Space Technology

SPACE TECHNOLOGY

Introduction

1. Space Technology refers to the application of scientific knowledge and engineering principles to develop systems for space exploration, satellite operations, communication, navigation, Earth observation and astronomical research.
2. It encompasses the design, development, launching and operation of satellites, launch vehicles, spacecraft, propulsion systems, ground stations and space-based scientific instruments.
3. Space technology has become an essential component of modern infrastructure, supporting services such as:
   • Satellite Communication: Television broadcasting, telecommunications and internet connectivity.
   • Navigation: Positioning, navigation and precise timing services.
   • Earth Observation: Monitoring natural resources, agriculture, land use and environmental changes.
   • Meteorology: Weather forecasting, cyclone tracking and climate monitoring.
   • Disaster Management: Early warning, damage assessment and emergency communication.
   • Space Exploration: Investigation of the Moon, planets, Sun and other celestial objects.
   • National Security: Surveillance, reconnaissance, secure communication and strategic applications.
4. Space begins gradually as Earth’s atmosphere becomes increasingly rarefied. The Kármán Line, conventionally placed at approximately 100 kilometres above mean sea level, is frequently used as a reference boundary between Earth’s atmosphere and outer space.
   
   
5. The Kármán Line is a conventional boundary rather than a sharp physical division because Earth’s atmosphere extends well beyond this altitude.
6. Space activities are broadly classified into:
   • Civilian Applications: Communication, scientific research, education, meteorology and resource management.
   • Commercial Applications: Satellite services, launch operations, geospatial information and space-based connectivity.
   • Strategic Applications: Military communication, surveillance, reconnaissance and space situational awareness.
7. India’s space programme has developed from modest sounding-rocket experiments into an extensive national programme involving satellite manufacturing, indigenous launch vehicles, planetary exploration, commercial services and human-spaceflight technologies.
8. The expansion of private participation and international collaboration has contributed to the emergence of a more diversified Indian space ecosystem.

Historical Development of Space Technology in India

Early Development

1. The development of modern space research in India began during the 1960s, under the leadership of scientists such as Vikram Sarabhai and Homi Jehangir Bhabha.
2. India’s space programme was initially guided by the objective of applying space technology to national development, particularly communication, education, meteorology and resource management.
3. The Indian National Committee for Space Research (INCOSPAR) was established in 1962, with Vikram Sarabhai as its founding chairman.
4. India’s first sounding rocket was launched from the Thumba Equatorial Rocket Launching Station (TERLS) near Thiruvananthapuram on 21 November 1963.
5. TERLS was selected partly because of its geographical proximity to the magnetic equator, which made it suitable for certain upper-atmospheric and ionospheric investigations.

Establishment of ISRO

1. The Indian Space Research Organisation (ISRO) was established on 15 August 1969, replacing INCOSPAR.
2. ISRO’s principal objective was to develop indigenous space technologies and apply them to national development.
3. The Department of Space (DOS) and Space Commission were established in 1972.
4. ISRO was brought under the administrative framework of DOS.
5. India’s first satellite, Aryabhata, was launched on 19 April 1975 using a Soviet launch vehicle.
6. On 18 July 1980, India successfully placed the Rohini RS-1 satellite into orbit using the indigenous Satellite Launch Vehicle-3 (SLV-3).

Important Milestones in India’s Space Programme

Objectives of India’s Space Programme

1. Develop indigenous satellites, launch vehicles and spacecraft technologies.
2. Strengthen national capabilities in satellite communication and remote sensing.
3. Support agricultural development, meteorology, oceanography and disaster management.
4. Expand satellite-based navigation and positioning services.
5. Conduct scientific exploration of the Moon, Sun, planets and wider Universe.
6. Establish technological capabilities for human spaceflight.
7. Promote commercial space activities and private-sector participation.
8. Strengthen national security and technological self-reliance.

Satellite Orbits: Meaning and Classification

Meaning of an Orbit

1. An Orbit is the trajectory followed by a celestial body or spacecraft under the influence of gravitational forces.
2. Artificial satellites generally remain in orbit because their tangential velocity causes them to continuously fall around Earth rather than directly towards its surface.
3. Orbital characteristics depend on factors such as:
   • Altitude.
   • Velocity.
   • Inclination.
   • Eccentricity.
   • Orbital period.
   • Gravitational forces and perturbations.
4. Earth’s satellites are classified according to altitude, orbital geometry, inclination and their relationship with Earth’s rotation.

Classification Based on Altitude

Classification Based on Inclination and Shape

1. Equatorial Orbit: An orbit lying approximately in Earth’s equatorial plane.
2. Polar Orbit: An orbit with inclination near 90°, allowing the satellite to pass over or near polar regions.
3. Inclined Orbit: An orbit whose plane is tilted relative to Earth’s equatorial plane.
4. Sun-Synchronous Orbit (SSO): An orbit designed so that its orbital plane precesses at a rate that maintains an approximately constant local solar time of passage.
5. Circular Orbit: An orbit with eccentricity equal to zero.
6. Elliptical Orbit: An orbit with non-zero eccentricity, in which the distance from Earth varies during revolution.

Important Orbital Terminology

Low Earth Orbit (LEO)

1. Low Earth Orbit (LEO) generally extends from approximately 160 to 2,000 kilometres above Earth’s surface.
2. Satellites in LEO move rapidly around Earth because relatively high orbital velocity is required at low orbital altitudes.
3. Their orbital periods are typically around 90–130 minutes, depending on altitude and orbital geometry.
4. LEO satellites provide relatively high-resolution observations and comparatively low communication latency.
5. A single LEO satellite covers only a limited geographical area at a given moment.

Advantages

1. Low Communication Latency: Shorter signal-propagation distances compared with higher satellite orbits.
2. High-Resolution Observation: Relatively close proximity to Earth facilitates detailed surface monitoring.
3. Lower Launch Energy Requirements: Reaching LEO generally requires less energy than reaching higher Earth orbits.
4. Scientific Accessibility: Suitable for many experimental and orbital research missions.
5. Satellite Constellations: Multiple satellites can work together to provide continuous or near-continuous coverage.

Applications

1. Earth Observation: Agriculture, forests, land use, disasters and environmental monitoring.
2. Satellite Communication: Broadband services using large satellite constellations.
3. Space Research: Scientific experiments and astronomical observations.
4. Human Spaceflight: Operation of crewed orbital platforms and spacecraft.
5. Reconnaissance: High-resolution imaging and other observation applications.

Challenges

1. Atmospheric Drag: Residual atmospheric gases gradually reduce the orbital energy of satellites.
2. Frequent Revisits: A single satellite may not continuously observe the same location.
3. Orbital Debris: Large numbers of operational and inactive objects increase collision risks.
4. Constellation Requirements: Continuous global services may require many satellites.
5. Orbital Maintenance: Some satellites need propulsion for orbit correction and collision avoidance.

Examples

1. International Space Station (ISS): Operates in LEO at an altitude of roughly 400 kilometres.
2. Hubble Space Telescope: Operates in LEO.
3. Cartosat Satellites: Used for high-resolution Earth observation.
4. RISAT/EOS Radar Satellites: Used for radar-based Earth observation.
5. Starlink Satellites: Form part of a large LEO communication constellation.

Medium Earth Orbit (MEO)

1. Medium Earth Orbit (MEO) refers to Earth orbits above the LEO region and below geosynchronous altitude.
2. It is particularly important for satellite navigation systems.
3. Satellites in MEO generally cover larger areas than those at comparable viewing geometries in LEO.
4. Their orbital periods are longer than those of typical LEO satellites.
5. MEO offers a balance between coverage, satellite numbers and signal-propagation distance.

Advantages

1. Wider Coverage: Individual satellites can cover relatively large regions of Earth.
2. Suitable for Navigation: MEO is particularly useful for global navigation constellations.
3. Lower Atmospheric Drag: Negligible atmospheric drag compared with LEO.
4. Reduced Constellation Size: Global services often require fewer satellites than similarly designed LEO constellations.

Challenges

1. Greater Signal Delay: Communication signals travel farther than in LEO.
2. Higher Launch Energy: Reaching MEO requires more energy than reaching typical LEO altitudes.
3. Radiation Exposure: Some MEO trajectories encounter portions of Earth’s radiation belts.
4. Coverage Management: Global navigation requires careful constellation design and orbital maintenance.

Applications and Examples

1. GPS satellites orbit at an altitude of approximately 20,200 kilometres.
2. MEO navigation systems provide global or extensive regional positioning, navigation and timing services.
3. Their applications include aviation, transportation, agriculture, surveying and telecommunications.

Geosynchronous and Geostationary Orbits

Geosynchronous Orbit

1. A Geosynchronous Orbit is an Earth orbit with an orbital period equal to Earth’s sidereal rotation period.
2. One sidereal day is approximately 23 hours, 56 minutes and 4 seconds.
3. A geosynchronous orbit may be circular or elliptical and may have a non-zero inclination.
4. Therefore, a geosynchronous satellite does not necessarily appear stationary in the sky.
5. Depending on inclination and eccentricity, its apparent position may trace a repeating pattern.

Geostationary Orbit

1. A Geostationary Orbit (GEO) is a special type of geosynchronous orbit.
2. It must be:
   • Circular.
   • Equatorial.
   • Prograde, in the direction of Earth’s rotation.
   • Have an orbital period equal to one sidereal day.
3. A geostationary satellite appears fixed above a particular longitude on Earth’s equator.
4. Its altitude is approximately 35,786 kilometres above mean sea level.
5. GEO is particularly useful for communication and meteorological satellites requiring continuous observation of a particular region.

Advantages of Geostationary Orbit

1. Continuous Regional Coverage: A satellite can continuously observe a large portion of Earth.
2. Fixed Ground Antennas: Ground-based communication antennas can point towards a nearly fixed position.
3. Broadcasting Services: Suitable for television and communication services.
4. Weather Observation: Enables continuous monitoring of cloud systems and large-scale atmospheric changes.
5. Regional Communication: Useful for providing connectivity to geographically dispersed areas.

Limitations

1. High Communication Latency: Signals must travel large distances between Earth and the satellite.
2. Poor Polar Coverage: Geostationary satellites have limited visibility of high-latitude regions.
3. High Launch Energy: GEO missions require substantial energy.
4. Orbital Congestion: The geostationary orbital region is subject to increasing demand for orbital slots and radio frequencies.
5. Station-Keeping Requirements: Satellites require periodic manoeuvres to maintain their assigned positions.

Geosynchronous Orbit versus Geostationary Orbit

Geosynchronous Transfer Orbit (GTO)

1. A Geosynchronous Transfer Orbit (GTO) is an elliptical orbit commonly used to transfer spacecraft towards geosynchronous or geostationary orbits.
2. A conventional GTO has:
   • A relatively low perigee.
   • An apogee near geosynchronous altitude.
3. A launch vehicle injects the satellite into the transfer orbit.
4. Subsequent propulsion manoeuvres raise the perigee and circularise the orbit.
5. Additional inclination correction may be necessary before the spacecraft enters its final operational orbit.
6. GTO enables efficient use of launch-vehicle and spacecraft propulsion capabilities.

Polar, Sun-Synchronous and Other Specialised Orbits

Polar Orbit

1. A Polar Orbit has an inclination close to 90° relative to Earth’s equatorial plane.
2. The satellite passes over or near Earth’s polar regions during successive revolutions.
3. As Earth rotates beneath the orbit, the satellite can observe different longitudes.
4. Polar orbits are particularly useful for:
   • Earth observation.
   • Polar-region studies.
   • Meteorology.
   • Environmental monitoring.
   • Mapping and reconnaissance.

Sun-Synchronous Orbit (SSO)

1. A Sun-Synchronous Orbit is designed so that the orbital plane precesses at approximately the same angular rate as Earth’s revolution around the Sun.
2. This enables the satellite to pass over a given latitude at approximately the same local solar time.
3. The resulting similarity in sunlight conditions supports comparisons of images acquired on different dates.
4. SSOs are usually near-polar and often retrograde, with inclinations greater than 90°.
5. Typical applications include:
   • Land-use mapping.
   • Agricultural monitoring.
   • Forest observation.
   • Climate studies.
   • Environmental surveillance.

Highly Elliptical Orbits

1. Highly Elliptical Orbits have substantial differences between their perigee and apogee distances.
2. A satellite moves more slowly near apogee than near perigee.
3. Consequently, it can remain visible over a selected region for an extended period.
4. Such orbits may be useful for communication and observation at high latitudes.
5. Molniya Orbits are important examples of highly elliptical Earth orbits.

Semi-Synchronous Orbits

1. A Semi-Synchronous Orbit has an orbital period equal to approximately half a sidereal day.
2. Satellites therefore complete approximately two revolutions during one Earth rotation.
3. Certain global navigation satellites use semi-synchronous or near-semi-synchronous orbital periods.
4. The orbit provides predictable repeating ground-track patterns.

Halo Orbits

1. A Halo Orbit is a three-dimensional periodic orbit associated with equilibrium regions in the restricted three-body problem.
2. Halo orbits are commonly studied near Lagrange Points in systems such as the Sun–Earth or Earth–Moon system.
3. These orbits are useful for scientific missions because they can offer favourable observation and communication geometries.
4. Many practical halo-orbit missions require periodic trajectory correction and station-keeping manoeuvres.
5. Aditya-L1 operates in a halo orbit around the Sun–Earth L1 region.

Comparison of Important Orbits

Types and Applications of Artificial Satellites

Meaning of an Artificial Satellite

1. An Artificial Satellite is a human-made object placed into orbit around Earth or another celestial body.
2. Satellites are designed for specific functions such as communication, navigation, meteorology, remote sensing, scientific experimentation and reconnaissance.
3. A satellite generally consists of two major systems:
   • Payload: Scientific instruments or equipment designed to perform the primary mission.
   • Satellite Bus: Supporting systems responsible for power supply, communication, attitude control, thermal management and other spacecraft operations.
4. Satellite classification may be based on:
   • Purpose.
   • Orbital altitude.
   • Orbital inclination.
   • Mass.
   • Power source.
   • Operational lifetime.

Classification Based on Function

Classification Based on Mass

Satellite mass categories vary among space agencies and industry classifications. The following categories are commonly used as broad engineering conventions.

1. Smaller satellites often have lower manufacturing and launch costs, although cost depends considerably on the payload and mission requirements.
2. They are particularly useful for technology demonstration, educational experiments and distributed satellite constellations.
3. The CubeSat Standard uses modular units, commonly beginning with a 1U configuration measuring approximately 10 × 10 × 10 centimetres.
4. CubeSats can be assembled in configurations such as 2U, 3U, 6U and larger formats.

Major Satellite Subsystems

Communication Satellites in India

Introduction

1. Communication Satellites relay electromagnetic signals between geographically separated locations.
2. They are widely used for:
   • Television broadcasting.
   • Telecommunication.
   • Broadband connectivity.
   • Satellite backhaul.
   • Emergency communication.
   • Maritime and aviation services.
3. Many communication satellites operate in geostationary orbit, while modern broadband constellations increasingly utilise LEO and other orbital configurations.
4. Communication satellites typically contain transponders or other communication payloads that receive, process, amplify or retransmit signals.

Indian National Satellite System (INSAT)

1. The Indian National Satellite System (INSAT) is a major satellite programme supporting communication and meteorological applications.
2. The INSAT programme began with the launch of INSAT-1A in 1982.
3. It helped expand:
   • Television broadcasting.
   • Telecommunications.
   • Meteorological observations.
   • Disaster-warning services.
   • Rural connectivity.
4. The system enabled communication services across geographically distant regions, including remote and underserved areas.
5. INSAT satellites have played a major role in integrating satellite communication with India’s national infrastructure.

Geosynchronous Satellite (GSAT) Series

1. The GSAT Series comprises Indian communication satellites developed for different communication requirements.
2. They support applications involving:
   • Television and digital broadcasting.
   • Broadband communication.
   • Telephony.
   • Satellite-based internet connectivity.
   • Strategic and institutional communication.
3. GSAT satellites use different communication frequency bands depending on payload design.

Important Communication Frequency Bands

1. Higher-frequency communication bands can support large bandwidths but may be more susceptible to atmospheric attenuation, particularly rain fade.
2. Satellite systems employ antenna design, power control and signal-processing techniques to maintain reliable communication.

Important Indian Communication Satellites

1. The GSAT-11 satellite significantly expanded India’s high-throughput satellite communication capabilities.
2. GSAT-24 was launched on 22 June 2022 and represented an important commercial satellite initiative of NSIL.
3. CMS-03 was launched using LVM3-M5 on 2 November 2025, reflecting continued advances in indigenous heavy communication-satellite launches.

Advantages of Satellite Communication

1. Provides connectivity across large geographical areas.
2. Supports communication in remote mountainous, island and border regions.
3. Enables emergency communication when terrestrial infrastructure is disrupted.
4. Supports broadcasting across geographically dispersed populations.
5. Supplements terrestrial telecommunications and fibre-optic networks.

Limitations

1. High satellite manufacturing and launch costs.
2. Communication latency, particularly for GEO systems.
3. Susceptibility to interference and atmospheric attenuation.
4. Limited availability of orbital slots and radio-frequency spectrum.
5. Space-debris and collision risks.

Earth Observation and Remote Sensing Satellites

Meaning of Remote Sensing

1. Remote Sensing refers to collecting information about an object, surface or phenomenon without direct physical contact.
2. Satellite remote sensing commonly involves detecting electromagnetic radiation reflected, emitted or scattered by Earth’s surface and atmosphere.
3. It is widely used for studying:
   • Land use and land cover.
   • Agricultural conditions.
   • Forest resources.
   • Water bodies.
   • Urban development.
   • Oceanographic processes.
   • Natural disasters.
4. Remote sensing supports large-area, repeated and geographically consistent observations.

Components of a Remote Sensing System

1. Energy Source: Solar radiation or energy generated by an active sensor.
2. Atmospheric Interaction: Radiation may be absorbed, scattered or transmitted through the atmosphere.
3. Target Interaction: Radiation interacts with land, water, vegetation or other surfaces.
4. Sensor: Detects reflected, emitted or backscattered electromagnetic energy.
5. Data Transmission: Sends recorded measurements to ground stations.
6. Data Processing: Converts sensor measurements into usable data products.
7. Interpretation and Application: Uses processed data for mapping, analysis and decision-making.

Remote Sensing Data Acquisition and Processing Sequence

1. Electromagnetic Radiation: Sunlight or active sensor emission.
2. Interaction with Earth’s Surface: Reflection, absorption, emission or backscatter.
3. Satellite Sensor: Measurement and recording.
4. Ground Station and Data Processing: Reception, calibration and analysis.
5. Geospatial Information: Mapping, monitoring and decision support.

Active and Passive Remote Sensing

Important Remote Sensing Sensors

1. Optical Sensors

1. 1. Detect electromagnetic radiation within selected visible, near-infrared or other wavelength bands.
   2. Useful for vegetation, land-cover and surface-feature mapping.
   3. Reflected-sunlight imaging depends on illumination conditions and is affected by cloud cover.

2. Thermal Infrared Sensors

1. 1. Detect thermal radiation emitted by surfaces.
   2. Used for estimating land-surface temperature and studying thermal characteristics.
   3. Useful in urban heat studies, agriculture and environmental research.

3. Synthetic Aperture Radar (SAR)

1. 1. SAR is an active microwave remote-sensing technology.
   2. It transmits radar signals and measures the returned backscatter.
   3. It can operate during day and night.
   4. Many SAR systems can observe Earth’s surface through clouds and rainfall conditions, depending on wavelength and environmental factors.
   5. Applications include:
      • Flood mapping.
      • Soil-moisture assessment.
      • Surface-deformation monitoring.
      • Disaster assessment.
      • Ocean and ice observation.

4. LiDAR

1. 1. Light Detection and Ranging (LiDAR) uses laser pulses to measure distances.
   2. It is used to generate high-resolution elevation and three-dimensional structural information.
   3. Applications include forestry, topographic surveys and infrastructure mapping.

Indian Remote Sensing Satellite Programme

1. The Indian Remote Sensing (IRS) programme has been an important component of India’s national space applications.
2. It supports resource management, environmental monitoring and developmental planning.
3. Important satellite series include:
   • Resourcesat: Resource monitoring, particularly agriculture and vegetation.
   • Cartosat: Cartographic and high-resolution Earth observation.
   • Oceansat: Oceanographic observations.
   • RISAT/EOS Radar Satellites: Microwave radar-based observation.
   • INSAT Meteorological Payloads: Weather monitoring and atmospheric observations.

Important Earth Observation Satellites

Applications of Satellite Remote Sensing

NISAR: NASA–ISRO Synthetic Aperture Radar Mission

1. NISAR stands for NASA–ISRO Synthetic Aperture Radar.
2. It is a joint Earth-observation satellite developed by NASA and ISRO.
3. NISAR was successfully launched on 30 July 2025, aboard GSLV-F16, from the Satish Dhawan Space Centre, Sriharikota.
4. The mission uses a dual-frequency radar system to observe changes in Earth’s land and ice-covered surfaces.
5. It represents an important example of international cooperation in advanced radar Earth observation.

Major Characteristics

1. Dual-Frequency Radar: Uses NASA’s L-band and ISRO’s S-band synthetic aperture radar systems.
2. Active Microwave Observation: Operates independently of sunlight.
3. All-Weather Capabilities: Can acquire observations through many cloud-cover conditions.
4. Large Deployable Reflector: Uses an approximately 12-metre radar reflector.
5. Wide-Swath Imaging: Designed for broad-area observations with high spatial resolution.
6. Repeat Observation: Supports repeated monitoring of Earth’s land and ice-covered regions.
7. Interferometric Capabilities: Enables the measurement of selected surface movements and changes over time.

Scientific Objectives

1. Land-Surface Deformation

1. 1. Measures changes in Earth’s surface position.
   2. Supports research on earthquake-related deformation and land subsidence.
   3. Helps investigate geological processes and surface instability.

2. Cryosphere Monitoring

1. 1. Observes glaciers and ice-covered regions.
   2. Supports studies of ice movement and ice-sheet changes.
   3. Contributes to understanding climate-related changes in frozen environments.

3. Vegetation and Ecosystems

1. 1. Monitors changes in vegetation structure.
   2. Supports forest and land-cover analysis.
   3. Helps investigate ecosystem responses to environmental change.

4. Water Resources

1. 1. Supports assessment of soil moisture and surface-water conditions.
   2. Contributes to flood monitoring and selected hydrological investigations.
   3. Provides information for resource planning.

5. Disaster Management

1. 1. Supports flood and landslide assessment.
   2. Enables monitoring of selected surface changes associated with earthquakes.
   3. Provides observations relevant to disaster-response planning.

Technological Significance

Satellite Navigation: GPS, NavIC and GAGAN

Satellite Navigation

1. Satellite Navigation uses signals transmitted by orbiting satellites to determine the position, velocity and timing of receivers.
2. Satellite navigation systems generally employ precise onboard clocks and known satellite orbital information.
3. Receivers estimate distances to satellites using signal propagation times.
4. Measurements from multiple satellites enable the calculation of receiver position and time.
5. Applications include:
   • Road, rail, aviation and maritime navigation.
   • Land surveying.
   • Precision agriculture.
   • Disaster management.
   • Telecommunications synchronisation.
   • Logistics and fleet management.

Global Navigation Satellite Systems (GNSS)

Navigation with Indian Constellation (NavIC)

1. NavIC stands for Navigation with Indian Constellation.
2. It was earlier known as the Indian Regional Navigation Satellite System (IRNSS).
3. NavIC is India’s independently developed regional satellite navigation system.
4. Its designed service region includes India and an area extending approximately 1,500 kilometres beyond the Indian landmass.
5. It was originally designed around a constellation of seven satellites in geostationary and inclined geosynchronous orbits.
6. The actual operational constellation can vary because of spacecraft ageing, failures, replenishment and new launches.
7. The NavIC system supports:
   • Positioning.
   • Navigation.
   • Timing.
   • Regional location-based applications.

NavIC Services

1. NavIC has traditionally used signals in the L5 and S frequency bands.
2. Newer-generation NVS satellites introduce support for the L1 band, improving compatibility with a wider range of navigation receivers.
3. Navigation performance depends on constellation availability, signal quality, receiver design and environmental conditions.

Important NavIC Satellites

1. IRNSS-1A: First satellite of the original regional navigation constellation, launched in 2013.
2. IRNSS-1G: Launched in 2016, completing the original seven-satellite constellation deployment.
3. NVS-01: Launched on 29 May 2023, as part of the newer generation of NavIC satellites.
4. NVS-02: Launched on 29 January 2025, but subsequent orbit-raising operations were unsuccessful.
5. NVS-03: Launched on 30 October 2026, aboard GSLV-F18, according to ISRO’s launch records.

NVS-02 was accurately injected into its planned transfer orbit, but its propulsion system could not perform the intended orbit-raising operation. An ISRO review identified a failure associated with transmission of the drive signal to a pyro valve in the oxidiser line. The successful launch of a navigation satellite must therefore be distinguished from its successful commissioning into an operational navigation orbit.

Applications of NavIC

1. Navigation for road transport and maritime operations.
2. Location-based public services.
3. Disaster response and emergency management.
4. Agricultural and geographical surveying.
5. Timing and synchronisation services.
6. Tracking of vehicles and assets.
7. Strategic navigation applications.

GPS Aided GEO Augmented Navigation (GAGAN)

1. GAGAN stands for GPS Aided GEO Augmented Navigation.
2. It is a Satellite-Based Augmentation System (SBAS) developed through cooperation between ISRO and the Airports Authority of India (AAI).
3. Its principal objective is to improve the accuracy, integrity and availability of satellite-navigation information for civil aviation.
4. GAGAN uses ground monitoring stations to assess navigation-satellite signals.
5. Correction and integrity information is transmitted to users through geostationary satellites.

Working of GAGAN

1. Ground reference stations receive signals from navigation satellites.
2. These stations detect errors and monitor signal integrity.
3. The data is processed at master control facilities.
4. Correction and integrity messages are transmitted through satellite uplinks.
5. Geostationary satellites broadcast the information to compatible receivers.
6. Aircraft navigation systems use this information to improve the reliability of satellite-based navigation.

Difference Between NavIC and GAGAN

Satellite Data Processing, Ground Infrastructure and Space Situational Awareness

Satellite Ground Segment

1. The Ground Segment consists of terrestrial infrastructure used to communicate with, monitor and control spacecraft.
2. Important components include:
   • Ground antennas.
   • Mission control centres.
   • Telemetry reception systems.
   • Tracking facilities.
   • Data processing centres.
   • Communication networks.
3. The ground segment ensures that satellites can be monitored and commanded during their operational lifetime.
4. It also enables the reception and processing of scientific or application-related data.

Telemetry, Tracking and Command

1. Telemetry

1. 1. Transmission of spacecraft health and operational information to ground stations.
   2. Includes measurements relating to power, temperature, orientation and other onboard systems.

2. Tracking

1. 1. Determination of the satellite’s position, trajectory and orbital characteristics.
   2. Supports navigation, orbit determination and collision avoidance.

3. Command

1. 1. Transmission of instructions from ground control to the spacecraft.
   2. Enables changes in operational modes, instrument settings and spacecraft manoeuvres.

Major Indian Ground and Data Institutions

Satellite Data Processing

1. Raw signals received from satellites require calibration, correction and processing before they can be used reliably.
2. Important stages include:
   • Data Acquisition: Receiving measurements from the satellite.
   • Radiometric Correction: Correcting sensor-related and other radiometric effects.
   • Geometric Correction: Aligning image data with geographical coordinates.
   • Image Enhancement: Improving visual or analytical interpretation.
   • Classification: Identifying land cover or other features.
   • Geospatial Analysis: Combining observations with geographical information.
3. Processed data supports maps, statistical analyses and decision-support systems.

Bhuvan Geoportal

1. Bhuvan is ISRO’s geospatial platform for accessing, visualising and analysing satellite-derived and other geographical information.
2. It is developed and supported through NRSC.
3. Bhuvan provides access to different geospatial datasets and mapping services.
4. Major functions include:
   • Satellite-image visualisation.
   • Thematic mapping.
   • Geospatial data services.
   • Terrain and resource-related information.
   • Tools supporting spatial analysis.
5. Its applications include:
   • Urban planning.
   • Natural-resource management.
   • Agriculture.
   • Disaster assessment.
   • Environmental monitoring.
   • Infrastructure planning.

Space Situational Awareness (SSA)

1. Space Situational Awareness refers to the ability to detect, track, catalogue and assess objects and hazards in the space environment.
2. SSA is important because Earth orbit contains:
   • Operational satellites.
   • Defunct spacecraft.
   • Spent rocket stages.
   • Fragments from collisions and break-ups.
   • Other artificial debris.
3. Collision risk assessment requires knowledge of orbital trajectories and their uncertainties.
4. SSA systems employ:
   • Ground-based radars.
   • Optical telescopes.
   • Tracking sensors.
   • Orbital prediction models.
   • Data-processing systems.

Project NETRA

1. Project NETRA stands for Network for Space Object Tracking and Analysis.
2. It aims to strengthen India’s indigenous capabilities in tracking objects in Earth orbit.
3. Its objectives include:
   • Detection and tracking of space debris.
   • Monitoring of selected near-Earth orbital objects.
   • Collision-risk assessment.
   • Protection of Indian space assets.
4. The project supports national space safety and operational independence.

IS4OM and Orbital Debris Management

1. ISRO System for Safe and Sustainable Space Operations Management (IS4OM) supports space-situational-awareness and related operational activities.
2. Its functions include:
   • Collision-avoidance analysis.
   • Monitoring orbital debris.
   • Supporting satellite operational safety.
   • Re-entry assessment.
   • Space-traffic-related analysis.
3. Space debris may threaten satellites because even small fragments possess high relative velocities.
4. Mitigation measures include:
   • Collision-avoidance manoeuvres.
   • Spacecraft passivation.
   • Controlled or planned end-of-life disposal.
   • Reducing fragmentation risks.
   • Post-mission deorbiting where appropriate.

Evolution of India’s Satellite Launch Vehicles

Meaning of Launch Vehicle

1. A Launch Vehicle is a rocket designed to transport satellites, spacecraft or other payloads to a specified trajectory or orbit.
2. It generates thrust through the expulsion of high-velocity exhaust gases.
3. Most orbital rockets use multiple stages to improve efficiency and achieve the required velocity.
4. Launch-vehicle development depends on advanced capabilities in:
   • Propulsion.
   • Structures and materials.
   • Guidance and navigation.
   • Flight control.
   • Aerodynamics.
   • Thermal protection.
   • Stage separation.
5. India’s launch-vehicle programme has evolved through successive generations of indigenous rockets.

Satellite Launch Vehicle-3 (SLV-3)

1. SLV-3 was India’s first indigenous experimental satellite launch vehicle.
2. It used a four-stage solid-propellant configuration.
3. Its principal objective was to develop the capability to place small satellites into low Earth orbit.
4. The first experimental launch in August 1979 was unsuccessful.
5. On 18 July 1980, SLV-3 successfully placed the Rohini RS-1 satellite into orbit.
6. The achievement established India’s indigenous orbital satellite-launch capability.
7. A. P. J. Abdul Kalam played a leading role in the SLV-3 programme.

Augmented Satellite Launch Vehicle (ASLV)

1. ASLV was developed to advance India’s launch-vehicle technology beyond SLV-3.
2. It used a five-stage solid-propellant configuration.
3. The programme focused on improvements in:
   • Guidance and control.
   • Staging.
   • Strap-on booster integration.
   • Flight dynamics.
4. ASLV experienced unsuccessful initial developmental flights.
5. Later flights demonstrated important technological improvements.
6. The programme provided valuable experience for the development of PSLV.

Polar Satellite Launch Vehicle (PSLV)

1. PSLV is one of ISRO’s most important and versatile launch vehicles.
2. It was developed primarily to place satellites into polar and Sun-synchronous orbits.
3. PSLV uses a combination of solid and liquid propulsion stages.
4. Its standard architecture consists of four stages:
   • First Stage: Solid propulsion.
   • Second Stage: Liquid propulsion using the Vikas engine.
   • Third Stage: Solid propulsion.
   • Fourth Stage: Liquid propulsion.
5. Different PSLV variants are designed to meet different payload and mission requirements.
6. PSLV has also supported interplanetary missions and multi-satellite deployments.

Major PSLV Achievements

1. First successful developmental flight in October 1994.
2. Launch of Chandrayaan-1 in 2008.
3. Launch of the Mars Orbiter Mission in 2013.
4. Launch of AstroSat in 2015.
5. Deployment of 104 satellites in a single PSLV-C37 mission in February 2017.
6. Launch of SpaDeX in December 2024.
7. Use of PSLV’s upper stage as an experimental orbital platform under POEM.

Geosynchronous Satellite Launch Vehicle (GSLV)

1. GSLV was developed to place heavier payloads into geosynchronous transfer orbits.
2. The GSLV Mk II architecture comprises:
   • Solid-propellant core stage.
   • Liquid-propellant strap-on boosters.
   • Liquid-propellant second stage.
   • Cryogenic upper stage.
3. The indigenous CE-7.5 Cryogenic Engine is associated with GSLV Mk II.
4. Cryogenic propulsion enabled India to advance its capability to launch heavier communication and navigation satellites.
5. Important GSLV missions include:
   • GSAT-14 (2014).
   • GSAT-6A (2018), although spacecraft communication was subsequently lost.
   • INSAT-3DS (2024).
   • NVS-01 (2023).
   • NISAR (2025).
   • NVS-03 (2026).

Launch Vehicle Mark-3 (LVM3)

1. LVM3, formerly called GSLV Mk III, is an Indian heavy-lift launch vehicle.
2. It uses:
   • Two S200 solid strap-on boosters.
   • An L110 liquid core stage.
   • A C25 cryogenic upper stage.
3. The cryogenic stage uses the CE-20 engine.
4. LVM3 has greater payload capacity than GSLV Mk II.
5. It is an important platform for:
   • Heavy satellite launches.
   • Lunar exploration missions.
   • Commercial launch services.
   • Human-spaceflight development.
6. LVM3 launched Chandrayaan-2 in 2019 and Chandrayaan-3 in 2023.
7. It has also supported commercial satellite launches, including OneWeb satellites and BlueBird Block-2 in December 2025.

Small Satellite Launch Vehicle (SSLV)

1. SSLV was developed to meet demand for responsive and comparatively low-cost launching of small satellites.
2. It uses a three-stage solid-propellant configuration with a liquid-propulsion-based velocity-trimming system.
3. It is designed for payloads of up to approximately 500 kilograms into suitable low Earth orbits.
4. Major characteristics include:
   • Relatively compact vehicle design.
   • Reduced launch-preparation requirements.
   • Support for dedicated small-satellite launches.
   • Potential for industrial-scale production.
5. The first developmental flight, SSLV-D1 in August 2022, did not achieve the intended mission.
6. SSLV-D2 in February 2023 successfully placed satellites into orbit.
7. SSLV-D3 in August 2024 successfully launched EOS-08.
8. In September 2025, an agreement was signed to transfer SSLV technology to Hindustan Aeronautics Limited (HAL), involving ISRO, NSIL and IN-SPACe.

Comparison of Major Indian Launch Vehicles

Rocket Propulsion, Engines and Advanced Launch Technologies

Principle of Rocket Propulsion

1. A Rocket generates thrust by expelling mass at high velocity.
2. Rocket propulsion is based on the conservation of momentum, consistent with Newton’s Third Law of Motion.
3. Unlike air-breathing engines, conventional rockets carry both fuel and oxidiser, enabling operation in the vacuum of space.
4. Rocket performance depends on:
   • Exhaust velocity.
   • Propellant mass.
   • Engine efficiency.
   • Structural mass.
   • Mission trajectory.
5. Rocket propulsion systems are broadly classified into chemical and non-chemical propulsion systems.

Chemical Rocket Propellants

1. Fuel: Substance that undergoes an energy-releasing reaction with an oxidiser.
2. Oxidiser: Substance that enables the chemical reaction, including where atmospheric oxygen is unavailable.
3. Propellant: The material expelled to generate thrust; in chemical rockets, it typically includes fuel and oxidiser.

Types of Chemical Propulsion

Solid Rocket Propulsion

1. In solid rocket motors, fuel and oxidiser are incorporated into a solid propellant grain.
2. Combustion occurs along exposed surfaces of the grain.
3. Hot gases are expelled through a nozzle to produce thrust.
4. Advantages include:
   • Relatively simple storage.
   • High thrust capability.
   • Mechanical simplicity.
5. Limitations include:
   • Limited throttling capability in conventional designs.
   • Difficulty stopping and restarting combustion.
   • Reduced flexibility compared with many liquid systems.

Liquid Rocket Propulsion

1. Liquid engines store propellant components in separate tanks or suitable feed systems.
2. Fuel and oxidiser are delivered into a combustion chamber.
3. The combustion products expand through a nozzle to produce thrust.
4. Advantages include:
   • Better control of thrust in suitable designs.
   • Potential for engine shutdown and restart.
   • Precise orbital manoeuvres.
5. Limitations include more complex plumbing, pumps, valves and control systems.

Vikas Engine

1. The Vikas Engine is an important liquid-propellant rocket engine used in Indian launch vehicles.
2. It operates using storable propellant combinations based on unsymmetrical dimethylhydrazine (UDMH) and nitrogen tetroxide-related oxidiser systems.
3. It has been employed in:
   • PSLV’s second stage.
   • GSLV’s liquid-propulsion stages.
   • LVM3’s L110 liquid core stage.
4. The engine has undergone modifications and performance improvements over time.
5. Its development significantly strengthened India’s indigenous liquid-propulsion capabilities.

Cryogenic Rocket Engines

1. Cryogenic Propulsion uses propellants stored at extremely low temperatures.
2. A common propellant combination is:
   • Liquid Hydrogen (LH₂) as fuel.
   • Liquid Oxygen (LOX) as oxidiser.
3. Liquid hydrogen requires temperatures near −253°C, while liquid oxygen boils near −183°C at atmospheric pressure.
4. Cryogenic engines can achieve high specific impulse, making them particularly suitable for certain upper-stage applications.
5. Important challenges include:
   • Thermal insulation.
   • Propellant storage.
   • Turbopump design.
   • Material behaviour at very low temperatures.
   • Complex ignition and control systems.

Indigenous Cryogenic Engines

1. Indigenous cryogenic propulsion represents a major technological achievement because of its engineering complexity.
2. The CE-20 engine operates using liquid hydrogen and liquid oxygen.
3. Cryogenic technology is important for launching relatively heavy payloads to high-energy trajectories.

Ramjet and Scramjet Engines

1. Ramjet

1. 1. A Ramjet is an air-breathing engine that uses the forward motion of the vehicle to compress incoming air.
   2. It generally operates efficiently at supersonic speeds.
   3. It does not require a conventional rotating compressor.
   4. Combustion occurs after the incoming airflow has been decelerated to subsonic conditions within the engine.
   5. Ramjets require an initial forward speed and cannot generate static thrust in the manner of a conventional rocket.

2. Scramjet

1. 1. Scramjet stands for Supersonic Combustion Ramjet.
   2. It is an air-breathing propulsion system in which combustion occurs while the airflow remains supersonic.
   3. Scramjets are intended for hypersonic flight regimes.
   4. They present challenges involving:
      • Supersonic combustion stability.
      • Fuel–air mixing.
      • High thermal loads.
      • Material durability.
      • Engine control.

Difference Between Ramjet and Scramjet

Dual-Mode Ramjet

1. A Dual-Mode Ramjet (DMRJ) is an air-breathing propulsion concept designed to operate across different high-speed flow regimes.
2. It can transition between conditions involving subsonic and supersonic combustion.
3. Its potential advantage is a wider operating envelope than a propulsion system restricted to a single combustion regime.
4. Major technical challenges include combustion stability and control of airflow during mode transitions.

Reusable Launch Vehicles

1. Reusable Launch Vehicles (RLVs) are designed so that selected rocket stages or spacecraft components can be recovered and used again.
2. Reusability may reduce costs by avoiding the need to manufacture every component for every mission.
3. Reusable systems require:
   • Controlled descent.
   • Thermal protection.
   • Precision navigation.
   • Landing systems.
   • Inspection and refurbishment.
4. Economic benefits depend on refurbishment costs, flight frequency and operational reliability.
5. ISRO has conducted important technology-demonstration experiments involving winged reusable launch vehicles and autonomous landing.

Next Generation Launch Vehicle (NGLV)

1. ISRO’s proposed Next Generation Launch Vehicle (NGLV) programme aims to develop advanced launch capabilities for future missions.
2. The programme is associated with higher payload capacity, modern propulsion and potential reusability.
3. It is intended to support future requirements involving:
   • Large satellites.
   • Commercial launches.
   • Space-station-related missions.
   • Human spaceflight.
   • More demanding exploration programmes.
4. The NGLV programme involves development objectives; its anticipated capabilities should not be confused with those of an already operational launch vehicle.

Major Space Exploration Missions of India

Chandrayaan-1 (2008)

1. Chandrayaan-1 was India’s first mission to the Moon.
2. It was launched on 22 October 2008, aboard PSLV-C11.
3. The spacecraft entered lunar orbit in November 2008.
4. Its objectives included:
   • Mapping lunar surface characteristics.
   • Studying lunar mineralogy.
   • Investigating the Moon’s chemical composition.
   • Supporting research on the lunar environment.
5. Important instruments included the Moon Mineralogy Mapper (M³) provided by NASA and other Indian and international payloads.
6. Observations from the mission contributed crucial evidence for water and hydroxyl-related signatures on the lunar surface.
7. Chandrayaan-1 significantly expanded scientific understanding of the Moon and established India’s lunar-orbit exploration capability.

Mars Orbiter Mission (Mangalyaan)

1. The Mars Orbiter Mission (MOM) was launched on 5 November 2013, aboard PSLV-C25.
2. It successfully entered orbit around Mars on 24 September 2014.
3. India became the first country to reach Martian orbit on its maiden Mars mission.
4. Its objectives included:
   • Demonstration of interplanetary spacecraft technology.
   • Deep-space navigation.
   • Autonomous spacecraft operations.
   • Scientific study of Mars.
5. Scientific instruments studied aspects of the Martian atmosphere, surface and exosphere.
6. The mission exceeded its original planned operational lifetime and ceased communicating in 2022.
7. Mangalyaan demonstrated India’s capability to conduct relatively cost-effective interplanetary missions.

Chandrayaan-2 (2019)

1. Chandrayaan-2 was launched on 22 July 2019, aboard GSLV Mk III-M1.
2. The mission consisted of:
   • Orbiter.
   • Vikram Lander.
   • Pragyan Rover.
3. It aimed to investigate the Moon’s surface, mineralogy, exosphere and polar environment.
4. The orbiter successfully entered lunar orbit on 20 August 2019.
5. The lander attempted a soft landing in September 2019, but the landing was unsuccessful.
6. ISRO subsequently identified deviations in landing performance that resulted in an unsuccessful touchdown.
7. The orbiter continued to provide scientific observations and contributed to lunar research.

Chandrayaan-3 (2023)

1. Chandrayaan-3 was India’s third lunar mission.
2. It was launched on 14 July 2023, aboard LVM3-M4.
3. The Vikram Lander successfully landed on the Moon on 23 August 2023.
4. India became:
   • The fourth country to achieve a successful soft landing on the Moon.
   • The first country to achieve a soft landing in the Moon’s southern high latitudes.
5. The mission comprised:
   • Propulsion Module.
   • Vikram Lander.
   • Pragyan Rover.
6. Its major objectives were:
   • Demonstrate safe and soft landing.
   • Demonstrate rover movement on the lunar surface.
   • Conduct in-situ scientific experiments.

Scientific Instruments of Chandrayaan-3

Significance of Chandrayaan-3

1. Demonstrated advanced autonomous lunar-landing technologies.
2. Strengthened India’s capabilities in guidance, navigation and control.
3. Provided in-situ scientific observations of the lunar surface.
4. Supported research on the Moon’s thermal, seismic and chemical characteristics.
5. Demonstrated rover movement under lunar environmental conditions.
6. The Pragyan rover travelled approximately 101 metres during its lunar surface mission.
7. The lander and rover were designed for approximately one lunar day, equivalent to about 14 Earth days.

Importance of the Lunar South Polar Region

1. Some permanently shadowed craters in the lunar polar regions may preserve water ice and other volatile substances.
2. Water ice could potentially support future scientific investigations and resource-utilisation technologies.
3. The polar environment contains areas with unusual illumination and thermal conditions.
4. Its geological history may provide information about lunar evolution.
5. Chandrayaan-3 landed in the southern high-latitude region, not directly at the lunar south pole.

Aditya-L1 Mission

1. Aditya-L1 is India’s first dedicated space-based solar observatory.
2. It was launched on 2 September 2023, aboard PSLV-C57.
3. The spacecraft was placed in a halo orbit around the Sun–Earth L1 point on 6 January 2024.
4. Its objectives include:
   • Studying the solar corona.
   • Investigating coronal heating.
   • Studying solar flares and coronal mass ejections.
   • Monitoring solar-wind properties.
   • Investigating solar magnetic activity.
5. The spacecraft carries seven scientific payloads designed for remote and in-situ observations.

Major Payloads of Aditya-L1

XPoSat

1. XPoSat stands for X-ray Polarimeter Satellite.
2. It was launched on 1 January 2024.
3. It investigates polarisation properties of X-rays emitted by high-energy astronomical sources.
4. Its principal payloads are POLIX and XSPECT.
5. Scientific targets include black-hole systems, neutron stars and other high-energy cosmic objects.

Space Docking Experiment (SpaDeX)

1. SpaDeX was launched on 30 December 2024, aboard PSLV-C60.
2. The mission used two spacecraft to demonstrate orbital rendezvous and docking technology.
3. On 16 January 2025, ISRO successfully docked the two satellites.
4. Undocking was demonstrated on 13 March 2025.
5. Further experiments demonstrated electrical power transfer between docked spacecraft.
6. The programme is important for future:
   • Space-station operations.
   • Orbital assembly.
   • Satellite servicing.
   • Human-spaceflight-related technologies.
7. India became the fourth country to demonstrate space docking capability.

Human Spaceflight, Gaganyaan and Indian Astronauts

Human Spaceflight

1. Human Spaceflight involves sending astronauts into space using spacecraft designed to sustain and protect human life.
2. Human-rated spacecraft require systems for:
   • Life support.
   • Environmental control.
   • Crew communication.
   • Emergency escape.
   • Radiation protection.
   • Guidance and navigation.
   • Safe re-entry and recovery.
3. Human spaceflight involves higher safety and reliability requirements than most uncrewed spacecraft missions.

Gaganyaan Programme

1. Gaganyaan is India’s human-spaceflight programme.
2. It aims to demonstrate India’s capability to send astronauts into low Earth orbit and return them safely.
3. The programme requires development and testing of:
   • A human-rated launch vehicle.
   • Crew Module.
   • Service Module.
   • Crew Escape System.
   • Environmental Control and Life Support System.
   • Re-entry and recovery systems.
4. The programme also involves astronaut selection, training, mission simulation and ground-support infrastructure.
5. The planned mission profile involves carrying a crew of up to three astronauts to an orbit around 400 kilometres altitude for a short-duration mission.

Major Components

Vyommitra

1. Vyommitra is a humanoid robotic system developed by ISRO for the Gaganyaan programme.
2. It is intended to support selected uncrewed mission demonstrations and testing.
3. Its name is derived from Sanskrit terms associated with space and friend.
4. It is designed to assist in evaluating aspects of spacecraft systems and human-machine interactions.
5. The system is not a replacement for astronauts or a complete simulation of human physiology.

Gaganyaan Development and Testing

1. ISRO has conducted numerous tests involving propulsion, crew escape, parachutes and spacecraft systems.
2. TV-D1, conducted in October 2023, demonstrated aspects of the Crew Escape System.
3. In July 2026, ISRO successfully conducted another integrated main-parachute air-drop test.
4. In October 2026, ISRO reported successful Crew Module–Service Module separation tests.
5. These tests contribute to the qualification of mission-critical systems before crewed flight.

Indian Astronauts

1. Rakesh Sharma

1. 1. Rakesh Sharma became the first Indian citizen to travel into space.
   2. He flew aboard the Soviet Soyuz T-11 spacecraft on 3 April 1984.
   3. He spent approximately eight days in space as part of the Soviet Intercosmos programme.
   4. His mission marked India’s first participation in human spaceflight.

2. Kalpana Chawla

1. 1. Kalpana Chawla was the first woman of Indian origin to travel into space.
   2. Her first spaceflight took place aboard Space Shuttle Columbia in 1997.
   3. She died on 1 February 2003, when Columbia broke apart during re-entry.
   4. Her achievements remain important in the history of astronautics and scientific exploration.

3. Sunita Williams

1. 1. Sunita Williams is an American astronaut of Indian heritage.
   2. She has participated in multiple long-duration space missions.
   3. Her work has involved International Space Station operations, scientific activities and spacewalks.
   4. Her career represents significant participation in modern human-spaceflight programmes.

4. Shubhanshu Shukla

1. 1. Group Captain Shubhanshu Shukla participated in the Axiom Mission 4 (Ax-4).
   2. The mission launched on 25 June 2025 using a SpaceX Falcon 9 rocket and Dragon spacecraft.
   3. He became the first Indian astronaut to visit the International Space Station (ISS).
   4. He conducted scientific activities, including experiments relevant to microgravity research.
   5. His participation supported India’s preparation for future human-spaceflight missions.

Space Technology Indigenisation and Emerging Indian Innovations

LVM3-M4 and Chandrayaan-3 Launch Technology

1. LVM3-M4 was the launch vehicle used for Chandrayaan-3.
2. Its three-stage configuration combined:
   • S200 solid boosters.
   • L110 liquid stage.
   • C25 cryogenic upper stage.
3. The mission demonstrated India’s ability to inject a relatively heavy lunar spacecraft into a suitable Earth-bound transfer trajectory.
4. The successful launch contributed to confidence in the LVM3 system for demanding space missions.

CE-20 Cryogenic Engine

1. The CE-20 is an indigenous cryogenic engine developed by ISRO.
2. It powers the C25 upper stage of LVM3.
3. It uses:
   • Liquid hydrogen as fuel.
   • Liquid oxygen as oxidiser.
4. Its development involved advanced work in turbomachinery, combustion, thermal management and engine control.
5. Improvements in manufacturing and testing have contributed to its performance and reliability.

PSLV Orbital Experimental Module (POEM)

1. POEM stands for PSLV Orbital Experimental Module.
2. It repurposes the spent fourth stage of PSLV as an experimental orbital platform.
3. The system provides opportunities to conduct experiments after the primary satellites have been deployed.
4. POEM may use additional:
   • Power systems.
   • Attitude-control mechanisms.
   • Communication systems.
   • Experimental payload interfaces.
5. It helps improve the scientific utilisation of launch-vehicle hardware that would otherwise have a limited post-launch function.

POEM-4

1. POEM-4 formed part of the PSLV-C60/SpaDeX mission, launched on 30 December 2024.
2. The platform carried 24 experimental payloads:
   • 14 from ISRO/DOS.
   • 10 from non-government entities, including academia and start-ups.
3. Experiments covered areas such as:
   • Space robotics.
   • Microgravity research.
   • Green propulsion.
   • Advanced sensors.
   • Space-based computing.
4. POEM-4 successfully completed its experimental activities.
5. It re-entered Earth’s atmosphere on 4 April 2025, demonstrating the value of planning end-of-life disposal.

RH-200 Sounding Rocket

1. The RH-200 is an Indian sounding rocket used primarily for atmospheric research.
2. The designation relates to its approximately 200-millimetre diameter.
3. Sounding rockets support experiments in the atmosphere and near-space environment.
4. They are generally suborbital and are not designed to place satellites into sustained Earth orbit.
5. Applications include:
   • Atmospheric measurements.
   • Ionospheric research.
   • Instrument testing.
   • Scientific experimentation.

Mission Shakti: Anti-Satellite Technology

1. Mission Shakti was conducted by India on 27 March 2019.
2. It involved the demonstration of a direct-ascent anti-satellite (ASAT) interception capability.
3. A missile system intercepted an Indian satellite in low Earth orbit.
4. The demonstration was conducted by the Defence Research and Development Organisation (DRDO).
5. India became the fourth country to demonstrate such a direct-ascent kinetic ASAT interception, after the United States, Russia/Soviet Union and China.

Significance and Concerns of ASAT Technology

Significance

1. 1. Demonstrates advanced tracking, guidance and interception capabilities.
   2. Strengthens indigenous strategic technological expertise.
   3. Highlights the military significance of space-based infrastructure.

Concerns

1. 1. Kinetic satellite interception can produce dangerous orbital debris.
   2. Debris may threaten other spacecraft and satellites.
   3. Such capabilities contribute to concerns about the militarisation and weaponisation of outer space.
   4. International discussions emphasise responsible behaviour and the long-term sustainability of space activities.

Launch Infrastructure Development

1. India’s principal established orbital spaceport is the Satish Dhawan Space Centre (SDSC SHAR) at Sriharikota, Andhra Pradesh.
2. It contains launch-pad infrastructure and important testing and operational facilities.
3. A new launch complex is being developed at Kulasekarapattinam in Tamil Nadu, with a particular focus on small-satellite launch operations.
4. The geographical location of a launch site affects trajectory design, safety requirements and access to particular orbits.
5. The expansion of launch infrastructure is intended to support a broader and more commercially active space ecosystem.

Indian Space Institutions, Private Sector and Space Policy

Department of Space (DOS)

1. The Department of Space (DOS) was established in 1972.
2. It functions under the direct responsibility of the Prime Minister of India.
3. It provides administrative oversight and policy direction for major government space activities.
4. Its responsibilities include:
   • Space policy and programme administration.
   • Development of national space capabilities.
   • Oversight of associated institutions.
   • Coordination of scientific and technological priorities.
   • International cooperation in space activities.

Indian Space Research Organisation (ISRO)

1. ISRO is India’s principal space research and technology-development organisation.
2. It was established in 1969.
3. Its major functions include:
   • Satellite and spacecraft development.
   • Launch-vehicle development.
   • Space exploration.
   • Space applications.
   • Space-science research.
   • Technological research and experimentation.
4. ISRO has developed indigenous capabilities in communication satellites, remote sensing, navigation and planetary exploration.

Major ISRO Centres

Other Important Indian Space Institutions

1. Indian Institute of Space Science and Technology (IIST)

1. 1. Located at Thiruvananthapuram.
   2. Provides higher education and research opportunities in space science and technology.
   3. Supports the development of specialised human resources for the space sector.

2. Physical Research Laboratory (PRL)

1. 1. Located in Ahmedabad.
   2. Undertakes research in planetary science, astronomy, space physics and related fields.

3. Indian Astronomical Observatory (IAO)

1. 1. Located at Hanle, Ladakh.
   2. Supports astronomical observations under high-altitude conditions.

4. Regional Academic Centres for Space (RAC-S)

1. 1. Established to strengthen academic participation in space research and technology.
   2. Promote research collaboration, training and scientific projects in different regions of India.

5. Academia–Industry Collaboration

1. 1. Universities and technical institutions increasingly contribute to satellite development and experimental missions.
   2. Such collaboration strengthens research capabilities and creates opportunities for students and start-ups.

Antrix Corporation Limited

1. Antrix Corporation Limited was incorporated in 1992.
2. It is a government company associated with India’s space-sector commercial activities.
3. Historically, Antrix served as an important commercial interface for ISRO.
4. Its activities have included:
   • Marketing space products and services.
   • Commercial launch-service arrangements.
   • Satellite-related commercial services.
   • Technology-related business activities.
5. The establishment of NSIL subsequently reorganised important aspects of India’s government space-sector commercial framework.

NewSpace India Limited (NSIL)

1. NewSpace India Limited (NSIL) was incorporated in March 2019.
2. It is a wholly owned Government of India company under DOS.
3. NSIL is responsible for developing and expanding commercial space activities associated with India’s space programme.
4. Its important functions include:
   • Commercial launch services.
   • Industry-based satellite and launch-vehicle production.
   • Marketing satellite communication services.
   • Technology commercialisation.
   • Transfer of ISRO technologies to industries.
5. NSIL helps facilitate the transition towards a more industrially diversified space ecosystem.

Indian National Space Promotion and Authorisation Centre (IN-SPACe)

1. IN-SPACe was established following India’s 2020 space-sector reforms.
2. It functions as an autonomous agency under DOS.
3. It promotes and facilitates the participation of Non-Government Entities (NGEs) in space activities.
4. Its responsibilities include:
   • Authorisation of specified space activities.
   • Support for private satellite and launch-vehicle development.
   • Facilitation of access to government space infrastructure.
   • Promotion of space start-ups.
   • Supporting a predictable and transparent space-activity framework.

Indian Space Policy, 2023

1. The Indian Space Policy, 2023 established a framework for expanding the role of non-government entities in the national space ecosystem.
2. It differentiates the responsibilities of major space-sector institutions.
3. Its broad objectives include:
   • Encouraging private-sector investment.
   • Supporting innovation and entrepreneurship.
   • Promoting indigenous manufacturing.
   • Commercialising space technologies.
   • Expanding space applications.
   • Strengthening international competitiveness.
4. The policy seeks to facilitate a more extensive space economy while maintaining government responsibilities for policy, authorisation and national interests.

Institutional Division of Responsibilities

Indian Private Space Industry

1. Private participation has expanded in areas such as:
   • Satellite design and manufacturing.
   • Launch vehicles.
   • Propulsion technologies.
   • Earth-observation services.
   • Space-data analytics.
   • Ground infrastructure.
2. Private enterprises can complement government space programmes through specialised manufacturing, innovation and commercial services.

Important Indian Private Space Enterprises

Agnibaan and Private Launch Innovation

1. Agnikul Cosmos is an Indian private aerospace company developing launch-vehicle technologies.
2. Its Agnibaan programme focuses on small-satellite launch capabilities.
3. The company has pursued additive manufacturing and advanced propulsion development.
4. In May 2024, Agnikul successfully conducted a suborbital test flight of its Agnibaan SOrTeD vehicle.
5. The flight demonstrated important privately developed launch technologies, but it was not an operational satellite deployment into orbit.

Vikram-S and Skyroot Aerospace

1. Skyroot Aerospace develops private-sector launch vehicles under the Vikram series.
2. Its Vikram-S rocket conducted a successful suborbital flight in November 2022, under the Prarambh mission.
3. It was India’s first privately developed rocket to reach space on a suborbital mission, under the convention used for its flight achievement.
4. The mission demonstrated private-sector capabilities in rocket structures, propulsion and launch operations.
5. Development of the Vikram series is intended to support future commercial orbital launch services.

India’s First Private Satellite: ExseedSat-1

1. ExseedSat-1 was developed by the Mumbai-based private company Exseed Space.
2. It was launched in December 2018 aboard a SpaceX Falcon 9 mission.
3. The satellite was designed as a small amateur-radio communication spacecraft.
4. Its objective included demonstrating private-sector satellite-development capabilities.
5. The achievement represented an important early milestone for India’s privately developed satellite sector.

Benefits of Private Participation

1. Encourages innovation and technical specialisation.
2. Expands opportunities for space-based entrepreneurship.
3. Supports commercial applications of satellite technology.
4. Can reduce certain manufacturing and service-delivery costs through competition and scale.
5. Generates high-skilled employment.
6. Strengthens domestic industrial supply chains.
7. Enables government research organisations to focus greater attention on complex scientific and strategic programmes.

Challenges Facing the Private Space Sector

1. High initial capital requirements.
2. Long research and development cycles.
3. Complex testing and certification.
4. Dependence on specialised materials and components.
5. Need for reliable access to launch and testing infrastructure.
6. Regulatory and insurance requirements.
7. International competition.
8. Limited domestic demand for certain advanced space products and services.

Importance, Challenges and Future of Space Technology in India

Socioeconomic Importance

1. Space technology supports essential public services and economic activities.
2. Satellite communication contributes to connectivity in remote and geographically difficult regions.
3. Remote sensing supports agriculture, land-resource management and environmental protection.
4. Satellite navigation improves transportation efficiency and location-based services.
5. Meteorological satellites support disaster preparedness and early-warning systems.
6. Scientific missions promote advanced research and technological development.
7. The space sector creates opportunities for skilled employment, manufacturing and high-technology entrepreneurship.

Agricultural Applications

1. Satellite imagery supports crop-area estimation and vegetation monitoring.
2. Remote sensing helps assess drought conditions and changes in agricultural land use.
3. Geospatial analysis improves irrigation planning and watershed management.
4. Navigation technologies support precision agriculture.
5. Satellite-derived information complements field observations and agricultural statistics.

Disaster Management Applications

Strategic Importance

1. Space-based systems support secure communication and national situational awareness.
2. Navigation satellites reduce dependence on foreign systems for certain essential services.
3. Reconnaissance and observation capabilities support national-security requirements.
4. Indigenous launch vehicles contribute to independent access to space.
5. Space situational awareness helps protect strategically important satellites.

Environmental and Sustainability Challenges

1. Space Debris

1. 1. Defunct satellites, rocket stages and fragments accumulate in Earth orbit.
   2. Orbital collisions can generate additional debris.
   3. Increasing orbital congestion raises risks for operational spacecraft.

2. Light and Radio Pollution

1. 1. Large satellite constellations can affect optical astronomical observations.
   2. Satellite transmissions may interfere with sensitive radio-astronomy instruments.

3. Atmospheric and Environmental Effects

1. 1. Launch operations produce emissions and may affect local environments.
   2. Spacecraft re-entry can introduce materials into the upper atmosphere.
   3. The magnitude and long-term effects of some environmental processes remain subjects of scientific research.

4. Orbital and Spectrum Congestion

1. 1. Increasing demand for satellite orbits and radio-frequency spectrum creates coordination challenges.
   2. Effective management requires technical standards, regulatory frameworks and international cooperation.

International Space Governance

1. Space activities are governed by international legal principles and agreements.
2. Important instruments include:
   • Outer Space Treaty, 1967.
   • Rescue Agreement, 1968.
   • Liability Convention, 1972.
   • Registration Convention, 1975.
   • Moon Agreement, 1979, which has limited participation.
3. The Outer Space Treaty establishes important principles concerning peaceful exploration, non-appropriation of celestial bodies and state responsibility for national space activities.
4. The United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) provides an important forum for international cooperation.
5. Space governance increasingly addresses debris mitigation, space-traffic coordination, commercial activities and sustainable use of outer space.

Future Priorities of India’s Space Programme

1. Human Spaceflight: Advancement of Gaganyaan and associated crewed mission capabilities.
2. Space Station Development: Research and technology development for India’s planned Bharatiya Antariksh Station.
3. Advanced Launch Vehicles: Development of higher-capacity and potentially reusable systems.
4. Lunar Exploration: Future orbital, landing and sample-return-related technologies.
5. Satellite Navigation: Modernisation and expansion of NavIC.
6. Earth Observation: Advanced radar, optical and multi-sensor missions.
7. Space Astronomy: Development of advanced space-based scientific observatories.
8. Private-Sector Expansion: Encouraging launch services, manufacturing and space-data enterprises.
9. Space Situational Awareness: Strengthening orbital tracking, collision avoidance and debris mitigation.
10. International Cooperation: Participation in collaborative scientific and exploration missions.