ALCM, designed in the 1970s utilising the simple low observable technologies then available, has an RCS of some 0.05 square metres, whilst advanced ‘stealthy’ cruise missiles such as the US AGM-129A will display an even smaller RCS. By comparison, a bird in flight displays an RCS of 0.01 square metres.

The value of stealth technologies to cruise missiles is that it makes them even harder to detect and intercept. Surface-to-Air Missiles (‘SAM’) depend heavily on the ability of their fire control radars to detect and lock onto their target. Cruise missiles with radar cross sections of less than 0.1 square metres are difficult to track by radar, and even if a SAM battery can detect the missile, it may not be able to lock onto the target accurately enough in order to engage it.

SUBMUNITIONS

Submunitions are warheads containing of a number of small devices or ‘bomblets’ designed for specialised roles such as anti-airfield or anti-personnel. Examples include the British JP-233 air base attack bomb which contains devices to penetrate and explode in concrete and anti-personnel mines to prevent repair.

Cruise missiles such as the French Apache and variants of the US Tomahawk can be equipped with a variety of submunitions warheads. Because a cruise missile is similar to a manned aircraft, submunitions designed for delivery by conventional strike aircraft can be adapted for use in cruise missiles with relative ease.

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the GPS now has got 30 satellites with 5 as reserve

This is why so many air forces outside Russia do not feel the cobra or hook are valid aircombat maneuvers. You are limited in your entry speed and once you perform it your aircraft has no energy, which makes you a real target!

And for that it is performed at a decently high altitude so as to dive to gain energy after the Cobra so that your target is beautifully placed with a clear sky as background, won’t that be a Good shot?

Again coordinated to —–

http://forum.keypublishing.co.uk/forumdisplay.php?f=18

and if possible merge it with the Russian cruise missile thead

At ur service always, except for some buffalos … appologise to the poor animal for using it …

tonnage armaments eetc etc??

Terran that was a grr8 fine, really good one, seems like a grr8 stuff, must have learnt a lot from the Russians

ha ha ha ….good one