Global Navigation Satellite System (GNSS)

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Global Navigation Satellite System (GNSS)

Postby FauSham » Sun Feb 01, 2009 7:33 pm

Global Navigation Satellite System (GNSS)
Selected and re-edited by FauSham from many resources as Informative sources for MFM Reader.

Did you know :D , we have many way to track our position?
Now let me explain....

What we are using right now is GPS or Geographic Positioning System :-' . GPS create by USA and early use just to USA army forces. Malaysia also used this GPS in MINDEF. This Global Positioning System (GPS) is a Global Navigation Satellite System (GNSS) developed by the United States Department of Defense. It uses a constellation of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave signals, which enable GPS receivers to determine their current location, the time, and their velocity. Its official name is NAVSTAR GPS.The GPS satellite constellation is managed by the United States Air Force 50th Space Wing.

We also have other positioning system and already been use by many countries. They are:
  • COMPASS (China)
  • GLONASS (Russia)
  • GALILEO (Europe)
  • IRNSS (India)

What is COMPASS or also known as Beidou-1 System or Beidou Satellite Navigation and Positioning System.
This system was develope by China in 2000 and start using it in 2007.Beidou 1A Satellite was launched on 30 October 2000, Beidou 1B followed on 20 December 2000, and Beidou 2A was put into orbit on 24 May 2003. The latest Beidou navigation satellite was successfully launched on 3 February 2007.In September 2003, China joined the Galileo positioning system project. China will invest €230 million ( :$gone: USD296 million, GBP160 million) in Galileo over the next few years. On November 2, 2006, China announced that from 2008 Beidou would offer open service with an accuracy of 10 meters. Till 2007, the resolution of Beidou navigation system already reached as high as 0.5m, thus China became the second country after USA which achieved < 1m resolution.

Beidou 1 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.To calculate a position, the following procedure is utilized:

  • A signal is transmitted skyward by a remote terminal.
  • Each of the geostationary satellites receive the signal.
  • Each satellite sends the accurate time of when each received the signal to a ground station.
  • The ground station calculates the longitude and latitude of the remote terminal, and determines the laltitude from a relief map.
  • The ground station sends the remote terminal's 3D position to the satellites.
  • The satellites broadcast the calculated position to the remote terminal.

The new system will be a constellation of 35 satellites, which include 5 geostationary orbit (GEO) satellites and 30 medium Earth orbit (MEO) satellites, that will offer complete coverage of the globe.

There will be two levels of service provided:
  • Free service for those in China
  • Licensed service for the military.

* The free service will have a 10 meter location-tracking accuracy, will synchronize clocks with an accuracy of 50 ns, and measure speeds within 0.2 m/s.
* The licensed service will be more accurate than the free service, can be used for communication, and will supply information about the system status to the users.

Two satellites for Beidou 2 have been launched in early 2007. In the next few years, China plans to continue experimentation and setup system operations.

The Global Navigation Satellite System (GLONASS) is based on a constellation of active satellites which continuously transmit coded signals in two frequency bands, which can be received by users anywhere on the Earth's surface to identify their position and velocity in real time based on ranging measurements. The system is a counterpart to the United States Global Positioning System (GPS) and both systems share the same principles in the data transmission and positioning methods. GLONASS is managed for the Russian Federation Government by the Russian Space Forces and the system is operated by the Coordination Scientific Information Center (KNITs) of the Ministry of Defense of the Russian Federation.The operational space segment of GLONASS consists of 21 satellites in 3 orbital planes, with 3 on-orbit spares. The three orbital planes are separated 120 degrees, and the satellites within the same orbit plane by 45 degrees. Each satellite operates in circular 19,100 km orbits at an inclination angle of 64.8 degrees and each satellite completes an orbit in approximately 11 hours 15 minutes.

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 St. Petersburg, Ternopol, Eniseisk, Komsomolsk-na-Amure.

The first GLONASS satellites were launched into orbit in 1982. Two Etalon geodetic satellites were also flown in the 19,100 km GLONASS orbit to fully characterise the gravitational field at the planned altitude and inclination. The original plans called for a complete operational system by 1991, but the deployment of the full constellation of satellites was not completed until late 1995 / early 1996.

GLONASS was officially declared operational on September 24, 1993 by a decree of the President of theRussian Federation. In January 2004 the Russian Space Agency (RSA) announced a joint venture deal with India's space agency,the Indian Space Research Organization, wherein the two government agencies would collaborate to restore the system to constant coverage of Russian and Indian territory by 2008 with 18 satellites, and be fully operational with all 24 satellites by 2010. Russia would build the satellites and that between 2006 and 2008 two satellites would be launched from India’s Satish Dhawan Space Centre in Andhra Pradesh state, using the Indian Geosynchronous Satellite Launch Vehicle (GSLV) rockets. India has yet to launch any satellites as part of this project. \:D/ During a December 2005 summit between Indian Prime Minister Manmohan Singh and Russian President Vladimir Putin, it was agreed that India would share some of the development costs of the GLONASS-K series and launch two of the new satellites from India, in return for access to the HP signal.

Galileo will be Europe’s own global navigation satellite system, providing a highly accurate, guaranteed global positioning service under civilian control. It will be inter-operable with GPS and GLONASS, the two other global satellite navigation systems. A user will be able to take a position with the same receiver from any of the satellites in any combination. By offering dual frequencies as standard, however, Galileo will deliver real-time positioning accuracy down to the metre range, which is unprecedented for a publicly available system. It will guarantee availability of the service under all but the most extreme circumstances and will inform users within seconds of a failure of any satellite. This will make it suitable for applications where safety is crucial, such as running trains, guiding cars and landing aircraft.
The first experimental satellite, GIOVE-A, was launched on 28 December 2005. The objective of this satellite is to characterize the critical technologies, which have already been developed under ESA contracts. Two further experimental satellites are planned: GIOVE-B, scheduled for launch end of 2007 and GIOVE-A2, to be ready for launch in the second half of 2008. The actual launch date of this satellite will be decided later, taking into account the situation of GIOVE-A and GIOVE-B.

Thereafter, four operational satellites - the basic minimum for satellite navigation in principle - will be launched by end 2008 / 2009 to validate the Galileo concept with both segments: space and related ground infrastructure . Once this In-Orbit Validation (IOV) phase has been completed, the remaining satellites will be installed to reach the Full Operational Capability (FOC).

The fully deployed Galileo system consists of 30 satellites (27 operational + 3 active spares), positioned in three circular Medium Earth Orbit (MEO) planes at 23 222 km altitude above the Earth, and at an inclination of the orbital planes of 56 degrees with reference to the equatorial plane. Once this is achieved, the Galileo navigation signals will provide good coverage even at latitudes up to 75 degrees north, which corresponds to the North Cape, and beyond. The large number of satellites together with the optimisation of the constellation, and the availability of the three active spare satellites, will ensure that the loss of one satellite has no discernible effect on the user.

Two Galileo Control Centres (GCCs) will be implemented on European ground to provide for the control of the satellites and to perform the navigation mission management. The data provided by a global network of twenty Galileo Sensor Stations (GSSs) will be sent to the Galileo Control Centres through a redundant communications network. The GCC’s will use the data from the Sensor Stations to compute the integrity information and to synchronise the time signal of all satellites with the ground station clocks. The exchange of the data between the Control Centres and the satellites will be performed through up-link stations. Five S-band up-link stations and 10 C-band up-link stations will be installed around the globe for this purpose.

As a further feature, Galileo will provide a global Search and Rescue (SAR) function, based on the operational COSPAS-SARSAT system. To do so, each satellite will be equipped with a transponder, which is able to transfer the distress signals from the user transmitters to the Rescue Co-ordination Centre, which will then initiate the rescue operation.At the same time, the system will provide a signal to the user, informing him that his situation has been detected and that help is under way. This latter feature is new and is considered a major upgrade compared to the existing system, which does not provide feedback to the user. When in operation, it will have two ground operations centers, one near Munich, Germany, and another in Fucino, 130 km east of Rome, Italy. Since 18 May 2007, at the recommendation of Transport Commissioner Jacques Barrot, the EU took direct control of the Galileo project from the private sector group of eight companies called European Satellite Navigation Industries, which had abandoned this Galileo project in early 2007.

Galileo is intended to provide more precise measurements than available through GPS or GLONASS (Galileo will be accurate down to the metre range) including the height (altitude) above sea level, and a better positioning services at high latitudes. The political aim is to provide an independent positioning system upon which European nations can rely on even in times of war or political disagreement, since Russia or the USA could disable use of their national systems by others (through encryption). Like with GPS, use of basic (open) Galileo services will also be free for everyone. However, more qualified services will be accessible with pecuniary or military restrictions.

Named for the Italian astronomer Galileo Galilei, the positioning system is officially referred to as just "Galileo". It is also sometimes colloquially described as the "Galileo positioning system"; however, since this abbreviates to GPS, the shorter astronomer's name is preferred to avoid confusion with the U.S. GPS. As with GPS, Galileo is just a sensor system that supports locating, there is no effector feature that would justify the positioning. However, as with all satellite navigation systems, the effecting of the desired course of a vehicle or other object on ground, at sea or in the air is subject of a combination of such sensor systems in combination with inertial navigation systems and propulsion and steering control systems.

Indian Space Research Organisation (ISRO) has taken up a project called Indian Regional Navigation Satellite System (IRNSS) for the establishment of an independent regional navigational infrastructure. The system main objective is to provide high positional accuracy (comparable to the existing constellations) real time position, velocity and time for various users in the region. IRNSS services will be available on a 24x7x365 basis irrespective of the availability of other constellations over Indian airspace. The system leverages the technological competence of ISRO in satellite, ground and other critical technologies

The Indian Regional Navigational Satellite System (IRNSS) is an autonomous regional satellite navigation system being developed by Indian Space Research Organisation, which would be under total control of Indian government. The requirement of such a navigation system is driven by the fact that access to Global Navigation Satellite Systems is not guaranteed in hostile situations.

IRNSS system provides dual frequency (S & L5 band) usage with a targeted position accuracy of less than 10 meters within India. At present one down link in S-band and three down links in L5 band are planned. The system can be augmented with local area augmentation for higher accuracy.

The government approved the project in May 2006, with the intention of the system to be completed and implemented by 2012. The first satellite of the proposed constellation, developed at a cost of Rupee 1,600 crore (16 billion rupees), is expected to be launched in 2009.

A goal of complete Indian control has been stated, with the space segment, ground segment and user receivers all being built in India. Three of the satellites in the constellation will be placed in geostationary orbit and the remaining four in geosynchronous inclined orbit.The navigation signals themselves would be transmitted in the S-band frequency (2-4 GHz) and broadcast through a phased array antenna to maintain required coverage and signal strength. The satellites would weigh approximately 1,330 kg and their solar panels generate 1,400 watts.

This IRNSS or Indian version of NAVSTAR, the US-run global positioning system, is expected to be functional by 2012 and India planing to build a constellation of 7 navigation satellites by 2012.

India also plan to build The ground segment consists of MCC, INRSS Ranging and Integrity Monitoring (IRIM) Stations and IRNSS telemetry and command stations. The function of MCC is to estimate and predicts the ephemeris; calculate corrections for SV clock & maintain IRNSS time, Ionospheric corrections and Integrity. The function of IRNSS IRIM stations will be receiving the data from the GEOs and GSOs, transmit the data to MCC and one way ranging of the GEOs & GSOs in S band. The function of IRNSS telemetry and command stations will be to receive telemetry from the IRNSS constellation, Telecomm and the IRNSS constellation and navigation updates.
FauSham @ Malaysia & Singapore Free Maps - MalFreeMaps

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