Space and Space Technology: UPSC Previous Year Questions (Science and Technology)

Explanation

Statement 1 is correct: The Polar Satellite Launch Vehicle (PSLV) is primarily used to place satellites in Sun-Synchronous Polar Orbits (SSO), which are ideal for Earth observation, remote sensing, and resource monitoring. The Geosynchronous Satellite Launch Vehicle (GSLV) is used to place communication satellites into Geostationary Transfer Orbit (GTO), from where they move into Geostationary Orbit (GEO) for telecom and broadcasting services.

Statement 2 is incorrect:

Geostationary satellites (which remain fixed over a location) are launched into Geostationary Orbit (GEO) at 35,786 km altitude, usually by GSLV, not PSLV. PSLV typically places satellites in Low Earth Orbit (LEO) or Sun-Synchronous Orbit (SSO), where they move relative to the Earth’s surface.

Statement 3 is incorrect:

GSLV Mk III (now LVM3) is actually a three-stage launch vehicle:

First stage: Two solid rocket boosters (S200) Second stage: A liquid-fueled core stage (L110) Third stage: A cryogenic stage (C25) There is no fourth stage in GSLV Mk III, making the statement incorrect.

Explanation

The terms ‘Event Horizon’, ‘Singularity’, ‘String Theory’, and ‘Standard Model’ are primarily associated with the observation and understanding of the Universe. Event Horizon is the boundary of a black hole where escape velocity exceeds the speed of light and thus nothing, including light, can escape once crossed. A gravitational singularity is a region in space where matter is infinitely dense, and gravitational forces become infinite. It is found at the center of black holes, where spacetime curvature becomes infinite, and the equations of general relativity fail to provide a meaningful description. String Theory is a theoretical framework in physics that attempts to reconcile quantum mechanics and general relativity by positing that fundamental particles are not point-like but rather one-dimensional "strings." It is a candidate for a theory of everything, aiming to explain all fundamental forces and particles in the Universe. Standard Model is the theory in particle physics that describes three of the four known fundamental forces (electromagnetic, weak, and strong interactions) and classifies all known elementary particles. It is a cornerstone of modern physics and helps explain the behavior of matter and energy in the Universe.

Explanation

The evolved Laser Interferometer Space Antenna (eLISA) is a mission led by the European Space Agency (ESA) to detect and measure gravitational waves. Gravitational waves are ripples in spacetime caused by massive cosmic events, such as merging black holes or neutron stars. eLISA aims to provide a new way of observing the universe by directly measuring these waves which are otherwise invisible to traditional telescopes. Unlike ground-based detectors like LIGO, eLISA will operate in space, allowing it to observe lower-frequency gravitational waves that cannot be detected on Earth.

Explanation

AstroSat is the first dedicated Indian astronomy mission aimed to study celestial sources in X-ray, optical and UV spectral bands. The payloads cover the energy bands of Ultraviolet (Near and Far), limited optical and X-ray regime (0.3 keV to 100keV). The ability to simultaneously observe multiple celestial objects at multiple wavelengths with a single satellite is one of the special aspects of the AstroSat project.

Statement 1 is incorrect: India has joined the exclusive club of nations with its own space observatory with the successful launch of ASTROSAT, joining the US, Japan, Russia, and Europe. ASTROSAT, India’s first dedicated multi-wavelength space observatory, will aid in the knowledge of the cosmos.

Statement 2 is incorrect: AstroSat with a lift-off mass of 1515 kg was launched into a 650 km orbit inclined at an angle of 6 deg to the equator by PSLV-C30 from Satish Dhawan Space Centre, Sriharikota.

Explanation

Mangalyaan/Mars Orbiter Mission (MOM), the maiden interplanetary mission of ISRO, was launched on PSLV-C25. It entered into Martian orbit in its first attempt. MOM had completed 1000 Earth days in its orbit well beyond its designed mission life of six months.

Statement 1 and 3 are correct: The Mangalyaan launched by ISRO is also called the Mars Orbiter Mission. With this India became the first Asian nation to reach Mars orbit, and the first nation in the world to do so in its first attempt.

Statement 2 is incorrect: It is India’s first interplanetary mission and ISRO has become the fourth space agency to reach Mars, after the Soviet space Programme, NASA and the EuropeanSpace Agency.

Explanation

The IceCube Neutrino Observatory is the first of its kind, designed to explore the cosmos from deep within the ice at the South Pole. It is operated by the IceCube Collaboration, an international team of scientists conducting research in this field. By detecting high-energy cosmic neutrinos, IceCube enables the study of some of the universe’s most violent astrophysical events, including stellar explosions, gamma-ray bursts, and catastrophic interactions involving black holes and neutron stars.

Statement 1 is correct: The IceCube Neutrino Observatory is the largest neutrino detector globally, occupying a cubic kilometer of ice at the South Pole. It detects high-energy neutrinos from cosmic sources like supernovae, black holes, and gamma-ray bursts.

Statement 2 is correct: IceCube plays a critical role in the search for dark matter by detecting neutrinos produced when dark matter particles, such as WIMPs (Weakly Interacting Massive Particles), interact or annihilate. This makes it a vital tool in astrophysical and particle physics research.

Statement 3 is correct: IceCube’s detectors are buried at depths between 1,450 meters and 2,450 meters in Antarctic ice. This depth reduces interference from cosmic rays and other particles, allowing it to detect faint light signals from neutrino interactions.

Explanation

Indian Remote Sensing (IRS) satellites developed by the Indian Space Research Organisation (ISRO) are primarily designed for Earth observation and resource management. Their applications encompass various fields, including agriculture, water resources, urban planning, rural development, mineral prospecting, environment, forestry, ocean resources, and disaster management.

Option (a) is correct: Indian Remote Sensing satellites play a crucial role in agriculture. They provide data on crop health, soil conditions and vegetation cover which are essential for assessing crop productivity. The satellites capture multispectral and hyperspectral images that help in monitoring crop growth, predicting yields, and identifying areas affected by drought or pests. IRS satellites are instrumental in identifying potential groundwater resources. They use remote sensing techniques to map geological features, soil moisture, and vegetation patterns that indicate the presence of groundwater. ISRO’s Bhuvan portal provides satellite-based groundwater prospect maps. IRS satellites are used in mineral exploration by providing detailed images of the Earth’s surface which help geologists identify mineral-rich areas based on spectral signatures of rocks and soils. This reduces the need for extensive ground surveys. The Geological Survey of India (GSI) collaborates with ISRO to use remote sensing data for mineral exploration. IRS satellites are not designed for telecommunications. Telecommunications satellites such as the Indian National Satellite (INSAT) series are used for communication purposes including television broadcasting, internet services, and telephony. Traffic studies typically rely on data from ground-based sensors, GPS and other real-time monitoring systems. While satellites can provide broad-scale urban planning data but IRS satellites are not specifically designed for traffic management.

Explanation

The Goldilocks Zone, or habitable zone, refers to the region around a star where conditions are "just right" for liquid water to exist on a planet’s surface--a key factor for life as we know it. This zone depends on the star’s size and temperature. Earth lies within the Sun’s Goldilocks Zone, enabling its rich biodiversity. Exoplanets within their star’s habitable zones, such as Kepler-452b, are prime candidates in the search for extraterrestrial life.

Explanation

Pair 1 is incorrectly matched: The Cassini-Huygens mission was a collaborative project between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to study Saturn and its moons, not Venus. Huygens probe landed on Titan, Saturn’s largest moon in 2005 and provided valuable data about its atmosphere and surface.

Pair 2 is correctly matched: The Messenger (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft was a NASA mission designed to study Mercury. It orbited Mercury and mapped its surface, studying its geology, and investigating its magnetic field and exosphere.

Pair 3 is correctly matched: The Voyager 1 and Voyager 2 spacecraft were launched by NASA in 1977 to explore the outer planets of the solar system. Voyager 1 flew by Jupiter and Saturn, providing detailed images and data about these planets and their moons. Voyager 2 visited all four outer planets:

Jupiter, Saturn, Uranus, and Neptune. The spacecraft are now in interstellar space, continuing to transmit data about the heliosphere and beyond.

Explanation

An optical illusion is characterized by visually perceived images that differ from object than reality. The information that is gathered by the eye is processed in the brain that gives a perception that does not tally with a physical measurement of the stimulus source.

Statement 1 is correct: There are no known objects of a similar size as the sun (or moon) when it is high in the sky. The sun, however, appears even larger when it is low in the sky because we can see distant objects near the horizon that we know to be large. Thus, the size of the sun at dusk is a visual illusion.

Statement 2 is correct: There are many different colours in light. Red is the colour that moves the farthest out of all of those others. As the sun sets, crimson (deep, rich red colour) is the final hue to be seen. Red is the last colour to appear when the other colours begin to fade. Therefore, the colour of the sun at dawn is due to optical illusion.

Statement 3 is incorrect: Moon being visible at dawn is not an optical illusion as the moon is visible somewhere in the sky at dawn during the entire half of the cycle of phases from Full Moon to just before New Moon.

Statement 4 is correct: Light is constantly emitted by stars. Before reaching our sight, this light passes through a number of layers of the earth’s atmosphere. Because different layers of atmosphere have different refractive indices, stars appear to be blinking/twinkling.

Statement 5 is incorrect: The Polestar (Pole Star or North Star) is visible because of its alignment with Earth’s rotational axis, not due to any optical effect.