IRNSS (Indian Regional Navigational Satellite System)

Prelims & Mains

IRNSS is an autonomous regional satellite navigation system being developed by ISRO 

IRNSS (Indian Regional Navigational Satellite System) is the regional satellite navigation system by the government of India approved in May 2006, with the intention of the system to be completed and implemented in the time frame 2016.

IRNSS (Indian Regional Navigational Satellite System) – Objective

The objective of the project is to implement an independent and indigenous regional space borne navigation system for national applications.

The IRNSS design requirements call for a position accuracy of < 20 m throughout India and within the region of coverage extending about 1500 km beyond. The system is expected to provide accurate real-time position, velocity and time observables for users on a variety of platforms with a 24 hour x 7 day service availability under all weather conditions.

The IRNSS is being developed parallel to the GAGAN (GPS Aided GEO Augmented Satellite Navigation) program, the ISRO SBAS (Satellite Based Augmentation System) version of an overlay system for GNSS signal corrections.

IRNSS (Indian Regional Navigational Satellite System) – Constellation

The IRNSS system will consist of a constellation of seven satellites and a supporting ground segment. Three of the satellites in the constellation will be placed in a geostationary orbit and the remaining four in a geosynchronous inclined orbit of 29º relative to the equatorial plane. Such an arrangement would mean all seven satellites would have continuous radio visibility with Indian control stations.

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ISRO has filed for 24 MHz bandwidth of spectrum in the L5-band (1164 – 1189 MHz) for IRNSS and for the second signal in S-band (2483.5 – 2500 MHz).

IRNSS (Indian Regional Navigational Satellite System) – Space segment:

The IRNSS satellites carry a navigation payload in a redundant configuration. A separate C-band transponder for precise CDMA ranging is included in the payload configuration.

The important functions of the IRNSS payload are:

  • Transmission of the navigational timing information in the L5 bands;
  • Transmission of navigation, timing information in S-band;
  • Generation of navigation data on-board, CDMA ranging transponder for precise ranging.

The navigation payload will have the following subsystems: NSGU (Navigation Signal Generation Unit), Atomic clock unit, comprising of Rubidium atomic clocks, clock management and control unit, frequency generation unit, modulation unit, high power amplifier unit, power combining unit and navigation antenna.

IRNSS spacecraft

Longitude (E)

Inclination

RAAN

Launch Date

1A

55.0º

29º (±2)

135º

July 1, 2013

1B

55.0º

29º (±2)

310º

April 4, 2014

1C

83.0º

274º

October 15, 2014

1D

111.75º

29º (±2)

135º

March 27, 2015

1E

111.75º

29º (±2)

310º

January 20, 2016

1F

32.5º

± 5º

270º

March 10, 2016

1G

129.5º

± 5º

270º

April 28, 2016

1H

Aug. 31 2017 (launch failure)

1I

55.0º

29º

April 11, 2018

The space segment consists of seven satellites:

• 3 satellites in GEO (Geostationary Orbit) at 32.5°, 83° and 131.5° East.

• 4 satellites in geosynchronous orbit placed at inclination of 29° with longitude crossing at 55° and 111.75° East

• Two spare satellites are also planned

• The satellites are specially configured for the navigation. Same configuration for GEO and GSO which is desirable for the production of the satellites.

• Plans call for the IRNSS satellites to be launched by the Indian launcher PSLV

IRNSS

IRNSS (Indian Regional Navigational Satellite System) – Space Craft

The IRNSS satellites are configured around the spacecraft bus I-1K, which is similar to ISRO’s meteorological satellite, Kalpana-1, with a dry mass of ~600 kg and a launch mass of 1,425 kg. The solar panels are generating a power of 1600 W (with a payload power requirement of 900 W.

The spacecraft are 3-axis stabilized. Attitude control of the satellite is provided with yaw steering, a capability to optimize the use of the solar panels and to support the thermal control of the satellite.

IRNSS (Indian Regional Navigational Satellite System)

IRNSS (Indian Regional Navigational Satellite System) – Ground segment:

The ground segment is responsible for the maintenance and operation of the IRNSS constellation. It contains a whole complement of the elements required for a basic constellation and is mainly comprised of:

Master Control Center for spacecraft control and navigation, IRNSS tracking and integrity monitoring stations, CDMA ranging stations, uplinking and telemetry stations, communication links and network timing center.

The IRNSS ground segment includes the major systems for controlling the satellite constellation and will consist of the IRNSS Spacecraft Control Facility (IRSCF), IRNSS Navigation Control Facility, IRNSS Range and Integrity Monitoring Stations , ranging stations, a timing center, IRNSS TTC and uplink stations, and the IRNSS Data Communication Network.

• IRSCF (IRNSS Satellite Control Facility). IRSCF controls the space segment through Telemetry Tracking & Command network. In addition to the regular TT&C operations, IRSCF also uplinks the navigation parameters generated by the INC.

– IRTTC (IRNSS TTC and Land Uplink Stations)

– IRSCC (IRNSS Satellite Control Center)

IRIMS (IRNSS Range and Integrity Monitoring Stations). IRIMS perform continuous one way ranging of the IRNSS satellites and are also used for integrity determination of the IRNSS constellation.

• INC (ISRO Navigation Center), located at Byalalu. INC is the nerve center of the IRNSS Ground Segment. INC primarily generates navigation parameters.

• IRDCN (IRNSS Data Communication Network). IRDCN provides the required digital communication backbone to IRNSS network.

Seventeen IRIMS sites will be distributed across the country for orbit determination and ionospheric modeling. Four ranging stations, separated by wide and long baselines, will provide two-way CDMA (Code Division Multiple Access) ranging. The IRNSS timing center will consist of highly stable clocks. The navigation center will receive all this data through communication links, then process and transmit the information to the satellite

User segment:

Specially designed receivers and antennas are needed to receive the IRNSS signals. The receivers are also planned for receiving multi-constellation signals inclusive of GPS, GLONASS, Galileo and IRNSS. It is planned to broadcast the time difference between the IRNSS time and the time of the other constellations to enable the users to take advantage of the signals available to them.

 

Raja Raja Cholan
About Raja Raja Cholan 659 Articles
Trainer & Mentor for aspirants preparing for civil service examination

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