UPSC CSE Prelims
Space Technology Previous Year Questions (PYQs)
Showing solved Previous Year Questions for Chapter: Space Technology
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Consider the following statements with regard to involvement of private entities in India's space programme :
- The Indian National Space Promotion and Authorisation Centre (IN-SPACe) is an autonomous agency formed to facilitate participation of private entities.
- Agnikul Cosmos launched the world's first flight using 3D-printed rocket engine.
- Skyroot Aerospace has developed liquid fuel for GSLV.
Which of the statements given above is/are correct ?
Detailed Explanation:
Statement 1 — Correct. IN-SPACe was established in 2020 as an autonomous, single-window nodal agency under the Department of Space (DOS). It acts as a bridge between ISRO and private players to promote, authorize, and facilitate private sector participation in India's space sector.
Statement 2 — Correct. In May 2024, Chennai-based startup Agnikul Cosmos successfully launched the Agnibaan SOrTeD suborbital rocket from its private launchpad at Sriharikota — marking the world's first flight powered by a single-piece, fully 3D-printed rocket engine (semi-cryogenic engine named Agnilet).
Statement 3 — Incorrect. Skyroot Aerospace develops its own independent launch vehicles (the Vikram series) and engines. It does NOT develop fuel or engines for GSLV. The GSLV is an ISRO-owned heavy-lift rocket whose liquid and cryogenic stages are developed entirely in-house by ISRO via the Liquid Propulsion Systems Centre (LPSC).
Key Trick: Statement 3 mixes two separate private players — Agnikul (3D engine) and Skyroot (Vikram rockets) — and falsely links Skyroot to GSLV.
Consider the following space missions:
I. Axiom-4
II. SpaDeX
III. Gaganyaan
How many of the space missions given above encourage and support micro-gravity research?
Detailed Explanation:
Among the given missions, Axiom-4 and Gaganyaan directly support and promote micro-gravity research, whereas SpaDeX is mainly a technology demonstration mission.
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Statement I is Correct: Axiom-4 carries scientific experiments and micro-gravity research payloads aboard the International Space Station (ISS).
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Statement II is Incorrect: SpaDeX (Space Docking Experiment) is designed to demonstrate autonomous docking technology, not primarily for micro-gravity research.
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Statement III is Correct: Gaganyaan includes several micro-gravity experiments to be conducted by Indian astronauts (Vyomanauts) in space.
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Therefore, only two missions support micro-gravity research, making Option B the correct answer.
Mission-wise Analysis
| Mission | Status | Explanation |
|---|---|---|
| I. Axiom-4 | ✅ Correct | Conducts scientific and micro-gravity experiments aboard the ISS. |
| II. SpaDeX | ❌ Incorrect | Primarily a space docking technology demonstration mission. |
| III. Gaganyaan | ✅ Correct | Includes micro-gravity research payloads and experiments. |
Micro-gravity Research
What is Micro-gravity?
Micro-gravity is a condition in space where objects experience very weak gravity and appear to be weightless.
Why is it Important?
Micro-gravity helps scientists study:
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Human health in space
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Material science
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Biotechnology
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Fluid dynamics
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Plant growth and agriculture
GPS-Aided Geo Augmented Navigation (GAGAN) uses a system of ground stations to provide necessary augmentation.
Which of the following statements is/are correct in respect of GAGAN?
I. It is designed to provide additional accuracy and integrity.
II. It will allow more uniform and high quality air traffic management.
III. It will provide benefits only in aviation but not in other modes of transportation.
Select the correct answer using the code given below.
Detailed Explanation:
GAGAN (GPS-Aided Geo Augmented Navigation) is India's Satellite-Based Augmentation System (SBAS), jointly developed by ISRO and the Airports Authority of India (AAI) to improve GPS-based navigation.
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Statement I is Correct: GAGAN enhances the accuracy and integrity of GPS signals.
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Statement II is Correct: It enables safer, more efficient, and uniform air traffic management.
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Statement III is Incorrect: GAGAN is useful not only in aviation but also in road transport, railways, maritime navigation, agriculture, surveying, and disaster management.
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Therefore, only Statements I and II are correct, making Option D the correct answer.
Statement-wise Analysis
| Statement | Status | Explanation |
|---|---|---|
| I. It is designed to provide additional accuracy and integrity | ✅ Correct | GAGAN improves GPS precision and reliability for navigation. |
| II. It will allow more uniform and high-quality air traffic management | ✅ Correct | Better navigation helps improve flight safety and air traffic efficiency. |
| III. It will provide benefits only in aviation | ❌ Incorrect | Its applications extend to several non-aviation sectors as well. |
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With reference to radioisotope thermoelectric generators (RTGs), consider the following statements:
- RTGs are miniature fission reactors.
- RTGs are used for powering the onboard systems of spacecrafts.
- RTGs can use Plutonium-238, which is a by-product of weapons development.
Which of the statements given above are correct?
Detailed Explanation:
Correct Answer: ✅ Option 2 (Statements 2 and 3 only)
Radioisotope Thermoelectric Generators (RTGs) generate electricity from the heat released during the natural radioactive decay of isotopes. They are widely used in deep-space missions where solar power is insufficient.
❌ Statement I is Incorrect: RTGs are not miniature fission reactors. They do not use nuclear fission; instead, they generate power from the natural decay of radioactive isotopes.
✅ Statement II is Correct: RTGs are used to power spacecraft, satellites, and planetary rovers, especially in deep-space missions where sunlight is weak.
✅ Statement III is Correct: RTGs commonly use Plutonium-238, which can be produced during nuclear weapons-related processes and is specifically manufactured for civilian space applications.
Short Notes: Radioisotope Thermoelectric Generators (RTGs)
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Convert heat from radioactive decay directly into electricity using thermocouples.
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Do not involve a nuclear chain reaction or fission process.
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Common fuel: Plutonium-238 (Pu-238).
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Pu-238 has a half-life of about 87.7 years, providing long-term power.
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Ideal for missions far from the Sun where solar panels are ineffective.
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Used in missions such as Voyager 1, Voyager 2, and Curiosity Rover.
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Reliable, maintenance-free power source for decades.
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Important for deep-space exploration and planetary missions.
Which one of the following countries has its own Satellite Navigation System?
Detailed Explanation:
Answer: Option 4 — Japan
Japan operates the QZSS (Quasi-Zenith Satellite System), which is a regional satellite navigation system designed to enhance GPS coverage and accuracy in the Asia-Oceania region, particularly over Japan. Among the given options, only Japan has its own satellite navigation system.
📝 Short Notes: Satellite Navigation Systems Worldwide
- Global Navigation Satellite Systems (GNSS): Four operational systems - GPS (USA), GLONASS (Russia), Galileo (European Union), and BeiDou (China) - provide worldwide coverage.
- Regional Navigation Satellite Systems: NavIC/IRNSS (India) covers Indian subcontinent and surrounding region up to 1,500 km; QZSS (Japan) enhances GPS signals in Asia-Oceania region.
- GPS (USA): First operational GNSS with 24+ satellites, launched in 1978, fully operational since 1995.
- GLONASS (Russia): Developed during Soviet era, fully operational since 2011 with 24+ satellites.
- Galileo (EU): European system providing high-precision positioning, became operational in 2016.
- BeiDou (China): Completed global coverage in 2020 with 35 satellites, serves both regional and global users.
- NavIC (India): Indian Regional Navigation Satellite System with 7 satellites, operational since 2018, provides positioning accuracy better than 20 meters.
- QZSS (Japan): Quasi-Zenith Satellite System with satellites in quasi-zenith orbits, providing enhanced positioning over Japan and neighboring regions.
Consider the following pairs :
Objects in space: Description
- Cepheids: Giant clouds of dust and gas in space
- Nebulae: Stars which brighten and dim periodically
- Pulsars: Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched?
Detailed Explanation:
Answer: Option 1 — Only one
This question tests the knowledge of celestial objects and their correct definitions. Out of the three pairs given, only the third pair (Pulsars) is correctly matched, while the first two pairs have their descriptions reversed.
❌ Pair 1 – Incorrect: Cepheids are not giant clouds of dust and gas; they are actually pulsating stars that brighten and dim periodically, making them important distance markers in astronomy.
❌ Pair 2 – Incorrect: Nebulae are not stars that brighten and dim periodically; they are giant clouds of dust and gas in space where stars are born or remnants of dead stars.
✅ Pair 3 – Correct: Pulsars are indeed rapidly rotating neutron stars formed when massive stars exhaust their nuclear fuel and collapse in supernova explosions, emitting regular pulses of radiation.
📝 Short Notes: Celestial Objects
| Celestial Object | Correct Description | Key Characteristics |
|---|---|---|
| Cepheids | Pulsating variable stars that brighten and dim periodically | Period-luminosity relationship makes them 'standard candles' for measuring cosmic distances; named after Delta Cephei |
| Nebulae | Giant clouds of dust and gas in space | Can be emission, reflection, or dark nebulae; sites of star formation (stellar nurseries) or remnants of dying stars |
| Pulsars | Rapidly rotating neutron stars | Emit regular pulses of electromagnetic radiation; formed from supernova explosions; extremely dense (teaspoon weighs billions of tons) |
| Quasars | Extremely luminous active galactic nuclei | Powered by supermassive black holes; among the most distant and luminous objects in the universe |
| Supernovae | Explosive death of massive stars | Can briefly outshine entire galaxies; create and disperse heavy elements; leave behind neutron stars or black holes |
If a major solar storm (solar-flare) reaches the Earth, which of the following are the possible effects on the Earth?
- GPS and navigation systems could fail.
- Tsunamis could occur at equatorial regions.
- Power grids could be damaged.
- Intense auroras could occur over much of the Earth.
- Forest fires could take place over much of the planet.
- Orbits of the satellites could be disturbed.
- Shortwave radio communication of the aircraft flying over polar regions could be interrupted.
Select the correct answer using the code given below:
Detailed Explanation:
Answer: Option 3 — 1, 3, 4, 6 and 7 only
Solar storms (solar flares and coronal mass ejections) release charged particles and electromagnetic radiation that interact with Earth's magnetosphere and ionosphere, causing various technological and atmospheric disturbances. The correct effects include disruption to satellite-based navigation, power grid damage, enhanced auroral displays, satellite orbital changes, and radio communication interference.
✅ Statement 1 – Correct: Solar storms disrupt the ionosphere, causing GPS signal delays and navigation system failures.
❌ Statement 2 – Incorrect: Tsunamis are caused by seismic or volcanic activity underwater, not by solar storms which affect electromagnetic and particle environments.
✅ Statement 3 – Correct: Geomagnetically induced currents (GICs) from solar storms can overload transformers and damage power grids, causing blackouts.
✅ Statement 4 – Correct: Enhanced solar wind energizes particles in the magnetosphere, creating intense auroras visible at lower latitudes than normal.
❌ Statement 5 – Incorrect: Solar storms do not directly cause widespread forest fires; they affect electromagnetic systems, not ignition sources on such a scale.
✅ Statement 6 – Correct: Increased atmospheric drag from heating during solar storms can alter satellite orbits, especially in low Earth orbit.
✅ Statement 7 – Correct: Ionospheric disturbances disrupt shortwave (HF) radio communications, particularly affecting polar routes where ionospheric effects are strongest.
📝 Short Notes: Solar Storms and Earth Effects
- Solar Storm Components: Solar flares (electromagnetic radiation) and Coronal Mass Ejections (CME - charged particles) that reach Earth in 1-3 days.
- Magnetosphere Interaction: Charged particles compress Earth's magnetosphere, inducing geomagnetic storms.
- Ionospheric Disruption: Solar radiation alters ionosphere density, affecting radio wave propagation and satellite communications.
- Geomagnetically Induced Currents (GICs): Magnetic field fluctuations induce currents in long conductors like power lines and pipelines.
- Aurora Formation: Charged particles collide with atmospheric gases (oxygen, nitrogen), producing light displays typically at 60-70° latitude, but extending to lower latitudes during major storms.
- Space Weather Monitoring: Organizations like NOAA's Space Weather Prediction Center track solar activity to issue warnings for critical infrastructure protection.
- Historical Events: Carrington Event (1859) caused widespread telegraph failures; Quebec blackout (1989) affected 6 million people for 9 hours.
Which one of the following statements best reflects the idea behind the "Fractional Orbital Bombardment System" often talked about in media ?
Detailed Explanation:
Answer: Option 3 — A missile is put into a stable orbit around the Earth and deorbits over a target on the Earth.
The Fractional Orbital Bombardment System (FOBS) is a nuclear weapons delivery system that launches a warhead into a low Earth orbit trajectory instead of a traditional high-arc ballistic path. The key characteristic is that the missile completes only a fraction of an orbit before deorbiting to strike its target, making it harder to detect by early warning systems designed for conventional ballistic missiles. This orbital approach allows the weapon to approach from unexpected directions and reduces warning time significantly.
❌ Option 1 – Incorrect: FOBS is not designed for asteroid defense but for delivering weapons to Earth-based targets via orbital trajectory.
❌ Option 2 – Incorrect: This describes planetary landing maneuvers, not FOBS which is specifically about weapon delivery systems orbiting Earth.
✅ Option 3 – Correct: Accurately describes FOBS as a missile placed in orbit that deorbits over a terrestrial target.
❌ Option 4 – Incorrect: This describes a comet rendezvous mission, unrelated to FOBS weapons systems.
📝 Short Notes: Fractional Orbital Bombardment System (FOBS)
- Concept: A weapons delivery system developed during the Cold War era, primarily by the Soviet Union in the 1960s
- Trajectory: Uses a low Earth orbit (LEO) path rather than a high ballistic arc, completing only a fraction of an orbit before deorbiting
- Strategic Advantage: Can approach targets from unexpected directions (including over the South Pole), bypassing radar systems oriented toward traditional ballistic missile trajectories
- Detection Challenge: Early warning systems designed to detect high-arc ballistic missiles may fail to identify low-orbit FOBS until late in the attack sequence
- Reduced Warning Time: The orbital path and lower altitude mean less time between detection and impact compared to intercontinental ballistic missiles (ICBMs)
- Modern Context: Recent reports suggest renewed interest in FOBS technology by certain nations, making it relevant to contemporary strategic discussions
- Treaty Status: The Outer Space Treaty (1967) prohibits placing weapons of mass destruction in orbit, though FOBS occupies a grey area as it doesn't complete a full orbit
“The experiment will employ a trio of spacecraft flying in formation in the shape of an equilateral triangle that has sides one million kilometres long, with lasers shining between the craft”. The experiment in question refers to
Detailed Explanation:
Answer: Option 4 — Evolved LISA
The description of three spacecraft flying in an equilateral triangle formation with sides one million kilometres long, using lasers for measurement, uniquely identifies the Evolved Laser Interferometer Space Antenna (eLISA) mission. This is a proposed space-based gravitational wave observatory designed to detect low-frequency gravitational waves by measuring tiny distance changes between the spacecraft using laser interferometry. Voyager and New Horizons are single-spacecraft exploration missions, while LISA Pathfinder was only a technology demonstrator for testing eLISA components, not the full mission itself.
📝 Short Notes: Gravitational Wave Detection Missions
- LISA (Laser Interferometer Space Antenna): Original concept for space-based gravitational wave detection proposed by ESA and NASA.
- Evolved LISA (eLISA): Redesigned version with three spacecraft in equilateral triangle formation, each separated by ~1 million km, using laser interferometry to detect gravitational waves.
- LISA Pathfinder (2015-2017): Technology demonstration mission that successfully tested drag-free flight and precision measurement technologies required for eLISA.
- Configuration: Three identical spacecraft maintain precise formation while measuring distance changes of picometers (10⁻¹² meters) caused by passing gravitational waves.
- Target: Detection of low-frequency gravitational waves (0.1 mHz to 1 Hz) from sources like merging supermassive black holes, binary star systems, and early universe events.
- Ground-based counterpart: LIGO (Laser Interferometer Gravitational-Wave Observatory) detects high-frequency gravitational waves on Earth.
For the measurement/estimation of which of the following are satellite images/remote sensing data used?
- Chlorophyll content in the vegetation of a specific location
- Greenhouse gas emissions from rice paddies of a specific location
- Land surface temperatures of a specific location
Select the correct answer using the code given below.
Detailed Explanation:
Answer: Option 4 — 1, 2 and 3
Remote sensing technology uses satellite images to detect and monitor physical characteristics of areas by measuring reflected and emitted radiation. All three parameters mentioned can be effectively measured or estimated using satellite-based remote sensing data.
✅ Statement 1 – Correct: Chlorophyll content in vegetation is estimated by measuring light reflectance, as chlorophyll absorbs specific wavelengths for photosynthesis and the reflected light indicates chlorophyll concentration.
✅ Statement 2 – Correct: Greenhouse gas emissions from rice paddies can be estimated by detecting radiations emitted by methane and other gases, combined with thermal and spectral signatures of waterlogged conditions.
✅ Statement 3 – Correct: Land surface temperatures are directly measured by satellite sensors that detect infrared radiation emitted by the Earth's surface.
📝 Short Notes: Remote Sensing Applications
- Remote Sensing: The science of obtaining information about objects or areas from a distance, typically using satellites or aircraft-mounted sensors.
- Spectral Reflectance: Different surfaces and materials reflect electromagnetic radiation differently; vegetation reflects strongly in near-infrared while absorbing visible light for photosynthesis.
- Thermal Infrared Sensing: Used to measure land surface temperature by detecting heat radiation emitted from the Earth's surface.
- Agricultural Monitoring: Remote sensing helps monitor crop health, soil moisture, irrigation needs, and greenhouse gas emissions from agricultural activities.
- Vegetation Indices: NDVI (Normalized Difference Vegetation Index) and other indices derived from satellite data help assess vegetation vigor and chlorophyll content.
- Methane Detection: Advanced satellite sensors can detect methane emissions from rice paddies, wetlands, and other sources by measuring specific absorption bands in the infrared spectrum.
Recently, scientists observed the merger of giant ‘blackholes’ billions of light-years away from the Earth. What is the significance of this observation?
Detailed Explanation:
Answer: Option 2 — 'Gravitational waves' were detected.
The merger of black holes is expected to generate powerful gravitational waves, which are ripples in spacetime caused by accelerating massive objects. Detecting these waves with instruments like LIGO (Laser Interferometer Gravitational-Wave Observatory) allows scientists to study these cosmic events even when they are too far away or obscured to observe directly with traditional telescopes. This observation opened a revolutionary new window for astronomical observations and confirmed a major prediction of Einstein's General Theory of Relativity.
❌ Option 1 – Incorrect: Higgs boson particles are detected in particle accelerators like the Large Hadron Collider (LHC), not through astronomical observations of black hole mergers.
❌ Option 3 – Incorrect: While wormholes are theoretical concepts in physics, no observation of black hole mergers has confirmed the possibility of intergalactic space travel through wormholes.
❌ Option 4 – Incorrect: While black hole mergers provide insights into extreme gravity, understanding the singularity (the point of infinite density at the center of a black hole) remains beyond current observational capabilities.
📝 Short Notes: Gravitational Waves
- Definition: Gravitational waves are ripples in the fabric of spacetime caused by violent cosmic events involving massive accelerating objects.
- Prediction: First predicted by Albert Einstein in 1916 as part of his General Theory of Relativity.
- First Detection: Directly detected for the first time in 2015 by LIGO (Laser Interferometer Gravitational-Wave Observatory).
- Sources: Merging black holes, colliding neutron stars, supernovae, and rotating neutron stars with asymmetries.
- Speed: Travel at the speed of light through spacetime.
- Significance: Opens a new field of gravitational wave astronomy, allowing observation of events invisible to electromagnetic telescopes.
- Nobel Prize: The 2017 Nobel Prize in Physics was awarded to Rainer Weiss, Barry Barish, and Kip Thorne for the LIGO detector and observation of gravitational waves.
With reference to the Indian Regional Navigation Satellite System (IRNSS), consider the following statements :
- IRNSS has three satellites in geostationary and four satellites in geosynchronous orbits.
- IRNSS covers entire India and about 5500 sq. km beyond its borders.
- India will have its own satellite navigation system with full global coverage by the middle of 2019.
Which of the statements given above is/are correct?
Detailed Explanation:
Answer: Option 1 — 1 only
IRNSS (Indian Regional Navigation Satellite System), also known as NavIC (Navigation with Indian Constellation), is India's independent regional navigation satellite system. Among the three statements, only the first statement correctly describes the satellite configuration of IRNSS.
✅ Statement 1 – Correct: IRNSS has three satellites in geostationary orbits (positioned at fixed points above the equator) and four satellites in geosynchronous orbits (inclined geosynchronous orbits at approximately 29° inclination).
❌ Statement 2 – Incorrect: IRNSS covers the entire India and extends approximately 1500 km beyond its borders (primary service area), not 5500 sq. km. The extended service area covers a much larger region from 30°S to 50°N latitude and 30°E to 130°E longitude.
❌ Statement 3 – Incorrect: IRNSS/NavIC is a regional navigation system, not a global navigation system. It provides coverage over India and surrounding regions only. India does not have a satellite navigation system with full global coverage as of 2019 or currently.
📝 Short Notes: IRNSS/NavIC
- Full Form: Indian Regional Navigation Satellite System (IRNSS), operational name NavIC (Navigation with Indian Constellation)
- Constellation: 7 satellites total - 3 in Geostationary Orbit (GEO) and 4 in Geosynchronous Orbit (GSO)
- Primary Service Area: India and region extending up to 1500 km from its boundary
- Extended Service Area: Region between 30°S to 50°N latitude and 30°E to 130°E longitude
- Operational Since: 2018 (all 7 satellites became operational)
- Applications: Terrestrial, aerial and marine navigation, disaster management, vehicle tracking, fleet management, integration with mobile phones, precise timing, mapping and geodetic data capture
- Administered by: Indian Space Research Organisation (ISRO)
- Ground Segment: IRNSS Spacecraft Control Facility (IRSCF) at Hassan and Bhopal, IRNSS Range and Integrity Monitoring Stations (IRIMS) at multiple locations, and Navigation Control Centres
In which of the following areas can GPS technology be used?
- Mobile phone operations
- Banking operations
- Controlling the power grids
Select the correct answer using the code given below:
Detailed Explanation:
Answer: Option 4 — 1, 2 and 3
GPS (Global Positioning System) is a satellite-based navigation system that provides precise geolocation and time information, making it useful across diverse applications beyond just navigation.
✅ Statement 1 – Correct: GPS is integral to mobile phone operations for location tracking, navigation apps, and location-based services like ride-hailing and food delivery.
✅ Statement 2 – Correct: GPS provides precise time-stamping for banking transactions, ensuring accurate record-keeping and synchronization across banking networks, and enables ATM location services.
✅ Statement 3 – Correct: GPS is crucial for synchronizing power grid operations by providing accurate time stamps for measurements, which is essential for grid stability and preventing blackouts.
📝 Short Notes: GPS Technology Applications
- GPS (Global Positioning System): A satellite-based navigation system owned by the US government, consisting of 24+ satellites orbiting Earth.
- Primary Function: Provides geolocation (latitude, longitude, altitude) and precise time information to GPS receivers anywhere on Earth.
- Timing Applications: GPS satellites carry atomic clocks that provide nanosecond-level time accuracy, critical for telecommunications, banking, power grids, and stock markets.
- Navigation Uses: Aviation, maritime, vehicle navigation, surveying, mapping, and military operations.
- Location-Based Services: Mobile apps, emergency services (911/112), asset tracking, agriculture (precision farming), and weather forecasting.
- Other Global Systems: GLONASS (Russia), Galileo (EU), BeiDou (China), and NavIC/IRNSS (India's regional system).
With reference to India’s satellite launch vehicles, consider the following statements:
- PSLVs launch the satellites useful for Earth resources monitoring whereas GSLVs are designed mainly to launch communication satellites.
- Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth.
- GSLV Mk III is a four-stage 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?
Detailed Explanation:
Answer: Option 1 — 1 only
Simple Explanation:
This question tests the basic difference between PSLV and GSLV launch vehicles.
✅ Statement 1 – Correct: PSLV is mainly used to launch Earth observation/remotely sensed satellites into Polar or Sun-Synchronous Orbits, while GSLV is designed to launch heavy communication satellites into Geosynchronous Transfer Orbit (GTO).
❌ Statement 2 – Incorrect: Satellites launched by PSLV do not remain fixed over one point on Earth. They move in Polar/Sun-Synchronous Orbits. Only geostationary satellites appear stationary in the sky.
❌ Statement 3 – Incorrect: GSLV Mk III (LVM3) is a three-stage launch vehicle, not a four-stage vehicle. It consists of two solid strap-on boosters, one liquid core stage, and one cryogenic upper stage.
📝 Short Notes: PSLV & GSLV
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PSLV (Polar Satellite Launch Vehicle) is mainly used for Earth observation and Sun-Synchronous Orbit (SSO) missions.
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GSLV is designed to place communication satellites into Geosynchronous Transfer Orbit (GTO).
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LVM3 (formerly GSLV Mk III) is a three-stage heavy-lift launch vehicle with a cryogenic upper stage.
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Cryogenic engines use liquid hydrogen (LH₂) and liquid oxygen (LOX) for high efficiency.
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PSLV is known as ISRO's "workhorse launcher" due to its high reliability.
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LVM3 successfully launched Chandrayaan-2, Chandrayaan-3, and the OneWeb satellite missions.
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Geostationary satellites remain fixed relative to Earth, while Polar satellites continuously move over different regions.
What is the purpose of ‘evolved Laser Interferometer Space Antenna (eLISA)’ project?
Detailed Explanation:
Answer: Option 2 — To detect gravitational waves
The evolved Laser Interferometer Space Antenna (eLISA), now known as LISA (Laser Interferometer Space Antenna), is a space-based gravitational wave observatory designed to detect low-frequency gravitational waves from cosmic sources. It uses laser interferometry to measure tiny distortions in spacetime caused by passing gravitational waves from events such as merging supermassive black holes, extreme mass ratio inspirals, and galactic binary systems. This ESA-led mission (with NASA contribution) operates in the millihertz frequency range, complementing ground-based detectors like LIGO that observe higher frequencies. The detection of gravitational waves opens a new window to observe the universe and test Einstein's general relativity in extreme conditions.
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