Skip to content

Nss Sat 12 Essay

Example of Cities covered

Bujumbura, Djibouti, Cairo, Alexandria, Giza, Shubra al-Khayma, Port Said, Suez, al-Mahallat al-Kubra, Tanta, al-Mansura, Luxor, Asyut, Bahtim, Zagazig, al-Faiyum, Ismailia, Kafr al-Dawwar, Assuan, Damanhur, al-Minya, Bani Suwayf, Qina, Sawhaj, Shibin al-Kawm, Bulaq al-Dakrur, Banha, Warraq al-Arab, Kafr al-Shaykh, Mallawi, Bilbays, Mit Ghamr, al-Arish, Talkha, Qalyub, Jirja, Idfu, al-Hawamidiya, Disuq, Asmara, Addis Abeba, Dire Dawa, Nazret, Gonder, Dese, Mekele, Bahir Dar, Sanaa, Aden, Taizz, Hodeida, al-Mukalla, Ibb, Nairobi, Mombasa, Kisumu, Nakuru, Machakos, Eldoret, Meru, Nyeri, Bangui, Brazzaville, Pointe-Noire, Blantyre, Lilongwe, Kigali, Lusaka, Ndola, Kitwe, Kabwe, Chingola, Mufulira, Luanshya, Mogadishu, Hargeysa, Kismaayo, Omdurman, Khartum, Sharq al-Nil, Port Sudan, Kassala, Obeid, Nyala, Wad Madani, al-Qadarif, Kusti, al-Fashir, Juba, Dar es Salaam, Dodoma, Mwanza, Zanzibar, Tanga, Mbeya, Morogoro, Arusha, Moshi, Tabora, N´Djaména, Moundou, Kampala,

Country/ies of origin India
TypeMilitary, Commercial
StatusDegraded /Non-operational [1]
CoverageRegional (up to 1,500 km from borders)
Accuracy10 m (public)
0.1 m (encrypted)
Constellation size
Total satellites7
Satellites in orbit6 (1 redundant)
First launch1 July 2013
Last launch31 August 2017 19:00 pm IST
Total launches8
Orbital characteristics
Regime(s)High Earth
Orbital height36,000 km (22,000 mi)[2]
Other details
CostUS$221 million

The Indian Regional Navigation Satellite System (IRNSS) with an operational name of NAVIC ("sailor" or "navigator" in Sanskrit, Hindi and many other Indian languages, which also stands for NAVigation with Indian Constellation[3]) 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. The system at-present consist of a constellation of 7 satellites,[2][4] with two additional satellites on ground as stand-by.[5]

The constellation is already in orbit and system was expected to be operational from early 2018[6][7] after a system check.[8] NAVIC will provide two levels of service, the 'standard positioning service' will be open for civilian use, and a 'restricted service' (an encrypted one) for authorized users (including military). Due to the failures of one of the satellites and its replacement no new dates for operational status has been set.

In 2017 all rubidiumatomic clocks on board IRNSS-1A failed, rendering the satellite redundant. ISRO's attempt to replace it with IRNSS-1H was unsuccessful when PSLV-C39 mission failed to deploy the satellite on 31 August 2017.[9]

There are plans to expand NavIC system by increasing constellation size from 7 to 11.[10]


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.[11] The Indian government approved the project in May 2006.


As part of the project, the Indian Space Research Organisation (ISRO) opened a new satellite navigation center within the campus of ISRO Deep Space Network (DSN) at Byalalu, in Karnataka on 28 May 2013.[12] A network of 21 ranging stations located across the country will provide data for the orbital 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.[13]

The total cost of the project is expected to be ₹1,420 crore (US$217 million), with the cost of the ground segment being ₹300 crore (US$46 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 an outlay of around ₹910 crore (US$139 million).[5][14][15] The NAVIC signal was released for evaluation in September 2014.[16]


In April 2010, it was reported that India plans to start launching satellites by the end of 2011, at a rate of one satellite every six months. This would have made NAVIC functional by 2015. But the program was delayed,[17] and India also launched 3 new satellites to supplement this.[18]

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.[19][20]IRNSS-1B was launched on 4 April 2014 on-board PSLV-C24 rocket. The satellite has been placed in geosynchronous orbit.[21]IRNSS-1C was launched on 16 October 2014,[22]IRNSS-1D on 28 March 2015,[23]IRNSS-1E on 20 January 2016,[24]IRNSS-1F on 10 March 2016 and IRNSS-1G was launched on 28 April 2016.[25]

Eighth satellite IRNSS-1H, which was meant to replace IRNSS-1A, was failed to deploy on 31 August 2017 as the heat shields failed to separate from 4th stage of the rocket.[9]

System Description[edit]

The IRNSS system comprises a space segment and a support ground segment.

Space segment[edit]

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.[26][27] The four GSO satellites will appear to be moving in the form of an "8".[28]

Ground Segment[edit]

Ground Segment is responsible for the maintenance and operation of the IRNSS constellation. The Ground segment comprises:[26]

  • 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 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.[26][29]


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 navigation signals themselves would be transmitted in 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 command center to send warnings to a specific geographic area. For example, fishermen using the system can be warned about a cyclone.[30]


The system is intended to provide an absolute position accuracy of better than 10 meters throughout Indian landmass and better than 20 meters in the Indian Ocean as well as a region extending approximately 1,500 km (930 mi) around India.[31] The Space Applications Centre in 2017 said NAVIC will provide standard positioning service to all users with a position accuracy up to 5 m.[30] 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). When low frequency signal travels through atmosphere, its velocity changes due to atmospheric disturbances. US banks on atmospheric model to assess frequency error and it has to update this model from time to time to assess the exact error. In India's case, the actual 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 frequency error and is more accurate than GPS.[32]

List of Satellites[edit]

The constellation consists of 7 active satellites. Three of the seven satellites in constellation are located in geostationary orbit (GEO) and four in inclined geosynchronous orbit (GSO). All satellites launched or proposed for the system are as follows:

SatelliteLaunch DateLaunch VehicleOrbitStatusRemarks
IRNSS-1A1 July 2013PSLV-C22Geosynchronous / 55°E, 29° inclined orbitFailed in orbitAtomic clocks failed.[33][34]
IRNSS-1B4 April 2014PSLV-C24Geosynchronous / 55°E, 29° inclined orbitOperational
IRNSS-1C15 October 2014PSLV-C26Geostationary / 83°E, 5° inclined orbitOperational
IRNSS-1D28 March 2015PSLV-C27Geosynchronous / 111.75°E, 31° inclined orbitOperational
IRNSS-1E20 January 2016PSLV-C31Geosynchronous / 111.75°E, 29° inclined orbitOperational
IRNSS-1F10 March 2016PSLV-C32Geostationary / 32.5°E, 5° inclined orbitOperational
IRNSS-1G28 April 2016PSLV-C33Geostationary / 129.5°E, 5.1° inclined orbitOperational
IRNSS-1H31 August 2017PSLV-C39Launch FailedThe payload fairing failed to separate and satellite could not reach the desired orbit.[9][35] It was meant to replace defunct IRNSS-1A.[33][10]
IRNSS-1IMarch-April 2018Under development[36]

Clock Failure[edit]

In 2017, it was announced that all three rubidiumatomic clocks on board IRNSS-1A had failed, mirroring similar failures in the European Union's 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 cannot be used for accurate measurements.[37] ISRO's attempt to replace it with IRNSS-1H was unsuccessful when PSLV-C39 mission failed on 31 August 2017.[10]. Due to the failure of the replacement satellite launch the system which was expected to go live in August 2017 is currently a degraded / non-operational state. [1]

Two more clocks in the navigational system had started showing signs of abnormality, thereby taking the total number of failed clocks to five.[10]

As a precaution to extend the operational life of navigation satellite, ISRO is running only one rubidium atomic clock instead of two in the remaining six satellites.[10] 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.[38][39] ISRO replaced the atomic clocks in two standby NavIC satellites.[10] The setback comes at a time when IRNSS is yet to start commercial operations.

Future developments[edit]

India's Department of Space in their 12th Five Year Plan(FYP) (2012–17) stated increasing the number of satellites in the constellation from 7 to 11 for extending coverage.[40] These additional 4 satellites will be made during 12th FYP and will be launched in the beginning of 13th FYP.[41] Also, development of space qualified atomic clocks was initiated, along with study & development initiative for All Optical Atomic Clock (ultra stable for IRNSS and Deep Space Communication).[42][40]

Global Indian Navigational System (GINS)[edit]

Study and analysis for Global Indian Navigational System (GINS) was initiated as part of the technology and policy initiatives in the 12th FYP (2012–17).[42] The system is supposed to have a constellation of 24 satellites, positioned 24,000 km (14,913 mi) above Earth. As of 2013[update], the statutory filing for frequency spectrum of GINS satellite orbits in international space, has been completed.[43]

See also[edit]


  1. ^ abVasudevan Mukund. "India's 'GPS' Remains Unfinished". The Wire. Wayback Machine. Archived from the original on 26 January 2018. Retrieved 26 January 2018. 
  2. ^ ab"Orbit height and info". Archived from the original on 30 December 2015. 
  3. ^"IRNSS-1G exemplifies 'Make in India', says PM". The Statesman. 28 April 2016. Archived from the original on 23 September 2016. Retrieved 28 April 2016. 
  4. ^"IRNSS details". Archived from the original on 10 March 2016. 
  5. ^ ab"Isro to launch 5th navigation satellite on Jan 20, first in 2016". 
  6. ^
  7. ^"Isro's PSLV-C32 places India's sixth navigation satellite IRNSS-1F in orbit". Times of India. 
  8. ^"ISRO puts seventh and final IRNSS navigation satellite into orbit". Times of India. 
  9. ^ abc"ISRO says launch of navigation satellite IRNSS-1H unsuccessful". The Economic Times. 2017-08-31. Retrieved 2017-08-31. 
  10. ^ abcdefIANS (2017-06-10). "Navigation satellite clocks ticking; system to be expanded: ISRO". The Economic Times. Retrieved 2018-01-24. 
  11. ^Srivastava, Ishan (5 April 2014). "How Kargil spurred India to design own GPS". The Times of India. Retrieved 9 December 2014. 
  12. ^"ISRO opens navigation centre for satellite system". 2013-05-28. Retrieved 30 June 2013. 
  13. ^"India Making Strides in Satellite Technology". Defence News. Archived from the original on 6 June 2013. Retrieved 26 July 2012. 
  14. ^"India's first ever dedicated navigation satellite launched". DNA India. 2 July 2013. Retrieved 24 July 2013. 
  15. ^"India's first dedicated navigation satellite placed in orbit". NDTV. 2 July 2013. Retrieved 24 July 2013. 
  16. ^"IRNSS Signal in Space ICD Released". 25 September 2014. Retrieved 7 September 2016. 
  17. ^S. Anandan (10 April 2010). "Launch of first satellite for Indian Regional Navigation Satellite system next year". Retrieved 2010-12-30. 
  18. ^H. Pathak. "3 Satellites To Be Launched By ISRO". Archived from the original on 17 April 2011. 
  19. ^"ISRO's Future programme". ISRO. Retrieved 18 May 2013. 
  20. ^"Countdown begins for PSLV-C22 launch". Retrieved 2013-06-29. 
  21. ^"Isro successfully launches navigation satellite IRNSS-1B". Times Of India. Retrieved 4 April 2014. 
  22. ^"ISRO puts India's Navigation satellite IRNSS 1B into orbit". IANS. Retrieved 4 April 2014. 
  23. ^"India successfully launches IRNSS-1D, fourth of seven navigation satellites – Times of India". Retrieved 7 September 2016. 
  24. ^"India launches 5th navigation satellite IRNSS-1E powered by PSLV rocket". Retrieved 2016-01-20. 
  25. ^Narasimhan, T. E. "India gets its own GPS with successful launch of 7th navigation satellite". Retrieved 7 September 2016. 
  26. ^ abcd"IRNSS". Retrieved 2017-06-08. 
  27. ^"First IRNSS satellite by December". Magazine article. Asian Surveying and Mapping. 5 May 2009. Retrieved 2009-05-05. [dead link]
  28. ^"How Kargil spurred India to design own GPS". The Times of India. 5 April 2014. Retrieved 28 April 2016. 
  29. ^K. Radhakrishnan (29 December 2013). "Mars and more, final frontier". Deccan Chronicle. Retrieved 28 April 2016. 
  30. ^ ab"Indian 'GPS' for public use by year-end – Times of India". The Times of India. Retrieved 2017-06-08. 
  31. ^A. Bhaskaranarayana Director SCP/FMO & Scientific Secretary Indian Space Research Organisation – Indian IRNSS and GAGANArchived 5 December 2010 at the Wayback Machine.
  32. ^
  33. ^ abMukunth, Vasudevan. "3 Atomic Clocks Fail Onboard India's 'Regional GPS' Constellation". Retrieved 2017-06-08. 
  34. ^D.S., Madhumathi. "Atomic clocks on indigenous navigation satellite develop snag". The Hindu. Retrieved 2017-06-08. 
  35. ^"IRNSS-1H launch unsuccessful, says ISRO". The Indian Express. 2017-08-31. Retrieved 2017-08-31. 
  36. ^"India's regional navigation satellite will soon get another satellite to improve its accuracy". Swarajya. Retrieved 26 February 2018. 
  37. ^D.S., Madhumathi. "Atomic clocks on indigenous navigation satellite develop snag". The Hindu. Retrieved 2017-01-31. 
  38. ^"SpectraTime to Supply Atomic Clocks to IRNSS | Inside GNSS". Retrieved 2017-06-21. 
  39. ^"Spectratime Awarded Contract To Supply Rubidium Space Clocks To IRNSS". Retrieved 2017-06-21. 
  40. ^ ab"Five Year Plan"(PDF). Department of Space. 12th FYP: 96. October 2011. 
  41. ^"12th Five Year Plan report, Department of Space, DST"(PDF). Retrieved 2017-06-21. 
  42. ^ ab
  43. ^"Global Indian Navigation system on cards". The Hindu Business Line. 2010-05-14. Retrieved 2017-06-22. 


  1. ^SATNAV Industry Meet 2006. ISRO Space India Newsletter. April – September 2006 Issue.

External links[edit]