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Successful launch of IRNSS –1A: A new milestone in Indian Space Programme

The successful launch of Indian Regional Navigation Satellite System (IRNSS) – 1A from Satish Dhawan Space Centre, Sriharikota, on July 1 opened a new page in the history of Indian space programme. Indian Space Research Organisation (ISRO) Chairman K. Radhakrishnan has congratulated the team and said, with this successful launch, India had entered a new era in space applications.

In the midnight launch, India’s workhorse Polar Satellite Launch Vehicle–C22 (PSLV–C22) lifted off at 11.41 pm on Monday night carrying the indigenous IRNSS -1A. The satellite was successfully injected into a sub geosynchronous transfer orbit, which has a 284-km perigee (nearest point to the Earth) and 20,650 km apogee (farthest point from the Earth).

With the increasing role and importance of satellite navigation systems in both military as well as civilian point of view, the IRNSS-1A launch can be considered as an important milestone in Indian space programme. The IRNSS project would provide India with an independent regional navigational satellite system. The IRNSS has wide ranging civilian and military applications and possession of such advanced navigation system is very crucial for a country like India, from both economic and strategic point of views.

This article provides an in-depth understanding about the IRNSS in the present context.

ABC of Satellite Navigation System
Identification and observation of the location and movement of a person/object/vehicle are called location positioning and navigation. These two activities play a very vital role in different civilian and military activities. Think about identifying the whereabouts of the stranded pilgrims in recent floods in Uttarakhand, or tracking a moving ship in the high seas, or army spotting the movements of the enemy at the country’s border, or even finding the address your friend’s new residence on your mobile phone or tablet. All these are positioning and navigation-based activities. Today, the satellite navigation systems have emerged as the prominent navigation systems.

A satellite navigation system is a system of satellites that provide autonomous geo-spatial positioning of a person or object. Satellites determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line-of-sight by radio from satellites. Receivers calculate the precise time as well as position, which can be used as a reference.

The position accuracy of NSS would be based up on the capacity of navigational equipment that is deployed on the satellites and their geometrical condition in the orbits. For example, while IRNSS could provide accuracy of better than 10 meters throughout Indian Landmass and its satellites can come up with better quality signals based on their position on the orbits.

Generally global coverage for each system is generally achieved by a satellite constellation of 20–30 Medium Earth Orbit (MEO) satellites spread between several orbital planes.

Based on their range of coverage, satellite navigation systems can be divided into Global Navigation Satellite System (GNSS) and Regional Navigation Satellite System (RNSS). While the GNSS would have full global coverage, the RNSS would have limited coverage intended for specific area.

For example, the US NAVSTAR Global Positioning System (GPS) and Russian Globalnaya Navigatsionnaya Sputnikovaya Sistema or Global Navigation Satellite System (GLONASS) are the examples of GNSS. Indeed they are the only two operational GNSSs in the world. India’s IRNSS and Japan’s Quasi-Zenith Satellite System (QZSS) are the examples for RNSS.

There is another technical variant of satellite navigation system, which is called Satellite-based Augmentation System (SABS). This system also takes the support of satellites; however, its basic function is not to provide location positioning data, but to strengthen the signals of source NSS through the use of additional satellite broadcast messages. The SABS augmentation improves the quality of signals of the source NSS. The SABSs are commonly composed of multiple ground stations, located at accurately-surveyed points. The ground stations take measurements of one or more of the GNSS satellites, the satellite signals, or other environmental factors which may impact the signal received by the users. Using these measurements, information messages are created and sent to one or more satellites for broadcast to the end users.

Wide Area Augmentation System (WASS) of the USA, European Geostationary Navigation Overlay Service (EGNOS) of Europe, GPS and Geo-Augmented Navigation System (GAGAN) of India and the QZSS of Japan are some of the examples of SABS.

NSS and SABS are not completely exclusive to each other; a single system can conduct the duties of both - the NSS and SABS. For instance, QZSS is both an RNSS and an SABS.

Need for independent navigation system
Satellite positioning has emerged as the most reliable navigation system in the world and its applications are manifold. Success of the NAVSTAR GPS of the US, the world’s first GNSS, has demonstrated the power of satellite navigation system to the world. The GPS has hundreds of thousands of U.S. and allied military users for its secure GPS Precise Positioning Service and tens of millions of civil, commercial and scientific users for its Standard Positioning Service.

The US claims that it provides all GPS civilian signal services for free of cost to anybody from any part of the world. However, the super power would not provide guaranteed access to GPS in hostile situations. The US government can block GPS signals whenever it wants and this leaves other countries vulnerable during the times of hostilities and difference with the super power.

This concern has prompted the major countries across the world, including India to develop their own satellite navigational systems. The commercial success of GPS is another incentive for other countries to start their own global positioning systems.

Satellite navigation systems of the world
So far, the USA, Russia, European Union, China, Japan, and India have their satellite navigation systems. While Russia has built its GLONASS and made fully operational, the other countries have been building their systems still, with parts of them being accomplished and operational already.

Here are the details of those systems -
The US has started its NAVSTAR GPS project in 1973 to overcome the limitations of previous navigation systems. The project was created and implemented by the US Department of Defense. The GPS was originally planned to run with 24 satellites. Since then the system has modernised thoroughly and presently operates with 31 satellites.

The GPS, which became fully operational by 1994, has revealed the vast possibilities that satellite supported navigation systems can offer to the consumer segment. It has become a byword for locational positioning systems across the world and the most popular of GNSSs. The civilian uses of GPS include astronomy, cellular telephony, cartography, disaster management, emergency services, fleet tracking, vehicle tracking, aircraft tracking, GPS for mining, recreation, robotics, surveying and telematics, among others.

Emulating itself, Russia has built GLONASS as an answer to American GPS. GLONASS consists of 24 satellites and has full global coverage. For its association with the project, India has acquired both military and civilian access to this system and it is the only country that has access to the military section of this GNSS. GLONASS is finding increasing acceptance in different quarters of the world. It is being clubbed with GPS for improved signal clarity. The GLONASS has become fully operational since October 2011.

European Union has started its own GNSS i.e. Galileo, due to the difficulties of complete dependence on the US’ GPS and doubts about plausible development of Russian GLONASS. According to the Galileo project official website, almost 6-7 % of EU GDP, which is about 800 billion Euros, depends on satellite navigation. This economic reason also has prompted the EU to opt for its own GPS. Galileo consists of 30 navigation satellites. The launch of first two satellites took place in October 2011 and the system would be operational at full by the end of 2019.

China is presently developing its own BeiDou Navigation Satellite System (BDS), which is a GNSS. The Chinese navigation system project can be divided into two parts, and has two separate constellations of satellites. The first constellation forms the BeiDou Satellite Navigation Experimental System or BeiDou-1, which is a regional navigation system. It consists of three satellites and they mainly cover China and its surrounding areas. BeiDou-1 has been offering navigation services, mainly for customers in China and neighboring regions, since 2000. The second constellation is an extension to BeiDou-1 and is known as BDS or Compass navigation system. It is a global navigation system and consists of total 35 satellites. BDS became operational in China since December 2011, with 10 satellites in use. The project is expected to be completed by the end of 2020.

Japan’s QZSS is a proposed three-satellite RNSS and SABS. It is targeted at mobile applications, to provide communications-based services (video, audio, and data) and positioning information, which would be receivable within Japan. The first satellite Michibiki was launched on 11 September 2010 and full operational status of this RNSS is expected by 2013. In March 2013, Japan has decided to add one more satellite to this system.

The structure of IRNSS
The IRNSS consists of two segments viz. - space and ground segments. India will have full control over the system with the all components of space segment, ground segment and user receivers being built in India.

The space segment comprises 7 navigation satellites, in which three of them would placed in geostationary orbit and remaining four would be positioned in geosynchronous orbit. The seven satellites revolve in the orbits in such a way that all of them would have continuous radio visibility with Indian control stations.

The IRNSS is expected to become fully functional by the end of 2015. Each satellite payload consists of three extremely accurate rubidium atomic clocks and electronic equipment to generate navigational signals.

The space segment comprises 7 navigation satellites, and expected to become fully functional by the end of 2015. The satellite payloads would consist of atomic clocks and electronic equipment to generate navigational signals. The seven satellites revolve in the geostationary orbits (GSO) in such a way that all of them would have continuous radio visibility with Indian control stations.

The ground segment includes a Master Control Centre (MCC) located at ISRO’s Deep Space Network (DSN) at Byalalu near Bangalore and 21 ranging stations located across the country to provide data for the orbit determination of the satellites and monitoring of the navigation signal.

While the MCC and some of the ground stations track and estimate the satellites' orbits and ensure the integrity of the network (IRIM), the other ground stations will monitor the health of the satellites with the capability of issuing radio commands to the satellites (TT&C Stations). The MCC would estimate and predict the position of all IRNSS satellites, calculate integrity, makes necessary ionospheric and clock corrections and run the navigation software. In pursuit of a highly independent system, an Indian standard time infrastructure would also be established.

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 around India.

The total cost of the project is expected to be 1,420 crore (US$ 240 million), with the cost of the ground segment being 300 crore (US$ 51 million) and each satellites costing 125 crore (US $ 21 million).

Usages of IRNSS
The IRNSS is an independent regional navigation system, which would be under complete control of Government of India.

The system would provide two services, with the Standard Positioning Service open for civilian use and the Restricted Service, encrypted one, only for authorised users of the military.

The civilian usages include Terrestrial, Aerial and Marine Navigation, Vehicle Tracking and Fleet Management, Integration with mobile phones, Precise Timing, Mapping and Geodetic data capture, Terrestrial navigation aid for hikers and travelers and Visual and Voice navigation for drivers. This service envisages several applications for commerce, banking, telecommunication, automobile, transportation and banking sectors.

Disaster management is another area which benefits heavily from this regional navigation system. For example, right after full commencement of GLONASS, Russia launched two projects in 2010: the introduction of a single helpline number (112) for all rescue services, medical and police services in emergency situations. The creation of an emergency response system in case of car accidents (ERA-GLONASS) is the second, which will become operational throughout Russia by 2014.

In civil aviation sector, India has already mooted an SABS project i.e. GPS and Geo-Augmented Navigation System (GAGAN). It is a regional SABS, which is being implemented for Airports Authority of India by the ISRO, for the upgradation of air traffic management across the country. GAGAN improves the accuracy of NSS receivers by providing additional reference signals. This in turn shall improve the accuracy in landing and takeoff of the flights, which means better air safety and more profits to airliners. The experience of GAGAN is expected to be utilised in the future operations of the IRNSS. The location positioning services thus have innumerable applications in civilian sectors.

The IRNSS also provides encrypted location positioning services to the Indian defence forces, like the GPS does to the US military. Tracking of the enemy movements in both sides of the boarders and missile tracking and targeting could two important military applications that IRNSS could provide. Possession of own NSS also gives thrust modernisation of Indian military communications. Though India has free access to military services of Russian GLONASS, it would be always imperative for a country of India’s stature to have its own encrypted location positioning services as it cannot entirely depend on any other country, howsoever friendly the other country is, for such vital requirement.

IRNSS-1A is the first three satellites which revolve in geostationary orbit of the IRNSS space segment. The weight and height of the satellite are 1,425 kg and 1.5 meters, respectively, and has 10 years of mission life.

IRNSS-1A is the first of the seven satellites constituting the IRNSS space segment. The weight and height of the satellite are 1,425 kg and 1.5 meters, respectively, and has 10 years of mission life.

The 1A was injected into orbit by PSLV–C22 in its XL format. The XL launch vehicle would have bigger strap-on motors than the general PSLV vehicle and this format is used when huge satellites are to be placed in the orbits.

Payloads - IRNSS-1A carries two types of payloads – Navigation Payload and Ranging Payload. The navigation payload will transmit navigation service signals to the users. Its signals consist of a Special Positioning Service and a Precision Service. The navigation payload will use L5 band and S band for transmission of its signals. A highly accurate Rubidium atomic clock is a part of the navigation payload of the satellite.

The ranging payload of IRNSS-1A consists of a C-band transponder which facilitates accurate determination of the range of the satellite. The satellite also carries Corner Cube Retro Reflectors for laser ranging.

Lift-off Mass 1425 kg
Physical Dimensions 1.58 metre x 1.50 metre x 1.50 metre
Orbit Geosynchronous, at 55 deg East longitude with 29 deg inclination
Power Two solar panels generating 1660 W, one lithium-ion battery of 90 Ampere-Hour capacity
Mission Life 10 years
Launch date Jul 01, 2013
Launch site SDSC SHAR Centre, Sriharikota, India
Launch vehicle PSLV - C22a
Source: ISRO Website

The PSLV-C22 has four stages, in which a solid propellant named Hydroxyl Terminated Poly Butadine (HPTB) was used in the first and third stages and a liquid propellant named Unsymmetrical dimethyl hydrazine + 25% Hydrazine Hydrate (UH 25) in its second and fourth stages. Nitrogen Tetroxide (N2O4) was used as oxidizer. In the fourth stage, Mono Methyl Hydrazine (MMH) was used as the propellant and Mono Methyl Hydrazine (MON-3) as oxidizer.

The PSLV used for the launch of IRNSSS-1A is called PSLV- XL and this is the fourth time such a configuration is being flown, the previous three being PSLV-C11/ Chandrayaan-1, PSLV-C17/ GSAT-12 and PSLV-C 19/ RISAT-1 missions. The length of PSLV–C22 vehicle is 44 meters, weight 320 tonnes during the lift off.

Published date : 03 Aug 2013 04:28PM

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