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. 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 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

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

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

Science and Technology