UPSC Prelims 2026 Revision Checklist: Top 35 Science and Technology topics that aspirants should revise

#1. Sodium-ion batteries

— It is way more abundant than lithium and can be extracted from seawater at relatively lower costs.

— It is more environmentally friendly.

— It can be transported at zero volt, making it safer, unlike lithium, which is less environmentally friendly and must be always stored with a minimum charge, increasing fire risks.

— It uses aluminum, which is cheaper than copper used in the lithium-ion battery tech.

— Sodium-ion batteries also have a higher operating temperature range and are hence safer, given that these can be used in more extreme temperatures without the risk of thermal runaway.

#2. Reverse osmosis

— Saline water contains significant concentrations of dissolved salts (ranging up to 35,000 ppm) and is otherwise unfit for human consumption. Given the scarcity of freshwater sources and a growing population, the need for additional water supplies has long been recognised.

— Desalination plants are highly energy-intensive and run on electricity generated from liquid fuels or natural gas, generating 500 to 850 million tons of carbon dioxide emissions annually. Another concern is that reverse osmosis, the predominant desalination method, generates large quantities of saltwater brine, which are typically discharged into the ocean. These can harm marine habitats and kill sea creatures such as plankton and fish larvae.

— Reverse Osmosis can be applied for desalination of brackish water, water reuse (in pharma /biotech, waste water, electrocoating, food and beverage industries) and radioactive waste treatment.

#3. Helioseismology

— Scientists used a method called helioseismology to detect the movements inside the Sun. This method is used to study the solar surface to understand the movements inside the Sun, the same way earthquakes are used to study the movements inside the Earth.

— They analysed more than a decade of solar observations collected by the Solar Dynamics Observatory, a satellite operated by NASA. In particular, they used measurements from the satellite’s Helioseismic and Magnetic Imager (HMI)– an instrument designed to track oscillations and magnetic activity across the Sun’s surface.

#4. Critical minerals

— Critical minerals are required for many modern energy technologies as well as the overall economy. For example, lithium, nickel, cobalt, manganese, and graphite are essential for battery performance.

— Rare earth elements are required for the permanent magnets found in wind turbines.

— Electricity networks require a large amount of aluminium and copper, the latter being the foundation of all electricity-related technologies.

#5. CAR T-cell therapy

— CAR T-cell therapy is a cutting-edge treatment that reprogrammes T-cells to better target cancer cells. Doctors collect T-cells from a patient’s blood and, in the lab, add a new gene that equips them with special receptors called chimeric antigen receptors (CARs). These receptors act like GPS trackers, guiding the T-cells to cancer cells. Once engineered, the cells are grown in large numbers and infused back into the patient.

— Globally, CAR T-cell therapy has been approved in the US and Europe for certain blood cancers such as leukemia and lymphoma. It is currently most effective in certain blood cancers (like leukemia and lymphoma), not all cancers.

#6. Oort Cloud

— The Oort Cloud is made up of ice space debris, some of which are larger than mountains and orbit our Sun at distances of up to 1.6 light years. This shell of material is thick, ranging from 5,000 to 100,000 astronomical units. One astronomical unit (AU) is the distance from the Sun to Earth, which is approximately 93 million miles (150 million km).

— The Oort Cloud is the boundary of the Sun’s gravitational influence, where orbiting objects can turn around and return closer to our Sun.

— The Oort Cloud is located beyond the Kuiper Belt’s outer edge. This massive spherical shell encircles our solar system. It has never been directly observed, but its presence is anticipated using mathematical models and observations of comets that are believed to originate there.

#7. Vehicle-to-Vehicle (V2V) safety technology

— V2V or vehicle-to-vehicle communication is a wireless technology that will enable the vehicles to communicate or talk with one another to share real-time information like speed, location, acceleration, braking, etc. It is the sub-category of Vehicle-to-Everything (V2X) and comes under the umbrella of the Intelligent Transport System.

— The system is similar to the aviation sector technology, where aircraft broadcast their position, speed, altitude, and the nearby aircraft and ground stations receive it. While this system is fortified in the aviation sector across the world, the road sector is still evolving, and V2V is working in a few countries, mostly developed nations.

— Usually, V2V systems have a range of 300 metres and can detect vehicles in this range. For instance, if a car applies brakes suddenly, the nearby vehicles will get an alert to slow down before seeing it. This will help in reducing crashes.

#8. Long Range Anti-Ship Hypersonic Missile (LR-AShM)

— The missile system is designed to meet the coastal battery requirements of the Indian Navy. The LR-AShM is capable of engaging static and moving targets and is designed to carry various payloads to a range of around 1,500 kilometers.

— This missile follows a quasi-ballistic trajectory with hypersonic speeds starting at Mach 10 (multiples of speed of sound) and maintaining average Mach 5 with multiple skips. Ballistic missiles are boost-powered initially and then travel unpowered on a high, arched trajectory. Quasi-ballistic missiles begin ballistically but fly lower and manoeuvre in flight to change course and evade interception.

— The LR-AShM is configured with a two-stage solid propulsion rocket motor system. These propulsion systems boost the missile to the required hypersonic velocities. Stage-1 of the vehicle is separated after it is spent. After Stage-II burnout, the vehicle performs an unpowered glide with required manoeuvres in the atmosphere before engaging the target.

— It has high aerodynamic efficiency which means that it moves through the air with minimal drag while generating effective lift and control, allowing it to fly farther, faster, or more accurately using the same amount of energy.

#9. GPS interference

— GPS interference includes spoofing and jamming, two types of deliberate cyber-attacks on Global Positioning System (GPS) signals that disrupt or confuse vehicle navigation systems. Spoofing and jamming are often used interchangeably, however they refer to significantly different types of interference.

— GPS jamming, also known as GPS intervention, occurs when a device (jammer) emits strong radio signals on GPS frequencies in order to overcome weaker signals. This impairs the operation of GPS systems by preventing receivers from determining location or time.

— GPS spoofing occurs when a device transmits signals on the same frequencies utilised by GPS satellites, overpowering or blocking GPS receivers from acquiring or sustaining the correct satellite signals. Unlike jamming, which completely interrupts transmissions, spoofing tricked the receiver into believing fake data.

#10. Cyanobacterial engineered living material (C-ELM)

— The biomaterial, known as a cyanobacterial engineered living material (C-ELM), incorporates living cyanobacteria within translucent panels that can be mounted on the interior walls of buildings. As the microorganisms grow through photosynthesis, they capture carbon dioxide from the air.

— Through a process called biomineralisation, the captured CO2 is converted into calcium carbonate, effectively trapping the carbon. A kilogram of C-ELM can capture up to 350g of carbon dioxide, while the same amount of traditional concrete would emit approximately 500g of CO2. A wall covered with 150 square metres of these panels could sequester about one tonne of carbon dioxide. C-ELM continues to capture CO₂ during use through ongoing photosynthesis. The potential of this biomaterial is immense. If scaled up and widely implemented, it could significantly reduce the construction industry’s carbon footprint.

#11. Working of the induction stoves

— Beneath the smooth ceramic or glass surface of an induction cooktop sits a tightly wound coil of copper wire. Switching the stove on completes the circuit and allows the flow of alternating current (AC) through the wire. The alternating current generates a rapidly fluctuating magnetic field directly above the cooktop.

— This changing magnetic field passes effortlessly through the glass surface and the surrounding air without heating either the surface or the air. This allows the cooktop surface to largely maintain its temperature. Any warmth it acquires is from contact with the hot pan.

— So when the metal pan sits inside this intensely fluctuating magnetic field, it acts as a conductor. And localised, swirling electrical currents are generated inside the bottom of the pan itself. Known as eddy currents, these are pivotal to the heat-generation process.

#12. Uranium enrichment

— Enrichment is the process by which the concentration of Uranium-235 (U235) is increased in a sample of natural uranium, which is primarily more than 99 per cent Uranium-238 (U238). U-235 has industrial applicability due to its fissile nature, meaning its nucleus can be broken down (or is fissionable) through a process that produces energy, and is capable of sustaining a chain reaction.

— The majority of civilian nuclear reactors use “low enriched uranium” that has been enriched to between 3% and 5%. This signifies that 3–5% of the uranium in the sample is now uranium-235. That is enough to sustain a chain reaction and generate power.

India’s three-stage nuclear programme

— The higher the uranium enrichment, the smaller and lighter the weapon can be.

#13. Ethanol production

— Ethanol production involves fermentation of sugar by yeasts. In molasses or cane juice, sugar is present as sucrose. Cereal grains contain starch, a complex carbohydrate that has to first be extracted and broken down into simple sugars before further fermentation, distillation and dehydration to ethanol with 99.99% alcohol concentration.

— Currently, ethanol is covered under the goods and services tax (GST) regime. The ethanol used for blending with petrol attracts 5% GST. But petrol remains outside GST, attracting both the Central excise duty and State value added tax. And both ethanol-blended petrol and pure petrol are treated as identical for taxation purposes.

— Till 2017-18, ethanol was produced by distilleries attached to sugar mills only from so-called C-heavy molasses, a dark brown liquid byproduct of cane processing. From 2018-19, mills began making ethanol from an earlier ‘B-heavy’ stage molasses (having higher sucrose content available for fermentation) and also directly from whole sugarcane juice or syrup. They were encouraged to do so by the Modi government’s decision to pay mills more for ethanol manufactured from the B-heavy and direct cane juice/syrup routes, in order to compensate them for the revenues foregone from lower/nil recovery and sale of sugar.

#14. Atomic clocks

— India’s regional navigation system has been plagued by problems affecting its positioning data. The Indian Space Research Organisation (ISRO) informed that the atomic clock of one of the five remaining satellites that were still providing this data stopped working — meaning positioning data from the satellite IRNSS-1F was also lost.

— Atomic clocks combine a quartz crystal oscillator with an ensemble of atoms to achieve greater stability. In an atomic clock, the frequency of the quartz oscillator is transformed into a frequency that is applied to a collection of atoms. If the derived frequency is correct, it will cause many electrons in the atoms to change energy levels. If the frequency is incorrect, far fewer electrons will jump. This will determine if the quartz oscillator is off-frequency and by how much. A “correction” determined by the atoms can then be applied to the quartz oscillator to steer it back to the correct frequency.

— Atomic clocks are used onboard GPS satellites that orbit the Earth. Up to 50 times more stable than the atomic clocks on GPS satellites, NASA’s Deep Space Atomic Clock is intended to be the most stable atomic clock ever flown in space. It achieves this stability by using mercury ions.

#15. Scramjet engine

— The Scramjet engine designed by ISRO uses Hydrogen as fuel and the Oxygen from the atmospheric air as the oxidiser.

— Ramjets work most efficiently at supersonic speeds around Mach 3, three times the speed of sound. However, the ramjet efficiency reduces once the vehicle reaches hypersonic speeds – above Mach 5. This is where the Supersonic Combustion Ramjet or Scramjet engine comes in. It efficiently operates at hypersonic speeds and allows supersonic combustion.

— The fundamental change in a scramjet is that the air does not slow down in its combustion chamber but stays supersonic throughout the engine. This makes the design, development and operation of the scramjet far more challenging.

#16. Earthset

— “Earthset” is a historic photograph taken on April 6, 2026, by the Artemis II crew, showing Earth dipping below the lunar horizon as seen from their spacecraft.

— The Artemis II crew, Nasa astronauts Reid Wiseman, Victor Glover, and Christina Koch, along with Canadian astronaut Jeremy Hansen, named the moment “Earthset” in reference to the famous “Earthrise” photograph taken during the Apollo 8 mission in 1968.

#17. Polar Satellite Launch Vehicle

— The PSLV, or Polar Satellite Launch Vehicle, is what is known as a four-stage rocket. The stages refer to different parts of the rocket, each of which have their own engines and fuel. Each of these stages sequentially take charge of propelling the mission. They get detached and discarded after doing their job. The stages are sometimes also used to refer to the different phases of the mission flight.

Stages of PSLV

— The first stage involves the lift-off. This is a near vertical journey till an altitude of about 50-60 km. This is the stage that requires the most work because the rocket has to fight gravity as well as atmospheric drag. For this reason, this stage needs a very heavy engine and lots of fuel.

— In the case of the PSLV, the first stage uses a solid propellant as fuel. The first stage forms a large part of the rocket, and constitutes the bulk of its weight. This stage lasts barely two minutes, during which a huge amount of fuel is consumed. After the fuel is spent, this part of the rocket becomes deadweight. So, it is jettisoned. It detaches from the main body of the rocket, and falls off, passing the baton to the second stage.

— During the second stage, the rocket continues to move vertically — and horizontally at the same time as it prepares to get into orbit. The second stage in the PSLV involves the famous, indigenously developed Vikas engine and a liquid fuel. This stage takes the vehicle to about 220-250 km from Earth’s surface before burning out.

— In the third stage, the vehicle is moving almost entirely horizontally, going around the Earth in an orbit, or rather a sub-orbital trajectory. To maintain this trajectory, and avoid falling towards the Earth, it needs to travel at very high velocities, usually 26,000 to 28,000 km per hour. The third stage is, therefore, about rapid acceleration. The PSLV rocket burns solid fuel to achieve this.

— The vehicle begins to go around the Earth at very high speeds, but does not yet reach its designated orbit. That happens in the fourth stage, which involves precisely placing the satellite in the intended orbit.

#18. Kessler Syndrome

— Scientists have long warned about the increasing amount of debris circling Earth. It could be anything from a dead satellite to fragments from earlier missions. The danger often raised is that of Kessler Syndrome – a scenario where collisions lead to even more space debris, which may increase the chances of other collisions.

— Most space junk moves very fast; sometimes, it moves faster than 17,500 mph. Experts estimate that, while millions of objects larger than a centimetre are in orbit, there are also tens of millions of even smaller fragments.

#19. Hydrofluorocarbons (HFCs)

— Hydrofluorocarbons (HFCs) are chemicals composed of carbon, hydrogen, and fluorine. Certain substances in this class of compounds are regarded by industry and scientists as long-term replacements to chlorofluorocarbons and hydrochlorofluorocarbons.

— Because HFCs do not contain chlorine, they have no direct effect on stratospheric ozone. Furthermore, pathways for ozone damage involving fragments formed during the decomposition of HFCs in the atmosphere (CF3 radicals) have been demonstrated to be minor.

— The most extensively utilised HFCs (HFC-134a and HFC-152a) have atmospheric lives of less than 12 years due to this reaction.

#20. Keytruda

— Keytruda is the brand name of pembrolizumab, an immunotherapy drug manufactured by US-based global pharma major Merck & Co (MSD) for treating several cancers. It belongs to a class called “checkpoint inhibitors” — drugs that remove the brakes preventing the body’s T cells, which are a crucial weapon in the body’s immune system, from attacking cancerous cells. In other words, it uses the body’s own immune system to fight cancer.

#21. Designer rice

— Scientists at CSIR – National Institute for Interdisciplinary Science and Technology in Thiruvananthapuram, Kerala, have developed this rice (a high-protein, low-GI innovation), which is touted to pack “three times the protein of normal grains while maintaining a low glycemic index to help manage diabetes”.

— The team of scientists did not opt for genetic modification. Instead they used “food-processing technology” where they took the broken rice, the bits usually sold at a discount, ground them into flour, and blended them with protein and micronutrients like iron, folic acid, and vitamin B12. They then “reformed” this mixture into grains that look, feel, and taste exactly like the rice we know, their press statement read.

#22. Fast Breeder Reactor (FBR)

— With India’s first indigenous fast breeder reactor (FBR) at Kalpakkam reaching criticality, indigenous FBRs are likely to play a critical role in the country’s long term energy security. While FBRs represent the future, pressurised heavy water reactors (PHWRs) will continue to play their pivotal role until the technology matures.

— India’s nuclear power programme is based on the sequential three-stage programme where in the first stage is PHWR using natural uranium. The fuel for FBR (in the second stage) comes from PHWR, which is plutonium. Because the yield of plutonium is very good in PHWR.

— As stated, the fuel for FBR is plutonium plus depleted uranium. FBRs initially use plutonium plus depleted uranium to obtain Uranium-233 (U-233) from the Thorium-232 (Th-232), which is used as a blanket in such reactors. Thus, we breed more fuel than we consume and hence it is named Breeder Reactor.

— In the third stage, it is Th-232 that will get converted into U-233, which would be fuel for the advanced reactors. This is how it completes the whole nuclear power programme and we will become self-independent as far as fuel is concerned. FBR is basically one of the intermediate steps in completion of our three stage programme.

— FBRs do not use light water as moderator or coolant; they rely on fast neutrons and typically use liquid sodium as coolant.

#23. Dark matter

— Dark matter is not the opposite of normal matter, but it does not get affected by electromagnetic forces and light, which means it lacks any electrons. This makes all dark matter invisible, as it cannot be interacted with at present with any matter created, since everything is created by atoms. This makes it extremely difficult to observe directly, as it can only be studied through its gravitational effects.

— According to the study, as dark matter particles slowly decayed in the early universe, they may have released small amounts of energy that changed the chemistry of the first gas clouds. Instead of that massive gas breaking down into stars – the usual route to black hole formation- some of these clouds may have collapsed directly into massive black hole seeds, effectively speeding up and skipping billions of years of cosmic biography.

#24. Magnesiochangesite-(Ce)

— Magnesiochangesite-(Ce) is a rare earth-bearing phosphate mineral with distinctive physical and chemical characteristics. Researchers describe it as colourless and transparent, with a glass-like lustre. It is fragile, tends to fracture like a shell, and emits a glow when exposed to UV light.

— The mineral was found in a lunar meteorite that was named Pakepake 005 and weighs about 44 grams. This meteorite was discovered in the Taklamakan Desert in 2024. It is recognised as a lunar meteorite because of its roundness and the black fusion crust created during its flight through Earth’s atmosphere.

#25. Diseases in News

(i) Hantavirus

— Named after the Hantan River in South Korea, hantavirus is a family of rodent-borne viruses that can cause serious illness and death in humans. However, the virus-carrying rats and other rodents do not fall ill to the virus.

— Human infection primarily occurs through contact with the urine, faeces, or saliva of infected rodents or by touching contaminated surfaces. It is also possible to get the infection by breathing air that contains viral particles stirred up from these droppings, according to the US Centers for Disease Control and Prevention (CDC).

— These viruses are generally not known to spread between people. However, some human transmission was recorded for the Andes strain, found in Argentina and Chile. The people on the ship are suspected to have been infected by the Andes hantavirus.

— Hantavirus pulmonary syndrome (HPS) is endemic to the Western Hemisphere and caused by New World hantaviruses. These are the deadlier of the two variants, killing a third of those who develop respiratory symptoms. The disease progresses from flu symptoms and fatigue to diarrhoea, vomiting and severe respiratory issues.

(ii) Thalassemia

— Thalassaemia is an inherited blood disorder in which the body does not produce enough haemoglobin, a red blood cell protein that transports oxygen throughout the body.

— When you have thalassaemia, your body produces less red blood cells, therefore you may experience symptoms of low blood count, or anaemia. Thalassaemia patients might have mild to severe anaemia. Severe anaemia can damage organs and cause death.

(iii) Nipah virus

— Nipah virus is a virus found in animals but can also affect humans.

— Fruit bats of the Pteropodidae family are the natural host of Nipah virus. Nipah virus usually transmits from infected bats and other animals to humans and can also be transmitted directly between people.

— There is currently no treatment or vaccine available for Nipah virus, however several candidate products are under development. Early intensive supportive care can improve survival.

(iv) Lysosomal storage disorders (LSDs)

— Lysosomal storage disorders (LSDs) are a diverse group of over 70 rare, inherited metabolic conditions that present significant diagnostic and therapeutic challenges, especially in genetically diverse and resource-limited settings like India.

— LSDs cause a buildup of toxic materials in the body’s cells. According to the Cleveland Clinic, patients with LSDs lack certain enzymes or the enzyme activator, a substance that helps the enzyme work. In their absence, the patient’s body fails to break down fats and sugars, which can accumulate and be harmful.

— There are treatments for only about 7% of rare diseases. Most patients who have treatable conditions also receive treatment intermittently.

(v) Lymphatic Filariasis (LF)

— Elephantiasis, also known as lymphatic filariasis, is a disfiguring disease caused by infection with nematodes (roundworms) from the Filariodidea family, which are transmitted through the bites of infected mosquitos.

— Lymphatic Filariasis (LF) is a disfiguring and debilitating disease that mainly develops in childhood. India aims to eliminate lymphatic filariasis (LF), often known as elephantiasis, by 2027.

— The disease is transmitted through the bite of a Culex mosquito that breeds in unclean or polluted water.

(vi) Bleeding eye virus

— MVD, sometimes known as the “bleeding eye virus,” is one of the worst diseases capable of infecting humans. Case mortality rates in previous outbreaks ranged from 24% to 88%, depending on the virus type and case care.

— Marburg is a filovirus, just like Ebola. Both infections are clinically identical and, while rare, can generate high-fatality epidemics.

— The first recognised MVD outbreak occurred in Marburg, Germany, in 1967. Following that, successive outbreaks have largely been recorded throughout Africa, most recently in Tanzania, Ghana, and now Rwanda.

(vii) Primary amoebic meningoencephalitis (PAM)

— PAM is a rare brain infection caused by Naegleria fowleri, also called ‘brain-eating amoeba’. The first case of PAM in India was reported in 1971, and the first case in Kerala was reported in 2016. From 2016 to 2023, the state had only eight cases. Last year, Kerala had 36 cases and nine deaths. PAM is caused by a different category of amoeba, which is found in dust and soil.

— Naegleria fowleri, a free-living amoeba or single-celled living organism, is the cause of PAM. It is found worldwide in warm, fresh soil and water, and it infects humans when it enters the body through the nose. It grows well at temperatures as high as 115°F (46°C), and it can endure brief exposure to warm temperatures. Warm freshwater environments including lakes and rivers, swimming pools, splash pads, surf parks, and other recreational areas with little or no chlorination are home to amoeba.

— People cannot get infected with Naegleria fowleri from drinking water contaminated with the amoeba. PAM is also non-communicable.

#26. Space Missions in News

(i) Voyager 1

— Launched in 1977, Voyager 1 is one of the most important space missions ever undertaken. It was originally sent to study the outer planets, including Jupiter and Saturn, but it went far beyond its initial goal. Today, it is the most distant human-made object in space, travelling through interstellar space at high speed.

— Its role has evolved. Currently, Voyager 1 serves as an asset for scientists to learn more about interstellar space conditions and the heliosphere, the area where the Sun has no influence. Together with its sister spacecraft, Voyager 2, it is the only probe that can deliver direct information from this previously unstudied region.

— The primary motivation for turning off the instrument suite was quite obvious. Voyager 1 had run out of power to operate all of its systems. The spacecraft is equipped with a radioisotope thermoelectric generator that utilises the heat generated by decaying plutonium and transforms it into electric power. The energy level, however, has declined gradually since the probes were launched; about 4 watts disappear every year.

(ii) Vikram-1 launcher

— Among Skyroot’s many small launch vehicle projects, Vikram-1 is a multi-stage launch vehicle with solid and liquid fuel-based engines designed for launching satellites weighing up to 350kg to low earth orbit. The low earth orbit is the region of space from 160 km to 2,000 km above the surface of Earth. The number of satellites being launched in this region has skyrocketed in recent years, with many being the Starlink communication satellites.

— What makes Vikram-1 different is that the rocket is made of carbon composite instead of metals, and houses a 3D-printed indigenously made engine — making its manufacturing and assembly easier, quicker and cheaper.

— The launch vehicle has been named to honour Dr Vikram Sarabhai, considered to be the father of the Indian space programme, and its propulsion systems honour several other scientific greats — the solid propulsion system is called Kalam, the liquid Raman, and the cryogenic Dhawan.

(iii) OSIRIS-REx mission

— OSIRIS-REx is the first U.S. mission to collect a sample from an asteroid. It returned to Earth on Sept. 24, 2023, to drop off a capsule with material from asteroid Bennu.

— After dropping off the sample capsule through Earth’s atmosphere, the spacecraft was renamed OSIRIS-APEX and sent on a new mission to explore asteroid Apophis in 2029.

(iv) Artemis II mission

— Artemis II builds on the success of the uncrewed Artemis I in 2022, and will demonstrate a broad range of capabilities needed on deep space missions. The Artemis II test flight will be NASA’s first mission with crew aboard the SLS (Space Launch System) rocket and Orion spacecraft.

Artemis II mission

— This was the first time humans travel beyond low-Earth orbit and circle the Moon since the final Apollo mission in 1972.

— The crew includes Nasa astronauts Reid Wiseman, Victor Glover, and Christina Koch, along with Canadian Space Agency astronaut Jeremy Hansen. Together, they will travel aboard the Orion spacecraft, which will loop around the Moon before returning to Earth. The mission is designed to test systems and procedures needed for future lunar landings.

(v) LVM-3

— LVM-3, earlier referred to as Geosynchronous Launch Vehicle Mark 3 or GSLV Mk 3, uses solid, liquid, as well as cryogenic-fuel based engines to put up to 8,000 kg in low earth orbit (up to an altitude of 2,000 km from Earth’s surface) and up to 4,000 kg in geosynchronous orbit (about 36,000 km).

— The GSLV-Mk3 rocket was later adapted in 2022, amid the Russia-Ukraine war, to launch 72 OneWeb satellites in two launches to low earth orbit, prompting the change in name of the rocket. The GSLV name implied it was meant to deposit satellites only to the geosynchronous orbit, but the OneWeb missions showed that this rocket could be used for other purposes as well.

(vi) Sentinel-6B

— Sentinel-6B was launched from the Vandenberg Space Force Base in California. It is an ocean-tracking satellite with six onboard science instruments that will measure the rising sea levels and its impacts on the planet.

— Sentinel-6B will orbit Earth at a speed of 7.2 km per second, completing one revolution every 112 minutes.

— Sentinel-6B is a joint mission between the United States’ NASA and NOAA, and the European Space Agency; it is the latest in a series of satellites launched since the 1990s, mainly by NASA, to measure the sea-level changes from space. Data from Sentinel-6B is expected to improve the accuracy of weather forecasts, including storm and flood predictions, enabling administrators to make better real-time decisions to safeguard public property and protect coastal infrastructure.

(vii) ESCAPADE

ESCAPADE is the first multi-spacecraft orbital science mission to the Red Planet. Its twin orbiters will conduct simultaneous observations from several places around Mars. The measurements will disclose how the planet responds to space weather in real time, as well as how the Martian magnetosphere changes over time.

ESCAPADE will investigate how Mars’ magnetic field directs particle fluxes around the planet, how energy and momentum are transferred from the solar wind through the magnetosphere, and what processes govern the flow of energy and matter into and out of the Martian atmosphere.

(viii) Vyommitra

— Vyommitra is India’s first humanoid robot developed by ISRO to assist in human space missions. With human-like expressions, speech, and intelligence, Vyommitra stands at the heart of Gaganyaan, India’s maiden human spaceflight programme.

— The ISRO unveiled Vyommitra in early 2020. The name is derived from Sanskrit — “Vyoma” meaning space, and “Mitra” meaning friend — literally, “friend in space”. — This humanoid robot is designed to act as an intelligent, anthropomorphic companion for astronauts, handling both mechanical tasks and communication duties aboard India’s crewed spacecraft.

(ix) NISAR mission

— The satellite was launched on the GSLV-F16 and put in a 734 km sun synchronous orbit — an orbit in which the satellite reaches over a place at the same time each day. The satellite will scan the entire globe every 12 days, providing a series of very detailed images of the Earth’s surface.

— NISAR, which stands for NASA-ISRO Synthetic Aperture Radar, will provide an unprecedented view of the planet. Weighing 2,392 kg it will be the first satellite ever to observe the Earth in two frequencies — NASA’s L-band and ISRO’s S-band. “Each system’s signal is sensitive to different sizes of features on Earth’s surface, and each specializes in measuring different attributes, such as moisture content, surface roughness, and motion,” according to NASA.

#26. Hydrogen as fuel

— Hydrogen is appealing because it burns cleanly: when combined with oxygen in a fuel cell, it produces electricity and releases only water vapour as exhaust. Unlike batteries, which must be recharged, hydrogen can be refueled quickly — much like petrol or diesel — making it attractive for long-haul trucks, buses, ships, and potentially even planes.

— The biggest challenge in implementing hydrogen as fuel is its low density. At room temperature, one kilogram of hydrogen would fill about 11 cubic meters — the size of a small bedroom. Petrol, by contrast, packs the same mass into just over a liter.

#27. Metal-Organic Frameworks (MOFs)

— MOFs are a class of materials composed of metal ions connected by organic molecules, forming a three-dimensional network with large, porous cavities. This design allows gases and liquids to flow through, making MOFs highly adaptable for various applications.

— Metals can form bonds in multiple directions, and thus metal ions are the anchors here, like joints in a scaffolding. Organic molecules link them together. Organic molecules are flexible, can form rings and chains, and can be designed to have chemical groups with specific properties.

— The unique properties of MOFs have led to their application in various fields:

(i) Water harvesting: MOFs can extract water from dry air, offering a potential solution for water-scarce regions.

(ii) Pollutant Removal: They can filter out harmful substances like PFAS from water, addressing environmental contamination.

(iii) Carbon capture: MOFs are effective in capturing carbon dioxide, aiding in efforts to mitigate climate change.

(iv) Hydrogen storage: Their porous nature allows for the safe storage of hydrogen, crucial for clean energy applications.

— Most MOFs are weak electrical conductors and so are not employed as conductors. Additionally, MOFs lack the chemical and mechanical stability required for long-term maritime corrosion protection.

#28. Doppler weather radars

— In radars, a beam of energy, called radio waves, is emitted from an antenna. When this beam strikes an object in the atmosphere, the energy scatters in all directions, with some reflecting directly back to the radar.

— DWR can provide information on both the position of targets as well as their movement. It does this by tracking the ‘phase’ of transmitted radio wave pulses; phase meaning the shape, position, and form of those pulses. As computers measure the shift in phase between the original pulse and the received echo, the movement of raindrops can be calculated, and it is possible to tell whether the precipitation is moving toward or away from the radar.

— In India, DWR of varying frequencies — S-band, C-band and X-band — are commonly used by the IMD to track the movement of weather systems and cloud bands, and gauge rainfall over its coverage area of about 500 km. The radars guide meteorologists, particularly in times of extreme weather events like cyclones and associated heavy rainfall. An X-band radar is used to detect thunderstorms and lightning, whereas a C-band radar helps in cyclone tracking.

#29. Measurement of pollutants in Air Quality Monitoring Stations

— Particulate matter is measured using Beta Attenuation Monitors (BAM), which rely on the beta ray attenuation principle. A small Carbon-14 or Krypton-85 source emits beta rays through a clean patch of filter tape. After air is drawn through and dust collects on the tape, the instrument re-measures the spot. Fewer beta rays pass through, and the decline in signal is used to calculate PM2.5 and PM10 concentrations.

— Sulphur dioxide is measured by UV fluorescence, which detects the weak glow SO2 emits under ultraviolet light.

— Ozone is measured by UV photometry, which tracks how much UV light it absorbs.

— Carbon monoxide is measured using non-dispersive infrared (NDIR) absorption, based on how much infrared light CO absorbs.

— Nitrogen oxides are measured through chemiluminescence, where instruments detect the faint light produced when the gases react with ozone inside the analyser.

— Ammonia is measured using optical spectroscopy based on its characteristic absorption of light.

#30. NUTEC Plastics

— NUTEC Plastics is the IAEA’s flagship initiative to address the global challenge of plastic pollution.

— It brings together governments and partners from all over the world to combat plastic pollution on two fronts: at the source by introducing innovative technology to enhance plastic recycling, and in the ocean, where the majority of plastic trash ends up.

— Nuclear science and technology can play a vital role on both fronts. Irradiation can be used to treat existing plastics and make them suitable for reuse, extending present recycling potential and allowing for broader and higher-value reuse, while nuclear science is used to identify, trace, and monitor plastics in the ocean, particularly microplastics.

#31. Green crackers

— Scientists sought to reformulate these mixtures by reducing toxic metals and introducing additives that suppress dust. Green crackers, branded as SWAS (Safe Water Releaser), STAR (Safe Thermite Cracker) and SAFAL (Safe Minimal Aluminium), typically replace barium nitrate with potassium nitrate or strontium salts, limit aluminium content, and add compounds like zeolite and iron oxide to capture soot.

— These compounds produce brilliant colours and loud bangs but also emit fine particulate matter (PM₂.₅ and PM₁₀), sulphur dioxide (SO₂), and nitrogen oxides (NOₓ) — all major contributors to smog.

#32. Brown dwarfs

— Brown dwarfs are curious celestial bodies that share some similarities with stars and others with planets. For instance, these objects form like stars from collapsing clouds of gas and dust. However, they do not have enough mass to consistently fuse hydrogen, a process that heats a star and makes it shine. That is why they are often known as “failed stars”.

— They have atmospheres similar to gas giant planets such as Jupiter and Saturn. Their atmospheres can consist of clouds and molecules like H2O. Brown dwarfs can also be up to 70 times more massive than Jupiter.

— Brown dwarfs can be difficult to detect as they are cold and faint. As a result, astronomers typically search for brown dwarfs orbiting companion stars, which often burn brighter. This also helps them study these celestial bodies because if a brown dwarf is part of a multiple system with a brighter star, the chances are they were formed out of the same material, at the same place and time.

#33. Integrated Air Defence Weapon System (IADWS)

— The ministry of Defence (MoD) said that the Defence Research and Development Organisation (DRDO) has successfully conducted the first flight-tests of an Integrated Air Defence Weapon System (IADWS). The test was conducted off the coast of Odisha, in which three different targets were simultaneously destroyed at different ranges and altitudes.

— The IADWS is a multi-layered air defence system, which includes three components — Quick Reaction Surface to Air Missiles (QRSAM), the advanced Very Short Range Air Defence System (VSHORADS) missiles, and a high-power laser-based Directed Energy Weapon (DEW).

#34. Small Modular Reactors (SMRs)

— SMRs are advanced nuclear reactors with power generation capacities ranging from less than 30 MWe to over 300 MWe. It offers a versatile, scalable, and cost-effective alternative to traditional big nuclear reactors.

— SMRs’ modular design enables factory-based manufacture, lowering construction deadlines and costs, making them suitable for both on-grid and off-grid applications, including distant deployment. India is extensively researching Small Modular Reactors (SMRs) as a critical component of its energy transition strategy, with the goal of achieving net-zero emissions while maintaining energy security.

#35. GLP-1

— GLP-1 is both an incretin hormone and a neurotransmitter. In physiology, it is secreted from the small intestine and from the hindbrain after we eat a meal.

— It travels to the pancreas, where it helps to regulate our blood sugar by increasing insulin and decreasing glucagon. This is what we call the incretin effect. This effect is blood glucose-dependent, meaning it is only if the blood glucose is elevated that it has an effect here.

— GLP-1 also impacts centres in the brain associated with control of hunger and satiety, to effectively tell us that we have had enough to eat and need to stop eating.

— There are receptors that GLP-1 binds to in many organs in the body, and GLP-1 also has beneficial effects in many of these organs, such as the kidney, liver, and cardiovascular system. GLP-1’s effects in the pancreas and brain are the important ones to help control blood glucose and body weight.

🚨 Click Here to read the UPSC Essentials magazine for May 2026. Share your views and suggestions in the comment box or at manas.srivastava@indianexpress.com🚨 

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