Indian Satellites

Indian Satellites

This article deals with ‘Indian Satellites‘. This is part of our series on ‘Science and Technology’ which is important pillar of GS-3 syllabus . For more articles , you can click here

Types of Orbits

To understand this topic, we will first study about the types of Orbits in which satellites orbit around the Earth

Low  Earth Orbit

  • 400 to 900 km above surface of the earth
  • Closest to earth
  • Satellites have to overcome huge drag due to atmosphere. HenceSatellites have shorter life span of 2-3 years
  • They appear to be moving in the sky & take approx 1.5 hours for one revolution.
  • It has following applications
    • Astronomical Telescopes (eg : India’s Astrosat)
    • Space Stations (eg : International Space Station (ISS) )

Geostationary Orbit

  • There is only one Geostationary Orbit at 36,000 km above the equator 
  • Orbit around the earth with an orbital period of one sidereal day (23hours 56 minutes and 4.1 seconds)
  • It is circular orbit lying in equatorial plane .
  • It has special property of remaining permanently fixed in exactly the same position in the sky, meaning that ground-based antennas do not need to track them but can remain fixed in one direction.
  • Such satellites are often used for communication and broadcast purpose (due to above property).

Geosynchronous Orbit

  • It is not circular & not equatorial (ie not in equatorial plane but inclined)
  • Rest all things are same as Geostationary Orbit ie distance from earth & time taken to complete one rotation are same .
  • From earth, these satellites don’t appear to be stationary.

Clarke’s Orbit

  • Single Geostationary Satellite can cover about 40% of earth’s surface. If three satellites are placed at proper longitude whole earth can be covered .
  • This was first conceptualised by Arthur C Clarke  & Geostationary orbit is sometimes referred to as Clarke’s Orbit in his honour

Polar Orbit

  • Polar Satellites passes  above both poles of Earth ie inclination of 90 degree from Equator
  • Used for earth-mapping , earth observation, reconnaissance satellites & weather satellites

Sun Synchronous Orbit

  • It is special type of Polar Orbit
  • In this , altitude & inclination are set in such a way that it guarantees same illumination 
  • It has same application as polar satellites.

Junk Orbit / Graveyard Orbit

  • When life of Geo-Stationary Satellite completes, they are send above Geostationary Orbit
  • That is known as Junk Orbit
  • Good way to tackle space junk.

Satellite Systems

1 . Remote Sensing Satellites

  • Remote sensing is the observation of the earth from the space (900 km above) ie space based earth observation system
  • These are in
    • Polar (Pole to Pole Movement)
    • Sun Synchronous   (so that illuminance of point is same )
    • Low earth orbit (900 Km)
  • Examples include Cartosat, Resourcesat, Scatsat, Oceansat etc.

Space borne remote sensing is better than ground surveys and air borne sensing because

  • Cheaper
  • Speedier
  • More accurate
  • Reliable
  • Multidimensional tool

Applications of Remote sensing Indian Satellites

Indian Satellites
Applications of Remote Sensing Satellites
  • Defence
    • Spy in the sky . Used for reconnaissance
    • Pick up the troop movements and deployments by the enemy
  • Agriculture
    • Assess net crop area
    • Movement of locust
    • Damage assessments
    • India divided into 15 Agro climatic zones based on data from IRS 1A and 1B
    • => Pradhan Mantri Fasal Bima Yojana will use data of these satellites extensively to estimate the damages 
  • Disaster Management
    • Early warning of cyclones, floods etc
    • Monitoring of the forest fires
  • Urban studies
    • Mapping Urban sprawl
    • Structural plans for cities
  • Governance
    • Geotagging of all the assets created under schemes like MNREGA, RKVY etc can be done.
  • Fisheries

By analysing the colour of the ocean, surface temperature and wind conditions from the Oceans , it is possible to identify areas in the sea where the fish school will assemble

2 . Geosynchronous Satellites – INSAT & GSAT

  • INSAT  (Starting Satellites of India)  series was built by Ford Aerospace Corporation of USA under contract 
  • GSAT – GSAT series of geosynchronous satellites is a system developed by ISRO with an objective to make India self-reliant in broadcasting services.
  • Satellites are monitored and controlled by the master control facility at Hassan (Kr) &  Bhopal (MP)

Applications

India is considered as a leader in the area of application of space technology to solve problems on Earth

Indian Satellites
Applications of Geosynchronous Satellites
Telecommunication – Responsible for Communication revolution in india
– Remote and far flung areas have been effectively connected  
Television DTH all over the country.  
Disaster management & meteorology – Warning mechanism for cyclone
– Short term weather forecasting
– Impact assessment for droughts and floods  
Navigation – IRNSS
– GAGAN too use 3 Geostationary satellites apart from GPS  
SAS&R Satellite aided search &rescue  

Some important Indian Satellites of ISRO

SARAL

  • Indo-French satellite
  • SARAL= Satellite with ARgos and ALtiKa.
  • It was launched  From Sriharikota, AP
  • Use :  meteorology, oceanography, climate monitoring etc

HySIS

  • India’s first Hyperspectral Imaging Satellite (HysIS)
  • Launched with PSLV in Polar Orbit

Hyperspectral Imaging Technology 

  • It combines the power of digital imaging and spectroscopy
  • Every pixel in the image contains much more detailed information about the scene  than a normal color camera
  • Earlier used in Chandrayaan-1 mission for mapping lunar mineral resources.

Application:

Hyperspectral remote sensing is used for a range of applications like

  • Mineral prospecting
  • Soil survey
  • Coastal water studied
  • Environment Studies + Detection of Pollution from industries

RISAT 2B

  • May 2019
  • Radar imaging earth observation satellite with an advanced technology of 3.6m radial rib antenna. 
  • The satellite is intended to provide services to Agriculture, Forestry and Disaster Management domains.

GSAT 11

  • Launched in Dec 2018
  • Heaviest satellite built by ISRO (5855 kg)
  • Launched with help of Ariane Aerospace from French Guiana 

South Asia Satellite (GSAT-09)

  • South Asia Satellite is  communication-cum-meteorology satellite by ISRO for the SAARC South Asia region.
  • Satellite Diplomacy
  • Announced in June 2014 & Launched in May 2017

Features:

  • Application : communication, tele- education, tele-medicine ,  disaster monitoring and other need based services.
  • Has 12 Ku Transponders with each nation getting atleast One Transponder
  • Earlier Pakistan was part but later it withdrew 
  • First Indian Satellite to use Electric Propulsion
  • Shows that India is willing to use its technological capabilities as a tool of diplomacy

GSAT – 19

  • Launched in June 2017 with Indian Launcher GSLV Mk – III with operational Cryogenic Stage from Sriharikota (first Satellite to be launched with this) – Earlier all GSAT were launched with help of French Agency Ariane Aerospace.
  • Geostationary Satellite (36,000 km Orbit)

Aditya – L1

  • India’s first dedicated scientific mission to study sun. 
  • Aditya L1 is to be the first satellite to study the magnetic field of the sun’s corona.
  • Will be placed at Langrange point (L1)

Note : NASA has announced it’s program called Parker which will study Corona by going to the Sun.

Cartosat – 2

  • Cartography  = science of drawing maps
  • Launched in Feb 2017
  • In 104 Satellite Launches, this was the primary satellite.
  • Primarily meant for military requirement (hence, ISRO moving from Civilian to Military uses too)

Cartosat satellites: Cartosat series are earth observation satellites in a sun-synchronous orbit. They have high resolution cameras installed on them . The imagery sent by satellite are useful for cartographic (science of drawing maps) applications

Cartosat 2s

  • Launched in 2018
  • Launched on PSLV-40 which was India’s 100th launch along with 30 other satellites

EMISAT

  • developed by DRDO
  • Provide information to armed forces about hostile radars placed at the borders

SCATSAT

  • Weather satellite => mainly focus on Cyclone formation
  • It has replaced Oceansat
  •  

UN Kalam Global Sat

  • A global satellite for Disaster Risk Reduction GlobalSat for DRR 
  • Launched at UN World Conference on Disaster Risk Reduction held at Sendai in Japan in March 2015.

ISRO Student Collaborations

  • ANUSAT (Anna University Satellite)
  • JUGNU : IIT Kanpur

This concludes our article on Indian Satellites . For rest of our series on Science and Technology, click on following link

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