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. Hence, Satellites 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
- Astronomical Telescopes (eg : India’s Astrosat)
- Space Stations (eg : International Space Station (ISS) )
- 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).
- 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.
- 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 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.
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
- More accurate
- Multidimensional tool
Applications of Remote sensing Indian Satellites
- Spy in the sky . Used for reconnaissance
- Pick up the troop movements and deployments by the enemy
- 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
- Geotagging of all the assets created under schemes like MNREGA, RKVY etc can be done.
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)
India is considered as a leader in the area of application of space technology to solve problems on Earth
|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
- Indo-French satellite
- SARAL= Satellite with ARgos and ALtiKa.
- It was launched From Sriharikota, AP
- Use : meteorology, oceanography, climate monitoring etc
- 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.
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
- 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.
- 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
SAARCSouth Asia region.
- Satellite Diplomacy
- Announced in June 2014 & Launched in May 2017
- 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
- Launched in 2018
- Launched on PSLV-40 which was India’s 100th launch along with 30 other satellites
- developed by DRDO
- Provide information to armed forces about hostile radars placed at the borders
- 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