India Close To Having Its Own Satellite Navigation System
"From four navigation satellites up in the sky, we will get the signals which would prove the concept on which the whole IRNSS has been designed. While the full range of services may not be available with the constellation of four satellites, a user would be able to locate his position," a senior official of the Indian space agency told IANS preferring not to be named.
The ISRO official said IRNSS-1D would be raised to its home slot.
Following that, characterisation of the navigation and ranging payloads would be done and later the satellite will be integrated with the ground stations.
The three satellites launched earlier have all been integrated with the ground stations and are working well.
Once IRNSS-1D also gets integrated then the Indian satellite navigation system would start transmitting navigation signals. This meets the minimum number of satellites necessary for enabling a navigation receiver to compute its position.
Thus with IRNSS-1D functioning in orbit, proof-of-concept of an independent regional navigation satellite system over India can be established.
According to officials, two more navigation satellites are expected to be launched in 2015 and the seventh and the last one of the system would in all probability go up in early 2016.
The full navigation services are expected to be offered from mid 2016 onwards, according to the officials.
Queried about the ground segment infrastructure, the official said a good part of that is in place and the balance would be ready soon.
He said the IRNSS system is unique as it consists of only seven satellites while other systems have more than 20 satellites.
However, while other systems are global, the Indian system is regional in nature.
Nevertheless, ISRO officials claim that India can replace the US GPS with the Indian system when full fledged operations begin.
The fully operational system is expected to provide accurate position information service to users across the country and the region, extending up to an area of 1,500 km. While ISRO is silent on the navigation systems strategic application, it is clear that IRNSS will be used for defence purposes as well.
Officials at ISRO say all the remaining navigation satellites are in different stages of production and would be launched to offer full services by the middle of next year.
The full system comprises of nine satellites - seven in orbit and two on the ground as stand-by.
Each satellite costs around 
150 crore and the PSLV-XL version rocket costs around 130 crore. The seven rockets would involve an outlay of around 910 crore.
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