The IRNSS, also known as Navigation Indian Constellation (NavIC), is an independent regional navigation satellite system developed by India.
IRNSS is a regional GNSS owned and operated by the Government of India.
It is designed as an autonomous system to provide accurate position information service to assist in the navigation of ships in the Indian Ocean waters, as well as air traffic.
It could replace the US GPS system in the Indian Ocean, up to approximately 1500 kilometres from the Indian boundary.
Space segment
Current Satellites
The IRNSS constellation consists of 8 satellites, one of which is suffering from a partial failure.
- IRNSS-1A no longer has a working atomic clock.
- IRNSS-1H failed to launch.
| Satellite | Date Launched | Orbit Configuration | Status |
|---|---|---|---|
| IRNSS-1A | 1 July 2013 | Geosynchronous (IGSO) / 55°E, 29° inclined orbit | Partial Failure |
| IRNSS-1B | 4 April 2014 | Geosynchronous (IGSO) / 55°E, 29° inclined orbit | Operational |
| IRNSS-1C | 16 October 2014 | Geostationary (GEO) / 83°E, 5° inclined orbit | Operational |
| IRNSS-1D | 28 March 2015 | Geosynchronous (IGSO) / 111.75°E, 31° inclined orbit | Operational |
| IRNSS-1E | 20 January 2016 | Geosynchronous (IGSO) / 111.75°E, 29° inclined orbit | Operational |
| IRNSS-1F | 10 March 2016 | Geostationary (GEO) / 32.5°E, 5° inclined orbit | Operational |
| IRNSS-1G | 28 April 2016 | Geostationary (GEO) / 129.5°E, 5.1° inclined orbit | Operational |
| IRNSS-1H | 31 August 2017 | Launch Failed | |
| IRNSS-1I | 12 April 2018 | Geosynchronous (IGSO) / 55°E, 29° inclined orbit | Operational |
Planned Satellites
The following additional Satellites are planned and will be launched within the future.
| Name | Orbit Type | Orbit Angle | Release Date |
| IRNSS-1J | Geosynchronous (IGSO), | 42° inclined orbit | Planned |
| IRNSS-1K | Geosynchronous (IGSO) | 42° inclined orbit | Planned |
| IRNSS-1L | Geosynchronous (IGSO) | 42° inclined orbit | Planned |
| IRNSS-1M | Geosynchronous (IGSO) | 42° inclined orbit | Planned |
| IRNSS-1N | Geosynchronous (IGSO) | 42° inclined orbit | Planned |
Ground segment
The IRNSS Ground Segment communicates with the satellite constellations which includes sending/receiving positioning messages and route updates, as well as providing maintenance.
Ground segment layout
- IRNSS Spacecraft Control Facility (IRSCF)
- ISRO Navigation Centre (INC)
- IRNSS Range and Integrity Monitoring Stations (IRIMS)
- Laser Ranging Stations
- IRNSS Network Timing Centre (IRNWT)
- IRNSS CDMA Ranging Stations (IRCDR)
- IRNSS Data Communications Network(IRDCN)
User Segment
The user segment is comprised of GPS receivers and antennas which are used to receive signals from the IRNSS.
The GPS devices are also capable of working interoperable between the various GNSS.
The plan is to to broadcast the time difference between the IRNSS time and the time of the other GNSS constellations to enable users to take advantage of the signals available to them.
Accuracy
The system was designed to provide positioning accuracy which does not exceed 10m throughout the Indian land region.
In addition to this, accuracy within the 1,500 ocean border was intended to be better than 20m.
In the year 2017, The Space Applications Centre advised that NavIC will provide standard positioning service to all users with a accuracy of positioning up to 5 m.
In comparison, GPS which is owned and operated by America had a position accuracy of 20-30m.
Another difference is that unlike GPS which operates on a single L-Band, NavIC has dual frequency support of the S & L bands.
As a result, when low frequency signal travels through the atmosphere, the velocity changes due to atmospheric disturbances.
US relies on the atmospheric model to assess frequency error and it has to update this model from time to time to assess the exact error.
In India’s case, the actual delay is assessed by measuring the difference in delay of dual frequency (S and L bands).
Therefore, NavIC is not reliant on any model to find the frequency error and is more accurate than GPS
Applications
IRNSS can be used in a multlitude of ways, some of the applications include:
- Marine, Aerial and Land Navigation
- Management of disasters
- Fleet Management & Vehicle Tracking
- Aerial Tracking
- Mobile Phone Navigation
- Precise Timing
- Geo spatial and Mapping data capture
- Terrestrial navigation aid for hikers and travelers
- Augmented Reality
The Future of NavIC
The NavIC constellation was launched primarily to provide accurate positioning and timing services in real time, with a 10-20 metres range of precision.
It was designed to be used over India’s Land and Ocean Territory.
Considering the NavIC system currently services it’s intended regions, along with the number of global GNSS that are already in service, ISRO have no plans now, nor in the future to make NavIC a global navigation system.