A satellite navigation system is a system of satellites that provide location (longitude, latitude, and altitude) to high precision (within a few metres) with small electronic receivers.
The electronic receivers calculate the current local time to high precision using time signals transmitted from satellites.
The first satellite navigation system is Global Positing Satellite System (GPS). GPS is built by USA and it provides global coverage with a constellation of 24 satellites. GPS is designed in such a way that four satellites are always visible on any part of earth.
As of there are only two fully working satellite navigation systems, GPS and GLONASS. GLONASS is a radio-based satellite navigation system, developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces. It is an alternative and complementary to the United States‘Global Positioning System (GPS).
China is in the process of expanding its regional BeiDou Navigation Satellite System into the global Compass navigation system by 2020. The European Union’s Galileo and Japan’s Quasi Zenith Satellite System are initial deployment phase.
Now the question is how India can lag behind in satellite navigation system?
And the answer is IRNSS (Indian Regional Navigation Satellite System). This is an independent Indian Satellite based positioning system for critical National applications. The main objective is to provide Reliable Position, Navigation and Timing services over India and its neighborhood, to provide fairly good accuracy to the user.
Unlike GPS, GLONASS, Galileo which are global navigation system (GNSS), IRNSS will be providing coverage to India and its subcontinent.
The proposed IRNSS system will consist of a constellation of seven satellites, three satellites in GEO stationary orbit (GEO) and four satellites in Geo Synchronous Orbit (GSO) orbit with inclination of 29° to the equatorial plane. Such an arrangement would mean all seven satellites would have continuous radio visibility within the Indian region.
Satellite will be broadcasting positing signals in two different frequencies: L5 band (1164 – 1189 MHz) and S band (2483.5 – 2500 MHz).
Space segment is compatible with single frequency receiver for Standard Positioning Service (SPS), dual frequency receiver for both SPS & Restricted Service (RS) service and a multi mode receiver compatible with other GNSS providers.
The Standard Positioning Service (SPS) is provided to all the users and Restricted Service (RS) is accessible only to the authorized users as it is an encrypted service. The IRNSS System is expected to provide a position accuracy of better than 20 m over the Indian ocean region, and < 10 m over main land India.
The IRNSS user receiver calculates its position using the timing information embedded in the navigation signal, transmitted from the IRNSS satellites. The timing information being broadcast in the navigation signal is derived from the atomic clock onboard the IRNSS satellite.
The first satellite (IRNSS-1A) was launched on July 1, 2013 on the PSLV-C22 vehicle from Satish Dhawan Space Center. The IRNSS-1B spacecraft was launched on April 4, 2014 on the PSLV-C24 vehicle from Satish Dhawan Space Center. The IRNSS-1C was launched on Oct. 15, 2014 on the PSLV-C26 vehicle from Satish Dhawan Space Center.
On Mar. 28, 2015, ISRO’s Polar Satellite Launch Vehicle, PSLV-C27, successfully launched IRNSS-1D from Satish Dhawan Space Centre, Sriharikota.
The subsequent launches are planned once in six months. The full constellation will be operational by 2016.
Some applications of IRNSS are:
- Terrestrial, Aerial and Marine Navigation
- Disaster Management
- Vehicle tracking and fleet management
- Integration with mobile phones
- Precise Timing
- Mapping and Geodetic data capture
- Terrestrial navigation aid for hikers and travellers
- Visual and voice navigation for drivers