Present Generation Systems
The present generation satellite navigational systems are more direct. The satellite broadcasts a signal with exact time of transmission and the position of the satellite. ‘The receiver compares the time of broadcast encoded in the transmission with the time of reception measured by an internal clock, thereby measuring the time-of – flight to the satellite. Several such measurements can be made at the same time to different satellites, allowing a continual fix to be generated in real time’ . The system overcomes various technical limitations like cases of fast-moving receivers. Errors are reduced by the various filtering techniques.
Globally, the best known satellite navigational system is the GPS (global positioning system). This US system has almost become synonymous with satellite navigation. Built under the US NAVSTAR programme in 1973, the GPS satellite constellation began with the launch of its first four satellites in 1978. It has brought about significant changes in military tactics and has also created new applications for the civilian use with a significant economic dimension. The GPS can be viewed as an application that covers almost every discipline of modern technology. It is said that GPS could be the next utility, like electricity, running water and the telephone, and could become a part of everyone’s daily life. The applications of this new high-tech capability are limited only by our imagination. GPS-based products will likely fuel the next economic expansion of the free world . In 1983, the then US president, Roland Reagan offered the GPS civil services to the world, free of direct charges in the aftermath of the loss of the KAL 007.
The two other systems apart from the GPS are the two major constellations, namely, the Russian GLONASS and the European Union’s (EU) GALILEO. The GLONASS went on to the drawing board in the mid-1970s while the launching of satellites began in the 1980s. There were 12 functional satellites when the USSR disintegrated in 1991. This constellation has witnessed various ups and downs mainly because of the Russian financial constraints. However, with improvement in its economic condition post 2000, Russia’s investments in its space programme in general and GLONASS in particular started increasing. Presently, the third – generation GLONASS-K programme is underway and is nearing global coverage. Russia currently has 22 fully operational GLONASS satellites in orbit. The complete GLONASS grouping must have 24 operational and 2-3 reserve satellites for it to have global coverage.
GALILEO is the global navigational satellite system being developed by the EU and European Space Agency (ESA). This twenty-first century system expected to the best in world is hampered by financial problems and has missed various deadlines till date. This system is mainly meant for civilian purposes and was initiated in 2003. On Oct 21, 2011 the first two European Galileo satellites intended to form part of the future 30-satellite navigation constellation were launched to validate the system and the next pair would be launched during Oct 2012.  Galileo may be able to offer an initial set of services by 2014; the system is unlikely to be fully operational before 2016 to 2019. Given its budget, Galileo is expected to provide the 4 IOV (in-orbit validation) and 14 FOC (full operational capability) satellites by 2014, which is 60% of its capacity.11
The United Nations General Assembly in 2006 set up an International Committee on Global Navigation Satellite Systems as an informal body to promote cooperation on the matters of mutual interest related to civilian satellite-based positioning, navigation, timing and value-added services. The committee would also address the issues related to the compatibility and interoperability of global navigation satellite systems. One of the main purposes of this forum is to promote the use of this system to support sustainable development, particularly in developing countries. Asian states are found taking keen interest in this programme, and the second meeting of the ICG Global Navigation Committee was held at Bangaluru, India, in 2007.