The first  successful  satellite launch by the Soviets in 1957 ushered in the space era. At initial  stages,  critical  military applications, national  prestige  and  enabling  space exploration  were  the main  drivers  for  the  development  of  satellites  and  satellite  launch vehicles.  In  later years, many  civilian applications  of  satellites have been  identified and extensively  developed.  Dominated by satellite  communications,  these  civilian applications  have  become the main motivating forces for the present-day indigenous efforts to pursue space programmes of many other countries. As for the future prospects,this new frontier of space research promises establishing space colonies and interplanetary  travel, and improving our understanding of the evolution of the universe. In  the  field of space applications, space-borne observations are looked upon as a very powerful and unique technique for a variety  of  applications  spanning from  weather forecasting to generation of information base relevant  to  sustainable  development  of natural resources.
India is amongst the first few countries to realise the potential of space technology and its applications. The pioneer of the Indian space programme, Dr. Vikram Sarabhai,  under whose chairmanship, the Indian National Committee  for Space  Research (INCOSPAR)  was formed in 1962, had cherished a dream that India should be second to none in the application of advanced technologies like space to solve the real problems of man and society.  In 1972, the Indian Space Programme was formally organised with the setting up of the Space Commission and  government funding through the Department of Space.
The potential of space technology for mass education, especially in terms of immediacy, omnipotence,  visual  power and outreach was recognised in the early 70's. Keeping in view the larger aspects of education, especially rural education, India undertook in 1975-76,  the Satellite  Instructional   Television  Experiment (SITE) to telecast a series of educational TV programmes on  health, family planning, agriculture, adult education etc., to cover 2,500 Indian villages via the US satellite, ATS-6. It was the largest sociological experiment ever carried   out in the world. The Satellite Telecommunication Experiment Project (STEP), conducted using Franco-German SYMPHONIE  satellite during 1977-79,  was  another  major demonstration of long distance satellite telecommunication application of space.  India also launched its  own  APPLE  (Ariane  Passenger  Payload Experiment),  an experimental communication satellite, in June, 1981 using the opportunity offered by the European Space Agency (ESA) to launch  this satellite on board the third developmental flight of ARIANE. 
A major development took place during 1980's, through establishment of the operational Indian National Satellite (INSAT) system, for providing indigenous services in telecommunications, TV broadcasting, meteorology and disaster warning. INSAT series, commissioned  in 1983, has today become one of the largest domestic satellite systems in the world, comprising five satellites. The last satellite  of  the second generation INSAT-2 series, INSAT-2E, was launched from Kourou, French Guyana on  April  3,1999. 
Work on INSAT-3 series of satellites has already begun. Five satellites in the INSAT-3 series have been planned and the first atellite, INSAT-3B has already been launched in March, 2000. 
INSAT system has a unique  design  combining  telecommunication,  television/radio broadcasting  and  meteorological  services into a single platform. The involvement of various users like Department of Telecommunication, Ministry of Information  and Broadcasting, India Meteorological Department  enabled proper tuning of INSAT system towards identified national developmental needs.
The demonstrated space applications in SITE and STEP of the 70's were transformed to practical and operational systems through INSAT. Today, INSAT links about 450 earth stations  set up in the country, including those located in inaccessible regions and off-shore islands.  Besides, there are about 8,500 Very Small Aperture Terminals (VSATs), including those installed by the National Informatics Centre and private networks catering to corporate houses. 
Television in India now reaches about 85 percent of its population through over 1000 TV transmitters linked via INSAT. Educational programmes for over100 hours are  telecast every week. INSAT system has become a powerful tool for training and developmental education  and  is  used by various agencies to provide continuing education, conduct in-situ training for industrial employees, social welfare personnel and training of Panchayat Raj (village governance) workers, etc.  
India continues to emphasise the use of INSAT for rural upliftment.  A pilot project that started in November, 1996 in a tribal district of Madhya Pradesh in Central India is now in progress to educate the tribal community on various aspects of health, hygiene, family planning, women's rights, etc. This project is being expanded to cover more villages and is expected to lead to a unique space based system that  will  be  dedicated  to  the development of rural society. Similar projects are being initiated in several other states.
Indian agriculture predominantly depends on the monsoons and precise forecasting of weather assumes a great significance. A large population of the country living on the east and  west-coast  face devastating cyclones very frequently.  Thus, precise weather forecasting  and  warnings on impending disasters is very important.  This is the reason why  India included meteorological instruments on its INSAT making it a unique multipurpose satellite system.  The cloud imageries collected by the satellites and over a hundred meteorological data collection platforms installed all over the country that relay local weather parameters via the INSAT have vastly contributed  in  improved meteorological  services in the country. The twin capability of communication and meteorological  imaging of INSAT is effectively used not only to predict the cyclone tracks  but  also to issue warnings to the likely to be affected population. About 250 disaster  warning receivers have been installed for this purpose along the cyclone-prone east  and  west-coast  of  India  (Fig-1:INSAT based Disaster Warning System) .  Several thousand lives have been saved by the INSAT disaster warning system by timely evacuation.
India  has  3.3  million  km2 land area with varied physical features ranging from snow-covered Himalayas  in  the north  to  tropical forests  in  south  and from regions in the east receiving  highest  rainfall  in  the world to deserts of Rajastan in the west.   India is also blessed with vast natural wealth but yet to be exploited fully.  A coastal belt of 7,500 km has a store of rich aquatic resources. What better way can be there to monitor and manage the natural resources for a large country like India than using the powerful tool of space-based observation  systems?    India  not only demonstrated the potential of space-based remote sensing in the 70's using data received from the US satellite, LANDSAT, but also built  its  own  experimental  satellites, BHASKARA-1  and  BHASKARA-2,  which  were launched in June 1979 and November 1981, respectively. India became one of the few countries  to develop its own operational Indian Remote Sensing Satellite (IRS-1A) in March 1988.  Today, India has the largest constellation of five remote sensing satellites, IRS-1B, IRS-1C, IRS-1D, IRS-P3, and IRS-P4 in operation. Among them are  IRS-1C and  IRS-1D,  which  are  the  best  civilian  remote  sensing  satellites  in  the  world.  IRS-P4 (OCEANSAT-1) launched in May 1999 is used for Ocean Resources monitoring and for understanding the atmosphere over the oceans. Two  more  satellites,  IRS-P5  for cartographic applications and IRS-P6 for resources survey, are planned for launch in the coming years.
IRS system has brought in a sea change in India's resources monitoring and management techniques. Data from IRS is used for estimation of acreage and yield of important crops like wheat, rice, sorghum, oil seeds and sugarcane, and other applications such as forest survey,  forecasting  drought  conditions, flood mapping and demarcation of flood-risk zones, land use and land cover mapping for agro-climatic planning, waste land mapping and their classification for possible reclamation, preparation of hydro-geo-morphological maps for locating sites for borewells, monitoring and development of irrigation command areas, snow-cover and snow-melt  run-off estimation  of Himalayan rivers for optimal use of  water,  etc. Data from IRS is also used in urban planning, alignment of roads and pipelines,  detection  of  underground  fires in collieries, marine resources survey, mineral  prospecting, etc. A unique application of data from IRS is in the Integrated Mission for Sustainable Development (IMSD) which is  aimed  at  generating  locale-specific prescriptions for development at micro-level. The impact of IMSD is  already  seen  in areas  where prescriptions generated have been actually implemented. Fig-2: Integrated Mission for Sustainable Development (IMSD) and IRS series of satellites developed and launched (both procured and indigenous) by ISRO. 
India realised quite early that sustaining the space program in the long run would depend on indigenous technological capabilities. Keeping this in view, besides building satellites, India  embarked on satellite launch  vehicle  development  in  the  early  70s. The first experimental launch vehicle SLV-3 was launched by India in 1980.  An augmented version of this vehicle, ASLV, was launched successfully  in 1992.  India  has  now acquired  a  significant  capability  in  the  launch  vehicle  area  with  the  successful development of Polar Satellite Launch Vehicle, PSLV, capable of  putting 1,000-1200  kg class satellite into 820 km polar sun-synchronous orbit. PSLV is being offered to launch satellites of other countries.  It launched two small satellites, one of Korea and another of Germany along with India's IRS-P4 in May 1999. More space agencies are expected to use PSLV for  placing  their  satellites  in  orbit;  a European satellite PROBA is scheduled for launch as a piggy back on board next PSLV. 
The Geo-synchronous Satellite Launch Vehicle (GSLV-D1) had its maiden  successful flight on April 18, 2001 from Sriharikota injecting the G-SAT 1 satellite into ~180  x 32,155  km  geo-synchronous  transfer  orbit (GTO).  Fig-3: Different types of sounding rockets and launch vehicles developed by ISRO.
Fig-4: List of satellites launched by ISRO so far

The initial thrust for Indian space programme came from the requirement of scientists to carry out investigations in aeronomy as well as in astronomy by conducting space-based experiments. Apart from developing technologies for sounding rocket and balloon borne instrumentation ISRO has established complementary ground based facilities particularly  for scientists from universities and academic institutions. The major areas of investigation in  space  sciences  have  been high energy cosmic ray variability using neutron/meson/Cerenkov  monitors, equatorial electrojet and spread-F ionisation irregularities, ozone, aerosol and cloud phenomena, middle  atmospheric  radiation,  dynamics  and electrodynamics, solar physics, IR astronomy, neutron star and black hole  astrophysics, planetary  science  and  origin/evolution  of  life etc. Also, India has recently launched
scientific  payloads  to  study  celestial  Gamma  Ray  Bursts  and  X-ray  sources.  For conducting atmospheric research with high resolution the Mesosphere, Stratosphere and Troposphere    (MST)  radar has been established at Gadanki near Tirupati. ISRO has enabled participation of scientists in major international science campaigns like monsoon experiment (MONEX), middle atmospheric program (MAP),  ISTEP,  INDOEX etc.  by providing the financial, technological and other assistance. Fig-5:facilities available to Indian scientists for conducting space science research.
Based on the interest and request of large number of space scientists in India, a number of new proposals and activities have been initiated by ISRO.  Some  of  the  major  ones include (a) ASTROSAT -a multi- wavelength dedicated satellite mission for high energy astronomy. The satellite is likely to carry soft and hard x-ray detectors and  imaging payloads,  all  sky  X-ray  monitors  and  a UV/optical telescope system, (b) SOXS - The Solar  X-ray Spectrometers payload development on board GSAT for studying solar active and flaring phenomena, (c) CRABEX: The Coherent Radio Beacon Experiment payload onboard  geo- stationary satellite and a ground based chain of receivers located at various  universities  and  research  institutions for developing ionospheric tomography or 3-D models of ionisation and its structure, (d) Planetary exploration/ science: competence building in planetary science studies and also development  of  sensors  for  planetary
probes/missions to moon/asteroids or nearby planets,(e) Microgravity science/exploration programme: National workshops and meetings have been  held to define novel scientific experiments for such a programme, proposals selected with potentials for space  borne experiments either in a balloon drop system or in a space recovery capsule.
The  national  investment  to  sustain the space programme can not only provide a significant and profitable domestic market for Indian industry, but also help it acquire technological muscle to enlarge  its capability for increasing the value added component in  other  areas  and eventually  capture  a part  of  the growing  international market in  high technology applications. Hence India encouraged an active participation of industries in its space programme that has resulted in the industry upgrading their own technological skills.  Also, as spin-off, a large number of technologies developed under space program have been transferred to industries for commercial applications.  A few of the major industries have now set up exclusive fabrication divisions to meet the demands of space program.  Large number of systems required on ground such as remote sensing data processing equipment, communication earth stations and terminal equipment, have opened up a fairly large market  for  the industry. 
A  constant  induction  of  manpower to carry on the task of continuous research and development is another requirement to sustain the  space  programme.  Towards  this, Indian  space  programme  has  established  a strong interface with academia.  One of the initiatives that has been taken in this direction is the scheme of Research Sponsored by ISRO (RESPOND) under which grants for undertaking research  projects  on  subjects relevant to space programme are selected and financially supported at  universities, academic and research institutions by ISRO. 
International  co-operation  has  been pursued  from the inception of the Indian Space programme. The establishment of Equatorial Rocket Launching Station at Thumba, conduct of space application demonstrations like SITE  and STEP and launches  of experimental satellite like Aryabhata, Bhaskara and APPLE, have involved co-operation with other  countries  including USA, the former Soviet Union,  France, Germany and international space agencies. India has co-operative agreements with several countries. India has set up two Local User Terminals (LUT) and Mission Control Centre (MCC) as part of the COSPAS-SARSAT network, under the International satellite aided search and rescue  programme.  India  also  shares its experience in space applications with other developing countries by training their personnel under a program called SHARES. The UN-affiliated  Centre for Space Science and Technology Education in Asia and the Pacific has begun its programme at postgraduate level in Remote Sensing  and Geographical Information  System,  Satellite  Communications,  Meteorology  and  Space Science for the  benefit of persons from Asia and the Pacific Region. India has hosted the second UN-ESCAP Ministerial Conference on space applications in November 1999. 
Even though Indian space programme is primarily directed towards establishment  of space systems  for  national  development, the capability that is built in the  process has started yielding economic benefits. The setting up of an exclusive commercial front under Department  of  Space,  ANTRIX Corporation, in 1992, for marketing hardware and services has acted as a catalyst in this endeavour.  Important commercial agreements include  world-wide  marketing  of  remote  sensing  data  from  Indian  satellites,  lease  of satellite capacity, launch of small satellites on board PSLV, supply of satellite hardware, providing tracking support for satellites using Indian ground stations and  training  of personnel. 
India has now established a well-integrated space programme with end-to-end capabilities  for the development and application of space technology for national benefits.  The  execution  of  the  programme  has  been  well  orchestrated--starting  with demonstration  of  end-use through large scale experiments, developing linkages with users, passing through experimental and developmental phases of  system development and finally, establishing state-of-the-art operational systems. 
That,  with  a  modest  overall expenditure of about US $ 2,400 million so far, India has built 29 satellites, developed three types of launch vehicles with thirteen flights in all so far, established an elaborate infrastructure to design, build and test communication and remote sensing satellites, their launch, and their in-orbit management as well as for data processing  and  application,  and  developed a strong manpower base for undertaking frontline R&D in space, proves that the Indian space programme has been one of the most  successful  and  cost effective,  especially,  when one looks at the benefit that has accrued to the nation in terms of communication, television broadcasting, meteorological services, disaster management, resources survey and management. 
As India enters the new millennium, it is  necessary  to  sustain  this programme  by continuously tuning it to the fast changing requirement and updating the technology that goes into the making of these sophisticated systems. The challenges continue to grow but that is what attracts and sustains the interests  of  personnel  working  in  the  space programme.  
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