Indian Regional Navigation Satellite System

The Indian Regional Navigation Satellite System ( IRNSS ) with an operational name of NAVIC ( “sailor” or “navigator” in Sanskrit , Hindi and Many other Indian languages, qui aussi stands for NAV igation with I Ndian C onstellation [2] ) is an Autonomous regional satellite navigation system, which 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. The present system consisted of a constellation of 7 satellites, [1] [3] with two additional satellites on ground as stand-by. [4]

The constellation is expected to be operational from early 2018 [5] [6] after a system check. [7] NAVIC will Provide two levels of service and the Standard Positioning Service ‘will be open for civilian use, and a’ restricted service (an encrypted one) for authorized users (Including military).

There are plans to expand NavIC system by increasing constellation size from 7 to 11. [8]

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Background

The system was developed partly because access to foreign government-controlled global navigation satellite systems is not guaranteed in hostile situations, as happened to the Indian military in 1999 when it was dependent on the American Global Positioning System (GPS) during the Kargil War . [9] The Indian government approved the project in May 2006.

Development

As part of the project, the Indian Space Research Organization (ISRO) opened a new satellite navigation center within the ISRO Deep Space Network (DSN) at Byalalu , in Karnatakaon 28 May 2013. [10] A network of 21 ranging stations Located Across the country will Provide data for the orbit determination of the satellites and monitoring of the navigation signal.

A goal of complete Indian control has been stated, with the space segment, ground segment and user receivers all being built in India. Its location in low latitudes facilitates a coverage with low- inclination satellites. Three satellites will be in geostationary orbit over the Indian Ocean . Missile targeting could be an important military application for the constellation. [11]

The total cost of the project is expected to be ₹ 1,420 crore (US $ 221 million), with the cost of the ground segment being ₹ 300 crore (US $ 47 million). Each satellites costing ₹ 150 crore (US $ 23 million) and the PSLV-XL version rocket costs around ₹ 130 crore (US $ 20 million). The Seven rockets Would Involve year outlay of around ₹ 910 crore (US $ 141 million). 14] [13] The NAVIC signal was released for evaluation in September 2014. [14]

Time-Frame

In April 2010, it was reported that India plans to launch satellite satellites by the end of 2011, at one satellite every six months. This would have made NAVIC functional by 2015. But the program was delayed, [15] and India also launched 3 new satellites to supplement this. [16]

Seven satellites with the prefix “IRNSS-1” will constitute the space segment of the IRNSS. IRNSS-1A , the first of the seven satellites, was launched on 1 July 2013. [17] [18] IRNSS-1B was launched on 4 April 2014 on-board PSLV-C24 rocket. The satellite has been placed in geosynchronous orbit . [19] IRNSS-1C Was Launched on 16 October 2014, [20] IRNSS-1D is 28 March 2015 [21] IRNSS-1E is 20 January 2016. [22] IRNSS-1F is 10 March 2016 and IRNSS-1G Was Launched on 28 April 2016. [23]

System Description

Coverage of the NAVIC.

The IRNSS system includes a space segment and a ground segment .

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 satellite furnaces are in geosynchronous orbit (GSO). Two of them cross equator at 55 ° East and two at 111.75 ° East. [24] [25]The furnace GSO satellites will appear in the form of an “8” . [26]

Ground Segment

Ground Segment is responsible for the maintenance and operation of the IRNSS constellation. The Ground segment included: [24]

  • IRNSS Spacecraft Control Facility (IRSCF)
  • ISRO Navigation Center (INC)
  • IRNSS Range and Integrity Monitoring Stations (IRIMS)
  • IRNSS Network Timing Center (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. IRIMS are currently operational and are supporting IRNSS operations. CDMAranging is being carried out by the IRCDR 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) wrt 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 wrt UTC and other GNSS , almanac , text message and earth orientation are generated and uplinked to the spacecrafts 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. [24] [27] Text message and earth orientation and spatial patterns. 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. [24] [27] Text message and earth orientation and spatial patterns. 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. [24] [27]

Signal

NAVIC signals will consist of a Standard Positioning Service and a Precision Service. Both will be carried on L5 (1176.45 MHz) and S band (2492.028 MHz). The SPS signal will be modulated by a 1 MHz BPSK signal. The Precision Service will use BOC (5,2) . The S-band frequency (2-4 GHz) and broadcast through a phased array antenna to maintain required coverage and signal strength. The satellites would weigh approximately 1,330 kg and their solar panels generate 1,400 watts.

A messaging interface is embedded in the NavIC system. This feature allows the user to send a warning message to a specific geographic area. For example, fishermen using the system can be warned about a cyclone. [28]

Accuracy

The system is intended to provide an absolutely accurate view of the Indian Ocean and the Indian Ocean. [29] The Space Applications Center in 2017 said NAVIC will provide standard positioning service to all users with a position accuracy up to 5 m. [28] The GPS, for comparison, had a position accuracy of 20-30 m. Unlike GPS which is dependent only on L-band, NAVIC has dual frequency (S and L bands). The low velocity changes due to atmospheric disturbances. This paper presents the results of the modeling of the problem. In India’s case, the delay is assessed by measuring the difference in delay of dual frequency (S and L bands). Therefore, NavIC is not dependent on any model to find the correct error and accurate GPS. [30]

List of Satellites

The constellation consists of 7 active satellites. Three of the seven satellites are in geostationary orbit (GEO) and four in the geosynchronous orbit (GSO). All satellites are:

IRNSS-1 satellite series [24]
Satellite Launch Date Launch Vehicle Orbit Status Remarks
IRNSS-1A 1 July 2013 PSLV-C22 Geosynchronous / 55 ° E, 29 ° inclined orbit Redundant Atomic clocks failed. [31] [32]
IRNSS-1B 4 April 2014 PSLV-C24 Geosynchronous / 55 ° E, 29 ° inclined orbit Operational
IRNSS-1C 15 October 2014 PSLV-C26 Geostationary / 83 ° E, 5 ° inclined orbit Operational
IRNSS-1D 28 March 2015 PSLV-C27 Geosynchronous / 111.75 ° E, 31 ° inclined orbit Operational
IRNSS-1E 20 January 2016 PSLV-C31 Geosynchronous / 111.75 ° E, 29 ° inclined orbit Operational
IRNSS-1F 10 March 2016 PSLV-C32 Geostationary / 32.5 ° E, 5 ° inclined orbit Operational
IRNSS-1G 28 April 2016 PSLV-C33 Geostationary / 129.5 ° E, 5.1 ° inclined orbit Operational
IRNSS-1H PSLV-C39 Planned, Aug 2017 To replace defunct IRNSS-1A. [31] [8]

Clock Failure

In 2017 it was announced that all three rubidium atomic clocks on board IRNSS-1A had failed, mirroring similar failures in the Galileo constellation. The first failure occurred in July 2016, following which two other clocks also failed. This rendered the satellite somewhat redundant and required replacement. Although the satellite still performs other functions, the data is coarse, and thus can not be used for accurate measurements. [33] ISRO plans to replace it with IRNSS-1H in July or August 2017. [8]

Two more clocks in the navigational system had started showing signs of abnormality, taking the total number of failed clocks to five. [8]

As a precaution to extend the operational life of satellite navigation, ISRO is running only one rubidium atomic clock instead of two in the remaining six satellites. [8] Each satellite has three clocks, therefore a total of 27 clocks for all satellites in the system (including standby satellites). The clocks of both IRNSS and GALILEO were supplied by SpectraTime. [34] [35] ISRO replaced the atomic clocks in two standby NavIC satellites. [8] The setback comes at a time when IRNSS is yet to start trading operations.

Future developments

India’s Department of Space in their 12th Five Year Plan (FYP) (2012-17), the number of satellites in the constellation from 7 to 11 for extending coverage. [36] These additional 4 satellites will be made during 12th FYP and will be launched in the beginning of 13th FYP. [37] Also, the development of space atoms was initiated, along with study and development initiative for All Optical Atomic Clock (ultra stable for IRNSS and Deep Space Communication ). [38] [36]

Global Indian Navigational System (GINS)

Study and analysis for the Global Indian Navigational System (GINS) was initiated as part of the technology and policy initiatives in the 12th FYP (2012-17). [38] The system is Supposed to-have a constellation of 24 satellites Positioned 24.000 km (14.913 mi) Above Earth. As of 2013 , the statutory filing for frequency spectrum of satellite orbits GINS in international space, has-been completed. [39]

See also

  • BeiDou Navigation Satellite System
  • Galileo (satellite navigation)
  • Global Positioning System
  • GLONASS
  • GPS Aided GEO Augmented Navigation
  • Satellite navigation

References

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