Indian Space Research Organisation

ISRO was founded by visionary Dr.Vikram Sarabhai in 1969 by superseding the already established INCOSPAR. Since its formation ISRO has upheld its mission of bringing space to the service of the common man and to the service of the nation. It has become one of the sixth largest space agencies in the world. ISRO is the most cost-efficient space organisation of the world as its per mission cost is far less than any other space agency of the world.

. ISRO has one of the largest fleet of Communication Satellites (INSAT) and Remote Sensing Satellites (IRS) to vouch for fast growing needs of reliable communication and earth observation. To achieve self-reliance it was necessary to develop cost-efficient and reliable launch systems, which took the form of Polar Satellite Launch Vehicle(PSLV) which went on to become very favoured carrier for satellites of various countries due to its cost efficiency and reliability. The Geosynchronous Satellite Launch Vehicle(GSLV) was developed for heavy payloads in faraway space up to 36000km.

INDIAN SPACE PROGRAMME It began in 2nd FIVE YEAR PLAN with the help of both USA &USSR.Before we begin to understand the Indian Space Programme, we need to know that UN Space Commission has provided two orbits to each country :


  • It is also called Sun-Synchronous Orbit.
  • Earth observatory or Remote Sensing Satellites are launched in this Orbit.
  • It ranges 600km to 1400km
  • Only in this orbit International Space Stations are established.


  • It is at 36000km from earth
  • All communication satellites are launched in this orbit.

To study the Indian Space Programme we may divide it into two departments:



India’s launch vehicles are broadly categorised in two categories; PSLV & GSLV

It is called WORKHORSE of ISRO. It was developed with the help of USA. First development was called SLV- Satellite launch vehicle and then later upgraded to ASLV-Advanced space launch vehicle and finally over the years came to be PSLV.

  • PSLV is 4-stage launch vehicle, which means it carries fuel in 4 compartments.
  • It is non- cryogenic, which means it does not have cryogenic fuel technology.
  • It has both solid and liquid fuel.
  • Solid fuel is less inflammable so it lasts longer but on the contrary it is heavier than the liquid fuel.
  • PSLV is used to launch satellites in both GEO and LEO.
  • Recently, PSLV has been upgraded to PSLV-XL which has 14 extra thruster motors and enhance the capability of PSLV to carry heavy load or cover more distance.
  • PSLV-XL was used to launch Chandrayan 1. It carried satellite weight of 800kg.
  • PSLV-C37 created a record by successfully carrying 104 satellites into space.
  • PSLV is developed at Thiruvantrapuram & Andhra Pradesh.
  • Initiated with the help of USSR.
  • It is 3-stage vehicle.
  • It is cryogenic i.e. it uses cryogenic fuel in third stage.
  • Cryogenic technology is developed at Mahendragiri (Tamil Nadu) at liquid propulsion system. It is based on the principle of Sublimation i.e. Solid to Gas and Gas to Solid which releases enormous energy. In cryogenic fuel Oxygen is used from atmosphere
  • GSLV can carry up to 2.5 tonnes to a distance of 36000km.
  • It is mainly used to launch Communication Satellites.
  • Recently ISRO developed GSLV MK3 to lift off 4 to 5 tonnes and it was used for CHANDRAYAN 2.


Satellite programme is divided into two categories:

  • Communication Satellites
  • Earth Observatory/Remote Sensing Satellites
  • They move from pole to pole.
  • They cover whole earth in 24 hours.
  • They are also called spying satellites.
  • Major instruments of Earth Observatories are Camera, Mapper and Sensor.

Working areas of remote sensing satellites:

  • Pollution estimation and control.
  • Control over hunting and poaching
  • For Disaster Management and Forest Fire Control.
  • Climate Change and related issues.
  • Land and Agriculture survey.
  • Ocean Relief and Coral reef Protection.
  • Early warning system for tsunamis and Earthquakes.
  • Monsoonal studies.

Some of the EO satellites launched by India are:

  • RAI SAT 1&2 : These are all weather satellites for spying. It was developed with the help of ISRAEL.
  • SKETCH SAT: India s first satellite to study tropical cyclones and thunder storm.
  • RESOURCE SAT: For Agriculture.
  • They always stick to one place and cover one-third of the earth at a time.
  • They are launched at GEO that is at 36000km
  • Path of rotation is same as earth
  • Major instruments of communication satellites are Transponders-Ku Ka Ks.
  • Transponders provide digital pathway called SPECTRUM which is used for telecommunication and internet. There are two types of spectrum technologies CDMA and GSM.
  • CDMA is costly as it provides individual lane to everybody so call drops are less. GSM is cheap as it does not provide individual lane so there is overlap and call drop. More satellites are being launched to decongest the GSM spectrum.
  • Communication satellites are of two types: INSAT- Indian

                                                                      G-SAT- Global

  • Communication satellites can be launched by both PSLV and GSLV.
  • India has largest Constellation of Communication Satellite in Indo Pacific


Working areas of Communication satellites:

  • E- Governance
  • DTH
  • Internet 4G , 5G
  • Satellite Telephone
  • Internal and External Security
  • Traffic management and Super Computing.

India has 3 major missions under communication satellites:

  • BHUVAN: Environmental Conservation & Monitoring.
  • IRNSS: Indian Regional Navigation Satellite System. Since India is dependent on USA for GPS to become self reliant India is launching 7 communication satellites.
  • GAGAN: GPS Aided Geo Augmented Navigation System for air traffic management. It is a joint project with Airport Authority of India.

BHUVAN, IRNSS and GAGAN are together called SATNAV.

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