Nuclear Detonation Detection System Since 1980, GPS satellites have carried a secondary payload consisting of nuclear detonation sensors that provides near-real-time three-dimensional location of nuclear detonations. The GPS Nuclear Detonation Detection System is managed as a joint program of the U.S. Air Force and the Department of Energy (DoE). The Nuclear Detonation (NUDET) Detection System (NDS) provides subsist capability to detect, locate and report any nuclear detonations in the earth's atmosphere or in near space in near-real time.
GPS Based Atmospheric Sounder (GRAS)Occultation methods based on effects connected with the refraction of electromagnetic waves in both the optical and astronomers for numerous investigations of planetary atmospheres over the last decades. The GNSS radio occultation technique is based on a satellite-to-satellite limb-sounding concept using GNSS signals to probe the Earth's atmosphere. The propagation of the electromagnetic signals is influenced by the atmospheric and ionospheric refractivity field resulting in slowing and bending of the signal. In order to investigate the climate change detection capability of GNSS occultation sensors, the excess phase path as the principle observable is measured with millimetric accuracy. It is the basis for high quality retrievals of atmospheric key climate variables such as temperature and tropospheric water vapor. Further products include geopotential or pressure as well as ionospheric electron density. A major benefit of GRAS project includes the trend in Numerical Weather Prediction towards using variation assimilation. Because of the low horizontal resolution, GRAS observations is expected to be most valuable in global forecasting over short-to-medium range (1–10 days). They also have a positive impact on regional and mesoscale forecasting by providing information over the sparsely observed ocean areas. Study of the heat exchange between the stratosphere and troposphere requires accurate measurements of the temperature profile across the tropopause. This phenomenon holds good at tropical latitudes and in regions where the sparse radiosonde network cannot provide enough data for the verification of theories and models. The very good temperature-measurement accuracy provided by GRAS at the locations where no permanent radiosonde or LIDAR measurement network exists will enable the verification and further study of many atmospheric theories and models. An end-to-end GNSS occultation observing system simulation experiment is presently happening for over 25-year period (2001 to 2025).
ROAD MAP OF POSITIONAL SATELLITESGLONASS Global Navigation Satellite System(Global Navigation Satellite System) is a radio satellite navigation system, the Russian counterpart to the United States GPS system and the European Union's embryonic Galileo positioning system. It is operated for the Russian government by the Russian Space Forces. At peak efficiency the system offers a standard positioning and timing service giving horizontal positioning accuracy within 55 meters, vertical positioning within 70 meters, velocity vector measuring within 15 cms and timing within 1 µs, all based on measurements from four satellite signals simultaneously. However, a higher accuracy signal is available for Russian military use.
Like GPS, the complete GLONASS constellation project also consists of 24 satellites, 21 operating and three on-orbit 'spares' placed in three orbital planes. Each plane contains eight satellites identified by "slot" number, which defines the corresponding orbital plane. The three orbital planes are separated by 120°, and the satellites equally spaced within the same orbital plane, ie 45° apart. The GLONASS orbits are roughly circular, with an inclination of about 64.8°. GLONASS constellation orbits the Earth at an altitude of 19,100 km (slightly lower than that of the GPS satellites). Each satellite completes an orbit in approximately 11 hours, 15 minutes. The spacing of the satellites in orbit is arranged so that a minimum of 5 satellites are in view at any given time. GLONASS satellite transmits two types of signal, standard precision (SP) and high precision (HP). A characteristic of the GLONASS constellation is that the satellite orbits repeat after 8 days. As each orbit plane contains 8 satellites, there is a non-identical repeat (i.e., another satellite will occupy the same place in the sky) after one sidereal day. This differs from the GPS identical repeat period of one sidereal day. 16 satellites are in operation by now. Following a joint venture deal with the Indian Government to launch two GLONASS-M satellites on its GSLV rockets, it is proposed to have the system fully operational with 18 satellites by 2008, providing full coverage of Russia territory, and with all 24 satellites by 2010.
GALILEO 
The positioning system is a proposed satellite navigation system, being built by the European Union (EU) as an alternative to the US military-controlled Global Positioning System and the Russian GLONASS. The system should be operational by 2010, two years later than originally anticipated. It is named after the Italian astronomer Galileo Galilee. The Galileo is intended to provide:
- Greater precision to all users than is currently available.
- Improved coverage of satellite signals at higher latitudes.
- A global positioning system that can be relied upon, even in times of war.
In 1999, the different concepts for Galileo (from France, Germany, Italy and United Kingdom) were compared and finalised by a joint team of engineers from all four countries. The system is designated primarily for civilian use. The European system will not be subject to shutdown for military purposes (though it may still be jammed by anyone with the right equipment), will provide a significant improvement to the signal available from GPS. On completion, it will be available at its full precision to all users, both civil and military. The European Union member states became strongly in favour of the Galileo system in late 2002 and the project has been appropriately funded. The planned number of satellites is 30, to be launched during the period 2006–2010. The final cost is estimated at Euro 3 billion, including the infrastructure on earth, which is to be constructed during 2006-07. At least two thirds of the cost will be invested by private companies and investors, the remaining costs are divided between the European Space Agency and the European Union. An encrypted higher bandwidth Commercial Service with improved accuracy will be available at an extra cost, while the base Open Service will be freely available to anyone with Galileo compatible receiver. The European Union has agreed to switch to a range of frequencies known as Binary Offset Carrier 1.1 (June 2004), which will allow both European and American forces to block each other's signals in the battlefield without disabling the entire system. The former US Secretary of State Colin Powell signed the pact with Loyola de Palacio, EU Transport Commissioner, at the EU-US summit at Dromoland Castle, Ireland to this effect. The change will allow either side to effectively jam the other's signal in a small area, such as a battlefield, without shutting down the entire system. More importantly from the civilian perspective, the agreement allows the systems to be meshed seamlessly, greatly benefiting manufacturers, service providers and consumers.
Services
The Open Service (OS) will be free for anyone to access. The OS signals will be broadcast in two bands, at 1164–1214 MHz and at 1563–1591 MHz. Receivers will achieve an accuracy of <4 m horizontally and <8 m vertically if they use both OS bands. Receivers that use only a single band will still achieve <15 m horizontally and <35 m vertically, comparable to what the civilian GPS service provides today. It is expected that most future mass market systems will process both the GPS and the Galileo OS signals, for maximum coverage.
The encrypted Commercial Service (CS) will be available for a fee and will offer an accuracy of better than 1 m. The CS can also be complemented by ground stations to bring the accuracy down to less than 10 cm. This signal will be broadcast in three frequency bands, the two used for the OS signals, as well as at 1260–1300 MHz.
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These services are largely compatible with existing GPS services, and it is expected that users may demand the added signal reliability, integrity, and functionality that a combined GPS and Galileo capability will provide when used together. Typical advantages to a user of a receiver utilising both systems will include:
- Twice as many satellites means twice the probability of receiving good signals from good parts of the sky even when visibility is reduced, ie, in a valley or in an urban centre.
- Cars in cities will have more signals and will suffer less from signal blockage.
- Surveyors will be able to make higher accuracy measurements consistently.
- Automated guidance for harvesters and sprayers will be more accurate.
- Difficult off-shore navigation will be safer and more reliable.
- The final approach and landing systems will have far greater signal redundancy providing improved safety.
GALILEO SYSTEM
- 30 spacecraft
- Orbital altitude: 23222 km (MEO)
- 3 orbital planes, 56° inclination (9 operational satellites and one active spare per orbital plane)
- Satellite lifetime: >12 years
- Satellite mass: 675 kg
- Satellite body dimensions: 2.7 m x 1.2 m x 1.1 m
- Span of solar arrays: 18.7 m
- Power of solar arrays: 1500 W (end of life)
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International involvement. During last few years, China, Israel, India, South Korea, Ukraine, Morocco and Saudi Arabia have joined the Galileo project. There is speculation that other countries might also join the Galileo project, including Argentina, Australia, Brazil, Canada, Chile, Japan, Malaysia, Mexico, Norway, Pakistan and Russia.
'Beidou' Navigation SystemThe Beidou Navigation System is a project of People's Republic of China to develop an independent satellite navigation system. "Beidou" is the Chinese name of the Ursa Major constellation. Beidou 1A was launched on 30 Oct 2000 and Beidou 1B followed on 20 Dec 2000. China plans to complete the system with a second pair. Beidou 2A was put into orbit on 24 May 2003. Unlike the GPS, GLONASS, and Galileo systems, Beidou uses satellites in geostationary orbit. This means that the system does not require a large constellation of satellites, but it also limits the coverage to areas on Earth where the satellites are visible. With the third launch, China claimed to have completed a constellation of three navigational satellites. The Beidou satellite navigational system provides positional information for highway, railway and marine transportation. The three satellites have formed complete satellite navigation and positioning system, which helps to ensure all-weather navigation and positioning information. The China-made system will play an important role in economic matters, offering efficient navigation and positioning services.. China is one of the few countries in the world capable of developing such a system on its own, and perhaps has also made some innovations in the positioning properties of the system.
European Geo-stationary Navigation Overlay SystemThe European Geo-stationary Navigation Overlay System (EGNOS) is a satellite navigation system under development by the European Space Agency, the European Commission and EUROCONTROL. It is intended to supplement the GPS and GLONASS systems by reporting on the reliability and accuracy of the signals. According to specifications, horizontal position accuracy should be better than 7 meter. It will consist of three geo-stationary satellites and a network of ground stations. It was intended to be operational in June 2005, but due to delays the date has been pushed to 2006. It is planned as a precursor to the Galileo positioning system. EGNOS offers all users of satellite radio navigation high-performance navigation and positioning service, superior to that currently available in Europe. The system is composed of three transponders installed in geostationary satellites and a ground network of 34 positioning stations and four control centres, all interconnected. EGNOS will be used foremost for safety-critical transport applications
RATIOCINATIONIn future, the combination of globalisation, real time, repetivity and synergetic processing of data with precision will be needed for decision making. The space exploration dreams are becoming a reality with dozens of countries channeling their major resources to space programme. The future applications from civil to military would be demanding better and better accuracy. Today, the challenge on the space front is to build from dreams & concepts to new technologies & destinations with the constant will to move forward. The space applications having unique characteristics are to be used for meeting enduring challenges of the 21st century.
References & AcknowledgementAll the images are taken from open sources; the text is based on the respectively authenticated documents related to policies, discussion & decision papers (D&D), and project presentations, available in the open domain. Authors acknowledge the contribution of Mr Anguraj Ganeshan and Ms Jasbir Sandhu in helping undertake comprehensive research in SBPN systems. For further lucubrated readings:
- Astrometric Positioning Of Geo-stationary Satellites by T. L_opez Moratalla, C. Abad, F. Beliz_on, J. C. Coma, F. J. Montojo, J. L. Mui~nos, J. Palacio,1 and M. Vallejo
- GPS and pseudo-satellites integration for precise positioning by Jinling Wang, Toshiaki Tsujii, Chris Rizos, Liwen Dai, Michael Moore
- New U.S. GPS Policy From a European Perspective
- U.S. space-based positioning, navigation, and timing policy
- United States Space Policy Challenges and Opportunities; George Abbey & Neal Lane
- Towards a European Space Policy The European Commission and the European Space Agency Joint Task Force Report
- The SpaceShuttle & GPS,A Safety-Critical Navigation Upgrade by John L. Goodman
- Analysis of GPS satellite allocation for the united states nuclear detonation detection system (USNDS) a thesis by Aaron j. bell,
- GPS history, chronology, and budgets,
- Possible Scenarios For Accidental Or Unauthorized Nuclear Use,
- Technology collection trends in the U.S. Defense , I
- Recent And Future Developments In Global Navigation Satellite Systems And Their Impact On National Geoinformation Infrastructures by Professor Paul Cross.
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