Explanation:

• LEO (Low Earth Orbit): Extends from about 160 km to 2,000 km. It is used for Earth observation satellites, remote sensing, weather monitoring, and the International Space Station (ISS). Navigation satellites are not placed here.
• MEO (Medium Earth Orbit): Extends from about 2,000 km to 35,786 km. It is mainly used for navigation satellites (e.g., GPS, Galileo, GLONASS, IRNSS/NavIC). The ISS is not in MEO.
• GEO (Geostationary Orbit): At about 35,786 km above the equator. It is ideal for communication, broadcasting, and weather satellites because they appear stationary relative to Earth.

👉 Thus, only pair 3 (GEO – communication satellites) is correctly matched.

Explanation:

• L1 (Lagrange Point 1): Lies between the Earth and the Sun (~1.5 million km from Earth). India’s Aditya-L1 Mission is placed here to continuously observe the Sun without Earth’s shadow. ✔️
• L2 (Lagrange Point 2): Lies on the opposite side of the Earth, about 1.5 million km away from Earth in the direction opposite the Sun. The James Webb Space Telescope (JWST) is stationed here for deep space observations. ✔️
• L3 (Lagrange Point 3): Lies on the far side of the Sun, directly opposite to Earth’s orbit. Though rarely used (due to communication difficulties), it is indeed located there. ✔️

👉 Hence, all three statements are correct.

Explanation:

What is a polar orbit?

• A polar orbit is defined by its inclination ≈ 90° to the equator.
• The satellite passes over or very near both poles on every revolution.
• Because Earth rotates beneath, successive ground tracks shift westward, allowing global coverage over time.

Why are most polar orbits nearly circular?

• Eccentricity (e) measures how stretched an orbit is (e = 0 is a perfect circle).
• Operational Earth-observation polar missions are designed with e ≈ 0 to very small values so that altitude is almost constant along the track.
• Constant altitude gives:
  • Uniform spatial resolution for cameras and sensors.
  • Predictable swath width and signal geometry.
  • Simpler power/thermal management and more stable drag environment.
  • Consistent revisit performance and easier mission operations.

So does R explain A?

• Yes. If e is close to zero, the orbit is nearly circular, which directly accounts for the shape stated in the Assertion. Hence A and R are both correct, and R explains A.

Key characteristics of polar orbits (for exam recall):

• Inclination: ~90° (near-polar for many missions).
• Altitude (typical): Low Earth Orbit, often 600–900 km for Earth observation.
• Orbital period: ~95–105 minutes (about 14–15 orbits/day).
• Coverage: Near-global; every pass crosses high latitudes; full Earth coverage over several days.
• Applications: Remote sensing, meteorology, environmental monitoring, mapping, ice and ocean studies, and reconnaissance.

Sun-Synchronous Orbit (SSO) note (common polar subtype):

• An SSO is a near-polar, usually nearly circular orbit with a carefully chosen altitude/inclination so that the orbital plane precesses ~1°/day, keeping local solar time of each pass nearly constant (consistent lighting).
• Typical inclination ~97–99°, altitude commonly ~600–800 km.

Caveat for completeness:

• “Polar” describes inclination, not shape. Polar orbits can be elliptical, but for practical Earth-observation reasons they are generally designed to be nearly circular. This is why the Assertion uses “generally.”

Explanation:

• Correct reasons:
  • Location near the equator: Provides additional velocity boost (~450 m/s) from Earth’s rotation, increasing payload efficiency.
  • Favorable Launch Azimuth Corridor: Allows both polar and geostationary launches effectively.
  • Strategic and Uninhabited Area: Ensures safety, ample space for infrastructure, and minimal displacement.
• Incorrect reasons:
  • Dense forest cover: Not a factor in choosing the location.
  • Higher altitude: Sriharikota is a barrier island at sea level, not at a high altitude.

👉 Therefore, 3 statements are correct (1, 2, and 3).

Explanation:

A. National Remote Sensing Centre (NRSC) – Hyderabad

• Deals with satellite data reception, processing, and distribution.
• Provides remote sensing data for applications like agriculture, forestry, water resources, urban planning, and disaster management.

B. ISRO Propulsion Complex (IPRC) – Mahendragiri (Tamil Nadu)

• Specialises in assembly, integration, and testing of propulsion systems.
• Handles cryogenic, liquid, and semi-cryogenic engines used in PSLV, GSLV, and LVM3 launch vehicles.

C. ISRO Inertial Systems Unit (IISU) – Thiruvananthapuram (Kerala)

• Develops inertial sensors, navigation, and control systems.
• Provides high precision guidance and navigation technology for launch vehicles and spacecraft.

D. Space Applications Centre (SAC) – Ahmedabad (Gujarat)

• Works on satellite payload development for communication, meteorology, remote sensing, and space science.
• Contributes to India’s INSAT, IRS, and NavIC programmes.

Explanation:

• NISAR (NASA–ISRO Synthetic Aperture Radar) is a joint mission of NASA (USA) and ISRO (India).
• It is the world’s first Earth-observation satellite to carry dual-frequency SAR (L-band from NASA and S-band from ISRO).
• Objective: To provide detailed data on climate change, agriculture, forests, ice-sheet melting, land deformation, earthquakes, and natural disasters.
• Launch Vehicle: Planned aboard a GSLV Mk-II rocket from Sriharikota.
• Significance:
  • Will strengthen India’s earth monitoring and disaster management.
  • Supports India’s climate commitments and sustainable development goals.

Other options are incorrect because:

• B (Human spaceflight mission) → Refers to Gaganyaan, not NISAR.
• C (Solar observatory mission) → Refers to Aditya-L1, not NISAR.
• D (Exoplanet study satellite) → Missions like TESS (NASA) or CHEOPS (ESA), not NISAR.

Explanation:

• The second rocket launchport of ISRO is being established at Kulasekarapattinam in Tamil Nadu.
• Need for new launchport:
  • Overburdening of Satish Dhawan Space Centre (SDSC-SHAR), Sriharikota due to increasing commercial launches and private sector participation.
  • To diversify launch services: Sriharikota for heavy-lift missions, Kulasekarapattinam for Small Satellite Launch Vehicles (SSLVs).
  • To provide dedicated infrastructure for private players in the space sector.
• Significance of Kulasekarapattinam site:
  • Offers direct southward trajectory for SSLVs without dogleg manoeuvring (avoiding Sri Lanka).
  • Saves fuel → crucial for small payload vehicles.
  • Near-equator location gives an extra velocity boost, enhancing payload capacity.

Explanation:

1. Statement 1 – Correct
   • PSLV (Polar Satellite Launch Vehicle): Primarily used for placing satellites into Polar Sun-Synchronous Orbits (SSO), useful for Earth observation, weather, and resource monitoring.
   • GSLV (Geosynchronous Satellite Launch Vehicle): Designed to launch communication satellites into Geosynchronous Transfer Orbit (GTO).
2. Statement 2 – Incorrect
   • Satellites launched by PSLV go into polar or sun-synchronous orbits, not geostationary orbit.
   • Satellites that appear fixed over one location (geostationary) are launched mainly by GSLV, not PSLV.
3. Statement 3 – Incorrect
   • GSLV Mk III (now called LVM3) is a three-stage vehicle, not four.
     • Stage 1: Two solid strap-on boosters (S200).
     • Stage 2: Liquid core stage (L110).
     • Stage 3: Cryogenic upper stage (C25).
   • Hence, the description of four stages is wrong.

👉 Therefore, only Statement 1 is correct.

Explanation:

• SpaceX → Correctly associated with Falcon 9 and Falcon Heavy, not New Shepard.
• Virgin Galactic → Uses SpaceShipTwo (VSS Unity) for suborbital space tourism, not Ariane.
• Blue Origin → Operates New Shepard (suborbital tourism) and New Glenn (under development), not Falcon 9.
• European Space Agency (ESA) → Uses Ariane launch vehicles (Ariane 5, Ariane 6), not SpaceShipTwo.

👉 Hence, all four pairs are incorrect.

Explanation:

1. Cassini-Huygens – Incorrect
   • Cassini-Huygens was a joint NASA–ESA mission to Saturn and its moon Titan, not Venus.
   • Cassini orbited Saturn and studied its rings and atmosphere, while Huygens landed on Titan in 2005.
2. Messenger – Correct
   • Messenger (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was a NASA mission to Mercury.
   • It orbited Mercury from 2011 to 2015, mapping its surface and studying its composition and magnetic field.
3. Voyager 1 and 2 – Correct
   • Launched in 1977, Voyager 1 and 2 explored the outer solar system (Jupiter, Saturn, Uranus, Neptune).
   • Voyager 1 is now in interstellar space, while Voyager 2 continues its extended mission.

👉 Hence, only pairs 2 and 3 are correctly matched.

Explanation:

1. Statement 1 – Correct
   • Mangalyaan is the informal name for ISRO’s Mars Orbiter Mission (MOM), launched on 5 November 2013 aboard a PSLV-C25.
2. Statement 2 – Incorrect
   • India was not the second but the fourth space agency to place a spacecraft in Mars orbit.
   • The order: NASA (USA), Soviet Union (Russia), European Space Agency (ESA), and then India (ISRO).
3. Statement 3 – Correct
   • India became the first country in the world to succeed on its very first attempt at sending a spacecraft to Mars.
   • Even USA, Russia, and ESA had earlier failed in their first attempts.

👉 Thus, only Statements 1 and 3 are correct.

Explanation:

• Statement 1 – Incorrect: Safe and soft landing was not an objective of Chandrayaan-1. This was targeted in Chandrayaan-2 and achieved in Chandrayaan-3 (2023).
• Statement 2 – Incorrect: Rover roving was not part of Chandrayaan-1. Rover experiments were planned under Chandrayaan-2.
• Statement 3 – Correct: Chandrayaan-1’s objectives included preparing a 3D atlas of both near and far sides of the Moon through high-resolution remote sensing. It also aimed to map chemical and mineral composition and detect water ice on the Moon.

👉 Thus, only one statement (3) was correct.

Explanation:

• The Lunar South Pole was chosen for Chandrayaan-2 (2019) and Chandrayaan-3 (2023) because of its unique scientific importance.
• Key reasons:
  • Permanently Shadowed Regions (PSRs): The South Pole has larger shadowed areas than the North Pole → possible presence of water ice.
  • Cold Traps in Craters: These preserve volatiles and can hold a fossil record of the early Solar System, valuable for planetary science.
  • Strategic importance: If water ice is confirmed, it can support future human habitation, fuel production, and life-support systems.
• Hence, it is considered one of the most promising regions for future lunar exploration and resource utilization.

Explanation:

• Statement 1 is correct. TSAT-1A is specifically designed to deliver high-resolution imagery with a resolution of less than one meter per pixel, catering primarily to the strategic needs of the Indian government and armed forces. This capability is crucial for various military applications, enhancing India’s self-reliance in critical geospatial intelligence.
• Statement 2 is also correct. The launch of TSAT-1A from the Kennedy Space Center using SpaceX’s Falcon 9 rocket signifies a notable achievement in India’s space industry, particularly highlighting the increasing role of private companies such as TASL in the national space sector. This launch is part of a broader initiative to enhance India’s space capabilities and encourage private sector participation, which is critical for diversifying and strengthening India’s space capabilities amidst growing geopolitical tensions.

Explanation:

• The International Astronomical Union (IAU) has officially approved ‘Shiv Shakti Station’ as the name for the landing site of Chandrayaan-3’s Vikram lander on the Moon. This decision not only honors Indian cultural heritage but also commemorates the successful landing and mission objectives of Chandrayaan-3. Each option was designed to sound plausible by incorporating terms associated with Indian space missions, testing the aspirants’ familiarity with the specific details of the mission and the IAU’s naming conventions.

Explanation:

• Mission Shakti, a joint program of DRDO and ISRO, aimed to demonstrate India’s indigenous capability in space warfare. By successfully launching an anti-satellite (A-SAT) weapon and targeting a decommissioned Indian satellite, India became the fourth country to acquire such a specialized and modern capability. This highlights the significance of Mission Shakti as it showcases India’s prowess in space technology and its commitment to enhancing its defense capabilities in the realm of space.

Explanation:

• Group Captain Shubhanshu Shukla created history by becoming the first Indian astronaut to visit the International Space Station (ISS), marking a major milestone in India’s space journey.
• He flew as part of the Axiom-4 private space mission, which was launched aboard SpaceX’s Falcon 9 rocket.
• This mission highlights India’s growing collaboration in human spaceflight, paving the way for the upcoming Gaganyaan Mission.

Explanation:

• Kessler Syndrome (proposed by Donald J. Kessler in 1978) describes a chain reaction where collisions in space generate debris that leads to more collisions.
• It is primarily a concern in Low Earth Orbit (LEO) (altitude up to ~2000 km), where:
  • Thousands of active satellites operate (e.g., Starlink, Earth observation, ISS).
  • There is already a high density of space debris (defunct satellites, rocket bodies, fragments).
• GEO and MEO also have debris, but density is lower → risk of cascading collisions is highest in LEO.
• Consequence: Certain orbital paths could become unusable for decades/centuries, threatening space exploration and satellite-based services.

Explanation:

• (1) Detection of microwaves in space → Correct
  • In 1963, Arno Penzias and Robert Wilson discovered the Cosmic Microwave Background Radiation (CMBR).
  • This was the remnant heat from the Big Bang, predicted by Gamow, Herman, and Alpher.
  • CMBR provided strong evidence for the Big Bang model and the ongoing expansion of the universe.
• (2) Observation of redshift → Correct
  • In 1929, Edwin Hubble measured the redshifts of distant galaxies.
  • He found that light from distant galaxies is shifted towards red (longer wavelength) → indicating galaxies are moving away from us.
  • This phenomenon is explained using the Doppler effect, proving the universe is expanding.
• (3) Movement of asteroids → Not Correct
  • Motion of asteroids provides insights into the Solar System’s dynamics, not evidence of the universe’s expansion.
• (4) Supernova explosions → Not Correct
  • Supernovae help study distribution of elements and stellar life cycles, but are not direct evidence of expansion.

👉 Therefore, statements 1 and 2 only are correct.

Explanation:

• Statement 1 is correct as these systems are conceptualized to operate in the stratosphere, about 20 kilometers above the Earth’s surface, serving as aerial base stations. This high altitude provides wide coverage areas and facilitates connectivity solutions that are economically favorable compared to traditional satellite deployments.
• Statement 2 is also correct. Operating from the stratosphere, HAPS provide a broad coverage area, significantly wider than that possible from ground-based towers. This makes them particularly valuable in areas where building terrestrial infrastructure is challenging or cost-prohibitive. They can thus serve as a viable alternative for delivering communications and other services in remote, rural, or difficult-to-reach areas, enhancing connectivity and surveillance capabilities without extensive ground infrastructure.

Explanation:

• Vyommitra is the name of the female humanoid robot developed by India to test critical systems in space prior to the manned mission Gaganyaan, scheduled for 2025. This robot will simulate human functions within the spacecraft to ensure that all systems are safe and functional for future astronauts. Vyommitra’s mission is integral to India’s preparations for its ambitious Gaganyaan project, aiming to validate the life support and safety mechanisms essential for a successful manned spaceflight.

Explanation:

1 (RAMBHA) corresponds to B: To measure the near surface plasma (ions and electrons) density and its changes with time.

2 (ChaSTE) corresponds to D: To carry out the measurements of thermal properties of lunar surface near polar region.

3 (ILSA) corresponds to A: To measure seismicity around the landing site and delineating the structure of the lunar crust and mantle.

4 (LRA) corresponds to C: It is a passive experiment to understand the dynamics of the Moon system.

• RAMBHA is designed to study plasma densities close to the moon’s surface, aiding in understanding the lunar ionosphere.
• ChaSTE aims to analyze the thermal properties of the moon’s surface, which is crucial for future lunar habitation and utilization studies.
• ILSA focuses on measuring seismic activities, which helps in understanding the internal structure of the moon.
• LRA, a passive experiment involving laser retroreflectors, is used to measure distances and movements very precisely, contributing to broader lunar studies including its orbit and rotation.

Explanation:

• Statement 1: Correct → NISAR will track Greenland’s & Antarctica’s ice sheets, sea ice, and glaciers, contributing to climate change studies.
• Statement 2: Correct → ISRO provides the S-band Radar system, data handling & downlink system, spacecraft bus, and the launch vehicle.
• Statement 3: Correct → NISAR will be placed in a Sun-synchronous orbit, ideal for Earth observation.
• Statement 4: correct → The launcher is GSLV Mk II

👉 Hence, only 1, 2, 3 and 4 are correct.

Explanation:

• Chandrayaan-1 (2008), India’s first lunar mission, made a landmark discovery of water molecules and hydroxyl on the Moon’s surface.
• The detection was done using NASA’s Moon Mineralogy Mapper (M³) instrument carried onboard Chandrayaan-1.
• This overturned the earlier belief that the Moon was a completely dry celestial body.
• Later, Chandrayaan-2 (2019) confirmed the presence of water ice in permanently shadowed regions near the lunar poles.
• Soviet missions Luna-1 (1959) and Luna-3 (1959) were pioneering lunar missions but did not detect water.

Thus, Chandrayaan-1 is credited with the first evidence of water molecules on the Moon.

Explanation:

• The Kuiper Belt is a region of the Solar System that extends beyond the orbit of Neptune (~30–55 AU from the Sun).
• It contains icy bodies, dwarf planets (like Pluto, Haumea, Makemake), comets, and dust.
• It is similar to the asteroid belt, but much larger and composed mostly of frozen volatiles like methane, ammonia, and water.
• The Kuiper Belt is a source of short-period comets (like Halley-type comets).
• It should not be confused with:
  • Asteroid Belt (between Mars and Jupiter).
  • Van Allen Belts (radiation belts around Earth).
  • Oort Cloud (a distant spherical shell of icy bodies surrounding the Solar System).

Explanation:

• PSLV is India’s most reliable workhorse launch vehicle.
• It uses a four-stage configuration:
  • First Stage (PS1) – Solid rocket motor, augmented by 6 solid strap-on boosters.
  • Second Stage (PS2) – Liquid stage powered by the Vikas engine.
  • Third Stage (PS3) – Solid propellant.
  • Fourth Stage (PS4) – Liquid propulsion.
• This alternating solid–liquid configuration makes PSLV unique compared to other Indian rockets.
• PSLV has been used to launch satellites for Earth observation, navigation, interplanetary missions (like Mangalyaan, Chandrayaan-1), and multiple foreign payloads.

Explanation:

• PSLV (Polar Satellite Launch Vehicle):
  • Designed mainly for placing satellites into Low Earth Orbit (LEO) and Sun-Synchronous Polar Orbits (SSPO).
  • Payload capacity: ~1,750 kg to Sun-Synchronous Orbit (SSO), ~1,400 kg to Geostationary Transfer Orbit (GTO).
• GSLV (Geosynchronous Satellite Launch Vehicle):
  • Developed to launch heavier communication satellites into Geostationary Transfer Orbit (GTO).
  • Payload capacity: ~2,500–4,000 kg to GTO (depending on variant: Mk II, Mk III).
  • Uses a cryogenic upper stage, which burns liquid hydrogen + liquid oxygen (LOX).
  • Cryogenic engines are more efficient (higher specific impulse) than other chemical rocket engines, enabling it to carry heavier payloads into higher orbits.
• Why Reason explains Assertion:
  • GSLV’s superiority over PSLV comes precisely from the use of the cryogenic upper stage, which provides the extra power needed to push satellites into higher orbits (like GTO/ GEO).
  • Thus, both A and R are correct, and R is the correct explanation of A.

Explanation:

• Escape velocity is the minimum velocity required for a body to completely overcome Earth’s gravitational pull and move away without further propulsion (~11.2 km/s for Earth).
• Satellites in orbit do not need escape velocity; instead, they need the right orbital velocity (e.g., ~7.9 km/s for a circular low Earth orbit at ~200 km altitude).
• A satellite remains in orbit because of the balance between gravitational pull and tangential velocity: it is constantly “falling” towards Earth, but its forward motion makes it keep missing Earth.
• Thus, while escape velocity is for leaving Earth permanently, orbital velocity is for staying bound in orbit.
• Therefore, both A and R are correct, and R correctly explains A.

Explanation:

• The Goldilocks Zone (also called the Habitable Zone) is the region around a star where conditions are “just right” for liquid water to exist on a planet’s surface.
• It is neither too hot (water would evaporate) nor too cold (water would freeze).
• Presence of liquid water is considered a key requirement for life as we know it.
• In recent years, NASA and ESA missions like Kepler Space Telescope and James Webb Space Telescope (JWST) have been identifying exoplanets in their stars’ habitable zones.
• Example: Exoplanets in the TRAPPIST-1 system are considered strong candidates.

Explanation:

Assessment of crop productivity → Correct

• IRS satellites provide multispectral and temporal data for crop health monitoring, yield estimation, and agricultural planning.

Locating groundwater resources → Correct

• Remote sensing helps in mapping groundwater potential zones by analyzing vegetation indices, surface features, soil moisture, and geomorphology.

Mineral exploration → Correct

• IRS data (like LISS, AWiFS) assists in mineral prospecting by detecting surface mineral signatures and geological structures.

Telecommunications → Not correct

• Telecommunications rely on communication satellites (INSAT/GSAT), not IRS (which are observation satellites).

Traffic studies → Not correct

• Traffic studies are handled through navigation systems (IRNSS/NavIC, GPS) and ground-based technologies, not IRS.

👉 Hence, only statements 1, 2, and 3 are correct.