Space technology: previous-year questions
71 real UPSC Prelims questions (2011–2026) with the official answer and a clear explanation. 28 of them came in the last five papers.
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Questions per year, counted from the official papers.
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Which one of the following countries has its own Satellite Navigation System?
Answer (d) & explanation
Japan has its own satellite navigation system (d). Japan's Quasi-Zenith Satellite System (QZSS), called Michibiki, is a regional system that boosts GPS accuracy over Japan and the Asia–Oceania region. Australia (a), Canada (b) and Israel (c) rely on others' systems. There are four global systems: GPS (USA), GLONASS (Russia), Galileo (European Union) and BeiDou (China). There are two regional systems: Japan's QZSS and India's NavIC.
Notice India's NavIC (IRNSS) covers India and about 1,500 km around it. Some of its satellites lost their atomic clocks, and ISRO is launching the new NVS series, starting with NVS-01 in 2023. Phones now carry chips that use NavIC.
Answer as per the official UPSC answer key.
With reference to Ayushman Bharat Digital Mission, consider the following statements :
- 1. Private and public hospitals must adopt it.
- 2. As it aims to achieve universal health coverage, every citizen of India should be part of it ultimately.
- 3. It has seamless portability across the country.
Which of the statements given above is/are correct ?
Answer (b) & explanation
Only statement 3 is correct (b). The Ayushman Bharat Digital Mission (2021) builds digital health infrastructure: the ABHA (Ayushman Bharat Health Account) health ID, and registries of health professionals and facilities. Statement 1 is wrong: joining is voluntary for both private and public hospitals. Statement 2 is wrong: it is also voluntary for citizens; no one must take an ABHA ID. Statement 3 is right: records linked to ABHA are portable across hospitals, labs and States, with the patient's consent.
Notice that ABDM is run by the National Health Authority, which also runs AB-PMJAY, the health insurance scheme of ₹5 lakh a family. In 2024, PMJAY was extended to all citizens aged 70 and above.
"Must" and "every citizen" are the words that rule out statements 1 and 2.
Answer as per the official UPSC answer key.
Consider the following :
- 1. Aarogya Setu
- 2. CoWIN
- 3. DigiLocker
- 4. DIKSHA
Which of the above are built on top of open-source digital platforms ?
Answer (d) & explanation
All four are built on open-source platforms (d). All four are part of India's digital public infrastructure, built on open-source code and open standards. Item 1 is right: Aarogya Setu, the COVID contact-tracing app, made its code open source in 2020. Item 2 is right: CoWIN, the vaccine registration platform, became an open-source stack (DIVOC) offered to other countries. Item 3 is right: DigiLocker stores official documents digitally on open standards. Item 4 is right: DIKSHA, the school learning platform, is built on Sunbird, an open-source framework.
Notice the India Stack: Aadhaar, UPI, DigiLocker and consent-based data sharing. India pushed DPI globally during its G20 presidency (2023), with the Global DPI Repository.
Answer as per the official UPSC answer key.
With reference to Web 3.0, consider the following statements :
- 1. Web 3.0 technology enables people to control their own data.
- 2. In Web 3.0 world, there can be blockchain based social networks.
- 3. Web 3.0 is operated by users collectively rather than a corporation.
Which of the statements given above are correct ?
Answer (d) & explanation
All three statements are correct (d). Web 3.0 is the idea of a decentralised internet built on blockchains. Statement 1 is right: users hold their own data and digital assets in wallets, rather than leaving them with big platforms. Statement 2 is right: applications, including social networks, can run on public blockchains. Statement 3 is right: decisions can be made by users collectively, for example through DAOs (decentralised autonomous organisations), rather than by one company.
Notice the earlier stages: Web 1.0 was read-only static pages; Web 2.0 is today's interactive, platform-run web of social media. Web 3.0 is linked with cryptocurrencies and NFTs. India taxes crypto gains at 30%, with 1% TDS.
Answer as per the official UPSC answer key.
With reference to “Software as a Service (SaaS)”, consider the following statements :
- 1. SaaS buyers can customise the user interface and can change data fields.
- 2. SaaS users can access their data through their mobile devices.
- 3. Outlook, Hotmail and Yahoo! Mail are forms of SaaS.
Which of the statements given above are correct ?
Answer (d) & explanation
All three statements are correct (d). In Software as a Service, the provider hosts the software in the cloud, and users reach it through a browser or app. Statement 1 is right: buyers can usually configure the user interface and change data fields to suit their needs. Statement 2 is right: users can reach their data from any device, including mobiles, over the internet. Statement 3 is right: webmail services such as Outlook, Hotmail and Yahoo! Mail are everyday examples of SaaS.
Notice the three cloud layers: SaaS (ready software, such as Gmail), PaaS (Platform as a Service, a platform for developers) and IaaS (Infrastructure as a Service, raw servers and storage). India's government cloud initiative is MeghRaj.
Answer as per the official UPSC answer key.
Which one of the following is the context in which the term “qubit” is mentioned ?
Answer (b) & explanation
A qubit relates to quantum computing (b). A qubit, or quantum bit, is the basic unit of quantum computing. An ordinary bit is either 0 or 1. Through superposition, a qubit can be 0 and 1 at once, and qubits can be entangled, so their states are linked. This lets quantum computers solve some problems, such as cryptography and molecular modelling, far faster. It is not a term from cloud services (a), visible light communication (c) such as Li-Fi, or wireless technology (d).
Notice India's National Quantum Mission (2023), with about ₹6,000 crore, which aims to build 50–1,000 qubit machines within eight years. 2025 was the UN's International Year of Quantum Science and Technology.
Answer as per the official UPSC answer key.
Consider the following communication technologies :
- 1. Closed-circuit Television
- 2. Radio Frequency Identification
- 3. Wireless Local Area Network
Which of the above are considered Short-Range devices/technologies ?
Answer (d) & explanation
All three are short-range technologies (d). Short-Range Devices (SRDs) are low-power radio transmitters that work over short distances and have little potential to interfere with other services. Item 1 is right: wireless CCTV links send video over short ranges. Item 2 is right: RFID tags, used in FASTag and shop security, are read from close range. Item 3 is right: Wireless LAN, or Wi-Fi, covers a home or office. Bluetooth, NFC, wireless alarms and car remotes are other SRDs.
Notice that the Department of Telecommunications delicenses many SRD bands, such as parts of the 2.4 GHz and 5 GHz bands for Wi-Fi, so no licence is needed. In 2024, it delicensed the lower 6 GHz band for Wi-Fi.
Answer as per the official UPSC answer key.
If a major solar storm (solar flare) reaches the Earth, which of the following are the possible effects on the Earth ?
- 1. GPS and navigation systems could fail.
- 2. Tsunamis could occur at equatorial regions.
- 3. Power grids could be damaged.
- 4. Intense auroras could occur over much of the Earth.
- 5. Forest fires could take place over much of the planet.
- 6. Orbits of the satellites could be disturbed.
- 7. Shortwave radio communication of the aircraft flying over polar regions could be interrupted.
Select the correct answer using the code given below :
Answer (c) & explanation
Effects 1, 3, 4, 6 and 7 are possible (c). A big solar storm disturbs Earth's ionosphere and magnetic field. Item 1 is right: it disrupts GPS and navigation signals. Item 3 is right: it induces currents that can damage power grids, as in Quebec in 1989. Item 4 is right: it spreads auroras to low latitudes. Item 6 is right: it heats the upper air, which drags satellites down; SpaceX lost about 40 Starlink satellites in 2022. Item 7 is right: it blocks shortwave (HF) radio over the poles. Items 2 and 5 are wrong: it cannot cause tsunamis or forest fires.
Notice the Carrington Event (1859), the strongest storm on record. India's Aditya-L1 (2023) studies the Sun from the L1 point.
Remove the two impossible effects, tsunamis and forest fires. Only option (c) is left.
Answer as per the official UPSC answer key.
Which one of the following is a reason why astronomical distances are measured in light-years?
Answer (d) & explanation
Light-years work because the speed of light is constant (d). A light-year is the distance light covers in one year in a vacuum, about 9.46 × 10¹² km. It can serve as a unit only because the speed of light in a vacuum is always the same, about 3 × 10⁵ km per second, for every observer. Option (a) is wrong: distances between stars and galaxies do change; the universe is even expanding. Option (b) is wrong: gravity of stellar bodies changes as they evolve. Option (c) is wrong: light does not always travel straight; gravity bends it (gravitational lensing).
Notice the other units: the astronomical unit (Earth–Sun distance, about 150 million km) and the parsec (about 3.26 light-years). The nearest star after the Sun, Proxima Centauri, is about 4.2 light-years away.
Answer as per the official UPSC answer key.
With the present state of development, Artificial Intelligence can effectively do which of the following ?
- 1. Bring down electricity consumption in industrial units
- 2. Create meaningful short stories and songs
- 3. Disease diagnosis
- 4. Text-to-Speech Conversion
- 5. Wireless transmission of electrical energy
Select the correct answer using the code given below :
Answer (b) & explanation
AI could do tasks 1, 3 and 4 in UPSC's 2020 key (b). By 2020, AI was already proven at cutting electricity use in industry (1), for example Google's DeepMind cutting data centre cooling energy by about 40%. It could help diagnose diseases (3) from X-rays, scans and eye images. It was widely used for text-to-speech (4). Statement 5 is wrong because wireless power transfer is a matter of physics, not AI. UPSC's key also left out writing meaningful stories and songs (2).
Keep the year in mind: since ChatGPT (late 2022), generative AI can clearly write stories and songs. Notice India's moves: the IndiaAI Mission (2024, ₹10,372 crore), the AI Impact Summit in New Delhi (February 2026) and AI governance guidelines (2025).
This answer reflects 2020. A question set today might count creative writing.
Answer as per the official UPSC answer key.
With reference to Visible Light Communication (VLC) technology, which of the following statements are correct ?
- 1. VLC uses electromagnetic spectrum wavelengths 375 to 780 nm.
- 2. VLC is known as long-range optical wireless communication.
- 3. VLC can transmit large amounts of data faster than Bluetooth.
- 4. VLC has no electromagnetic interference.
Select the correct answer using the code given below :
Answer (c) & explanation
Statements 1, 3 and 4 are correct (c). Visible Light Communication (VLC), also called Li-Fi, sends data by switching LED lights on and off very fast, too fast for the eye to notice. Statement 1 is right because it uses visible light, about 375–780 nm. Statement 3 is right because it can carry large amounts of data faster than Bluetooth, even faster than Wi-Fi in labs. Statement 4 is right because light causes no radio-frequency interference, so it suits hospitals, aircraft and mines. Statement 2 is wrong because light cannot pass through walls, which makes VLC a short-range technology.
Harald Haas coined the term "Li-Fi" in 2011. Notice that the IEEE 802.11bb standard (2023) brought Li-Fi into the Wi-Fi family.
Answer as per the official UPSC answer key.
With reference to “Blockchain Technology”, consider the following statements :
- 1. It is a public ledger that everyone can inspect, but which no single user controls.
- 2. The structure and design of blockchain is such that all the data in it are about cryptocurrency only.
- 3. Applications that depend on basic features of blockchain can be developed without anybody’s permission.
Which of the statements given above is/are correct ?
Answer (d) & explanation
Statements 1 and 3 are correct (d). A blockchain is a distributed ledger: a chain of linked, time-stamped records copied across many computers. Statement 1 is right because a public blockchain can be inspected by anyone, and no single user controls it; changes need agreement across the network. Statement 2 is wrong because it can record any data, such as land titles, supply chains, medical records, voting or certificates, not just cryptocurrency. Statement 3 is right because open, permissionless chains let anyone build applications, such as smart contracts, without asking permission.
Notice India's uses: land records pilots, Vishvasya, the national blockchain framework (2024), and the RBI's e-rupee (CBDC). India taxes crypto gains at 30% but has not banned crypto.
Answer as per the official UPSC answer key.
Consider the following activities :
- 1. Spraying pesticides on a crop field
- 2. Inspecting the craters of active volcanoes
- 3. Collecting breath samples from spouting whales for DNA analysis
At the present level of technology, which of the above activities can be successfully carried out by using drones ?
Answer (d) & explanation
Drones can do all three (d). Drones are used to spray pesticides and fertilisers on crops (1), saving time and reducing farmers' exposure to chemicals. India promotes Kisan drones and the Namo Drone Didi scheme (2023), which gives drones to women's SHGs. Drones fly over active volcanoes to inspect craters and sample gases (2), where it is too dangerous for people. In the SnotBot project, drones collect breath samples from spouting whales (3) for DNA, hormone and health studies, without disturbing them. So any option leaving one out is wrong.
Notice India's drone policy: the liberal Drone Rules, 2021, the PLI scheme for drones, and the ban on most imported drones (2022). Drones were used widely in Operation Sindoor (2025).
Answer as per the official UPSC answer key.
“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
Answer (d) & explanation
The experiment is Evolved LISA (d). The Laser Interferometer Space Antenna, in its evolved form (eLISA), plans three spacecraft flying in an equilateral triangle millions of kilometres on a side, with lasers shining between them. Tiny changes in the distance between them will reveal gravitational waves from sources such as merging giant black holes. LISA Pathfinder (c), launched in 2015, was a single craft that only tested the technology. Voyager-2 (a) is exploring interstellar space. New Horizons (b) flew past Pluto in 2015.
The mission, now just called LISA, was approved by the ESA in January 2024, with launch planned around 2035 and arms of about 2.5 million km. Notice its ground-based cousins: LIGO, Virgo, KAGRA and LIGO-India.
Pathfinder was a test of the technology using one spacecraft. The three-spacecraft triangle is the full mission.
Answer as per the official UPSC answer key.
In India, the term “Public Key Infrastructure” is used in the context of
Answer (a) & explanation
PKI refers to digital security infrastructure (a). Public Key Infrastructure is the system of encryption keys, digital certificates and certifying authorities that makes digital signatures and secure online transactions possible. Each user has a public key, which anyone can see, and a private key, kept secret. A certifying authority vouches that a public key belongs to a particular person. In India, the Controller of Certifying Authorities, under the IT Act, 2000, oversees PKI and runs the Root Certifying Authority of India. It has nothing to do with food (b), health and education (c), or transport (d).
Notice the everyday uses: Aadhaar eSign, income tax filing with digital signatures, e-tendering, and the HTTPS padlock on websites.
Answer as per the official UPSC answer key.
With reference to communication technologies, what is/are the difference/differences between LTE (Long-Term Evolution) and VoLTE (Voice over Long-Term Evolution)?
- 1. LTE is commonly marketed as 3G and VoLTE is commonly marketed as advanced 3G.
- 2. LTE is data-only technology and VoLTE is voice-only technology.
Select the correct answer using the code given below.
Answer (d) & explanation
Neither statement is correct (d). Statement 1 is wrong because LTE, short for Long-Term Evolution, is marketed as 4G, not 3G. VoLTE is a service on that 4G network, not "advanced 3G". Statement 2 is wrong because LTE is mainly for data, but VoLTE carries voice calls as data packets over the same 4G network. So voice and data run together, giving clearer HD voice, faster call set-up, and data use during calls. VoLTE is not voice-only.
India's 4G growth took off when Reliance Jio launched an all-VoLTE network in 2016. Notice the newer steps: 5G rolled out from October 2022, BSNL's indigenous 4G stack went live in 2025, and VoNR carries voice over 5G.
Answer as per the official UPSC answer key.
In the context of digital technologies for entertainment, consider the following statements :
- 1. In Augmented Reality (AR), a simulated environment is created and the physical world is completely shut out.
- 2. In Virtual Reality (VR), images generated from a computer are projected onto real-life objects or surroundings.
- 3. AR allows individuals to be present in the world and improves the experience using the camera of smart-phone or PC.
- 4. VR closes the world, and transposes an individual, providing complete immersion experience.
Which of the statements given above is/are correct?
Answer (b) & explanation
Statements 3 and 4 are correct (b). Statements 1 and 2 swap the definitions. Augmented Reality (AR) keeps you in the real world and adds digital images on top of it, usually through a phone camera or smart glasses (3). Examples are Pokémon Go, Snapchat filters, and apps that show furniture in your room. Virtual Reality (VR) shuts out the real world and places you in a fully simulated one, usually through a headset, giving complete immersion (4).
Mixed reality combines both, letting digital objects interact with the real world, as in Apple Vision Pro. Notice the uses beyond games: training surgeons and pilots, virtual tours of heritage sites, and India's AVGC-XR policy for animation, gaming and extended reality.
Answer as per the official UPSC answer key.
Consider the following statements :
A digital signature is
- 1. an electronic record that identifies the certifying authority issuing it
- 2. used to serve as a proof of identity of an individual to access information or server on Internet
- 3. an electronic method of signing an electronic document and ensuring that the original content is unchanged
Which of the statements given above is/are correct?
Answer (c) & explanation
Only statement 3 is correct (c). A digital signature is an electronic method of signing a document using public-key cryptography. The signer uses a private key, and anyone can check it with the matching public key. It proves who signed and shows the content has not been changed (3). Statement 1 is wrong because the record that identifies the certifying authority is the digital signature certificate, not the signature itself. Statement 2 is wrong because identity for logging in to a server is proved by certificates, passwords and logins, not a digital signature as such.
In India, digital signatures are legally valid under the IT Act, 2000. The Controller of Certifying Authorities licenses issuers. Notice Aadhaar-based eSign and DigiLocker, used widely for e-governance.
Do not confuse the signature with the certificate. Statements 1 and 2 describe what a certificate does.
Answer as per the official UPSC answer key.
In the context of wearable technology, which of the following tasks is/are accomplished by wearable devices?
- 1. Location identification of a person
- 2. Sleep monitoring of a person
- 3. Assisting the hearing impaired person
Select the correct answer using the code given below.
Answer (d) & explanation
Wearables do all three tasks (d). Smartwatches and fitness bands use GPS to identify a person's location (1), useful for tracking runs or finding children and elderly people. They monitor sleep using motion sensors and heart-rate sensors (2). Smart hearing aids and earbuds with hearing-assist modes help people with hearing loss (3); for example, some AirPods models were approved as hearing aids in 2024. So any option leaving one out is wrong.
Wearables also measure heart rate, blood oxygen and ECG, and detect falls. Notice the issues: privacy of health data under the DPDP Act, and India's growing home-grown wearable makers such as boAt and Noise, helped by the PLI scheme for electronics.
Answer as per the official UPSC answer key.
Recently, scientists observed the merger of giant ‘blackholes’ billions of light-years away from the Earth. What is the significance of this observation?
Answer (b) & explanation
The merger proved gravitational waves exist (b). In September 2015, LIGO in the USA detected gravitational waves, ripples in space-time, from two black holes merging about 1.3 billion light-years away. This confirmed a prediction of Einstein's General Relativity made a century earlier. Weiss, Barish and Thorne won the 2017 Physics Nobel. Option (a) is wrong because the Higgs boson was found at CERN's Large Hadron Collider in 2012. Option (c) is wrong because wormholes remain theoretical. Option (d) is wrong because the observation did not explain the singularity at a black hole's centre.
Notice India's role: LIGO-India, approved in 2023, is being built at Hingoli, Maharashtra. Indian scientists also helped detect the GW250114 signal in 2025.
Answer as per the official UPSC answer key.