Science and Technology Quick Revision Part-3

by | Feb 6, 2025 | APPSC Group-2 Mains Paper-2 Science and Technology

Space Technology

  • What is Space Technology?
    • Space technology refers to the scientific and engineering tools, techniques, and innovations used for space exploration, satellite communication, remote sensing, and interplanetary missions.
    • It includes spacecraft, satellites, space stations, launch vehicles, and scientific instruments used in space missions.
  • Key Components of Space Technology
    • Satellites – Artificial objects placed in orbit for communication, navigation, weather forecasting, and research.
    • Satellites Types: Communication, Weather, Navigation, Earth Observation, Scientific, Military.
    • Launch Vehicles – Rockets designed to transport payloads (satellites, probes, humans) into space (e.g., PSLV, Falcon 9).
    • Rocket Types: Expendable (e.g., PSLV, GSLV, Falcon 9, Soyuz), Reusable (e.g., SpaceX Starship, ISOR RLV-TD).
    • Propulsion: Chemical (liquid/solid fuel), electric, nuclear, and ion propulsion.
    • Orbits: Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Polar Orbit, Geostationary (GEO), Sun-synchronous Orbit, Geosynchronous Orbit, Halo Orbit.
    • Space Probes – Unmanned spacecraft sent to explore celestial bodies (e.g., Voyager, Chandrayaan, Perseverance Rover).
    • Space Stations – Habitable artificial structures in orbit (e.g., International Space Station – ISS, China’s Tiangong).
    • Rovers & Landers – Robotic vehicles exploring planetary surfaces (e.g., Curiosity, Pragyan Rover).
    • Telescopes – Space-based telescopes provide clearer images of deep space (e.g., Hubble, James Webb).
  • Applications of Space Technology
    • Communication & Broadcasting: Satellites enable global communication, TV broadcasting, and internet services (e.g., Starlink, INSAT).
    • Navigation & GPS: Systems like NavIC (India’s Navigation System), GPS, and Galileo provide precise positioning and timing services.
    • Earth Observation & Remote Sensing: Used for weather forecasting, disaster management, environmental monitoring, and agriculture (e.g., ISRO’s RISAT, NOAA’s GOES).
    • Space Exploration & Astronomy: Missions like Chandrayaan-3 (India’s Moon Mission) and Mars Rover (NASA’s Perseverance) help in planetary exploration.
    • Military & Strategic Uses: Satellites are used for reconnaissance, surveillance, and missile guidance (e.g., GSAT-7A, DRDO’s surveillance satellites).
    • Space Tourism & Commercialization: Private companies like SpaceX, Blue Origin, and Virgin Galactic are developing space tourism programs.
    • Astrobiology & Planetary Science: Search for extraterrestrial life, study of exoplanets, and Mars colonization efforts (e.g., Mars Sample Return, Europa Clipper).
  • Future of Space Technology
    • Lunar Bases: Establishing permanent human presence on the Moon.
    • Mars Colonization – NASA, SpaceX, and other agencies are working towards human missions to Mars.
    • Reusable Rockets – Technologies like SpaceX’s Falcon 9 and ISRO’s RLV-TD aim to reduce costs.
    • Space Mining – Extracting minerals from asteroids could be a future industry.
    • Interstellar Travel – Research on warp drives, solar sails, and nuclear propulsion for deep space missions.
    • AI in Space – AI-driven robotic explorers, automated satellite monitoring, and predictive space analytics.
    • Quantum Communication: Secure satellite-based communication.

Indian Space Research Organisation (ISRO)

  • Space research was placed under the jurisdiction of Department of Atomic Energy in 1961 by India’s first prime minister, Jawaharlal Nehru.
  • Department of Atomic Energ director Homi Bhabha (Father of India’s atomic programme) then established the Indian National Committee for Sapce Research (INCOSPAR) with Dr. Vikram Sarabhai as Chairman in 1962.
  • ISRO was established on August 15, 1969. It replaced INCOSPAR.
  • Government of India constituted the Space Commission and established Department of Space (DOS) in June 1972 and brought ISRO under DOS in September 1972.
  • Space Commission formulates the policies and oversees the implementation of the Indian space program.
  • Antrix Corporation was established in 1992 as a government owned company, markets the space products and services.
  • ISRO’s journey began with the launch of sounding rockets in the 1960s.
  • These rockets were used for atmospheric research and scientific experiments.  
  • First sounding rocket launch from Thumba, Kerala in 1963 marked the beginning of India’s space program.

Autonomous Bodies of ISRO

  • Physical Research Laboratory (PRL), Ahmedabad
    • Engaged in basic research in the areas of Astronomy and Astrophysics.
    • Studies of stellar and solar astronomy are conducted from the Infra-red Observatory at Mt. Abu, and a lake site Solar Observatory in Udaipur, respectively.
    • Another campus at Thaltej, Ahmedabad, hosts the planetary exploration (PLANEX) programme.
  • National Atmospheric Research Laboratory (NARL), Tirupati
    • Centre for atmospheric research.
    • NARL carries out its research activities under seven major groups.
  • North Eastern Space Applications Centre (NE-SAC), Shillong
    • Joint initiative of DOS and North Eastern Council (NEC) to provide developmental support to the North Eastern Region (NER) using space science and technology.
  • Indian Institute of Space Science and Technology (IIST), Thiruvananthapuram
    • Asia’s first Space University.
    • Established at Thiruvananthapuram in 2007.
    • Offers high quality education in space science and technology.

ISRO Centres & Units

  • Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram
    • Lead centre of ISRO responsible for the design and development of launch vehicle technology.
    • VSSC has extension Centres at Valiamala.
    • Ammonium Perchlorate Experimental Plant (APEP) has been set up by VSSC at Aluva near Kochi.
  • Liquid Propulsion Systems Centre (LPSC)
    • Develops liquid propulsion stages for ISRO’s Launch Vehicles.
    • Consists of two campuses – LPSC Valiamala (Thriruvananthapuram) and LPSC Bengaluru, Karnataka.
    • LPSC Valaimala is responsible for R&D, System Design.
    • LPSC Bengaluru is responsible for design and realisation of propulsion systems.
  • Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota
    • First Spaceport of India since 1971.
    • Provides Launch Base Infrastructure for the Indian Space Programme.
    • It has two launch pads from where the rocket launching operations of PSLV and GSLV are carried out.
    • SDSC SHAR has a separate launch pad for launching sounding rockets.
    • India’s second spaceport located at Kulasekharapattinam in Tamil Nadu’s Thoothukudi district
  • U R Rao Satellite Centre (URSC), Bengaluru
    • Formerly known as ISRO Satellite Centre (ISAC).
    • Lead centre for building satellites and developing associated satellite technologies.
    • URSC has a unit called Laboratory for Electro Optics System (LEOS) in Peenya, Bengaluru.
    • LEOS is mainly responsible for research, development and productionisation of Sensors.
  • Space Applications Centre (SAC), Ahmedabad
    • Development of space borne and air borne instruments / payloads and their applications for national development and societal benefits.
  • National Remote Sensing Centre (NRSC) at Hyderabad
    • Responsible for remote sensing satellite data acquisition and processing, data dissemination, aerial remote sensing and decision support for disaster management.
    • NRSC Ground station at Shadnagar acquires Earth Observation data from Indian remote-sensing satellites as well as from different foreign satellites.
  • Human Space Flight Centre (HSFC), Bengaluru
    • Responsible for implementation of GAGANYAAN Project.
    • Dr. K Kasturirangan inaugurated HSFC in 2019.
    • A full scale model of GAGANYAAN’s crew module was also unveiled during this event.
  • ISRO Propulsion Complex (IPRC), Mahendragiri
    • Develops cutting edge propulsion technology products for the Indian space programme.
    • Activities carried out at IPRC, Mahendragiri are: assembly, integration and testing of earth storable propellant engines, cryogenic engines.
  • ISRO Inertial Systems Unit (IISU), Thiruvananthapuram
    • Design and development of Inertial Systems for Launch Vehicles and Spacecraft programmes of ISRO.
    • Major systems like Inertial Navigation Systems based on mechanical gyros.
  • ISRO Telemetry, Tracking and Command Network (ISTRAC), Bengaluru
    • Provides tracking support for all the satellite and launch vehicle missions of ISRO.
  • Master Control Facility (MCF) at Hassan in Karnataka and Bhopal in Madhya Pradesh
    • Monitors and controls all the geo-stationary satellites of ISRO.
    • MCF carries out operations related to initial orbit raising of satellites, in-orbit payload testing, and on-orbit operations throughout the life of these satellites.
  • Laboratory for Electro-Optics Systems (LEOS)
    • Situated at Peenya Industrial Estate, Bengaluru where first India satellite was fabricated in 1975.
    • LEOS deals with the design, development and production of Attitude Sensors for all LEO, GEO and interplanetary missions.
  • Indian Institute of Remote Sensing (IIRS) at Dehradun
    • It is a premier institute with the objective of capacity building in Remote Sensing and Geo-informatics and their applications through education and training programmes at postgraduate level.
    • Also provides support to the Centre for Space Science and Technology Education in Asia and the Pacific (CSSTE-AP), affiliated to the United Nations.
  • Indian National Space Promotion and Authorisation Centre (IN-SPACe)
    • It is a single-window, independent, nodal agency that functions as an autonomous agency in the Department of Space (DOS).
    • It is formed following the Space sector reforms to enable and facilitate the participation of private players.
    • IN-SPACe is responsible to promote, enable authorize and supervise various space activities of non-governmental entities.
    • IN-SPACe acts as an interface between ISRO and Non-Governmental Entities (NGEs).

Central Public Sector Enterprises : ANTRIX and NSIL

  • Antrix Corporation Limited (ACL), Bengaluru
    • It is a wholly owned Government of India Company
    • Functions under the administrative control of Department of Space.
    • Incorporated as a private limited company owned by Government of India in September 1992.
    • Marketing arm of ISRO for promotion and commercial exploitation of space products.
    • Antrix is engaged in providing Space products and services to international customers worldwide.
  • NewSpace India Limited (NSIL), Bengaluru
    • Incorporated on 6 March 2019 (under Companies Act 2013) is a wholly owned Government of India company.
    • Functions under the administrative control of Department of Space. 
    • NSIL is the commercial arm of ISRO with the primary responsibility of enabling Indian industries to take up high technology space related activities.

Launch Vehicles of India

  • Satellite Launch Vehicle (SLV):
    • Satellite Launch Vehicle-3 (SLV-3) was India’s first experimental satellite launch vehicle.
    • Successfully launched on 18 July 1980
    • Rohini satellite (RS-1) was placed in the orbit.
    • India became 6th nation to have its own satellite launch capability.
    • Note: First experimental flight of SLV-3, in August 1979, was only partially successful.
    • SLV-3 Specifications:
      • All solid, four stage vehicle.
      • Weight 17 tonnes
      • Height 22 mts
      • Payload capacity 40kg (into LEO).
  • Augmented Satellite Launch Vehicle (ASLV):
    • ASLV was an improvement over the SLV-3, with a capability to launch heavier satellites.
    • Can place satellites into 400 km circular orbits.
    • ASLV-D3 was successfully launched on 20 May 1992.
    • SROSS-C (106 kg) was put into LEO.
    • ASLV Specifications
      • Five stage, all-solid propellant vehicle.
      • Weight 40 tonnes
      • Height 24 mts
      • Payload capacity 150 kg
  • Polar Satellite Launch Vehicle (PSLV):
    • First Flight: 20th September 1993.
    • PSLV is the third generation launch vehicle of India.
    • PSLV places satellites to Low Earth Orbits, Geosynchronous and Geostationary orbits.
    • PSLV can also take up to 1750 kg of payload to Sun-Synchronous Polar Orbits of 600 km altitude.
    • PSLV is also known as “Workhorse of ISRO”.
    • PSLV was used to launch
      • India’s first lunar probe Chandrayaan-1 on 22 October 2008.
      • India’s first interplanetary mission – Mars Orbiter Mission (Mangalyaan) on 5 November 2013.
      • India’s first space observatory – Astrosat on 28 September 2015.
      • India’s first Solar mission, Aditya-L1 on September 2, 2023.
    • PSLV Specifications
      • 4 Stages (solid and liquid propulsion systems alternately)
      • Lift Off Mass: 320 tonnes (XL)
      • Height: 44 mts
      • Diameter: 2.8 mts
    • PSLV is the first Indian launch vehicle to be equipped with liquid stages.
    • PSLV uses Vikas engine for its second stage.
      • Developed by Liquid Propulsion Systems Centre (HQ: Thiruvananthapuram).
      • It is an Earth storable liquid rocket engine.
  • Geosynchronous Satellite Launch Vehicle (GSLV):
    • GSLV was developed to launch communication satellites in Geosynchronous transfer orbit (GTO).
    • GSLV’s primary payloads are INSAT class of communication satellites.
    • GSLV uses a three stage launching system – Solid, Liquid and Cryogenic.
    • GSLV (Mark I): This was the initial version of GSLV. It relied on a Russian-supplied cryogenic upper stage (the engine that provides the final push to put the satellite into its intended orbit). Payload Capacity: 2 to 2.5 tons into Geosynchronous Transfer Orbit (GTO).
    • GSLV Mark II uses an indigenously developed cryogenic upper stage. Payload Capacity: 2.5-ton class into GTO.
    • GSLV Mark I: Used a Russian cryogenic engine for the final stage.
    • GSLV Mark II: Uses an Indian cryogenic engine for the final stage.
  • GSLV Mk-II:
    • GSLV Mark II Specifications
      • Lift Off Mass: 420 tonnes
      • Height: 51.73 mts
      • 3 Stages
      • Payload to GTO: 2250 kg
      • Payload to LEO: 6000 kg
    • Third Stage: Cryogenic Upper Stage
      • CE-7.5 is India’s first cryogenic engine.
      • Developed by Liquid Propulsion Systems Centre.
    • First Flight: 18 April 2001
    • First Flight (With Indigenous Cryogenic Third Stage): 5 January 2014
  • GSLV Mk-III (LVM3):
    • ISRO has renamed GSLV Mark-III as LVM-3.
    • Launch Vehicle Mark-III (LVM3) is a three stage launch vehicle.
    • LVM3 gives ISRO full self-reliance in launching heavier communication satellites that weigh up to 4000 kg in GTO.
    • Payload to GTO: 4000 kg (4 tonnes)
    • Payload to LEO: 8000 kg
    • GSLV Mark III Specifications
      • Lift Off Mass: 640 tonnes
      • Height: 43.5 mts
      • Diameter: 4.0 mts
      • 3 Stages
    • GSLV MkIII-M1 successfully launched the 3840 kg Chandrayaan-2 spacecraft into an earth orbit on 22 July 2019.
      • This mission included an Orbiter, Vikram Lander, and Pragya Rover to explore the Moon’s south polar region.
      • On September 02, 2019, Vikram Lander was separated from the Orbiter in preparation for landing.
      • Vikram Lander descent was as planned and normal performance was observed upto an altitude of 2.1 km.
      • Subsequently communication from lander to the ground stations was lost.
  • Small Satellite Launch Vehicle (SSLV):
    • 3 stage Launch Vehicle
    • Liquid module as terminal stage
    • Capable of launching 500kg satellite in 500km planar orbit.
    • Weight ~120 tonnes
    • Length 34mts
    • Diameter 2mts
  • Reusable Launch Vehicle – Technology Demonstrator (RLV-TD):
    • It is a fully reusable launch vehicle.
    • It has a winged body, resembling a space shuttle, designed for horizontal landing.
    • Has symmetrically placed active control surfaces called Elevons and Rudder.
    • Successfully flight tested on 23 May 2016.
  • Scramjet Engine – TD:
    • It is a test vehicle designed to demonstrate and validate scramjet engine technology.
    • First experimental mission successfully conducted on 28 August 2016.
    • Scramjet engine uses Hydrogen as fuel and the Oxygen from the atmospheric air as the oxidiser.
    • A ramjet is a form of air-breathing jet engine.

Types of Orbits

  • What is an Orbit?
    • An orbit is the curved path that an object (like a satellite, planet, or moon) follows around another object in space due to the force of gravity.
    • Objects in orbit are in a continuous state of freefall but move forward fast enough to avoid crashing into the object they are orbiting.
  • Low Earth Orbit (LEO)
    • Altitude: 160 – 2,000 km
    • Orbital Period: 90 – 120 minutes
    • Close to Earth, allowing low-latency communication.
    • Requires more fuel for maintaining orbit due to atmospheric drag.
    • Examples: ISS (International Space Station), Earth observation satellites (Sentinel, Cartosat)
  • Medium Earth Orbit (MEO)
    • Altitude: 2,000 – 35,786 km
    • Orbital Period: 2 – 12 hours
    • Covers larger areas than LEO, with moderate latency.
    • Used mainly for navigation and communication satellites.
    • Examples: GPS satellites (20,200 km altitude), GLONASS, Galileo navigation systems.
  • High Earth Orbit (HEO)
    • Altitude: Above 35,786 km.
    • Long orbital period (more than 24 hours).
    • Applications: Scientific missions (e.g., studying the Sun or deep space).
  • Geostationary Orbit or Geostationary Earth Orbit (GEO)
    • Altitude: 35,786 km
    • Orbital Period: 24 hours (matches Earth’s rotation)
    • Stays fixed above one point on Earth (equatorial orbit).
    • Orbits directly above the equator.
    • Ideal for weather forecasting, broadcasting, and communication.
    • Example: INSAT (India’s communication satellites)
  • Geo-Synchronous Orbit (GSO)
    • Altitude: 35,786 km
    • Orbital Period: 24 hours
    • Similar to GEO but can have inclined or elliptical orbits.
    • Appears to move in a figure-eight pattern over time.
    • Passes over the same locations daily but not fixed over one spot.
    • Examples: Military surveillance satellites, special communication satellites
  • Sun-Synchronous Orbit (SSO)
    • Altitude: 600 – 800 km
    • Orbital Period: ~100 mins
    • Passes over the same location at the same local solar time daily.
    • Covers the entire Earth over time.
    • Ideal for Earth observation, climate monitoring, and remote sensing.
    • Examples: Cartosat, Landsat, NOAA weather satellites
  • Polar Orbit
    • Altitude: 500 – 800 km
    • Orbital Period: ~100 mins
    • Inclination: 90° (passes over the poles)
    • Covers the entire Earth over multiple orbits.
    • Used for climate monitoring, mapping, and global surveillance.
    • Examples: Spy satellites, Earth mapping satellites like Sentinel, RISAT
  • Highly Elliptical Orbit (HEO)
    • Altitude: Varies (300 km – 40,000 km or more)
    • Orbital Shape: Elliptical (oval-shaped orbit)
    • Stays longer over one hemisphere.
    • Used for communication in high-latitude regions (e.g., Russia, Arctic).
    • Examples: Molniya satellites (Russia), Tundra orbit satellites
  • Transfer Orbits
    • Used for: Moving satellites from one orbit to another.
    • Examples: Geostationary Transfer Orbit (GTO) – Used to reach GEO from LEO.
  • Hohmann Transfer Orbit – Energy-efficient method for transferring between two circular orbits.
  • Lagrange Points
    • Special points in space where gravitational forces balance, allowing objects to remain in a stable position relative to two larger bodies (e.g., Sun-Earth L1 for solar observation).
    • A halo orbit is a three-dimensional orbit that a spacecraft follows around a Lagrange point ((L1), (L2), or (L3)).
    • Halo orbits are periodic and are often used for scientific missions.
  • Key Takeaways
    • GEO – Always above the same point on Earth (used for communication & weather satellites).
    • GSO – Same orbital period as GEO but inclined, moving in a figure-eight pattern.
    • SSO – Passes over every location at the same solar time, ideal for imaging & weather monitoring.

Indian Space Science Missions

  • Lunar Missions
    • Chandrayaan-1 (22 October 2008) – PSLV-C11
      • India’s first Moon mission.
      • Discovered water molecules on the Moon.
      • Carried 11 scientific instruments from ISRO, NASA, ESA, and Bulgaria.
    • Chandrayaan-2 (22 July 2019) – GSLV Mk-III M1
      • Aimed to study the Moon’s south pole.
      • Consisted of Orbiter, Vikram Lander, and Pragyan Rover.
      • The Orbiter is still operational and sending data.
      • The lander failed to soft-land due to technical issues.
    • Chandrayaan-3 (14 July 2023) – LVM3 M4
      • Successful soft landing near the Moon’s south pole.
      • Carried Vikram Lander & Pragyan Rover.
      • India became the 4th country to land on the Moon after the USA, USSR, and China.
      • Discovered Sulfur, Oxygen, and other elements in the Moon’s surface.
    • Lunar Polar Exploration Mission: Collaboration with Japan for lunar exploration (Upcoming).
  • Mangalyaan (Mars Orbiter Mission – MOM) (5 November 2013)
    • India’s first interplanetary mission.
    • First country to reach Mars in its first attempt.
    • Launched using PSLV-C25.
    • Studied Mars’ atmosphere, surface, and methane presence.
    • Operated for 8 years (2013-2022) despite a 6-month planned mission.
  • Solar Mission – Aditya L1 (2 September 2023) – PSLV-C57
    • India’s first solar mission.
    • Positioned at Lagrange Point L1 (1.5 million km from Earth) for continuous Sun observation.
    • Studies solar flares, coronal mass ejections, and Sun-Earth interactions.
  • Astrosat (28 September 2015) – PSLV-C30
    • India’s first dedicated space observatory.
    • Observes X-rays, UV, and optical light from space.
    • Used for black hole studies, star evolution, and galaxy formation.
  • XPoSat – PSLV-C58
    • India’s first X-ray polarimeter satellite.
    • Launched on January 1, 2024 to study black holes and neutron stars.
    • 2 Payloads: POLIX (Polarimeter Instrument in X-rays) and XSPECT (X-ray Spectroscopy and Timing).
  • Gaganyaan Mission (Upcoming)
    • India’s first human spaceflight mission.
    • 3 Indian astronauts (Vyomanauts) will be sent to Low Earth Orbit (~400 km).
    • Uses the Gaganyaan crew module and GSLV Mk III (LVM3) rocket.
    • Test flight (TV-D1) successfully conducted in October 2023.
    • This test demonstrated the Crew Escape System (CES) during a high-altitude abort test.
  • Shukrayaan-1 (Upcoming – Venus Mission)
    • India’s first mission to Venus (Expected launch: 2025-2028).
    • Will study Venus’ atmosphere, surface, and climate.
  • Earth Observation Missions
    • RISAT (Radar Imaging Satellite) – Used for defense & all-weather surveillance.
    • Cartosat Series – Used for mapping, urban planning, and disaster management.
    • Oceansat-3 (2022) – Studies ocean surface and climate changes.
  • NavIC (Navigation with Indian Constellation)
    • India’s GPS-like navigation system.
    • Provides accurate positioning within India & surrounding areas.
  • NISAR (NASA-ISRO Synthetic Aperture Radar):
    • Joint mission of ISRO and NASA for Earth observation.
    • First satellite to use two different radar frequencies (L-band and S-band) to observe Earth’s surface.
    • L-band radar from NASA and S-band radar from ISRO.
    • It is expected to be launched in 2025.
  • Space Station (Planned – 2035)
    • India plans to build an independent space station after Gaganyaan.
    • It will be known as “Bharatiya Antriksh Station”.

Source: ISRO website, GOI Webistes, Internet