IRNSS 1- A Step Towards an Indigenous Satellite Navigation System

The first of the proposed seven navigation satellites of the Indian Regional Navigational Satellite System (IRNSS), IRNSS-1, was successfully placed in initial orbit by PSLV- C22 (Polar Satellite Launch Vehicle), on the night of 01-02 Jul 13. This is another well deserved achievement for ISRO as it takes the initial step towards joining the select group of nations having capability to launch and operate such a system.

Besides providing Position, Navigation and Timing services (PNT), the Global Navigation Satellite System (GNSS) technology has spurred linked and dependent applications in myriad fields that have a direct bearing on the security and economic growth of nations. While GPS has become the synonym for GNSS, off late, the need to shift from the U.S. GPS system has been felt by most countries. This has been spurred by the fear of the collapse of multitude services, were the GPS to switch off/ degrade due to natural reasons or at the behest of the controlling state. (The GPS provides only degraded accuracy to civilian and non U.S. customers and the U.S. government also has the option of selectively degrading its accuracy whenever it deems fit). The disruption to the security and socio economic fields could be potentially catastrophic. While recognising this need, ISRO also realised that a global navigation system, like the GPS, would be expensive in terms of the number of satellites required and the requirement of a global network of ground based systems. It thus limited the scope of the programme to a regional network that could be supported by terrestrial stations on the Indian mainland.

The satellite, with a life span of around 10 years, would form part of the regional navigational system that would provide 24x7 terrestrial, aerial and marine navigation services, under all weather conditions, over the subcontinent. In the coming days, five orbit manoeuvres will be conducted from Master Control Facility to position the satellite in its Geosynchronous Orbit at 55 deg East longitude. While IRNSS1 would provide ISRO an opportunity to test performance parameters related to availability, accuracy and reliability of the upcoming system, the system would become operational only when all seven satellites are in place, the target timeline being 2015-16.

The fully operational system will have three segments viz.

Space segment – Out of the seven satellites, three will be placed in the geostationary equatorial orbit (i.e. they would be stationary with respect to the Earth) at a height of 36000 kms at 34° E, 83° E and 131.5° E longitudes over the equator. The other four (two pairs) will be placed in two geosynchronous orbits (an orbit around the Earth matching the Earth's rotation period)[1] inclined at 29 degree to the equator, crossing the equator at 55 degree East and 111 degree East. All the seven satellites will have continuous radio visibility with Indian control stations. Two spare satellites are also planned.

Ground segment. There will be an extensive ground segment consisting of control and ranging stations that would be responsible for controlling the IRNSS satellites and generating the navigation data. These stations would monitor all aspects of the satellites including their health, orbital positions and network integrity. The satellites would then be controlled by issue of radio commands by the Telemetry, Tracking and Command Systems (TT&C) stations. While the control stations are at Bangalore and Bhopal, about 15 other stations are spread across the country.

User segment. IRNSS would provide two basic services, the Standard Positioning Service (SPS) for common civilian users and as is available with GPS, a Restricted Service (RS) for special authorized users – military and other government clients, using encrypted signals. The system design allows for it to be compatible and inter operable with GPS and Galileo systems. ISRO releases say that the organisation has been working with industry to develop receivers for the IRNSS.

The IRNSS is expected to provide positional accuracies of 10m over Indian landmass and 20m over the Indian Ocean in a region centred around the country with a coverage extending up to 1,500 km from India between longitude 40° E to 140° E and between latitude ± 40°. The system can be augmented with local area augmentation for higher accuracy. ISRO Chairman, K Radhakrishnan, while lauding the successful launch of the satellite said that if necessary, the coverage area around India could be enhanced by adding four more satellites.

While various official commentaries are silent on the system's strategic and defence related aspects, it is already being construed that requirements related to missile targeting and its applicability to current and future military systems played an important part in the decision to establish an independent system. As Indian defence continues to upgrade its security hardware and software, it cannot be dependent on foreign systems that may be unreliable during conflict situations. For the Indian defence services, there would not be much change in the application and training as the system is similar to the GPS as far as the provision of PNT services is concerned. However, there is a need to involve the services during the designing and development of the user devices and interface to replace the existing GPS receivers.

The only other fully operational global navigation system besides GPS is GLONASS of Russia. Also in the advanced stages of implementation are other global systems - Galileo system of Europe (expected to be fully operational by 2019) and Beidou of China (expected to be fully operational by 2020). Japan has also planned a regional JAXA system for the Asia Pacific region and has already launched its first satellite. Besides the stated security related concerns, commercial aspects of such systems cannot be overlooked. Within a few years, the GPS industry has become a multibillion dollars worth worldwide service with linked benefits to the local manufacturing industry. Other nations have their eyes on a share of this ever expanding pie. However, they realise the difficulties in shifting existing users from the established American GPS systems and are hence targeting nascent markets with relatively lesser exposure to GPS. Europe wants Galileo to become its de-facto system and is also taking initiatives for its spread to Africa. Thailand, Pakistan, Sri Lanka, Laos and Brunei have already subscribed to the Chinese Beidou system. This is where ISRO would also face its biggest challenge and may require the Indian government, defence forces and industry to rally behind it.

The success of the system notwithstanding, its limitations in terms of coverage area and vulnerabilities need to be kept in mind and regular efforts made to overcome them. GNSS being dependent on radio wave transmissions, space weather accounts for the most substantial errors experienced by these systems. It is also vulnerable to jamming, interference and spoofing and its military applications have spurred an industry targeting these vulnerabilities. Thus the threats are natural and manmade (both unintentional and intentional). Other operators continue to improve upon effective countermeasures and mitigation techniques and ISRO can benefit from work already done. While these are mostly in the technological domain, there is also a requirement of simple measures like failure warnings and the ability of the user devices to shift to alternate systems in case of failure.

These limitations have forced the operators to consider the aspects of interoperability and compatibility of systems that if successful would provide redundancy in case of failure of one system and would enable better accuracy and seamless coverage if more than one system can be used simultaneously. ISRO, an active member of International Committee of GNSS (ICG), having recognised the benefits of multi GNSS and interoperability has participated in many bilateral discussions with GPS, GALILEO etc. on interoperable and compatible signal structure. However, considering the superiority that the GPS enjoys globally and the economic angle, it is difficult to visualize U.S. letting go of its advantage.

References:

1. "ISRO Press Release," 02 July 2013, accessed at

http://www.isro.org/pressrelease/scripts/pressreleasein.aspx?Jul02_2013

2. "Satellite Navigation Program, IRNSS," Presentation by Indian delegation

at STSC-UNCOPUOS, Vienna Feb, 2012, accessed at http://www.oosa.unvienna.org/pdf/pres/stsc2012/tech-43E.pdf

3. "The Dangers of GPS/ GNSS," Börje Forsell, Mycoordinates, Feb 2009, accessed at

http://mycoordinates.org/the-dangers-of-gpsgnss/

4. "Analysis of IRNSS over Indian Subcontinent," Vyasaraj Guru Rao, Gérard Lachapelle, Vijay Kumar S, accessed at

http://plan.geomatics.ucalgary.ca/papers/ion_itm11_rao%20et%20al_jan11.pdf

5. "An Indian mission to another frontier in space," N. Gopal Raj, The Hindu, 01 Jul 13, accessed at

http://www.thehindu.com/todays-paper/tp-opinion/an-indian-mission-to-another-frontier-in-space/article4867732.ece

6. "IRNSS: India's Own Satellite Navigation System," Dr. Rajeswari Pillai Rajagopalan, Observer Research Foundation, 29 June 2013, accessed at

http://www.observerindia.com/cms/sites/orfonline/modules/analysis/AnalysisDetail.html?cmaid=53783&mmacmaid=53784

7. "Africa and the EU: implementing satellite navigation technologies", CTA, Brussels Office Blog, 13 March 2013, accessed at

http://brussels.cta.int/index.php?option=com_k2&id=7562&view=item&Itemid=1

Geostationary orbit is a kind of geosynchronous orbit. The satellite placed over the equator stays stagnant with relation to the earth. In case of a geosynchronous orbit, the satellite not placed over the equator, traces out a path with respect to earth, returning to the same point over the earth after completion of the orbit. Such orbits help in continuous coverage of a particular area over the earth.

The author is a Senior Fellow at CLAWS

Views expressed are personal