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“IRNSS is expected to be realized by 2014-15”

Sep 2012 | No Comment

Says S K Shivakumar, Director, ISRO Satellite Centre (ISAC), India while sharing his priorities and views on various issues related to GNSS

What are the challenges as Director of ISAC? Would you also like to highlight your priorities?

The primary objective of ISAC is to build satellites to meet national requirement of the country in various application areas like satellite-based communication, navigation, national natural resources management, oceanography, meteorology, cartography and exploration of outer space and other planets, etc.

The major challenges today are to blend cutting edge technology development through R&D efforts with due emphasis on production of space-worthy hardware from ISAC, along with Indian industry partners.

The technology developments should lead to newer missions and need concentrated efforts to give a good shape in the areas of High power-High bandwidth(Ka-band)- multiple beams and heavier communication satellites, next generation remote sensing satellites with high stability and agility, very high resolution cameras, microwave imaging satellites, multi spectral imaging technologies, Rendezvous and Docking experiments, Inter-satellite communications links, etc. Challenges include establishment of IRNSS constellation consisting of 7 satellites for Indian Regional Navigation Satellite System and Space science missions for in-depth studies of our universe and interplanetary missions, which would provide India a pre-eminent place among space faring nations. In this regard, ASTROSAT, the first multi wavelength observatory mission, Mars orbiter mission, first mission to MARs planet, Chandrayaan-2, a follow on mission of successful Chandrayaan-1 and Aditya-1, India’s first mission to study the solar coronagraph are all in the pipeline. New frontiers like Astro-biology and Material Science (space systems) require serious considerations to enable micro gravity experiments relevance to the scientists.

In the facilities front, ISAC has already established state-of-the-art facilities for building satellites. Keeping abreast with the latest technology, a world class clean room for multiple satellite integration, production facility and an end-to-end spacecraft testing has been established.

The other major challenges ahead are the total establishment of the Space Research complex, Chellakare, Chitradurga for building satellites with advanced technology.

To meet the enormous challenges ahead, we have to train and develop a new breed of talented engineers and space scientists to realize the vision of ISAC and enable them to reach new frontiers of space technology for the benefit of the nation. Finally, we have to be one among the top space faring nations in the world.

You had been associated with Chandrayaan-1 mission. Is there any plan for Chandrayaan-2?

India as one among the very few space faring nations, has made a mark in the global scenario with the success of Chandrayaan-1, the first mission to Moon. The mission has provided valuable data to the scientific community that includes the discovery of water molecule on the Moon.

Chandrayaan-2, a follow on the first mission, has been envisaged during 2014- 15 timeframe. It comprises an orbiter craft & Lander along with Rover. The lander & rover craft will descend on to the terrain of the Moon, while the rover will conduct in-situ experiments on the lunar surface. In-situ analysis of lunar samples is configured to be carried out using alpha/neutron/X-ray Florescence spectroscopy. The orbiter craft is similar to Chandrayaan-1 which carries payloads like Solar X-ray Monitor, Synthetic aperture radar, Imaging IR spectrometer, neutral mass spectrometer, Terrain Mapping camera, etc. The payload/Instruments are meant for imaging, study of mineralogy, chemistry, alpha/neutron spectrometry.

What is the update on GAGAN?

After the installation, integration and testing of all GAGAN ground based elements and space segment, GAGAN Final System Acceptance Test (FSAT) was successfully completed on July 16-17, 2012. During the Final System Acceptance Test, the system performance in the integrated live environment using the satellite signals and ground based systems were validated. The FSAT results have successfully demonstrated that GAGAN Signals meets the civil aviation requirements of integrity, accuracy, continuity and availability. GAGAN signal in space is available through GSAT-8 GEO satellite with PRN127 and it is being used by non aviation users across the country. GSAT-10 with PRN128 is getting ready for launch during September 2012. The certification activities are in progress and GAGAN system is to be certified by DGCA for safety critical civil aviation applications.

How do you plan to harness the vast potential of nonaviation use of GAGAN?

GAGAN system is being established jointly by ISRO and AAI, primarily for Civil Aviation applications over India. However, it has enormous potential for non aviation users also. To create awareness among the user community and to highlight the advantages of using GAGAN signal for non-aviation purposes, a Global Navigation Satellite System (GNSS) User Meet was organized at ISRO Satellite Centre, Bengaluru, early this year. Over 250 delegates from the government, industry, academia and user community participated in the meet. The objective of the user meet was to provide a thrust in the development of GNSS-based applications and user receivers utilizing GAGAN and IRNSS navigation signals in India. The meet provided an opportunity for experts from industry, Users and service providers to interact and exchange information.
Similar meets, symposiums/workshops will be frequently organised for the user community to tap the potential of this new emerging field of navigation. An effort is on the anvil to establish a potential user group for developing GAGAN and IRNSS-based applications.

How do you plan to involve the industry for developing user segment equipment for GAGAN system?

Any GPS receivers capable of receiving SBAS signals can receive GAGAN signals and use it. GAGAN compatible receivers are already available in the market. The industry needs to produce application oriented receivers for location based services, surveying, agriculture, scientific research, Geodesy, intelligent transportation system, maritime applications, indoor application, etc. The challenge for industries is in large scale manufacture of miniaturized, robust receivers at reduced cost for various applications. ISRO is essentially a satellite service provider, but is open to interact with the industry on a case-to-case basis for technology development in relevant areas.

What is the timeline for IRNSS?

Indian Regional Navigational Satellite System (IRNSS-1), the first of the seven satellites of the IRNSS constellation is planned to be launched onboard PSLV in the first quarter of 2013. Thereafter, the rest of the 6 satellites will be launched and the full constellation of IRNSS is expected to be realized by 2014-15 timeframes.

How do you see the emergence of multi-GNSS scenario in near future?

The emergence of multi-GNSS scenario in the future is good for the user community. By using multi-mode receiver, the user need not depend on a single system. Also better accuracy, continuity and availability can be achieved by using signals from different constellations. Since various GNSS constellations are developed to fulfill their local and regional requirements, there are many systems to aid seamless navigation across the globe through interoperability. GPS and GLONASS are already operational. COMPASS, GALILEO are in various stages of development. India’s IRNSS and QZSS of Japan are also coming up. In addition, the augmentation systems like WAAS, EGNOS, MSAS and GAGAN are already available to the user. While the benefits are quite significant, the associated challenges in terms of realizing common time, reference systems, code, frequency allocations, transmitted power, signal interference, etc., are yet to be resolved. These issues are however, addressed at various international forums.

What will be the significance of GAGAN once IRNSS is in place?

GAGAN is a Satellite Based augmentation system, whereas IRNSS is an independent regional navigation system. Both have their own significance.

GAGAN, being an augmentation system, supports safety of life applications. As against this, IRNSS offers PVT solutions like other GNSS. Once IRNSS is in orbit, multimode receivers capable of receiving both the signals will perform precise positioning providing m/cm level accuracies.

GNSS systems are said to be vulnerable to threats of jamming, interference and spoofing. How do you see it as a challenge and measures to counter it?

The threat to GNSS signals is similar in nature to any other RF system. For each of the interference, effective countermeasure techniques and mitigation techniques are the need of the hour. Anti Jamming techniques like adaptive filtering, antennae techniques and timefrequency domain processing are being utilized. For anti-spoofing, encryption, longer codes and implementation of pilot and secondary codes, data processing techniques are employed. The increased usage of PPDs and other EM wave devices (intentional and non-intentional) are found to interfere with GNSS signals. While methods to mitigate these interferences are being investigated, regulatory measure also needs to be worked out.

There has been a lot of concern regarding Space Weather becoming a source for the cause of errors in GNSS systems? What is your view on it?

Space weather accounts for the most substantial errors experienced by GPS/ GNSS systems and their users. It is the single largest contributor to the singlefrequency GPS error budget and this needs to be estimated and accounted. Space weather predictions, better models and products/services, TEC maps over India, Ionosphere modeling, dual frequency receivers, etc., will help in mitigating the effects of the errors introduced. IRNSS is conceived as a dual frequency system and for GAGAN Grid based Ionospheric corrections are transmitted to remove the major error source of Ionospheric delay.

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