Satellite technology utilization for Rural and Urban India S. Pal*DFIETE & V. S. Rao**FIETE Key words: satellite communication, satellite technology for rural India, remote sensing. ABSTRACT: Communication capabilities in various forms provided by the modern spacecraft are bridging the gap between modernized cities and backward rural villages. The remote sensing satellites are equally helping rural India by providing useful information to increase farm yield, fish catching and also helping to save lot of lives by disaster warning and weather forecasting. This paper describes the utilization of the satellite technology in various forms for Indian masses particularly rural India.. INTRODUCTION: The society having a better and quicker means of communications is considered to be an advanced and forward looking society. Most of our country’s population in the past was
not served by the telephone and television networks that so greatly influence cities and western societies. There is a great influence of present day fast evolving technologies particularly the digital techniques on the development of the society. It includes present day computers and Satellite Communication. Present day technological tools support and complement each other to complete the total communication scenario. Satellites are
perceived largely as a means to reach isolated places. Because of the broadcasting nature of the satellites, a signal sent up to the satellite comes down everywhere over a wide area, thus providing connectivity to the inaccessible parts of the country. Satellites bring the television to the homes even in remote villages. Television is an extremely powerful medium for education, literacy rate in rural areas can be improved through tele-education services based on satellite technology. Being a tropical country with long coast line, natural disasters often knock at the country and the rural people are often the victims. Terrestrial links and transport systems cripple very often. Satellites come to the rescue in such events for disaster management, which requires real time decision making and action. The introduction of space communication and the present era of information technology has changed the current scenario and we have seen the third technological revolution (information + communication = Information Technology) in the last decade of the last century. The present era is called the IT era. The technological evolutions which have taken place in the last century are simply beyond one's imagination. Many technological reversals have been seen, like the telephone which should have been on the wired network has become wireless while the TV which was wireless, works on cable. * Out Standing Scientist/ Program Director, SATNAV, Deputy Director, ISRO Satellite Centre, Air port Road, Bangalore-560 017, India. (
[email protected]) ** Group Head, Communication Systems Group, ISRO Satellite Centre, Air port Road, Bangalore-560 017, India. (
[email protected])
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Many individual spheres of working have become almost universal, like education has come to the drawing room from school and colleges, sectors like banking, medicines, hospitals etc which were location specific are available on net. With the development of space technology, time and distance have lost their conventional meaning, thereby permitting men and women all over the world to share their experiences, frustrations and successes with great ease. Sophisticated and expensive medical treatment has been made reachable to those underprivileged society living in inaccessible parts of India through telemedicine project conceived with satellite technology. In a nutshell, the present day world has become a global village and thereby we are in a shrinking globe and expanding universe. There is tremendous convergence and fusion of communications, computers and associated technology in the present era. Space communication technology takes all this technological advancement to the rural areas which are backbone of Indian democracy. DESCRIPTION: As we become increasingly networked, our world will grow smaller and bigger simultaneously. Communication is at the root of the progress of every society. Society is often described as essentially people in communication. The conventional communication tools are: ♦ Telegraphy using copper wire line ♦ Telephony using copper wire line ♦ Television ♦ New papers, books, etc. ♦ Means of Transport All these have undergone tremendous changes and the new technologies emerged are ♦ Mobile Satellite Telephone - Personal Communication Systems ♦ INFOSAT (information satellite) ♦ A major shift from analogue to digital domain ♦ An increase in the value of software as opposed to hardware content ♦ Extension of optical technology towards the local loop coupled with increasing use of optical switches and optical processing ♦ Use of wireless in access technology - New access & Modulation codes ♦ Ultra broad band services ♦ Extensive use of spread spectrum and code division multiple access techniques. Services planned / in existence are: ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦
Virtual Private Networks PCS - Personal Communication Services Call Collect Services Desk top Video conferencing Card Phone Services Teleshopping Video Telephone Telehealth
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♦ Tele-education ♦ Interactive Video & Video on demand ♦ Multimedia transmission / reception ♦ e-mail ♦ e-Governance ♦ e-commerce ♦ Global positioning/timing system along with SATNAV ♦ Digital TV, Direct TV to Home MOST IMPORTANT - THE INTERNET & WORLD WIDE WEB All these need either terrestrial or satellite channels to serve the user. The present day scenario can be best summarized by fig-1. Here space communication becomes an important tool irrespective of the large growth in terrestrial communication networks particularly when the technology is to be taken to rural India.
Television
Internet TV
Cable TV
Video on Demand
AUDIO SYSTEM
Space
DVD Internet Cellular
Telephone Cellular Pager
Internet Telephony
Fax
World Wide Web
Home Banking Network Computing
Printer VideoCamera
Video conferencing
Desktop PC
Terrestrial
PDA Credit Card
VILLA GE
Smart Card
A FUTURE COMMUNICATION SCENARIO
Space Communication is provided by satellites in various orbits. Satellites have been put in to all these orbits and successful communication links have been established. It will be a matter of large discussion if one starts explaining the pros & cons of the orbits & their satellites. Satellite communication started with fixed services and expanded to greatest
potential applications in the mobile and broad cast services. Satellites have innate advantage that make them an attractive alternative or complement to terrestrial broadband circuits. Satellite communication provides reliable means of providing information or monitoring inaccessible areas even in the case of severe cyclones and disasters and when the entire terrestrial network fails. The conventional services provided by satellites are: Telephony/TV Broadcasting/Data reception and distribution/Direct Television broadcasting/Disaster warning/Continuous weather monitoring/Spacecraft Vehicle Tracking and Commanding/ Inter satellite links/ Mail /Internet/Data mining, Position (GPS) and time determination / Moving motor vehicle tracking etc. 3
Mobile Personal Communications: Most of the time technological advancements have taken place due to defense requirements. However in the area of communications where more than the military requirements, it is the business requirements which have given a big flip to the overall scenario of communication and ushered us from fixed copper wire communication era to the era of mobile communication - meaning an individual (stationary or on move) carrying small inexpensive hand held communicator and being reached by voice, fax or data with a single telephone number independent of location. Basically it means to provide communication to and from users located anywhere on the globe and possessing a portable light weight hand held mobile telephone. This could be termed as Personal Communication Services (PCS). Today, a hand held mobile phone has become a personal hold and has become affordable by every citizen across societies. This service is available only in densely populated cities and towns. Even today, the cellular mobile service is a dream for people in remote areas. This can be fulfilled with mobile Satellite Communication though it is yet to take off commercially. The advantage of space communications is that one does not have to be at a particular place to derive its benefits. The Communication through space is independent of place and time and geo political limit. Though the Irridium and Global Star mobile satellite communication projects have failed due to the astronomically high terminal & service cost as compared to terrestrial based systems, on engineering account the two projects cannot be considered as failures since the projects were engineering led - rather than marketing led. In spite of cellular telephones and other mobile services, the two systems have shown their usefulness over others in Afghanistan operations and also communications to inaccessible places. In the foreseeable future new equipments and techniques may be used in mobile satellite technology to bring down the costs and make the system affordable. The day is not far off for providing the benefits of technological advancement being enjoyed by urban people to the people in rural inaccessible India. Internet over satellite: It will be quite important and relevant to talk about latest arrival on the communication technology scene: the internet and the web. Today, the internet provides a vast array of services with high bandwidth links that can simultaneously carry telephone, video (Television) and data and is accessible from anywhere through a variety of information appliances ranging from personal computers and hand-held digital assistants to screen phones and televisions, not to mention the computers embedded in everything from automobiles to vending machines. The Net is a phenomenon that cannot be ignored. It is an agent of change in all sectors of society. . In turn, this will lead to truly profound changes in society & the present technological paradigm.
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To help all these & to spread the net at a faster pace even to inaccessible & remote places satellite communication plays a major role, besides the conventional terrestrial links, optical links etc., which cater to cities and larger population bases owning to the economics. It is expected that the space based high speed internet service will reflect triple digit growth rate. As of today internet is the greatest thing to happen in the satellite industry. For many space segment operators INTERNET is the biggest earner. As of today internet is going towards zero tolerance for failure. The goal is more & more critical services to NET. The availability of internet services through space is a big boon to rural folk to get all the information required for increasing their knowledge including agricultural productivity. Services Provided by ISRO: ISRO had mainly three types of satellites viz., Communication satellites mainly for communication operating in GEO, Remote sensing satellites deployed in LEO and scientific satellites; for various applications driving the growth and development of entire India. Many applications are mainly focused towards upliftment of rural areas by bringing education, health etc. to the door steps of rural homes/community centres. INSAT Utilization: Satellite Television broadcast was first introduced by ISRO in India 32 years back when the Satellite Instructional Television Experiment (SITE), targeted for rural areas, was commenced on August 1, 1975. The video conference involved the use of INSAT2C and INSAT-3B satellites. Over the years, ISRO has also conducted interactive training and distance education programmes through the INSAT satellite system. INSAT series satellites deployed in GEO orbit are mainly providing • Telecommunication • Television • Search and Rescue • Meteorology • Radio Networking. The Indian Space Research Organisation (ISRO) signed Memorandum of Understanding with various state governments for establishing a satellite-based communication network using the Ku-band capacity of INSAT system. The Ku-band capacity of INSAT will be used for promoting satellite based communication, specifically, in the areas of distance education, tele-medicine, agricultural extension, e-governance, self-help groups, marketing and HRD, community internet centres, etc. While ISRO will provide the transponder capacity on board INSAT and the technical support of the state governments will operate the satellite communication network for the various objectives afore-mentioned. ISRO has already helped the Orissa State Government in the implementation of Vidya Vahini Yojana. Besides, it has established the Jhabua Developmental Communication project in Madhya Pradesh that is in progress since 1996. ISRO has also started the
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INSAT training and developmental communication channel in 1995 that is being used by several private and Government agencies for industrial training, training of panchayat workers, agricultural extension workers, etc. The MOU signed with Andhra Pradesh marks yet another milestone in the implementation of a countrywide Gramsat network for grassroots level development Video-conferencing facility provided by INSATs is a great achievement in bringing various segments of administration together. To give an example, the facility enabled then Prime Minister, Mr Atal Behari Vajpayee, on August 01, 2000 to have a virtual "tete-a-tete" with the chiefs of Panchayat Raj Institutions from 14 video/studio link centres spread across the states of Uttar Pradesh, Gujarat and Karnataka. In an hourlong conversation, the Prime Minister had a first hand assessment of the nitty-gritty of the local problems being faced at the grassroots level in the country. The video conferencing centres had been established at Bakshi ka Talab, Gaurabaug, Sarojini Nagar, Nishatganj and Cantonment Park Road in Lucknow district (UP), Himmat Nagar, Mehsana, Nadiad, Palanpur and Gandhinagar in Gujarat and at Mangalore, Dharwar, Raichur and Tumkur in Karnataka. Lauding the role of science in the rapid strides being made by the nation, the Prime Minister congratulated the scientists and engineers for their endeavor to make the video conference a reality. Mr Vajpayee said that this would bridge gaps and open up new vistas of growth and communication. Video conference provided a platform for the Prime Minister to give a patient hearing to the Panchayat representatives and, at the same time, apprised them of the limitations and practical problems faced by the government at times and to discuss vast array of issues viz., specific problems faced by panchayat institutions like education, water shortage, and irrigation. Telemedicine: The advances and convergence of IT and telecommunication can bring the entire health care services to the patient’s doorstep. Telemedicine is delivery of health care information across distances using telecom technology. This includes transfer of images like X-rays, CT, MRI, ECG, etc. from patient to expert doctors seamlessly, apart from the live video conferencing between the patient at remote hospital with the specialists at the super speciality hospital for tele-consultation and treatment. ISRO has been spearheading satellite based telemedicine programme in the country with remote district hospitals connected to Super Specialty Hospitals in major cities using INSAT satellite (Fig.2). The advantage of telemedicine in reaching out to the rural and remote population has been well established through the experience of this present telemedicine network. However, there is a need to provide a common platform to all concerned agencies like communication systems/software and medical equipment providers, super-specialty hospitals, healthcare administrators, various departments of Government, trust and private hospitals, NGOs and corporate hospitals dealing with healthcare both in India and abroad. It will also help to exchange ideas, practices and methodology to effectively implement and use the emerging telemedicine technology
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Reaching the un-reached
Referral Hospitals
Empowerment at the grassroots through information dissemination and
Health Specialist Centre
Video Conferencing
Cardiology
Pathology
Video Conferencing A M BU LA N C E
Panel of Doctors
Fig.2 Telemedicine via satellite In the field of telemedicine, the first pilot project was started in Andhra Pradesh in 2000 connecting Apollo Hospitals at Chennai and Aragonda village and ISRO's hospital at Satish Dhawan Space Centre, SHAR, Sriharikota, in Nellore District. The telemedicine network is extended to more hospitals. DTH-TV Broadcasting Common entertainment today is through Television. Television broadcasted by satellites enabled every citizen in all parts of the country to have the benefits. DTH – TV broadcasting comes under BSS (Broadcasting services) as well as under FSS (Fixed Satellite Services). Under FSS services it is from point to multipoint but whose location is known while under BSS it is always in universal broadcast mode. With digital TV in 36 MHz standard transponder, one can transmit almost 12 TV channels using latest compression, error correcting codes etc, where even at low SNR better TV quality can be received. This will give rise to the possibility of reducing orbital separations between DTH Satellites. This is only the means to provide entertainment communication to rural inaccessible areas.
Village Resource Centres (VRC): Communication Satellites are effectively used to provide all most all the useful information needed for the village folks by establishing village resource centres/information kiosks (Fig. 3). This is another highly successful project to bring technology to the benefit of rural areas.
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VRC project strives to promote a need based single window delivery system for providing services in the areas of education, health, nutrition, weather, environment, agriculture and livelihoods to the rural population to empower them to face challenges. This satellite based project, aims for digital connectivity to remote villages for providing multiple services such as telemedicine, tele-education and remote sensing applications through a single window. The setting up of VRC is yet another saga of adventure that has been taken up by ISRO to benefit the rural society.
INFO SERVICE PROVIDER VILLAGE INFO Kiosk
STUDI O
BROADCAST MODE
2-WAY SYM/ASYM MODE
VIDEO TRANSFER NETWORK * NETWORK MANAGEMENT
VOICE
DATA BASE
VOICE
DATA
Empowerment at the grassroots through information dissemination and decision support NR INFO ACCESS IRRIGATION SCHEDULE TRAINING ENTITLEMENTS
AGR. ADVISORY MET. INFO SERVICE EDUCATION MARKET ADVISORY HEALTH SERVICES ENTERTAINMENT MAIL TRANSACTIONS BROWSING
Fig.3 Village community information kiosks The VRC concept has been evolved and implemented by integrating ISRO's capabilities in satellite communications and satellite based earth observation to disseminate a variety of services emanating from the space systems and other Information Technology tools to address the changing and critical needs of rural communities. The VRC is a totally interactive VSAT (Very Small Aperture Terminal) based network. Users located at one node of this network can fully interact with others located at another node through video and audio links. Each of the nodes can be further extended using other technologies like Wi-Fi, Wireless and Optical Fibre. These extensions may serve as local clusters around the areas where the VRC is located. The information provided will be in the form of geo-referenced land record, natural resources, suitable sites for drinking water as well as sites for recharging to replenish ground water, water harvesting, wastelands that can be reclaimed, rural employment creation, watershed, environment, infrastructure, alternate cropping pattern, and so on. By suitably blending the information derived from earth observation satellites with ground derived and weather related information, locale-specific community advisory services can be provided. Community based vulnerability and risk related information, provision of timely early warning and dissemination of severe weather
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related information can lead to reliable disaster management support at the village level. VRCs can also provide a variety of services like tele-education, telemedicine, online decision support, interactive farmers' advisory services, tele-fishery, e-governance services, weather services and water management. By providing tele-education services, the VRCs act as virtual community centric learning centres. At the same time, VRCs will provide connectivity to speciality hospitals thus bringing the services of expert doctors closer to the villages. In addition, VRCs will facilitate access to spatial information on important subjects like land use/land cover, soil and ground water prospects which can enable the farmers to get support in taking important decisions based on their query. Besides, VRCs will enable online interaction between the local farmers and agricultural scientists. Fishermen can obtain information on sea state and wave heights. Provision of information on many governmental schemes, location and farming system specific action plans based on weather, community specific advice on soil and water conservation are the other services rendered by VRCs. Search & Rescué: The search and rescue facility provided by satellites is a breakthrough in technology in ensuring safety and providing support in case of disasters/accidents to the tourists, fishermen etc. Meteorology: All the first generation INSATs and INSAT-2A, 2B and 2E in the second generation in the operational INSAT system were configured for multi purpose mission with transponders for telecommunication & broadcasting and Meteorological payloads. To meet the demanding requirements of Indian Meteorological Department’s, ISRO launched a satellite with dedicated meteorological payloads - Very High Resolution Radiometer (VHRR) and Data Relay Transponder (DRT), and is named as Kalpana-1 after launch in the memory of Late (Ms) Kalpana Chawla, Indian born American Astronaut. Very High Resolution Radiometer (VHRR) is a three band VHRR capable of imaging the earth in three spectral bands namely Visible(VIS), Water Vapor (WV) and Thermal Infra Red (TIR), to provide both day and night coverage. The weather data relay transponder (DRT) receives 402.75 MHz signals from unattended weather data collection platforms, translates them to 4506.05 MHz and retransmits it to a central facility - Meteorological Data Utilization Centre, IMD, Delhi. This data is being used along with the VHRR imageries for weather forecasting. Satellite derived products data are increasingly used in conjunction with conventional meteorological observations in the synoptic analysis and conventional weather forecasts to extract information of relevance to various sectors in India. The impact
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of satellite data is phenomenal in certain areas of meteorological applications such as thunderstorm forecasts, Tropical Cyclone monitoring, aviation forecasts etc. The major application of satellite data has been the monitoring of Synoptic weather systems ranging from thunderstorms, fog detection to cyclones and planetary scale phenomena such as monsoon. Synoptic applications of satellite imagery are in use at Indian Meteorological Department. Following satellite data products are derived from Kalpana-1 and the same are also archived and displayed on IMD website daily. • Earth cloud imagery in visible, IR bands and water vapor every hour on black & white and color. • Clouds Motion vectors over Bay of Bengal, Arbian Sea and Indian Ocean at 00, 07, 12 and 18 UTC and being disseminated over GTS. • Outgoing long wave radiation (OLR) on daily/weekly/monthly basis at 0600UTC. • Sea surface Temperature (SSTs) at 0600 UTC is being derived over Bay of Bengal, Arabian Sea and Indian Ocean. • Quantitative Precipitation Estimates (QPE) on daily/weekly/monthly basis. Satellite bulletins based on 3 hourly / 1 hourly Kalpana-1 cloud imageries are prepared and transmitted to all the forecasting offices on Global Telecom Service (GTS) through RTH, New Delhi. Satellite imageries and animations are also put on the IMD website on regular basis for the users and public. Heavy rainfall advisory, bulletins are also transmitted regularly for IMD forecasting offices and other centres daily. During the tropical cyclones in Arabian Sea and Bay of Bengal hourly special satellite bulletins with intensity and position are also issued for all the users by the satellite Div., IMD. During winter season, fog formation is one of the most important weather events over northern parts of India which affects the aviation badly. The Kalpana-1 imageries are regularly utilized for capturing such events. IRS utilization: Remote Sensing satellites launched and operated by ISRO are highly successful in providing vital information regarding earth resources and also in providing cartographic maps for town planning and development. Data from Indian Remote Sensing Satellite is used for various applications of resources survey and management under the National Natural Resources Management System (NNRMS). • • • • • • •
Preharvest crop acreage and production estimation of major crops. Drought monitoring and assessment based on vegetation condition. Flood risk zone mapping and flood damage assessment. Hydro-geomorphological maps for locating underground water resources for drilling well. Irrigation command area status monitoring Snow-melt run-off estimates for planning water use in down stream projects Land use and land cover mapping
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• • • • • • •
Urban planning Forest survey Wetland mapping Environmental impact analysis Mineral Prospecting Coastal studies Integrated Mission for Sustainable Development for generating locale-specific prescriptions for integrated land and water resources development in 174 districts.
Many state governments are utilizing the remote sensing data for various applications including town planning. For example, Andhra Pradesh has been extensively using ISRO satellites for societal applications. Andhra Pradesh is one of the foremost in the utilisation of remote sensing technology for management of land and water resources and disaster management. Remote sensing technology is used for watershed management in drought prone districts of Adilabad, Ananthapur, Kurnool, Mahaboobnagar, Nizamabad and Ranga Reddy. Management plans for major irrigation projects like Srirama Sagara and Nagarjuna Sagara have been planned using remote sensing data. More than 35,000 bore wells have been drilled using remote sensing data with better than 90 percent success rate. Oceansat The 1050 kg satellite placed in a Polar sunsynchronous orbit of 720 km height. IRSP4 carried on board an Ocean Colour Monitor (OCM) and a Multifrequency Scanning Microwave Radiometer (MSMR). OCM is a solid state camera operating in eight narrow spectral bands. The camera is used to collect data on chlorophyll concentration, detect and monitor phytoplankton blooms and obtain data on atmospheric aerosols and suspended sediments in the water. The Microwave Scanning Radiometer (MSMR) which operates in four microwave frequencies both in vertical and horizontal polarisation with its all weather capaility is useful for measuring sea surface temperature and meteorological parameters like Sea Surface Temperature (SST), Atmospheric Water Vapor and Sea Surface Winds. The Oceansat data helped fisherman to a great extent in locating fish concentration in the sea and in increasing the fish produce. The satellite data also helped to study the ocean behaviour and to provide safety guidelines and precautions to fisherman, divers and navy to a great extent. INFOSAT: The future Telecommunication spacecrafts will be developed from transmission in to Information Satellites (INFOSAT). They will be given many of the properties of terrestrial telephone exchanges and signal processing equipments and it will be possible to integrate them directly into future global networks. They will thus permit immediate applications of many existing and future services. Because of their inherent built up flexibility, these satellites will be able to support and speed up the 11
initial experimental phase of many new services before their trial on terrestrial networks. These type of satellites will enable new services to be tried out over a large area before being put in to the market and optimally adapted to suit the most appropriate transmission medium. The future INFOSATS will be of three types: National / Regional, International & Relay. Future technologies will enable the construction of an INFOSAT network in which the above three will be connected to each other. The onboard processors will ensure that the signals to be exchanged between the satellite and the terrestrial subscribers are combined using Time Division and Space Division multiplexing techniques and distributed in accordance with the user requirements. Special coding techniques will ensure the security of transmissions. Configuration of INFOSAT: The satellite platform will have multiple reconfigurable antennas/transmitters with dynamic power sharing / Receivers in X various frequency ranges / large reconfigurable switching matrices at baseband and at RF level / intersatellite links permitting signals to be exchanged between satellites according to changing requirements / complex and efficient analog / optical / digital signal processors / New modulation technique and multiple access techniques. It will be sufficiently broadband systems & may have even optical space communication components. The satellites besides their autonomous control and power generation equipment may have sensors to observe the earth’s atmosphere and pass the data to an appropriate station after processing. This will help to deal with the situation like Orissa Cyclone. Such a system will obviously have Geo synchronous spacecrafts with some orbiting satellites to take care of North/South pole regions.
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Fig. 4 INFOSAT configuration
The INFOSAT Network (Fig.4) is to be an integral component of the planned worldwide broadband telecommunication network. Therefore it will be necessary for planning of the satellite network and the terrestrial network to be closely coordinated. Until now satellites have connected the terrestrial networks of various countries and organizations. Services to be provided by INFOSAT: Radio and data distribution services to many users which are spread over a large area. Data collection services for large areas with many data transmitter stations (multi point-to-point operation : weather, oil, electricity & water meter reading etc.). Telecommunication services for thin routes Telecommunication services with ships, aeroplanes, space vehicles, etc). In the area of business communications demand is growing for broad band internet & multimedia communication facilities which can be applied flexibly using satellites. Worldwide Radio paging Video conferencing and high resolution TV broadcast trials. Mobile radio services can be combined with location finding services and be used for automatically locating subscribers. Earth observation with special warning mechanism and environmental protection services in close coordination with terrestrial sensors. By integrating INFOSAT into terrestrial network, it will be possible to supply all the subscribers of a future global network with all essential information. This will make the location of the user quite irrelevant. Conclusion: There is a great influence of present day fast evolving technologies particularly the digital techniques on the development of the society. Satellite technology bridges the gap between urban and rural areas in utilizing the technologies. Inspite of advancement of technology to a great extent, many parts of India are still backward and inaccessible by terrestrial means. Satellite technology connects total country irrespective of location. This paper briefed about the services provided by satellites to bring the cutting edge technology and benefits to the rural and inaccessible area. References: 1. 2.
Surendra Pal, Advanced Satellite Communication Technology-A Perspective, Journal of Spacecraft Technology, Vol.12, No.2, July 2002. Lectures delivered by the author Dr. Surendra Pal on Satellite Communication and various studies carried out in the area.
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