The Global Positioning System (GPS), is a global navigation satellite system (GNSS) that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. Each one transmits information about its position and the current time at regular intervals. These signals, traveling at the speed of light, are intercepted by your GPS receiver. GPS receivers then calculate the distance of each satellite based on how long it took for the messages to arrive. It requires only three satellites to provide the location. The other satellites add to the accuracy. The more satellites there are in the sky, the more accurately GPS can tell you about your location.
GPS has become ubiquitous technology that provides real-time positioning, navigation and timing (PNT) data in cars, boats, planes, trains, smartphones and wristwatches, and has enabled advances as wide-ranging as driverless cars, precision munitions, and automated supply chain management.
However, Global Positioning System is controlled by USA Govt. If they want, they can switch off this GPS without any explanation. This happened during the Kargil war in 1999, when Pakistani troops took the position in high mountains, and one of the first things Indian military was trying to get their hands on was GPS data of the region. GPS could’ve provided vital information, but the United States denied access to India. This can be considered as an act of Information warfare.
The Indian Government launched development of Indian Regional Navigation Satellite System (IRNSS) in 2006, with aim to develop an autonomous regional satellite navigation which would be under complete control of the Indian government. American monopoly on satellite based navigation is all set to end now as ISRO has developed the Indian Regional Navigation Satellite System (IRNSS), an independent and indigenous regional spaceborne navigation system for national applications.
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 Indian languages), is an autonomous regional satellite navigation system that provides accurate real-time positioning and timing services. 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.
ISRO indicates that eventually NavIC applications will support: 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 travellers, Visual and voice navigation for drivers. In addition, India have combined NavIC capability with its satellite-based air traffic control system for civil aviation called GAGAN (GPS Aided Geo Augmented Navigation). Hardware companies are producing GPS receiver modules specifically for the emerging Indian market that are compatible with GPS and GAGAN.
Further, the IRNSS is recognised by the International Maritime Organisation (IMO) as a part of the World Wide Radio Navigation System (WWRNS). “The Maritime Safety Committee of IMO during its recent meeting held from 4 to 11 November 2020 has approved the recognition of the IRNSS as a component of the World-wide radio navigation system,” the statement said. This achievement is considered as a significant step towards the ‘Atmanirbhar Bharat’ initiative of the Union government.
The main goal behind designing the Indian Regional Navigation Satellite System (IRNSS) is to provide accurate position information services to assist in the navigation of ships in Indian Ocean waters. For getting the recognition, the Director General of Shipping (DGS) had approached the IMO for granting recognition to the IRNSS as a component of the WWRNS. Apart from India, the other three countries who already have their own navigation systems recognised by the IMO includes the US, Russia and China.
While talking about the IRNSS, Kumar said that it is a modern and more accurate navigation system and over 2,500 merchant vessels in Indian waters at any given time will now be able to use the system. Further, the IRNSS will be utilized to assist in the navigation of ships in ocean waters within the area of approximately 1,500 km from the Indian boundary, according to Kumar. Details of the tests carried out on merchant ships with regard to the accuracy of the system were included in the report prepared by Indian Space Research Organisation (ISRO) which was submitted to IMO for consideration,” as per his statement.
The additional precision and resilience increase the scope of projects that can support India’s economic development. They include supporting the Archaeological Survey of India in protecting India’s heritage sites, assisting the fishing industry to locate the best fishing areas, development of transportation networks (especially bridges, flyovers and elevated expressways), help in defining accurate land records, and supporting the Indian railways to reduce accidents at automated railway crossings in addition to improving real-time railway operations. IRNSS shall also be very vital for military by providing intelligence about Enemy units and weapons in battlefield, and providing guidance to precision munitions.
As per National Defense Authorization Act (NDAA) 2020, United States Secretary of Defense in consultation with Director of National Intelligence will designate NavIC, Galileo and QZSS as allied navigational satellite system.
Indian Regional Navigation Satellite System (IRNSS)
The Indian Regional Navigation Satellite System is quite unique in comparison, with a satellite constellation size of 7 that track only 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 envisages establishment of a regional navigation system using a combination of geostationary earth orbit (GEO) and geosynchronous orbit (GSO) satellites. The IRNSS constellation comprises three GEO and four GSO satellites. 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 authorised users. The IRNSS System is expected to provide a position accuracy of better than 20 m in the primary service area.
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 space segment consists of the IRNSS constellation of eight satellites, NavIC 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.
Three satellites are located in suitable orbital slots in the geostationary orbit and the remaining four are located in geosynchronous orbits with the required inclination and equatorial crossings in two different planes. All the satellites of the constellation are configured identically. The satellites are configured with I-1K Bus to be compatible for launch on-board PSLV.
The IRNSS satellites carry a navigation payload in a redundant configuration. The NavIC signals are dual-band consisting of a Standard Positioning Service and a Precision Service. Both will be carried on L5 (1176.45 MHz) and S-band (2492.028 MHz). ISRO 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 dual-band signals actually give NavIC better accuracy than GPS in crowded places as the latter only uses L-Band signals.
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 system has an accuracy of 10 metres throughout the Indian landmass which is better than GPS’s 20-30 m accuracy.
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.
The ground segment is responsible for the maintenance and operation of the satellites and consist of RNSS 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 and IRNSS Data Communication Network(IRDCN).
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(monitoring and maintaining satellite health and position), CDMA ranging stations(determining the satellites’ position in space using radio and laser), uplinking and telemetry stations, communication links and network timing center.
ISRO’s 32-meter, fully steerable antenna at Byalalu (just outside Bangalore) is the primary element in the Indian Deep Space Network. On 28 May 2013, Byalalu formally became the ISRO Navigation Centre (INC) and the centre of NavIC’s ground segment of 15 sites that operate the NavIC service 24/7.
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. All components were built in India including the space segment, ground segment and user receivers. The initial total cost was INR 14.2 billion but it was bumped up to INR 22.46 billion as two replacement satellites and PSLV-XL launches were further added to the cost.
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. ISRO’s PSLV-C41 successfully launched the 1425 kg IRNSS-1I Navigation Satellite (on April 11, 2018, 22.34 UTC) from SDSC (Satish Dhawan Space Center) SHAR, Sriharikota With successful launch of IRNSS-1G, the seventh and final member of IRNSS constellation, signifies the completion of the IRNSS constellation.
The first satellite, IRNSS-1A, was launched on 1 July 2013, and the last satellite of the seven, IRNSS1-G, was launched three years later on 28 April 2016. Bad news came soon after that. In late 2016, ISRO reported that all three (the primary and both backups) Rubidium atomic clocks onboard IRNSS-1A had failed. In the absence of an accurate clock, the constellation could not function as designed. IRNSS-1H was launched on 31 August 2017 as a replacement for IRNSS-1A, but a failure of the payload fairing resulted in IRNSS-1H being trapped inside the final stage of the launch vehicle. It never made it to its designated orbit and the mission was considered a failure. The replacement for the replacement, IRNSS-1I, was launched on 11th April 2018 and successfully arrived at its intended orbit four days later. With that, India completed the NavIC constellation, with three in geostationary orbit (at 34E, 83E and 131.5E) and four (in two pairs) in geosynchronous orbit inclined at 29 degrees to the equatorial plane with their longitude crossings as 55 E and 111.5 E.
A number of ground facilities responsible for satellite ranging and monitoring, generation and transmission of navigation parameters, etc., have been established in eighteen locations across the country. The requirement of such a navigation system is driven because access to foreign government-controlled global navigation satellite systems is not guaranteed during hostile situations, as the Indian military experienced denial of services by America during the Kargil War.
NavIC is currently on a handful of smartphones. The Redmi Note 9 Pro and Redmi Note 9 Pro Max from Xiaomi supports NavIC navigation system. Similarly, the Realme 6 Pro is another smartphone that comes with NavIC support. Apart from this, Qualcomm has already revealed that smartphones that will use its Snapdragon 720G, Snapdragon 662, and Snapdragon 460 will support NavIC.
Paid L and S band signals of NavIC receivers are available to cater the Security and Air Travel industries. Besides providing a leading technological edge over GPS, IRNSS will enable handheld devices to receive seamless S-Band signals. Additionally, once a simple code is added in the mobile phones, they would be able to receive L-band signals as well.
ISRO have developed NavIC enabled chips, which can be used in handheld devices such as smart phones. ISRO has already achieved the miniaturization of chipsets that are used in wireless devices. The agency’s SAC (Space Application Center ) is reportedly working on the development of NavIC user receiver, which is key to finding user position. The final version would be an 11-channel chipset (7 NavIC satellites and four GPS satellites) operating under dual frequency (S- and L- bands), which Misra says actually delivered higher accuracy than GPS. . In fact, SAC has already built a chip with 32 channel IRNSS receiver.
IRNSS Capabilities better than GPS
Though GPS has 24 satellites, the number of satellites visible to the ground receiver is limited. The 24 satellites are in Medium Earth Orbit. At any time, at any given location at least four satellites must be within the view of the receiver. In the case of IRNSS, the seven satellites are in geosynchronous orbits hence always visible to a receiver in a region 1500Km around India. SRO Chairman A.S Kiran Kumar and he said, “24 functional satellites of GPS is for the entire globe, while 7 satellites of IRNSS is covering only India and its neighboring countries. All these 7 satellites will be visible to the ground receiver all the time.”
Another point is that the satellites are nearly vertical over India and therefore visibility in ‘urban canyons’ is much better than in the case of the GPS. Tapan Misra, Director of Satellite Application Center [SAC], believes that NavIC is going to be better than GPS. “While GPS is using only L-Band signals, NavIC is using both L AND S Band. Since our signals are coming vertically from stationary reference, our NavIC is going to work better than GPS in crowded places. If you use both L and S bands, our accuracy is more than 5 meters. This has a better potential than a 20-meter accuracy GPS, which is actually supplemented by the GPRS information. But our NavIC can give you the accuracy that GPRS and GPS give combined and that accuracy is not only for cities but every rural part of the country.”
With plans of an upgrade to an 11 satellite constellation, IRNSS could soon be accurate to 2m. Almost 10 times better than GPS average accuracy of 20 metres. At present, however, one can still expect an accuracy of 10-12 metres.
A team of Finnish researchers describe the results of a successful campaign to track signals from the Indian Regional Navigation Satellite System using a software designed receiver, the FGI-GSRx. Initial results indicate that, despite the receiver location well outside the satellites’ intended coverage area. Finland lies north of 60°N latitude more than 5,000 kilometers away from India. Astonishingly, the achieved accuracy was of 95% circular error probability (CEP), considering that only 2 IRNSS satellites were used in the position solution, the accuracy figures are consistent with a GPS-only scenario.
This proves how powerful the IRNSS system really is, ISRO has been able to achieve such expansive range coverage with only 2 satellites whereas GPS & GLONSS have launched more than 24 satellites to cover the globe, hypothetically given the results of the Finnish experiment ISRO may be able to achieve global coverage with just 15-18 satellites.
A senior ISRO official said, “Both these L and S band signals received from seven satellite constellation of the IRNSS are being calculated by a special embedded software which reduces the errors caused by atmospheric disturbances significantly. This in turn gives superior quality location accuracy than the American GPS system,”
IRNSS ran into problem because of reliability of atomic clocks
However the program is facing problems due to its atomic clocks, critical components that keep time. Each satellite has three clocks and a total of 27 clocks for the navigation satellite system were supplied by the same vendor. The clocks are important to provide precise data.
ISRO had announced in July 2017 that all three atomic clocks on IRNSS-1A, the first of the seven satellites that was launched on July 1, 2013, had malfunctioned, rendering that satellite ineffective. Now, sources associated with ISRO’s satellite navigation program say four more atomic clocks on the other six satellites are not performing as required.
The failure of seven of the 21 clocks in the constellation has, however, raised concerns. “Six of the seven satellites are still working,” said a senior ISRO official associated with the program. “There are, however, inherent hardware problems on the rubidium atomic clocks in some of these. These clocks developed the same problems when used in the Galileo satellite system by ESA (European Space Agency).” The Rubidium atomic clocks were manufactured by the Swiss company Spectracom.
The unplanned cost of replacing two satellites, poor procurement decisions and administrative failings have increased the initial budget and resulted in a delay of around 7 years. ISRO’s contribution was assessed by an official audit report published in March 2018. The report highlighted delays in “sites not being ready, revisions in the technical specifications, non-compliance with contract specifications by the contractor, delays in shipment and delays in completion of civil works”
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 to extend coverage. These additional four satellites will be made during 12th FYP and will be launched in the beginning of 13th FYP in geosynchronous orbit of 42° inclination. Also, the development of space-qualified Indian made atomic clocks was initiated, along with a study and development initiative for an all optical atomic clock (ultra stable for IRNSS and deep space communication). IRNSS-1J, IRNSS-1K, IRNSS-1L, IRNSS-1M and IRNSS-1N are next batch of spacecraft in development.
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