Table of Contents:

  1. Evolution of Universe- Big Bang theory
  2. Dark Energy
  3. Dark Matter
  4. God particle
  5. Large Hadron Collider
  6. Neutrinos- Observatories in India and Globally
  7. Stars and their life cycles
  8. Black Hole
  9. Gravitational waves
  10. LIGO
  11. Solar system and it’s part
  12. Kuiper belt
  13. Asteroid Belt
  14. Ploonet
  15. Exoplanet
  16. Goldilocks zones
  17. Asteroids, Meteor, Meteorite, Meteoroids, Comets
  18. ISRO, International cooperation
  19. Space debris


Evolution of Universe- Big Bang theory

It is believed that universe was born about 13.8 billion years ago in an event called Big Bang. It is most prevailing cosmological model for birth of the universe.

Big Bang Theory: it states that at some moment all of space was contained in a single point of very high-density and high-temperature state from which the universe has been expanding in all directions ever since.

  • After the initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles and later simple atoms.
  • The majority of atoms produced by the Big Bang were hydrogen and helium along with trace amounts of lithium and beryllium.
  • Giant clouds of these primordial elements (hydrogen and helium) later coalesced through gravity to form stars and galaxies.


Dark Energy:

  • Dark energy is an unknown form of energy which is hypothesized to permeate (spread throughout) all of space, tending to accelerate the expansion of the universe.


Dark Matter:

  • Dark matter is a hypothetical form of matter that is thought to account for approximately 85% of the matter in the universe. Dark energy plus dark matter constitutes 95% of the total content of the universe.
  • It is believed that dark matter considered as the factors for unexplained motion of stars in galaxies.
  • The majority of dark matter is thought to be composed of some as-yet-undiscovered subatomic particles.
  • Dark matter does not appear to interact with observable electromagnetic radiation, such as light, thus invisible to the entire electromagnetic spectrum, making it extremely difficult to detect.
  • Dark matter interacts with the rest of the universe only through its gravity.


God Particle:

Higgs Boson or God particle is theoretically responsible for mass, without which there would be no gravity and no universe. So, called as “God particle”.

The Higgs particle was proposed in the 1960s by British physicist Peter Higgs as way of explaning why other particles have mass.

Discovery of Higgs Boson validated the standard Model of physics, also predicted that 60% of the time a Higgs boson will decay to a pair of bottom quarks.

Standard Model: is a theory of particle physics. It says materials are made up of 12 matter particles(known as Fermions). The other 11 particles predicted in models have been found. CERN used Large Hadron Collider(LHC) to find God particle.


Large Hadron Collider(LHC):

  • The LHC is the world’s largest and most powerful particle accelerator.
  • It consists of a 27-kilometre ring of superconducting magnets with many accelerating structures to boost the energy of the particles along the way.
  • LHC started operation in 2008, it is a Global collaboration project led by CERN (the European Organization for Nuclear Research).Its first research took place in March 2010&discovered the elusive (difficult to find, catch, or achieve) Higgs Boson in July 2012.
  • The LHC is situated underneath the earth’s surface at a depth of 175 metres on border between France and Switzerland near Geneva.
  • Purpose: LHC was built to study some of the fundamental particles (like proton, Higgs Boson etc.,) and how they interact and behaved as well as to find answers to other unsolved questions of physics like the dark matter.



  • Neutrinos are the second most widely occurring particle in the universe, only second to photons, the particle which makes up light.
  • These were first proposed by Swiss scientist Wolfgang Pauli in 1930.
  • Characteristics:
    1. They are elementary weakly interacting subatomic
    2. They have little mass or are nearly massless.
    3. They are no-charge particles that only interact with weak nuclear force.
    4. Least harmful of all elementary particles, as they seldom react with solid bodies.
    5. Gave astronomical information like beta decay of star or supernova .
  • In 2015, the Nobel Prize in physics was awarded to Takaaki Kajita and Arthur B. Mcdonald for discovering neutrino oscillations demonstrating that neutrinos have mass.
  • There are three typesof neutrinonamely, electron neutrino (Ve),Muon neutrino (Vμ)&Tau neutrino (Vτ).



  • INO is a multi-institutional effort aimed at building a world-class underground laboratory with a rock cover of approximately 1200 m for Non-accelerator based high energy and nuclear physics research in India.It is situated at theni (Tamil Nadu ).
  • It is a mega-science project jointly funded by the Department of Atomic Energy (DAE) and the Department of Science and Technology (DST).
  • The initial goal of INO is to study Neutrinos.


Why detect Neutrinos?

  • Neutrinos hold the key to important and fundamental questions on the origin of the Universe and the energy production in stars.
  • For Neutrino tomography of the earth, that is a detailed investigation of the structure of the Earth from core onwards. This is possible with neutrinos since they are theonly particles which can probe the deep interiors of the Earth.


The INO project includes:

  1. Construction of an underground laboratory and associated surface facilities at Pottipuram in Bodi hills of Theni District of Tamil Nadu.
  2. Construction of an Iron Calorimeter (ICAL) detector for studying neutrinos.
  3. Setting up of National Centre for High Energy Physics at Madurai, for the operation and maintenance of the underground laboratory.

Note: Japan is planning to build a Hyper-Kamiokande neutrino detector which will be the world’s largest neutrino observatory.


Stars and their life cycles:

Formation: Stars are formed in clouds of gas and dust, known as nebulae. Nuclear reactions(fusion- hydrogen to helium) at the centre (or core) of stars provides enough energy to make them shine brightly for many years.

Lifetime: The exact lifetime of a star depends very much on its size. Very large, massive stars burn their fuel much faster than smaller stars and may only last a few hundred thousand years. Smaller stars, however, will last for several billion years, because they burn their fuel much more slowly.

Phases: When hydrogen fuel that powers the nuclear reactions within stars will begin to run out, they enters into the final phases of their lifetime. Over time, they will expand, cool and change color to become red giants. The path they follow beyond that depends on the mass of the star.

Small stars, like the Sun, will undergo a relatively peaceful and beautiful death that sees them pass through a planetary nebula phase to become a white dwarf, which eventually cools down over time and stops glowing to become a so-called “black dwarf” which emits no energy.

Massive stars, will experience a most energetic and violent end, which will see their remains scattered about the cosmos in a enormous explosion, called a supernova. Once the dust clears, the only thing remaining will be a very dense star known as a neutron star, these can often be rapidly spinning and are known as pulsars. If the star which explodes is especially large, it can even form a black hole.

Chandrasekhar Limit: of 1.4 solar masses, is the theoretical maximum mass a white dwarf star can have and still remain a white dwarf. Above this mass, electron degeneracy pressure is not enough to prevent gravity from collapsing the star further into a neutron star or black hole.

The limit is named after Nobel laureate Subrahmanyan Chandrasekhar, who first proposed the idea in 1931.


Black Hole:

  • A black hole is an object in space that is formed after the death of a star(core runs out of fuel) and is so dense and has strong gravity that no matter or light can escape its gravity pull. Because no light can escape, it is black and invisible.


Types of Black holes:

Steller-mass black holes: small black holes, have masses about five to 20 times the mass of the sun.

Super-massive black holes: which are millions to billons time more massive than the sun.

Super-massive black holes are found at the centre of most galaxies. The super-massive black hole in our own galaxy, Milky way is called Sagittarius A*.


Event Horizon:

  • The boundary at the edge of black hole is called the event horizon. This is “point of no return”, beyond which it is impossible to escape the gravitational effects of the black hole.
  • Anything that crosses the event horizon, falls to the very centre of black hole and squished into single point with infinite density, called the


Event Horizon Telescope project:

  • EHT is group of 8 radio telescopes used to detect radio waves from space.
  • In 2019, Scientists from EHT project released the first-ever optical image( or shadow image) of a Black hole located in the center of galaxy Messier 87 in the constellation Virgo.
  • Sagittarius A* is the 2nd black hole to get photographed.

Nobel Prize in Physics, 2020 – “for the discovery that black hole is a robust prediction of general theory of relativity” to Roger Penrose and “ for the discovery of supermassive compact object at the centre of our galaxy to Reinhard Genzel and Andrea Ghez.


Gravitational waves:

  • Gravitational waves are the distortions or ‘ripples’ in fabric of space-time.
  • Gravitational waves are produced when objects accelerate, and travels with speed of light.
  • The strongest gravitational waves are produced by catastrophic events such as on merger of black holes, collapse of steller cores(supernovae), coalescing neutron stars or white dwarf.
  • Gravitational waves were first proposed by Albert Einstein, 100 years ago as part of the Theory of Relativity.
  • In 2016, scientists at Laser Interferometer Gravitational-wave Observatory (LIGO) first detected the gravitational waves.
  • Nobel prize in Physics, 2017 – “for decisive contributions to LIGO detector and the observation of gravitational waves” to Rainer Weiss, Barry Barish and Kip thorne.
  • The gravitational waves can work as sirens to measure the expansion rate of the universe and to understand the origin and the future of the universe.
  • Hubble’s Law: the farther away galaxies are, the faster they are moving away from Earth ― accelerating expansion of the universe).
  • Hubble constant: a unit of measurement that describes the rate at which the universe is expanding.


Laser Interferometer Gravitational-wave Observatory (LIGO):

  • World largest gravitational wave observatory for detecting cosmic gravitational waves and for carrying out experiments.
  • Comprises of two enormous laser interferometers located thousands of kilometers apart, each having two L-shaped arms of 4km length.
  • Two LIGO detectors are already operational in the U.S, at Livingston and Hanford.
  • The Japanese detector, KAGRA recently joined the international network.

LIGO- India – InDIGO:

  • LIGO-India project is Indian Initiative in Gravitational wave observations, expected to be completed by 2025.
  • aims to move one advanced LIGO detector from Hanford to Maharashtra(Hingoli district), India.
  • Project is piloted by dept. of Atomic Energy(DAE) and dept. of Science and Tech(DST).
  • This project will help Indian scientists to be a major player in emerging research frontier of GW astronomy.


Solar System and it’s parts

The Solar system is the gravitationally bound system of the sun and the objects orbit around it.

The planets of our solar system are divisible in two groups: Terrestrial planets and Jovian planets.

Terrestrial planets or inner plants:- lie between sun and the belt of asteroids, Earth like planets made up of rocks and metals and relatively high densities. E.g. Mercury, Venus, Earth, Mars.

Jovian planets or outer planets:- gas giants or Jupiter like planets, larger size and less dense materials, have thick atmosphere, mostly of helium and hydrogen. E.g. Jupiter, Saturn, Uranus, Neptune.



  • The Kuiper Belt is a ring of icy rocks & dust bodies just outside of Neptune’s orbit, known as Kuiper belt objects or
  • Pluto is the largest known Kuiper Belt Object instead of 9th planet of our Solar system.
  • There are bits of rock and ice, comets, and dwarf planets.

Planet definition as per International Astronomical Union:

  1. Orbits around the sun.
  2. Has sufficient mass to assume hydrostatic equilibrium- a nearly round shape.
  3. Has removed debris and small objects from the area around its orbit.



  • Asteroids are remnants of planetary formation mainly composed of refractory rocky and metallic minerals and some ice, that circle the sun in a zone lying between Mars and Jupiter. The circular chain of asteroids is called asteroid belt or main asteroid belt.
  • The remnants of planetary formation failed to coalesce due to gravitational interference of Jupiter.
  • Recently, NASA’s OSIRIS-Rex spacecraft briefly touched down on the surface of asteroid Bennu to collect rock and dust samples. The mission aims to complete by 2023.
  • Hayabusa2 – It is an asteroid sample return mission operated by Japanese space agency, JAXA.



  • a celestial objects, which are orphaned moons that have escaped the bonds of their planetary parents.
  • The researchers explain that the angular momentum between the planet and its moon results in the moon escaping the gravitational pull of its parent planet.
  • A new study finds that Earth’s own Moon is slowly spiraling away from the planet; it may also end up as a ploonet in some 5 billion years.



  • Planets orbiting the other stars(outside our solar system) are called “exoplanets.”
  • Exoplanets are hard to see, they are hidden by the bright glare of the stars they orbit.
  • Scientists use Gravitational lensing and the “wobbling methods” to detect exoplanets.
  • Proxima Centauri b is closest exoplanet to earth and inhabits the “habitable zone” of its star.
  • Gravitational lensing: Light around a massive object, such as a black hole, is bent, causing it to act as a lens for the things that lie behind it.


Ariel space mission:

  • Ariel (Atmospheric Remote sensing Infrared Exoplanet Large survey)- By European space agency(ESA), will be launched in 2029.
  • To study the nature, formation and evolutions of over a thousand exoplantes over a period of four years.
  • First mission of its kind dedicated to large scale survey of Exoplanets.



  • The ‘Goldilocks Zone,’ or habitable zone – ‘the region around the star where a planet could sustain liquid water on its surface’.
  • Our Earth is in the Sun’s Goldilocks zone. If Earth were where the dwarf planet Pluto is, all its water would freeze; on the other hand, if Earth were where Mercury is, all its water would boil off.
  • Some Earth- size planets like TOI 700 d and Kepler-186f has been discovered in their Goldilocks zone.



  • Big chunks of rocks floats through space and orbit the sun, mostly found in main asteroid belt i.e. between Mars and Jupiter.
  • The biggest one is Ceres(940km wide), as twice as big as Grand Canyon.



  • Smaller rock pieces that breaks off from asteroid, it floats through interplanetary space.
  • Can be as small as grain of sand or as large as a metre across.



  • When meteoroid enters into earth atmosphere, it begins to burn up and fall to the ground.
  • This burning trail is known as meteor or ‘falling stars’.
  • Meteors and comets both create bright trails through night, but comets are made up of ice and dust, not rock – like a gaint dirty snowball.



  • If a meteoroid rock doesn’t completely burn up as it falls to Earth– the rock left behind is called meteorite.


Asteroids, Meteoroid, Meteor and Meteorite.


  • are frozen leftovers from the formation of the solar system composed of dust, rock and ices, ranges from few miles to tens of miles wide.
  • Orbits closer to the sun, they heat up and spew gases and dust into a glowing head visible in atmosphere.
  • Comets have highly elliptical orbits, unlike planets which have near-circular orbits.


Space Debris:

  • Refers to a natural debris(asteroids, comets and meteoroides) found in solar system or debris from artificially created objects( artificial satellites and old rockets) in space, especially earth orbit.
  • Space debris can be hazardous to spacecrafts and satellites.
  • Space debris tracked by radar and optical detectors.
  • Kessler Syndrome: is a possible effect that if one satellite produces debris that hot another satellite, this will create a chain reaction that will obliterate every orbiting object in low earth orbit(LEO), and thus creating a thick cloud of white dots travelling at high speed.
  • Project Netra: an early warning system by ISRO in space to detect debris and other hazards to Indian satellites.



  • Nodal space research agency of Government of India
  • Founded on 15th August, 1969. Headquarter – Bengaluru, Karnataka
  • Managed by Department of Space (DOS), which reports directly to PM.


ISRO Commercial Arms:

Indian National space, Promotion & Authorization Centre (IN-SPACe):

  • Under Department of space to encourage, promote and hand hold the private sector for their participation in space sector.
  • Private players will also be able to use ISRO infrastructure through IN-SPACe.


NewSpace India Limited(NSIL):

  • A public sector undertaking (PSU) under the department of Space.
  • It will commercially exploit the research and development work of space agency,
  • Co-produce PSLV and launch satellite through SSLVs.



  • Antrix Ltd is another PSU under dept.of Space, that acts as a commercial arms of ISRO and markets the products and services of ISRO.
  • NSIL differs from Antrix Ltd. Antrix will handle ISRO’s commercial deals for satellites and launch vehicles with foreign customers.
  • NSIL will deal with capacity building of local industry for space manufacturing.



  • Chandrayaan-1: ISRO maiden mission to Moon, Chandrayaan-1 was the joint mission of ISRO-NASA, to discovery of water molecules on the Moon surface.
  • MEGHA- TROPIQUES: The Indo-French joint satellite mission launched in 2011 for the study of tropical atmosphere and climate related aspects such as monsoons, cyclones etc.
  • Saral(Satellite for ALTIKA and ARGOS): Joint mission with France for studying ocean from space using altimetry launched in 2013.
  • NISAR: NASA-ISRO Synthetic Aperture Radar, joint satellite mission for earth sciences studies.
  • Unnati: ISRO 8-week capacity building progamme on nano satellite development, as an initiative of UNISPACE+50, participants from several countries trained successfully.



  • Satellites are generally characterized by the distance from the earth at which they revolve and on basis of application of the Earth.


  • On basis of height-
    1. LEO Satellite (Lower Earth Orbit)
    2. MEO Satellite (Middle Earth Orbit)
  • On basis of application-
    1. Geo- Synchronous Earth Orbit
    2. Geo- Stationary Earth Orbit

Low Earth Orbit (LEO)

· LEO is commonly used for communication and remote sensing satellite systems, as well as the International Space Station (400km) and Hubble Space Telescope (560km).

· The satellites in LEO complete multiple revolutions in 24 hours (Lower the orbit, higher should be the speed).

Medium Earth Orbit

· MEO is commonly used for navigation systems, including the U.S. Global Positioning System (GPS).





Geosynchronous Orbit (GSO) & Geostationary Orbit (GEO)

· Objects in GSO have an orbital speed that matches the Earth’s rotation, yielding a consistent position over a single longitude.

· An orbit is called sun-synchronous when the angle between the line joining the centre of the Earth and the satellite and the Sun is constant throughout the orbit.

· It enables the on-board camera to take images of the earth under the same sun-illumination conditions during each of the repeated visits

· The idea of a geosynchronous orbit for communications spacecraft was first popularized by science fiction author Sir Arthur C. Clarke in 1945, so it is sometimes called the Clarke orbit.

· GEO is a kind of GSO. It matches the planet’s rotation, but GEO objects only orbit Earth’s equator, and from the ground perspective, they appear in a fixed position in the sky.

· GSO and GEO are used for telecommunications and Earth observation.



Geosynchronous Transfer Orbit (GTO)

· To attain geosynchronous (and also geostationary) Earth orbits, a spacecraft is first launched into an elliptical orbit with an apoapsis altitude in the neighbourhood of 37,000 km. This is called a Geosynchronous Transfer Orbit (GTO).

· The spacecraft then circularizes the orbit by turning parallel to the equator at apoapsis and firing its rocket engine.



Polar Orbit

· Polar orbits are 90-degree inclination orbits, useful for spacecraft that carry out mapping or surveillance operations.

· Within 30 degrees of the Earth’s poles, the polar orbit is used for satellites providing reconnaissance, weather tracking, measuring atmospheric conditions, and long-term Earth observation.

Sun-Synchronous Orbit (SSO) · A type of polar orbit, SSO objects are synchronous with the sun, such that they pass over an Earth region at the same local time every day.
Highly Elliptical Orbit (HEO)

· An HEO is oblong, with one end nearer the Earth and other more distant. Satellites in HEO are suited for communications, satellite radio, remote sensing and other applications.




A satellite is a moon, planet or machine that orbits a planet or star. Thousands of artificial, or man-made, satellites orbit Earth.


Astronomical Satellites: These satellites are used for the observation of distant stars and other objects in space. Ex: Hubble Telescope
Communications Satellites: They are used for communicating over large distances. Ex: INSAT series.

Earth Observation


These satellites are used for observing the earth’s surface and as a result, they are often termed geographical satellites. The data is used for several applications covering agriculture, water resources, urban development, mineral prospecting, environment, forestry, drought and flood forecasting, ocean resources and disaster management. Ex: OCEANSAT
Navigation Satellites: Used for navigation purposes. Ex: IRNSS (India), GPS (USA)
Reconnaissance Satellites: Also called spy satellites, is an Earth observation satellite or communications satellite deployed for military or intelligence applications.



  • Launchers or Launch Vehicles are used to carry spacecraft to space.
  • Historic launchers: SLV, Augmented Satellite Launch Vehicle (ASLV)
  • India has two operational launchers: Polar Satellite Launch Vehicle (PSLV) and Geosynchronous Satellite Launch Vehicle (GSLV).
  • GSLV with indigenous Cryogenic Upper Stage has enabled the launching up to 2 tons class of communication satellites.
  • The next variant of GSLV is GSLV Mk III, with indigenous high thrust cryogenic engine and stage, having the capability of launching 4 tons class of communication satellites.
  • Vikram Sarabhai Space Centre, located in Thiruvananthapuram, is responsible for the design and development of launch vehicles.
  • Liquid Propulsion Systems Centre and ISRO Propulsion Complex, located at Valiamala and Mahendragiri respectively, develop the liquid and cryogenic stages for these launch vehicles.
  • Satish Dhawan Space Centre, SHAR, is the spaceport of India and is responsible for the integration of launchers. It houses two operational launch pads from where all GSLV and PSLV flights take place.



  • SLV-3was India’s first experimental satellite launch vehicle.
  • Which was an all solid, four-stage vehicle
  • Capable of placing 40 kg payloads in Low Earth Orbit (LEO).
  • First successful launch: Rohini Satellite on 18/July/1980 from Sriharikota.
  • This made India the sixth member of an exclusive club of space-faring nation’s.



  • Designed to augment the payload capacity to 150 kg, thrice that of SLV-3, for Low Earth Orbits (LEO) in 1987.
  • ASLV proved to be a low-cost intermediate vehicle to demonstrate and validate critical technologies.



  • PSLV is the third generation launch vehicle of India, operationalized in 1994.
  • It is the first Indian launch vehicle to be equipped with liquid stages.
  • PSLV is a 4-stage launch vehicle that uses an alternate combination of liquid and solid-fueled rocket stages.
  • 1st & 3rd stages are solid-fueled.
  • 2nd & 4th stages are liquid-fueled.
  • PSLV emerged as the reliable and versatile workhorse launch vehicle of India with 39 consecutively successful missions by June 2017.
  • Primarily used to launch remote sensing satellite.
  • PSLV can deliver payloads of up to:
    1. 3,250kg to LEO (Low Earth Orbit)
    2. 1600 kg to SSO (Sun Synchronous orbit)
    3. 1400 kg to GTO (Geosynchronous Transfer Orbit)
  • Most famous launches by the PSLV:
    1. Chandrayaan-1 in 2008 and
    2. Mangalyaan/Mars Orbiter Mission in 2013.
    3. PSLV-C37 launched 104 satellites on February 15, 2017, the highest number of satellites launched in a single flight so far
  • Currently, PSLV rockets have 4 variants:
    1. PSLV-CA (core alone)
    2. PSLV-DL (Dual strap-on motors)
    3. PSLV-QL (4 strap-on motors)
    4. PSLV-XL (6 strap-on motors)


  • GSLV is a 3-stage Launch vehicle with solid fuel in the 1st stage, liquid in the 2nd stage and cryogenic in the 3rd stage.
  • It was developed primarily to launch communication satellites (INSAT Series) of 2.5-tonne class in Geostationary Transfer Orbit and about 4.5 tons class in Low Earth Orbit.



  • This is the largest launch vehicle developed by India, which is currently in operation.
  • This fourth-generation launch vehicle is a three-stage vehicle with four liquid strap-ons.
  • The indigenously developed Cryogenic Upper Stage (CUS) forms the third stage of GSLV Mk II.
  • Liftoff mass: 4.14 tones.



  • This is a 3-stage heavy-lift rocket with an indigenous cryogenic engine in the 3rd stage.
  • GSLV Mk III (ISRO’s Fat boy) is designed to carry 4-ton class of satellites into Geosynchronous Transfer Orbit (GTO) or about 10 tons to Low Earth Orbit (LEO), which is about twice the capability of the GSLV Mk II.
  • Most famous launches: injected Chandrayaan-2, India’s second Lunar Mission, into Earth Parking Orbit on July 22, 2019, from Satish Dhawan Space Centre SHAR, Srihari kota.
  • Further, India’s first human space flight Gaganyaan to be launched using GSLV Mk III in 2022.



  • These are one or two-stage solid propellant rockets used for probing the upper atmospheric regions and for space research.
  • They also serve as easily affordable platforms to test or prove prototypes of new components or subsystems intended for use in launch vehicles and satellites.
  • The launch of the first sounding rocket from Thumba near Thiruvananthapuram, Kerala on 21 November 1963, marked the beginning of the Indian Space Programme.
  • RH-75, with a diameter of 75mm was the first truly Indian sounding rocket.



  • Designed by ISRO’s Vikram Sarabhai Space Centre, to launch payload capacity of 500 kg to Low Earth orbit&300 kg to Sun-synchronous orbit for launching small satellites.
  • Objective: to commercially launch small satellites at a lower price and higher launch rate as compared to PSLV.
  • Unlike the PSLV and GSLV, the SSLV can be assembled both vertically and horizontally.
  • The first three stages of the vehicle will use a solid propellant, with a fourth stage being a velocity-trimming module.






  • The Indian National Satellite (INSAT) systems are the set of communication satellites launched in Geo-synchronous orbit at an altitude of about 36,000 km.
  • Applications: The INSAT system with more than 200 transponders in the C, Extended C and Ku-bands provides services to telecommunications, television broadcasting, satellite newsgathering, societal applications, weather forecasting, disaster warning and Search and Rescue operations.



  • Launched into a Geosynchronous Transfer Orbit (GTO) on January 17, 2020, from Kourou launch base, French Guiana by Ariane-5 VA-251 vehicle.
  • Aims to provide communication services from Geostationary orbit in C and Ku bands.
  • Weighing 3357 kg, GSAT-30 is to serve as a replacement to INSAT-4A spacecraft services with enhanced coverage.
  • Lifespan: 15 years.
  • Applications: DTH, connectivity to VSATs for ATMs, Stock exchange, Television unlinking and Teleport Services, Digital Satellite News Gathering (DSNG) and e-governance applications.



  • Starting with IRS-1A in 1988, ISRO has launched many operational remote sensing satellites.
  • They are mostly polar, sun-synchronous satellites in low- earth orbit (LEO) at about 800 km from the earth surface.
  • Currently, 13 operational satellites are in Sun-synchronous orbit: RESOURCESAT-1, 2, 2A CARTOSAT-1, 2, 2A, 2B, RISAT-1 and 2, OCEANSAT-2, Megha-Tropiques, SARAL and SCATSAT-1, and 4 in Geo-stationary orbit: INSAT-3D, Kalpana& INSAT 3A, INSAT -3DR.
  • They are commonly called as remote sensing satellites as they collect information of any object on Earth through the measurement of radiation of the Sun that is reflected and scattered by objects on the surface of the earth.
  • Applications covering agriculture, water resources, urban planning, rural development, mineral prospecting, environment, forestry, ocean resources and disaster management.



  • EOS-01 is an earth observation satellite, intended for applications in agriculture, forestry and disaster management support. Launch Vehicle: PSLV-C49. From Satish Dhawan Space Centre (SDSC) SHAR, Srihari kota on November 07, 2020.
  • RISAT-2BR1 is radar imaging earth observation satellite (placed at 576km altitude). The satellite will provide services in the field of Agriculture, Forestry and Disaster Management. Launch Vehicle: PSLV-C48 from SDSC, Srihari kota on Dec-11, 2019.
  • CARTOSAT-3 will address the increased user’s demands for large scale urban planning, rural resource and infrastructure development, coastal land use and land cover etc. Launch Vehicle: PSLV-C47. From SDSC, Sriharikota on Nov-27, 2019.



(HSI) is a technique that analyzes a wide spectrum of light instead of just assigning primary colors (red, green, blue) to each pixel.


Hyperspectral Imaging Satellite (HysIS):

· India’s first hyperspectral imaging satellite.

· Placed in Sun-synchronous polar orbit, 636 km above the surface of the earth. Launch Vehicle: PSLV-C43. From SDSC, Sriharikota on Nov-29, 2018.

· Primary objective: to study the earth’s surface in the visible, near-infrared and shortwave infrared regions of the electromagnetic spectrum.

· Application: It can be used for a range of activities from monitoring the atmospheric activity and climate change, studies of Earth’s magnetic field, agriculture, forestry, water management, coastal patterns, minerals exploration &military surveillance.



  • IRNSS (also known as NavIC) is an independent regional navigation satellite system being developed by India.
  • It is designed to provide accurate position information service to users in India as well as the region extending up to 1500 km from its boundary.
  • IRNSS will provide two types of services, namely:
    1. Standard Positioning Service (SPS) which is provided to all the users and
    2. Restricted Service (RS), which is an encrypted service provided only to authorized users.
  • The IRNSS System is expected to provide a position accuracy of better than 20 m in the primary service area.
  • There are currently seven IRNSS satellites (1A to 1G) in orbit.
    1. 4 satellites: A, B, F, G – are placed in a Geosynchronous Orbit. (1A is replaced by 1I recently)
    2. 3 satellites: C, D, E – are located in Geostationary Orbit


Applications of IRNSS:

· Terrestrial, Aerial and Marine Navigation

· Disaster Management

· Vehicle tracking and fleet management

· Integration with mobile phones

· Precise Timing

· Mapping and Geodetic data capture

· Terrestrial navigation aid for hikers and travelers

· Visual and voice navigation for drivers



  • SAS is a communication satellite (Ku-band) built by ISRO to provide a variety of communication services over the South Asian region.
  • Launch Vehicle: GSLV-F09.
  • From SDSC, Srihari kota.
  • Weight: 2230 kg. Into Geosynchronous Transfer Orbit (GTO) on May 05, 2017.
  • The initial proposal to name it as “SAARC Satellite” was changed to “South Asia Satellite” following Pakistan’s refusal.
  • SAS/GSAT-9 to boost communication and improve disaster links among India’s six Neighbours has “opened up new horizons of engagement” in the region and helped it carve a unique place for itself in space diplomacy.
  • SAS covers six SAARC countries namely, Afghanistan, Bangladesh, Bhutan, Maldives, Nepal and Sri Lanka (except Pakistan).



  • It will be a set of satellites that will track, send and receive information from other Indian Satellites in space.
  • IDRSS satellites of the 2,000 kg class would be launched on the GSLV launcher to geostationary orbits around 36,000 km away.
  • It is primarily meant for providing continuous/real-time communication of Low-Earth-Orbit satellites including human space mission to the ground station.
  • Need for IDRSS:
    1. India is dependent on foreign space agencies (like NASA) for information related to satellites in space.
    2. To assist ISRO’s 1st human to space project the ‘Gaganyaan’ of 2022.
    3. A data relay satellite instead in the geostationary orbit can overcome the need for a large number of ground-based stations.
  • It will be useful in monitoring launches and vital for ISRO which has planned in future several advanced Low Earth Orbit (LEO) missions such as space docking, space station, as well as distant expeditions to the moon, Mars and Venus.








· India’s first mission to Moon.

· Launched successfully on October 22, 2008 (G. Madhavan Nair was ISRO chairman) from SDSC, Sriharikota, Andhra Pradesh.

· The spacecraft orbited around the Moon at an altitude of 100 km &200 km from the lunar surface for chemical, mineralogical and photo-geologic mapping of the Moon.

· Findings: Detection of Water and Hydroxyl (OH), new spinel-rich rock, X-rays.











· The second lunar exploration and 1st lander and rover mission of ISRO | Launcher: GSLV MK III

· It is the world’s 1st lunar mission to the South Pole of the Moon’s near side.

· The South Pole of the lunar surface remains in shadow is much larger than that at the North Pole.

· Aims at studying not just one area of the Moon but all the areas combining the exosphere, the surface as well as the sub-surface of the moon in a single mission.

· The Orbiter will observe the lunar surface and relay communication between Earth and Chandrayaan 2’s Lander Vikram.

· The lander was designed to execute India’s first soft landing on the lunar surface.

· The lander-rover integrated module was supposed to soft-land near South Pole (about 600 km) of the moon.

· The rover was a 6-wheeled, AI-powered vehicle named Pragyan, which translates to ‘wisdom’ in Sanskrit.

· However, a last-minute software glitch led to crash-landing of Vikram and Pragyan.


1. To find traces of Water and Helium-3

2. On-site chemical analysis of the surface

3. To click pictures of the moon via the orbiter.


Recently ISRO has announced Chandrayaan-3, another attempt to soft landing mission, after the failure of Vikram Lander under Chandrayaan-2.



  • Also called Mars Orbiter Mission, it is India’s 1st interplanetary mission
  • Launched using PSLV C-25 on Nov-5, 2013 & reached Mars on 24th Sept 2014.
  • It costs 450 crores, weight 1350 kg, travelled for 300 days covered 65 crore km.
  • ISRO has become the 4th space agency to reach Mars, after the Soviet space program, NASA, and the European Space Agency.
  • It is the first Asian nation to reach Mars orbit, and the first nation to do so on its first attempt.
  • Objective: Exploration of Martian surface features, morphology, mineralogy and atmosphere.
  • Important payloads:
    1. Atmospheric studies (Lyman-alpha Photometer (LAP), Methane Sensor for Mars (MSM))
    2. Particle environment studies (Mars Exospheric Neutral Composition Analyzer (MENCA)),
    3. Surface imaging studies (Thermal Infrared Imaging Spectrometer (TIS), Mars Colour Camera (MCC))

NOTE: ISRO is also planning a Lander mission to Mars under Mangalyaan-2 by 2024withthe main objective is to study the surface geology, magnetic fields and interplanetary dust.



  • India’s 1st Human spaceflight programme (announced in 2018) to be launched by 2022.
  • It will make India the 4th country to send manned mission after Russia, USA and China.
  • Over the years, the ISRO has developed and tested many technologies that are critical to a human space flight.
  • These include a Space Capsule Recovery Experiment (SRE-2007), Crew module Atmospheric Reentry Experiment (CARE-2014), GSLV Mk-III (2014), Reusable Launch Vehicle- Technology Demonstrator (RLV-TD), Crew Escape System and Pad Abort Test.
  • It will include two unmanned flights to be launched in December 2020 (deferred) and July 2021 and one human space flight to be launched in December 2021.
  • GAGANYAAN expected to carry 3 astronauts to a Low Earth Orbit on board GSLV Mark III vehicle, for at least 7 days.
  • ISRO has signed a pact with the Russian firm Glavkosmos to train astronauts (selected from Indian Air Force) for this project.
  • Also, ISRO will receive assistance from the French space agency CNES, in terms of expertise in various fields including space medicine, astronaut health monitoring, radiation protection and life support.






· Vyoma (space) + mitra (friend) à Vyomamitra

· It is a Gynoid (female humanoid robot).

· ISRO has planned to send Vyomamitra in the unmanned crew module of Gaganyaan.

· Objective: To test the Environmental Control & Life Support System of Ganganyaan to detect environmental changes.

· It has been developed by scientists at IISc in collaboration with ISRO.


Human Space Flight Centre (HSFC)

· It was established by ISRO in 2019 to coordinate with Indian Human Spaceflight Programme (HSP) and will be responsible for the implementation of Gaganyaan Mission.

· The proposed set up comes at Challakere, Chitradurga district of Karnataka.



  • ISRO’s planned orbiter mission to Venus by 2023
  • Main goals are to study:
    1. The atmosphere and its chemistry
    2. Surface and sub-surface features
    3. Interaction of the planet with solar radiation


  • India’s 1st first mission to study the Sun to be launched in early 2020 (deferred)
  • Its main objective is to study the solar corona.
  • Initially, Aditya-1 was meant to observe solar corona only.
  • Now additional payloads under Aditya-L1 (L1-Lagrange point orbit) with observing corona, chromosphere and photosphere.
  • It will have 7 payloads onboard to study Sun’s corona, solar emissions, solar winds and flares, and Coronal Mass Ejections, and will carry out round-the-clock imaging of Sun.




· A Lagrange point is a location in space where the combined gravitational forces of two large bodies, such as Earth and the sun or Earth and the moon, equal the centrifugal force felt by a much smaller third body.

· These points are named after Joseph-Louis Lagrange, an 18th-century mathematician who wrote about them in the “three-body problem” in 1772.

· The first Lagrange point (L1) is located between the Earth and the Sun, giving satellites at this point a constant view of the Sun.



ARTEMIS program NASA will land the first woman and next man on the Moon by 2024


· Mars Rover Mission

· Launched in 2011

· Goal: Determine if Mars was ever able to support microbial life.


· Aimed at exploring the solar system

· Various missions under the New Frontiers Program are:

1. New Horizons: Launched in 2006 to investigate distant solar system object including Pluto and its moons and Kuiper Belt.

2. Juno: launched in 2016 to study Jupiter.

3. OSIRIS-REx mission: to collect samples from an asteroid Bennufor further study.

4. Dragonfly: to be launched in 2026 to study Saturn and its icy moons.

InSights Mission · The first mission to explore Mars’ deep interior.

· It is part of NASA’s Discovery Program.

PUNCH (Polarimeter to Unify the Corona and Heliosphere) mission · To image regions beyond the Sun’s outer corona.

· It is expected to be launched in 2022.

· It is focused on understanding the transition of particles from the Sun’s outer corona to the solar wind that fills interplanetary space.



· It is the only spacecraft to study all four of the solar system’s giant planets, the Jupiter, Saturn, Uranus and Neptune at close range.

· Like Voyager 1, Voyager 2 was designed to find and study the edge of our solar system.


SOLO (SOLar Orbiter mission)

· It is a collaborative mission between the European Space Agency (ESA) and NASA dedicated to solar and helio-spheric physics.

· It will study the origins of the Universe, emergence of life and the fundamental physics at work in the Universe.

Parker Solar Probe · launched in 2018 with the mission of making observations of the outer corona of the Sun.



BEPI COLOMBO · A joint mission of ESA and JAXA (Japan Aerospace Exploration Agency) to Mercury
JUICE (JUpiterICy moons Explorer) · Orbiter mission to explore Jupiter and three of its icy moons: Europa, Callisto and Ganymede by ESA (European Space Agency)

· 1st non-American outer Solar System mission

Chang’e-4 · China’s lunar programme.

· It is the first mission to land on the far side of the Moon.

· It landed at the South Pole- Aitken Basin.

HOPE/ Emirates Mars Mission · UAE’s 1st Mars mission.

· It was launched in July-2020 from Japan by a Japanese H-IIA rocket.

Hayabusa-2 · It is an asteroid (Ryugu) sample-return mission operated by the Japanese state space agency JAXA.
TIANGONG-2 · The successor of Tiangong-1 (Chinese Space station)

· Launched in 2016.

· Aims to test capabilities for long-term human presence in space.

NISAR (NASA-ISRO Synthetic Aperture Radar) · Joint earth observation project of NASA and ISRO.

· It is the 1st dual-band radar imaging satellite. (L-Band and S-Band).

· Objective: to observe natural processes, including ecosystem disturbances, ice-sheet collapse, and natural hazards such as earthquakes, tsunamis, volcanoes and landslides etc.,




· One of the largest multi-wavelength space telescopes.

· It’s a Joint project of NASA and ESA

· 600 km above the surface of the earth.

· Can observe objects in visible, near-ultraviolet, and near-infrared light.


· The successor of Hubble Space Telescope to be launched in 2021.

· Times bigger than HST and 6 times more powerful.

· JWST will orbit the Sun. (not earth like HST)




· TMT project is an international partnership between the USA, Canada, Japan, China, and India.

· It will allow deeper exploration into space and observe cosmic objects with unprecedented sensitivity.

· Installation site: Mauna Kea in Hawaii.

· TMT has been developed by close collaboration between the 2020 Physics Nobel Laureate Prof. Andrea Ghez and Indian astronomers.


· An array of 30 fully steerable parabolic radio telescopes of 45-metre diameter.

· Located near Pune, India.

· Can scale deep space objects such as a galaxy, neutron star, pulsar, etc.


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