GS Notes

19. Science and Technology Notes 02

19 min read

Elaborate Notes

  • Geostationary Transfer Orbit (GTO)

    • Concept and Purpose: A Geostationary Transfer Orbit is an intermediate, highly elliptical orbit used to transition a satellite from a low-altitude parking orbit, typically a Low Earth Orbit (LEO), to a high-altitude Geostationary or Geosynchronous Orbit (GEO/GSO). This method is a practical application of the Hohmann transfer orbit, an orbital maneuver that uses two engine impulses to move a spacecraft between two coplanar circular orbits. It is the most fuel-efficient way to achieve a high-altitude orbit.
    • Orbital Characteristics:
      • Perigee (closest point to Earth): The perigee of a GTO is typically at the altitude of the initial LEO, usually between 180-250 km.
      • Apogee (farthest point from Earth): The apogee is set at the altitude of the target geostationary orbit, which is approximately 35,786 km above the Earth’s equator.
    • Maneuver Sequence:
      1. A launch vehicle, like India’s GSLV, first injects the satellite into a LEO.
      2. From the LEO, the rocket’s upper stage fires its engine at a precise point (perigee) to push the satellite into the elliptical GTO.
      3. The satellite then coasts upwards towards its apogee.
      4. Upon reaching the apogee, an onboard engine, known as the Apogee Kick Motor (AKM) or Liquid Apogee Motor (LAM), is fired. This provides the necessary thrust (a “boost”) to circularize the orbit at 35,786 km and adjust its inclination to zero degrees (for a geostationary orbit), matching the Earth’s rotational speed.
    • Historical Context & Examples: The concept of geostationary communication satellites was first proposed by the science fiction writer Arthur C. Clarke in a 1945 paper titled “Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?“. India’s key launch vehicle, the Geosynchronous Satellite Launch Vehicle (GSLV), is specifically designed to place satellites into GTO. Missions like Chandrayaan-2 (2019) and Mangalyaan (2013) also initially used Earth-bound orbits and transfer maneuvers, demonstrating the fundamental utility of this orbital mechanic principle for interplanetary missions as well.

  • Sun-Synchronous Orbit (SSO)

    • Concept: A Sun-Synchronous Orbit is a specific type of near-polar Low Earth Orbit (LEO) where the satellite passes over any given point on the Earth’s surface at the same local solar time. This means the angle between the satellite’s orbital plane and the Sun remains relatively constant throughout the year.
    • Scientific Principle - Orbital Precession: This is achieved by utilizing the phenomenon of orbital precession. The Earth is not a perfect sphere; it is an oblate spheroid (slightly flattened at the poles and bulging at the equator). This gravitational anomaly exerts a torque on the satellite, causing its orbital plane to rotate or “precess” around the Earth’s axis. In an SSO, this precession rate is deliberately matched to the rate at which the Earth revolves around the Sun (approximately 360 degrees in 365.25 days, or about 0.986 degrees per day).
    • Orbital Characteristics:
      • Altitude: Typically between 500 km and 800 km.
      • Inclination: The angle between the orbital plane and the equatorial plane is usually between 94 to 98 degrees (a retrograde orbit). This high inclination is what makes it a “near-polar” orbit. The precise inclination is calculated to achieve the required precession rate at a given altitude.
    • Applications and Significance: The constant illumination angle is invaluable for Earth observation.
      • Comparative Analysis: As noted by earth scientists, this allows for consistent lighting conditions, making it possible to compare images of the same location taken on different days, months, or years without the data being skewed by changes in shadows or solar illumination. This is critical for monitoring deforestation, urbanization, agricultural crop health, and glacial retreat.
      • Examples: Most Earth observation and remote sensing satellites, such as India’s Cartosat series and Resourcesat series (now part of the EOS series), are placed in SSO. The joint NASA-ISRO NISAR mission will also operate from an SSO.

  • Types of Satellites

    • Communication Satellites:

      • Function: These act as relays in space, receiving signals from a ground station (uplink) and transmitting them to another location (downlink). They bridge vast geographical distances, overcoming the line-of-sight limitation of terrestrial communication.
      • Orbit: Primarily placed in Geostationary Orbit (GEO) to ensure they remain at a fixed point relative to the Earth’s surface, allowing ground antennas to be permanently pointed at them.
      • Indian Context: ISRO’s Indian National Satellite (INSAT) system, initiated in 1983, is one of the largest domestic communication satellite systems in the Asia-Pacific. The satellites were later named GSAT (Geosynchronous Satellite). In a recent move towards a more application-centric approach, ISRO has renamed this series to CMS (Communication Satellite), with CMS-01 (formerly GSAT-12R) being the first in 2020.
      • Applications:
        • Telecommunications & Broadcasting: Direct-to-Home (DTH) television, radio networking, and internet services.
        • Education: The EDUSAT (or GSAT-3), launched by ISRO in 2004, was India’s first thematic satellite dedicated exclusively to serving the educational sector. It provided satellite-based two-way communication to classrooms for delivering educational content.
        • Telemedicine: Connecting rural primary health centers with super-specialty hospitals in urban centers for expert consultation.
        • VSAT (Very Small Aperture Terminal): These are small ground stations (dish antennas of 1-4 meters) used for reliable data transmission for services like banking (connecting ATMs), e-governance, and enterprise networks.
        • Search and Rescue: The Cospas-Sarsat Programme is an international satellite-based system for distress alert detection and information distribution. Satellites detect and locate signals from emergency beacons on ships, aircraft, or individuals. India is a member and provider of ground segment equipment and services, with mission control centers in Bengaluru and Lucknow.

    • Earth Observation (EO) or Remote Sensing Satellites:

      • Function: These satellites are designed to observe Earth from orbit, collecting data about its physical, chemical, and biological systems using advanced sensors. This is known as remote sensing—gathering information about an object without being in direct physical contact with it.
      • Orbit: Typically placed in LEO, especially Sun-Synchronous Orbits, to get high-resolution imagery with consistent lighting. For continuous monitoring of a large area (like weather systems over the Indian subcontinent), they may also be placed in Geostationary Orbit (e.g., INSAT-3D, INSAT-3DR).
      • Technologies: They employ various sensing technologies:
        • Optical Imaging: Capturing images in the visible and infrared spectrum.
        • Synthetic Aperture Radar (SAR): An active sensing technique that transmits microwave signals and records the echoes. It can “see” through clouds, darkness, and rain, making it an all-weather, day-and-night observation tool. RISAT series from ISRO are examples.
        • LiDAR (Light Detection and Ranging): Uses laser pulses to measure distances and create precise 3D maps of the Earth’s surface.
        • Spectroscopy/Hyperspectral Imaging: Captures data across hundreds of narrow spectral bands, allowing for detailed identification of materials, minerals, vegetation types, and soil composition.
      • Indian Context: ISRO began its EO program with the Indian Remote Sensing (IRS) satellite series, starting with IRS-1A in 1988. This has now been consolidated and renamed the EOS (Earth Observation Satellite) series.
      • Applications: Agriculture (crop acreage and health monitoring), forestry (mapping forest cover), geology (mineral exploration), disaster management (flood mapping, cyclone tracking, landslide risk assessment), urban planning, and national security.

  • NISAR Mission

    • Collaboration and Full Form: A joint mission between the National Aeronautics and Space Administration (NASA) and the Indian Space Research Organisation (ISRO). The name NISAR stands for NASA-ISRO Synthetic Aperture Radar.
    • Objective: It is an advanced Earth observation mission designed to systematically map the Earth using two different radar frequencies (L-band and S-band). It will measure changes in our planet’s surface with unprecedented detail, typically on the order of centimeters.
    • Technical Specifications:
      • It will be the first satellite mission to use two different radar frequencies simultaneously. NASA is providing the L-band SAR payload, while ISRO is providing the S-band SAR payload, the spacecraft bus, and the launch vehicle (GSLV Mk-II).
      • The use of SAR allows it to operate day and night and in all weather conditions.
    • Scientific Goals and Applications:
      • Environmental Monitoring: Tracking changes in ecosystems, biomass, sea-level rise, and the dynamics of ice sheets and glaciers.
      • Disaster Monitoring: Providing critical data for managing natural disasters like earthquakes (by monitoring crustal deformation), tsunamis, volcanic eruptions, and landslides. Its rapid revisit time will enable quick damage assessment.
      • Geological Studies: Understanding the processes of Earth’s crust and monitoring groundwater resources.

Prelims Pointers

  • Geostationary Transfer Orbit (GTO):
    • An intermediate, highly elliptical orbit.
    • Perigee is at Low Earth Orbit (LEO) altitude (e.g., ~200 km).
    • Apogee is at Geostationary Orbit (GEO) altitude (~35,786 km).
    • Used to move satellites from LEO to GEO in a fuel-efficient manner.
  • Sun-Synchronous Orbit (SSO):
    • A type of near-polar, Low Earth Orbit (LEO).
    • Satellite passes over a point on Earth at the same local solar time.
    • Altitude: 500-800 km.
    • Inclination: 94-98 degrees (retrograde).
    • The orbital precession (due to Earth’s equatorial bulge) is matched with Earth’s revolution rate around the Sun.
    • Ideal for Earth observation and remote sensing satellites.
  • Communication Satellites:
    • Typically placed in Geostationary Orbit (GEO).
    • ISRO’s series: INSAT → GSAT → CMS (current nomenclature).
    • EDUSAT (GSAT-3): India’s first satellite exclusively for education, launched in 2004.
    • VSAT: Very Small Aperture Terminal; small ground station antennas.
    • Cospas-Sarsat: International satellite-aided search and rescue program. India is a member.
  • Earth Observation (EO) Satellites:
    • Also known as Remote Sensing satellites.
    • Mostly placed in Sun-Synchronous Orbits (SSO).
    • ISRO’s series: IRS → EOS (current nomenclature).
    • Technologies used: Synthetic Aperture Radar (SAR), LiDAR, Hyperspectral Imaging.
    • Examples: Cartosat series, Resourcesat series, RISAT series.
  • NISAR Mission:
    • A joint project between NASA and ISRO.
    • Full form: NASA-ISRO Synthetic Aperture Radar.
    • Objective: Earth observation, disaster and environmental monitoring.
    • World’s first dual-frequency (L-band and S-band) radar imaging satellite.
    • To be launched by ISRO’s GSLV Mk-II.

Mains Insights

  • Socio-Economic Significance of India’s Satellite Program (GS-III)

    • From Self-Reliance to Global Service Provider: India’s space program, envisioned by Vikram Sarabhai, was founded on the principle of using advanced technology for societal good. This has evolved from achieving self-reliance in launch capabilities (PSLV, GSLV) to becoming a commercially viable player through organizations like NSIL (NewSpace India Limited), providing launch services and satellite data globally.
    • Empowering Governance (GS-II): Space technology is a force multiplier in public service delivery.
      • Cause-Effect: The use of satellite imagery (from EOS satellites) for crop yield estimation directly impacts the implementation and settlement of claims under PM Fasal Bima Yojana. Geo-tagging of assets created under MGNREGA using the ‘Bhuvan’ platform enhances transparency and accountability.
    • Bridging the Digital and Development Divide:
      • Communication satellites (INSAT/GSAT/CMS series) have been pivotal in expanding tele-education to remote areas (EDUSAT) and tele-medicine for rural healthcare, addressing issues of accessibility and quality. VSAT networks have been the backbone for banking services in under-connected regions.

  • Space Technology in Disaster Management (GS-III)

    • A Holistic Framework: Satellites play a crucial role across the entire disaster management cycle, shifting the paradigm from a relief-centric approach to one of preparedness and mitigation.
    1. Pre-Disaster Phase:
      • Early Warning: Meteorological satellites (e.g., INSAT-3DR) provide timely and accurate tracking of cyclones, forecasting their intensity and path, enabling mass evacuations.
      • Vulnerability Mapping: High-resolution data from EOS satellites helps in creating maps of landslide-prone zones, floodplains, and areas vulnerable to seismic activity.
    2. During-Disaster Phase:
      • Real-time Monitoring: SAR satellites (like RISAT) can penetrate cloud cover to provide images of flooded areas, helping to direct rescue teams.
      • Communication Support: In the event of terrestrial communication breakdown, communication satellites provide emergency connectivity for response agencies.
    3. Post-Disaster Phase:
      • Damage Assessment: Comparing pre and post-disaster satellite imagery provides a quick and accurate assessment of damage to infrastructure, agriculture, and housing, which is crucial for planning relief and reconstruction.
      • Example: The National Remote Sensing Centre (NRSC) provides near real-time flood inundation maps to state and central agencies during monsoon seasons.

  • International Cooperation and Space Diplomacy (GS-II)

    • Collaborative Missions: Missions like NISAR (with NASA) demonstrate India’s growing stature as a credible partner in advanced scientific research. It signifies a move from being a recipient of technology to a co-developer.
    • SAARC Satellite: The launch of the South Asia Satellite (GSAT-9) in 2017, offered as a ‘gift’ to neighboring countries, is a prime example of space diplomacy, using space assets to foster regional cooperation and goodwill.
    • Global Programs: India’s active participation in programs like Cospas-Sarsat and the International Charter ‘Space and Major Disasters’ showcases its commitment to using space for global humanitarian good.

Previous Year Questions

Prelims

  1. With reference to the Indian satellites and their launchers, consider the following statements: (UPSC Prelims 2019)

    1. All the INSAT series of satellites and their launchers were launched from abroad.
    2. PSLV was used to launch the Chandrayaan-1.
    3. India has launched the first satellite with the name Aryabhata in the year 1975.
    4. ISRO has built the first satellite with the name Aryabhata and was launched from abroad. Which of the statements given above are correct? (a) 1, 2 and 3 (b) 2, 3 and 4 (c) 1, 2 and 4 (d) 1, 3 and 4 Answer: (b) (Statement 1 is incorrect as several INSAT/GSAT satellites were launched by GSLV from India. Statements 2, 3, and 4 are factually correct.)

  2. In which of the following areas can GPS technology be used? (UPSC Prelims 2018)

    1. Mobile phone operations
    2. Banking operations
    3. Controlling the power grids Select the correct answer using the code given below: (a) 1 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3 Answer: (d) (GPS is used for precise timing, which is critical for all three: synchronizing mobile networks, time-stamping banking transactions, and managing power grids (synchrophasors).)

  3. Consider the following statements: The satellite navigation system is/are operated by (UPSC Prelims 2023)

    1. BeiDou - China
    2. Galileo - European Union
    3. GLONASS - Japan
    4. NavIC - India
    5. QZSS - Russia How many of the above pairs are correctly matched? (a) Only two (b) Only three (c) Only four (d) All five Answer: (b) (BeiDou-China, Galileo-EU, and NavIC-India are correct. GLONASS is Russian, and QZSS is Japanese.)

  4. With reference to India’s satellite launch vehicles, consider the following statements: (UPSC Prelims 2018)

    1. PSLVs launch the satellites useful for Earth resources monitoring whereas GSLVs are designed mainly to launch communication satellites.
    2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth.
    3. GSLV Mk III is a four-staged launch vehicle with the first and third stages using solid rocket motors; and the second and fourth stages using liquid rocket engines. Which of the statements given above is/are correct? (a) 1 only (b) 2 and 3 (c) 1 and 2 (d) 3 only Answer: (a) (Statement 1 is correct. Statement 2 is incorrect; it describes geostationary satellites launched by GSLV, not satellites in polar orbits launched by PSLV. Statement 3 is incorrect; GSLV Mk-III is a three-stage vehicle.)

  5. What is the purpose of the ‘evolved Laser Interferometer Space Antenna (eLISA)’ project? (UPSC Prelims 2017) (a) To detect neutrinos (b) To detect gravitational waves (c) To detect the effectiveness of missile defence system (d) To study the effect of solar flares on our communication systems Answer: (b) (eLISA is a space-based observatory designed to detect and measure gravitational waves.)

Mains

  1. Discuss India’s achievements in the field of Space Science and Technology. How the application of this technology has helped India in its socio-economic development? (UPSC Mains 2016, 200 words) Answer Framework:

    • Introduction: Briefly mention the vision of Vikram Sarabhai and the establishment of ISRO. Highlight India’s journey from a nascent space power to a global leader.
    • Achievements in Space Science and Technology:
      • Launch Vehicles: Development of self-reliant launch capabilities with PSLV (the workhorse) and GSLV (for heavier satellites), including the indigenous cryogenic engine.
      • Satellite Systems: Mastery in building world-class satellites for communication (INSAT/GSAT), remote sensing (IRS/EOS), and navigation (NavIC).
      • Space Exploration: Success of interplanetary missions like Chandrayaan (Moon) and Mangalyaan (Mars) on a budget, demonstrating technical prowess.
    • Application in Socio-economic Development:
      • Agriculture: Crop monitoring, drought assessment, and wasteland management.
      • Governance: Resource mapping, urban planning, and transparent monitoring of schemes like MGNREGA.
      • Disaster Management: Early warning for cyclones, flood mapping, and damage assessment.
      • Connectivity: Bringing tele-education, tele-medicine, and DTH services to remote corners of the country.
      • Security & Navigation: Enhancing national security through surveillance and providing an independent navigation system (NavIC).
    • Conclusion: Conclude by stating that ISRO’s achievements have not only brought international prestige but have been fundamentally integrated into India’s national development fabric, acting as a catalyst for growth and inclusion.

  2. India has achieved remarkable successes in unmanned space missions including the Chandrayaan and Mars Orbiter Mission. But has failed to land a man on the moon. What are the scientific and technological challenges for manned space missions? (UPSC Mains 2019, 250 words) Answer Framework:

    • Introduction: Acknowledge India’s success with unmanned missions like MOM and Chandrayaan, which are technologically less complex and less risk-intensive than manned missions. State that manned missions represent the next frontier.
    • Scientific and Technological Challenges for Manned Missions (like Gaganyaan):
      • Launch Vehicle Reliability: Need for a human-rated, highly reliable launch vehicle (like the Human-rated GSLV Mk-III) with a robust Crew Escape System.
      • Life Support System: Developing a closed-loop system to provide a habitable environment in space – managing oxygen, water, food, and waste, and protecting against temperature extremes.
      • Radiation Shielding: Protecting astronauts from harmful cosmic and solar radiation outside Earth’s magnetic field is a major challenge.
      • Re-entry and Recovery Technology: Developing heat shields that can withstand extreme temperatures during atmospheric re-entry and ensuring safe splashdown and recovery of the crew module.
      • Zero Gravity Effects: Countering the adverse physiological effects of microgravity on the human body, such as bone density loss and muscle atrophy.
      • Training and Psychological Health: Rigorous training for astronauts to handle emergencies and manage the psychological stress of confinement and isolation.
    • Conclusion: Conclude that while the challenges are formidable, ISRO’s Gaganyaan mission is a systematic step towards overcoming them. Success in manned missions will elevate India to a select group of space-faring nations and spur technological innovation across various sectors.

  3. What is India’s plan to have its own space station and how will it benefit our space programme? (UPSC Mains 2019, 150 words) Answer Framework:

    • Introduction: State India’s plan to set up its own space station by 2035, as announced by ISRO, as a logical follow-up to the Gaganyaan manned spaceflight mission.
    • Details of the Plan:
      • The space station is envisioned as a small module (~20 tonnes) for conducting microgravity experiments.
      • It will be placed in a Low Earth Orbit (approx. 400 km altitude).
      • It will serve as a platform for astronauts to stay for 15-20 days. The Gaganyaan program will serve as the technological stepping stone for developing the necessary capabilities.
    • Benefits to the Space Programme:
      • Scientific Research: Provides a platform for long-duration research in microgravity, with applications in materials science, biology, and medicine.
      • Technological Advancement: Drives development of critical technologies like life support systems, docking mechanisms, and in-space manufacturing.
      • Sustained Human Presence in Space: Marks a significant leap from short-duration missions to a continuous human presence, opening avenues for future deep-space exploration.
      • Global Prestige & Collaboration: Establishes India as a major space power, enhancing opportunities for international collaboration.
    • Conclusion: Conclude that the Indian space station will be a symbol of national capability and a hub for scientific innovation, ensuring India’s long-term presence and relevance in space exploration.

  4. Discuss the role of space technology in disaster management. Give suitable examples from recent events. (UPSC Mains, similar questions asked frequently) Answer Framework:

    • Introduction: Define space technology as a critical tool for effective disaster management, covering all phases from preparedness to recovery.
    • Role in Pre-Disaster Phase (Mitigation & Preparedness):
      • Vulnerability Mapping: High-resolution satellite imagery helps identify areas prone to landslides, floods, and earthquakes.
      • Early Warning: Meteorological satellites like INSAT-3D provide advance warnings for cyclones. Example: Accurate tracking of Cyclone Fani (2019) and Amphan (2020) enabled timely evacuations, saving thousands of lives.
    • Role in During-Disaster Phase (Response):
      • Real-time Monitoring: SAR satellites (e.g., RISAT) provide all-weather monitoring of flood progression. Example: During the Kerala floods (2018), NRSC provided near real-time flood inundation maps.
      • Communication Support: Satellites provide emergency communication links when terrestrial networks fail.
    • Role in Post-Disaster Phase (Recovery & Reconstruction):
      • Damage Assessment: Comparing pre- and post-disaster images helps quantify the extent of damage to infrastructure and agriculture for efficient resource allocation. Example: Used for damage assessment after the Uttarakhand floods (2013) and Nepal earthquake (2015).
      • Reconstruction Planning: Data helps in planning resilient infrastructure and new settlement zones.
    • Conclusion: Conclude that integrating space technology with ground-based systems has revolutionized disaster management in India, shifting the focus from reaction to proactive risk reduction, thereby saving lives and property.

  5. What are the applications of satellite communication in India? Discuss the recent policy changes aimed at boosting the private sector’s role in this domain. (UPSC Mains, contemporary theme) Answer Framework:

    • Introduction: Briefly introduce satellite communication as the backbone of India’s connectivity, especially in remote and inaccessible regions, pioneered by ISRO’s INSAT/GSAT series.
    • Key Applications of Satellite Communication:
      • Broadcasting: Direct-to-Home (DTH) TV and radio services.
      • Telecommunications: Satellite phone services, VSAT networks for ATMs, e-governance, and business connectivity.
      • Internet Services: Providing satellite-based broadband (Satcom) in areas where terrestrial fiber is unfeasible.
      • Tele-education & Tele-medicine: Bridging the urban-rural divide in education and healthcare.
      • Disaster Management: Providing emergency communication channels.
      • Navigation: Aiding the NavIC constellation with timing and data dissemination.
    • Recent Policy Changes for Private Sector Participation:
      • IN-SPACe (Indian National Space Promotion and Authorization Center): Created in 2020 as a single-window nodal agency to promote, authorize, and supervise private sector space activities. It acts as an interface between ISRO and private players.
      • NewSpace India Limited (NSIL): A Central Public Sector Enterprise established to commercially exploit ISRO’s products and services, transferring mature technologies to Indian industries.
      • Draft Spacecom Policy 2020 & Indian Space Policy 2023: These policies aim to create a predictable regulatory regime, encourage foreign investment, and allow private companies to establish and operate satellite communication systems, ground stations, and provide services directly to consumers.
    • Conclusion: Conclude that by opening up the space sector, India aims to move from a government-led model to a more inclusive ecosystem. This will foster innovation, attract investment, and enhance the nation’s share in the global space economy, ultimately benefiting the end-users with better and more affordable services.

Graph View