Indian Regional Navigation Satellite System

Indian Regional Navigation Satellite System

The Indian Regional Navigational Satellite System (IRNSS) is a regional Satellite System Owned by the Indian Govt. The System is being developed by Indian Space Research Organization (ISRO) (http://www.isro.org).

In April 2016, with the last launched of the constellation’s satellite, IRNSS was renamed Navigation Indian Constellation (NAVIC) by India’s Prime Minister Narendra Modi.

IRNSS Introduction

IRNSS Will be an independent and autonomous regional navigational system aiming a service area of about 1500 kilometers around India. The system will be under complete Indian Control, with the space segment, ground segment and user recivers all being built in INDIA. It will have a range of application including personal navigation.

IRNSS Architecture

IRNSS is planned to have a7 satellite complemented with the appropriate ground infrastructure as a minimum. As it is traditional in GNSS system, the architecture is described next in three segments: the Space Segment, The ground Segment, and the User segment.

The Space Segment

The constellation consists of 7 satellites. Three of the seven satellites are located in geostationary orbit (GEO) at 32.5° East, 83° East, and 131.5° East longitude, approximately 36,000 km (22,000 mi) above earth surface. Remaining four satellites are in inclined geosynchronous orbit (GSO). Two of them cross equator at 55° East and two at 111.75° East. The four GSO satellites will appear to be moving in the form of an "8".

The ground Segment

Ground Segment is responsible for the maintenance and operation of the IRNSS constellation. The Ground segment comprises:

• IRNSS Spacecraft Control Facility (IRSCF)
• ISRO Navigation Centre (INC)
• IRNSS Range and Integrity Monitoring Stations (IRIMS)
• IRNSS Network Timing Centre (IRNWT)
• IRNSS CDMA Ranging Stations (IRCDR)
• Laser Ranging Stations
• IRNSS Data Communication Network(IRDCN)

The INC established at Byalalu performs remote operations and data collection with all the ground stations. 14 IRIMS are currently operational and are supporting IRNSS operations. CDMA ranging is being carried out by the four IRCDR stations on regular basis for all the IRNSS satellites. The IRNWT has been established and is providing IRNSS system time with an accuracy of 2 ns (2.0×10⁻⁹ s) (2 sigma) w.r.t UTC. Laser ranging is being carried out with the support of ILRS stations around the world. Navigation Software is operational at INC since 1 August 2013. All the navigation parameters viz. satellite ephemeris, clock corrections, integrity parameters and secondary parameters viz. iono-delay corrections, time offsets w.r.t UTC and other GNSS, almanac, text message and earth orientation parameters are generated and uplinked to the spacecraft’s automatically. The IRDCN has established terrestrial and VSAT links between the ground stations. Seven 7.2 m FCA and two 11 m FMA of IRSCF are currently operational for LEOP and on-orbit phases of IRNSS satellites.

The User segment

The IRNSS user segment is made of the IRNSS receivers. They will be Dual frequency receivers (L5 and S band Frequencies) or single frequency (L5 or S band frequency) with capability to receive ionospheric correction. They will be able to recive and process navigation data from other GNSS constellation and the seven IRNSS satellites will be continuously tracked by the user receiver. The user reciver will have a minimum gain G/T of -27 dB/k.

IRNSS Services and Performances

There will be two kinds of Services-

A.      Special Positioning Service (SPS)

B.      Precision Service (PS)

Both services will be carried on L5 (1176.45 MHz) and S band (2492.08 MHz). The navigation signals would be transmitted in the S-band frequency (2–4 GHz) and broadcast through a phased array antenna to keep required coverage and signal strength.

The data structure for SPS and PS is under study; it is being planned to take advantage of the fact that the number of satellites is reduced -7 instead of the 30 used in other constellations- to broadcast ionospheric corrections for a grid of 80 points to provide service to single frequency users. The clock, ephemeris, almanac data of the 7 IRNSS satellites will be transmitted with the same accuracy as in legacy GPS, GLONASS & Galileo.

The Performances expected for the IRNSS system are: Position accuracy around 20 m over the Indian Ocean Region (1500 km around India) and less than 10 m accuracy over India and GSO adjacent countries.

IRNSS Development

The Indian government approved the project in May 2006, with the intention of the system to be completed and implemented by 2015.

The first satellite of the proposed constellation was successfully launched on the 1st of July 2013. It is IRNSS-1A one of the three Geosynchronous satellites that will is compose the entire constellation. Despite the first launch was executed slightly later than the planned, at that time India has announced the deadline of 2015-2016 to launch the remaining six satellites. As in the first launch the forthcoming will place in orbit only one satellite at a time. For that it is scheduled regular launches in every six months. As of 18 July 2013 the Indian Space Research Organisation (ISRO) announced that the satellite successfully reached its defined inclined geosynchronous orbit and that the verification tests would start one week after. Before that, in 23 July the German Aerospace Center was able to receive a signal transmitted in the L5 band from the IRSNSS-1A satellite. From the analysis of the received signal researchers from German Aerospace Center concluded that the signal structure is consistent with what was announced as IRNSS Signal Plan by ISRO. On October 16, 2014, India’s Indian Space Research Organisation (ISRO) successfully launched its third navigation satellite IRNSS-1C abord a Polar Satellite Launch Vehicle (PSLV) rocket from Satish Dhawan Space Centre, Sriharikota. The fourth IRNSS-1D satellite was successfully placed in orbit onboard the Polar Satellite Launch Vehicle (PSLV-C27), on March 28, 2015. The ISRO's Master Control Facility took over the control of the satellite and after that conducted several maneuvers in order to position the satellite in the geosynchronous orbit at 111.75 degrees East longitude with 30.5 deg inclination. The satellite reached its intended orbit slot on April 9th, 2015.

The fifth satellite of the IRNSS constellation was launched on January 20, 2016. That launch was closely followed by the 6th launch of a IRNSS satellite on March 10, 2016. The seventh and final satellite was launched on April 28, 2016.

List of Satellites

Satellite	Launch Date	Launch Vehicle	Orbit	Status	Remarks
IRNSS-1A	1 July 2013	PSLV-XL-C22	Geosynchronous / 55°E, 29° inclined orbit	Failed in orbit	Atomic clocks failed
IRNSS-1B	4 April 2014	PSLV-XL-C24	Geosynchronous / 55°E, 29° inclined orbit	Operational
IRNSS-1C	16 October 2014	PSLV-XL-C26	Geostationary / 83°E, 5° inclined orbit	Operational
IRNSS-1D	28 March 2015	PSLV-XL-C27	Geosynchronous / 111.75°E, 31° inclined orbit	Operational
IRNSS-1E	20 January 2016	PSLV-XL-C31	Geosynchronous / 111.75°E, 29° inclined orbit	Operational
IRNSS-1F	10 March 2016	PSLV-XL-C32	Geostationary / 32.5°E, 5° inclined orbit	Operational
IRNSS-1G	28 April 2016	PSLV-XL-C33	Geostationary / 129.5°E, 5.1° inclined orbit	Operational
IRNSS-1H	31 August 2017	PSLV-XL-C39		Launch Failed	The payload fairing failed to separate and satellite could not reach the desired orbit. It was meant to replace defunct IRNSS-1A
IRNSS-1I	12 April 2018	PSLV-C41	Geosynchronous / 55°E, 29° inclined orbit	Operational