NAVIC

IRNSS
Title	NAVIC
Author(s)	GMV
Level	Basic
Year of Publication	2011

The Indian Regional Navigational Satellite System (IRNSS) is an autonomous regional satellite navigation system owned by the Indian government and developed byIndian Space Research Organization (ISRO) .

IRNSS Introduction

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  ISRO logo

IRNSS will be an independent regional navigation system covering an area of about 1500 kilometers around India. The system will be under complete Indian control, with the space segment, ground segment and user receivers all being built in India.

IRNSS Architecture

IRNSS is planned with 7 satellites and a commensurate ground segment.

• The IRNSS Space Segment: 3 of the 7 satellites are geostationary (GEOs) and they will be located at 34º East, 83º East and 132º East longitude. There will be 4 GSOs in orbits of 24,000 km apogee and 250 km perigee inclined at 29 degrees. Two of the GSOs will cross the equator at 55º East and two at 111º East. The life span of the GEOs is 9.5 years and 11 years in the case of the GSOs. The Constellation Design Considerations have been mainly :
  • Minimizing the Maximum DOP
  • Minimum number of satellites
  • Orbital slots for India for a continuous visibility with the control stations

IRNSS Architecture

• The IRNSS Ground Segment will consist of:
  • IRNSS Space Craft Control Centre (SCC)
  • IRNSS Navigation Centre (INC)
  • IRNSS TTC & Uplinking Stations (IRTTC)
  • IRNSS Range and Integrity Monitoring Stations (IRIMS)
  • IRNSS Timing Centre (IRNWT)
  • CDMA Ranging Stations (IRCDR)
  • Laser Ranging Station (ILRS)
  • Data Communication Network (IRDCN)

The SCC and the INC will be the core of the ground segment, and they are in charge of estimating and predicting IRNSS satellites position, calculation of integrity, ionospheric and clock corrections and running the navigation software.

• The IRNSS User segment: the IRNSS user segment is made of the IRNSS receivers. They will be dual-frequency receivers or single frequency with capability to receive ionospheric correction. They will be able to receive and process navigation data from other GNSS constellations and the seven IRNSS satellites will be continuously tracked by the user receiver. The user receiver will have a minimum power G/T of -27 dB/K.

IRNSS Services and Performances

There will be two kinds of services:

• Special Positioning Service (SPS): The IRNSS signal of this service will be modulated by a 1 MHz BPSK signal.
• Precision Service (PS): this service will use BOC(5,2).

IGP GRID to be used in IRNSS

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 RS is under study, but it is expected to use a navigation data structure similar to SBAS systems, including a grid model. Since the number of satellites in IRNS is 7 as against 30 for GPS, the field available for extra satellites is used up for inserting a 80 grid points ionospheric model for the benefit of single frequency user. 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 2014. The first satellite of the proposed constellation is expected to be launched by end 2011. The reports that came in April 2010 stated that India plans to launch the first satellite by end of 2011 and the rest with six months periodic launches. This means that the IRNSS system would be functional by 2014.