Indian Regional Navigation Satellite System

 IRNSS is an autonomous regional satellite navigation system being developed by ISRO (Indian Space Research Organization). The government of India approved the project in May 2006, with the intention of the system to be completed and implemented in the timeframe 2016.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. The proposed 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.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).

The Indian Regional Navigation Satellite System (IRNSS), with an operational name of NavIC (acronym for Navigation with Indian Constellation; also, nāvik ‘sailor’ or ‘navigator’ in Sanskrit, and many other Indian languages), is an autonomous regional satellite navigation system that provides accurate real-time positioning and timing services. It covers India and a region extending 1,500 km (930 mi) around it, with plans for further extension. An extended service area lies between the primary service area and a rectangle area enclosed by the 30th parallel south to the 50th parallel north and the 30th meridian east to the 130th meridian east, 1,500–6,000 km (930–3,730 mi) beyond borders. The system currently consists of a constellation of seven satellites, with two additional satellites on ground as stand-by.

The IRNSS constellation architecture consists of the following elements:

  • 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.

The IRNSS spacecraft are dedicated for navigation services and they are configured to be of a class that can be launched by the Indian launcher PSLV. The design incorporates most of the proven subsystems available indigenously tailoring it specifically for the navigation.

  • 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, up linking and telemetry stations, communication links and network timing center.

 

 

  • 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.

 

Space segment:

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
  • The first satellite will be launched in the summer of 2013. The subsequent launches are planned once in six months. The full constellation will be operational by 2016.

The IRNSS constellation with the daily lemniscuses projection of the 4 GSO spacecraft onto Earth (image credit: ISRO)

Spacecraft:

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.

 

 

Launch mass

1432 kg, dry mass of 614 kg

Spacecraft size (launch configuration)

1.58 m x 1.5 m x 1.5 m

EPS (Electrical Power Subsystem)

Two solar panels generating 1660 W, one lithium-ion battery of 90 Ah capacity

ADCS (Attitude Determination and Control Subsystem)

Zero momentum system, orientation input from sun & star sensors and gyroscopes; reaction wheels, magnetic torquers and 22 Newton thrusters as actuators

Mission design life

10-12 years

Propulsion

440 N LAM (Liquid Apogee Motor) with twelve 22 N thrusters

                                          Parameters of the IRNSS-1 spacecraft

 

Some Pictures of Working of IRNSS

(a)Preliminary view of a deployed                    

(a)Preliminary view of a deployed                      

               

                                                                                                                                                                (b) Blow-up view of the IRNSS spacecraft

                                                                                                                                                                     IRNSS spacecraft

(c)IRNSS-1A undergoing tests in the

(d) IRNSS-1A after its integration with thePSLC-C22

Special or superior And Capability

IRNSS is an independent regional navigation satellite system being developed by India. It is designed to provide accurate position information service to users in India as well as the region extending up to 1500 km from its boundary, which is its primary service area. An Extended Service Area lies between primary service area and area enclosed by the rectangle from Latitude 30 deg south to 50 deg North, Longitude 30 deg East to 130 deg east.

IRNSS will provide two types of services, namely, Standard Positioning Service (SPS) which is provided to all the users and Restricted Service (RS), which is an encrypted service provided only to the authorized users. The IRNSS System is expected to provide a position accuracy of better than 20 m in the primary service area.

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 travelers
  • Visual and voice navigation for drivers

The IRNSS Signal-in-Space Interface Control Document (ICD Ver. 1.1) for Standard Positioning Service (SPS) is released to the public to provide the essential information on the IRNSS signal-in-space, to facilitate research & development and aid the commercial use of the IRNSS signals for navigation-based applications.

Reference

https://en.wikipedia.org/wiki/Indian%20Regional%20Navigation%20Satellite%20System

https://www.planetary.org/blogs/guest-blogs/how-india-built-navic.html

https://directory.eoportal.org/web/eoportal/satellite-missions/content/-/article/irnss

https://www.isro.gov.in/irnss-programme

https://www.isro.gov.in/spacecraft/satellite-navigation

https://gssc.esa.int/navipedia/index.php/NAVIC

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