Space Technology MCQs for UPSC Prelims

Correct answer: A - Only one

Only one pair is correctly matched, so the answer is Only one. The Pulsars pair is right, as pulsars are rotating neutron stars left behind when massive stars collapse. The first two pairs are swapped, since Cepheids are actually stars that brighten and dim periodically while nebulae are the giant clouds of dust and gas. Because the descriptions for Cepheids and Nebulae are interchanged, only the Pulsars pairing is correct.

Correct answer: A - 1 and 2

Statements 1 and 2 are cited as evidence, so (a) is correct. The redshift of light from distant galaxies, increasing with distance (Hubble's law), is the classic signature that space is expanding. The cosmic microwave background detected in space is the cooled relic radiation of the early universe; its existence and falling temperature are consistent only with a universe that has been expanding since the Big Bang, so it is cited alongside redshift. Statement 3 is wrong because asteroid motion is governed by solar system gravity and says nothing about cosmology. Statement 4 is wrong as supernova explosions by themselves are not the evidence (although distance measurements using Type Ia supernovae later revealed accelerated expansion, the occurrence of explosions is not what is cited).

Correct answer: B - 1 and 3 only

Correct answer (b) 1 and 3 only. Asteroids are small rocky and metallic planetoids while comets are icy bodies of frozen gases bound with rock and dust, so statement 1 is correct. Comets develop a glowing tail of gas and dust as they near the Sun, whereas asteroids do not, so statement 3 is correct. Statement 2 is wrong because the main asteroid belt lies between the orbits of Mars and Jupiter, not between Venus and Mercury, and comets originate far beyond in the Kuiper Belt and Oort Cloud. Options (a) and (d), which include statement 2, are incorrect.

Correct answer: B - Only two

The Axiom-4 mission to the International Space Station and India's Gaganyaan human spaceflight programme both involve crewed orbital activity that supports microgravity experiments, so two missions qualify. SpaDeX is a space docking experiment designed to demonstrate rendezvous and docking technology, not primarily microgravity research. Hence only two of the missions support microgravity research.

Correct answer: B - To detect gravitational waves

eLISA is a planned space-based laser interferometer designed to detect gravitational waves, the ripples in spacetime predicted by Einstein, by measuring minute changes in distance between free-floating test masses, so option B is correct. Neutrinos are detected by underground detectors like IceCube, not laser interferometry. eLISA has no role in assessing missile-defence systems. Studying solar flare effects on communications is the work of space-weather satellites, not eLISA. Hence its purpose is to detect gravitational waves.

Correct answer: B - 2 and 3 only

Pairs 2 and 3 are correct: Messenger mapped and investigated Mercury, and Voyager 1 and 2 explore the outer solar system. Pair 1 is wrong because Cassini-Huygens studied Saturn and its moon Titan, not Venus. Hence 2 and 3 only.

Correct answer: D - Japan

Japan is correct because it operates the Quasi-Zenith Satellite System (QZSS), also called Michibiki, a regional satellite navigation system that augments GPS over Japan and the Asia-Oceania region. Australia, Canada and Israel do not maintain their own independent navigation satellite systems and rely on systems like GPS. Hence Japan is the only correct answer.

Correct answer: D - 1, 2 and 3

All three quantities can be estimated from space. Chlorophyll content is routinely derived from vegetation indices such as NDVI using visible and near-infrared bands. Methane emissions from rice paddies can be estimated using greenhouse gas monitoring satellites like GOSAT and Sentinel-5P, which sense trace gas concentrations, combined with land use data. Land surface temperature is measured directly through thermal infrared sensors on satellites such as those in the Landsat and MODIS programmes. Since remote sensing covers statements 1, 2 and 3, option (d) is correct.