Astronomy & Space Technology

Context: Indian Space Research Organisation (ISRO) has announced the launch of its first analog or simulated space mission at Leh in Ladakh. 

What are Analog Space Missions?

• Analog missions are field tests in locations that have physical similarities to the extreme space environments. NASA engineers and scientists work with government agencies, academia, and industry to gather requirements for testing in harsh environments before they are used in space. 
• Tests include:
  • New technologies, robotic equipment, vehicles, habitats, communications, power generation, mobility, infrastructure, and storage. 
  • Behavioural effects – such as isolation and confinement, team dynamics, menu fatigue etc.
• Significance: Analog missions provide space agencies with data about strengths, limitations, and the validity of planned human-robotic exploration operations. They also define ways to combine human and robotic efforts to enhance scientific exploration. 

India’s first Analog Mission: 

• Located in Leh, Ladakh, the mission includes a compact, inflatable habitat named Hab-1 which will simulate life in an interplanetary habitat.
• Aim: To study the challenges of extra-terrestrial conditions, as part of efforts towards developing a long-term human spaceflight programme.
• Hab-1 is designed to mimic environments on Mars and the Moon. The simulation will explore the conditions of an interplanetary habitat, testing new technologies, robotic equipment, vehicles, habitats and communications. 
• The mission is spearheaded by ISRO’s Human Spaceflight Centre and brings together partners from AAKA Space Studio, the University of Ladakh, IIT Bombay, and is supported by the Ladakh Autonomous Hill Development Council. 

Why was Ladakh chosen?

• Ladakh’s extreme isolation, dry climate, and barren, high-altitude terrain make it ideal for simulating conditions similar to Mars and the Moon.
• Similarities: 
  • Both Moon and Ladakh have extremely dry environments. 
  • Ladakh experiences significant temperature fluctuations, similar to both the Moon and Mars. 
  • Ladakh’s rocky, barren terrain resembles the terrain of the Moon and Mars. 
•  Dissimilarities:
  • The Moon has virtually no atmosphere, whereas Mars has a thin atmosphere, whereas, Ladakh is a part of Earth’s atmosphere.
  • The Moon has no water vapour in its atmosphere, Mars has some water vapour, whereas Ladakh's atmosphere, through dry, still contains some moisture. 
  • The Moon has an intense thermal radiation caused by the direct sunlight which is hard to replicate on Earth.    

Significance:

• Hab-1 allows scientists to study the effects of isolation and confinement on human health and performance and includes essentials such as a hydroponics farm, kitchen, and sanitation facilities. This setup will help study the challenges astronauts will face in a base station beyond Earth and prepare them accordingly.
• Ladakh’s environment presents an opportunity for researchers to gather critical data that will support India’s Gaganyaan program and future missions. 

Context: The Union Ministry of Earth Sciences has approved an X-band radar to be installed in Kerala's Wayanad district, which was hit by devastating floods and landslides killing more than 200 people in July 2024. 

How do radars work?

• Radar is short for ‘radio detection and ranging’. The device uses radio waves to determine the distance, velocity, and physical characteristics of objects around the device. A transmitter emits a signal aimed at an object whose characteristics are to be ascertained (in meteorology, this could be a cloud). A part of the emitted signal is echoed by the object back to the device, where a receiver tracks and analyses it.
• One of the important kinds of radars is Weather radar or a Doppler radar. 
  • The Doppler effect is the change in frequency of sound waves as their source moves towards and away from a listener. 
  • In meteorology, Doppler radars can reveal how fast a cloud is moving and in which direction based on how the cloud’s relative motion changes the frequency of the radiation striking it. 
  • Modern Doppler radars can monitor weather conditions and anticipate new wind patterns, the formation of storms, etc.

What is an X-band radar?

• Doppler radar relies on Rayleigh scattering, when the scatterer is much smaller than the wavelength of the radiation. A radar trying to ‘see’ smaller particles like rain droplets or fog will need to use radiation of lower wavelengths, like in the X-band. 
• An X-band radar is radar that emits radiation in the X-band of the electromagnetic spectrum: 8-12 GHz, corresponding to wavelengths of around 2-4 cm (this is in the microwave part of the spectrum.)
  • Due to operating at a smaller wavelength, X-band radars are more sensitive and can detect smaller particles compared to other radar bands. The smaller wavelengths allow the radar to produce images of higher resolution.
  • However, the greater the frequency of any radiation, the faster it will be attenuated. So, X-band radars have a relatively shorter range. 
  • X-band radars are typically used for studies about cloud development and light precipitation due to their abilities to detect tiny water particles and snow.
• Significance: In Wayanad, the new radar is expected to be able to monitor the movements of particles, such as soil, to inform landslide warnings. The device will also perform high temporal sampling, i.e., rapidly sample its environs, allowing it to spot particle movements happening in shorter spans of time.

How many radars does India have?

• The India Meteorological Department (IMD) started using radar for weather applications in the early 1950s. The first indigenously designed and manufactured X-band storm detection radar was installed in 1970 in New Delhi. In 1996, IMD replaced 10 outdated X-band radars with digital X-band radars. In its X-band radar network, India has both wind-finding and storm-detecting radars, and some with dual capabilities. 
• The country also uses S-band radars (2-4 GHz) for long-range detection. The first S-band cyclone detection radar was installed in Visakhapatnam in 1970 and the first locally made variant was commissioned in Mumbai in 1980.
• In September 2024, the Ministry of Earth Sciences said India is set to have 56 additional Doppler radars in a few years. On September 11, the Union Cabinet cleared the ₹2,000-crore ‘Mission Mausam’ to upgrade meteorological infrastructure in the country. This includes installing up to 60 meteorological radars until 2026 under the Mission’s first phase.
• The government has started the process to procure and install 10 X-band Doppler radars to improve weather forecasting in the northeast States and in Himachal Pradesh’s Lahaul and Spiti district.

A telescope is an optical instrument that allows us to observe distant objects by collecting and focusing light. 

• Contrary to the common belief that telescopes are primarily designed to make objects appear larger, their main function is to increase the brightness of celestial objects. This is achieved through their light-gathering power, which determines how much light they can collect from faint or distant sources.
• The key factor that influences a telescope’s light-gathering ability is its aperture (the size of the opening through which light enters). The larger the aperture, the more light the telescope can capture, resulting in brighter and clearer images of celestial bodies.
  • Aperture refers to the diameter of the telescope's opening (objective lens) that controls how much light is allowed to pass through. A larger aperture allows more light to be gathered, making faint objects, such as distant stars and galaxies, visible.
  • For instance, when the human eye’s pupil is fully dilated, its aperture area is about 153.9 square millimetres. In contrast, a small 0.07-meter reflecting telescope (commonly available as a toy) has an aperture area of 18,241.4 square millimetres. This means the telescope has 118.5 times more light-collecting area than the human eye, allowing it to capture much more light and make dim objects easier to see. 

Two types of telescopes:

Celestial objects emit light in all directions. But only light rays travelling in the direction of the earth will reach us. And when these rays reach us after a lengthy journey, they are virtually parallel.

There are two ways to concentrate these rays and create an image. 

Reflecting Telescopes:

• In a reflecting telescope, rays reflected by the primary mirror (concave mirror) are diverted to a secondary mirror, which reflects them into an eyepiece with a small lens (convex lens) to enhance the image. 
• The image produced by this reflecting telescope is real, inverted, and smaller. Most contemporary telescopes are such reflecting telescopes. E.g., Hubble Space Telescope, James Webb Space Telescope, Very Large Telescope (Chile) etc. 
• Primarily used for Deep-Sky observation: Reflecting telescopes have larger mirrors (and thus larger apertures). Larger apertures allow reflectors to gather more light, which is crucial for viewing faint objects like distant galaxies, nebulae, and star clusters. 

• Advantages:
  • More cost-effective to produce larger mirrors (for reflecting telescopes) than larger lenses (used in refracting telescopes).
  • No chromatic aberration since mirrors reflect all wavelengths equally.
• Disadvantages:
  • Requires regular maintenance (e.g., mirror alignment).

Refracting telescope:

• A refracting telescope is an optical instrument that uses lenses to gather and focus light in order to magnify distant objects. It typically consists of two main lenses:
  • Objective Lens: The primary lens that collects light and brings it to a focus, forming an image.
  • Eyepiece Lens: The secondary lens that magnifies the image formed by the objective lens for viewing.
• Primarily used for high-magnification observations: Refractors excel at viewing bright objects (e.g., planets, Moon, stars) because their lenses can focus light sharply without the interference of additional mirrors. They are better suited for high-magnification observations where sharp, clear images are priority. E.g., Yerkes Observatory Refracting Telescope, the US. 

• Advantages:
  • Produces sharp, high-contrast images, especially for planetary observations.
  • Generally easier to maintain than reflecting telescopes.
• Disadvantages:
  • Can become expensive as lens size increases. (Can be more expensive than reflecting telescopes of the same aperture)
  • Limit on lens size: To observe fainter cosmic objects, much bigger lenses are required, which will slump under their own weight and distort the image. The maximum practicable lens size in a refracting telescope is around 1 m. The world’s largest refracting telescope is at Yerkes Observatory in the U.S., with a 1.02-m lens. 
  • Chromatic aberration (colour fringing) can occur, especially in larger refractors.

Chromatic aberration:

• Chromatic aberration is a type of optical distortion that occurs when a lens fails to focus all colours of light at the same point. This results in a blurred image with colour fringes around objects, especially noticeable in high-contrast scenes.
• Cause: Light consists of various wavelengths (colours). Lenses bend (refract) light differently based on its wavelength. Shorter wavelengths (blue light) are bent more than longer wavelengths (red light).
• Since, mirrors reflect light (not refract), so, chromatic aberration is present in lenses, not in mirrors. Reflection does not depend on the wavelength of the light, all colours of light are reflected uniformly. 

Limits to reflecting telescopes: 

• A telescope with a higher limiting magnitude (Limiting magnitude is the brightness of the faintest object visible to an optical instrument) is required to look deep into the universe, which demands a larger primary mirror. However, there is a limit to the size of the primary mirror. A mirror wider than around 8.5 m will sink under its own weight, distorting its surface.
• Hence, instead of a single primary mirror, today’s large reflecting telescopes have many small mirrors. Each piece is small enough to remain firm without slumping. And when they are combined, the overall light-collecting area (aperture) is still large. E.g., James Webb Space Telescope’s primary mirror is composed of 18 hexagonal segments. These segments work together to form a single, large mirror with a diameter of 6.5 metres. 

Advanced telescopes around the world: 

• Large Binocular Telescope: The largest telescope to date is the Large Binocular Telescope (LBT), which has two 8.4-m-wide mirrors and an effective combined aperture of 11.9 m. It is located at the Mount Graham International Observatory in Arizona, USA.
• Extremely Large Telescope: The Extremely Large Telescope (ELT) is under construction atop the Cerro Armazones in the Atacama Desert in Chile, as part of the European Southern Observatory. It has five mirrors and a combined aperture of 39.3 m. It is expected to be completed by 2028. The ELT’s light-gathering power will exceed that of any telescope to date. Our eyes can discern two lights burning 30 cm apart and kept 1 km away. In perfect conditions, the ELT can distinguish two lights kept 30 cm apart from 12,000 km away.
• Subaru Telescope is an 8.2-m-wide Japanese telescope located at the Mauna Kea Observatory in Hawaii. It recently used 10 hours of exposure time to capture a faint celestial object with a visual magnitude of 27.7, which is 100-million-times fainter than what any human eye can detect. 
• James Webb Space Telescope (JWST): Launched in 2021 by NASA, JWST is orbiting the Sun at the L2 Lagrange point (1.5 million km from Earth). The infrared telescope has a 6.5 metre primary mirror. It detects near-infrared and mid-infrared wavelengths to observe faint and distant objects.

Why are telescopes setup on mountains?

The earth’s tumultuous atmosphere interferes with the telescope’s functioning. Telescopes are often set up on mountains for several key reasons:

• Reduced Atmospheric Interference: At higher altitudes the atmosphere is thinner. The thinner atmosphere absorbs and scatters less light, improving the visibility of faint celestial objects.
• Less Air Turbulence: Higher altitudes often experience less air turbulence compared to lower elevations, where weather systems can cause more turbulent air movement. This reduces blurring or distortion of images caused by atmospheric turbulence.
  • Space telescopes are more than 400 km above sea level, allowing them to entirely escape atmospheric disturbances. That is why the Hubble Space Telescope has a resolving power of around 0.04 arcsec, 10-times greater than the best ground-based telescopes.
• Clearer Skies: Higher elevations generally have lower humidity levels, which means there is less water vapour in the atmosphere. This helps reduce cloud cover and atmospheric absorption, allowing for more frequent and prolonged observations.
• Minimised Light Pollution: Mountain locations are often remote and away from large cities, which helps reduce light pollution and makes high-altitude locations ideal for clear, unobstructed observations.

Context: Two NASA astronauts aboard Boeing's Starliner will remain on the International Space Station for an extended period due to a malfunctioning propulsion system, which has been plagued by helium leaks. Meanwhile, SpaceX's Polaris Dawn mission has faced delays due to helium-related problems with ground equipment. This issue with helium leaks is not unique; similar problems have impacted past missions, including ISRO's Chandrayaan 2 and ESA's Ariane 5.

Helium’s unique properties:

• As the second lightest element after hydrogen, helium has an atomic number of 2 and is chemically inert-meaning it does not react with other substances or combust.
• This makes it ideal for pressurization and cooling systems in rockets and spacecraft.

Inert gases: 

• An inert gas is a type of gas that resists reacting chemically with other substances.
• These gases are less likely to form chemical compounds due to their low reactivity.
• The primary function of inert gases is to prevent unwanted chemical reactions, such as oxidation and hydrolysis, which can degrade sensitive samples.

Typically, the term ‘inert gas’ includes:

• Noble Gases: Helium, neon, argon, krypton, xenon, and radon.
• Pnictogen: Nitrogen.
• Chemical Compound: Carbon dioxide.
• However, the classification of gases as inert can be context-dependent.
• While noble gases are generally considered inert due to their stable electron configurations, some of them, including nitrogen and carbon dioxide, can react under specific conditions.
• Argon is the most frequently used inert gas. Its popularity is attributed to its high natural abundance (making up about 1% of the Earth's atmosphere) and its relatively low cost.

The non-reactivity of these gases is largely due to their complete valence electron shells, which contribute to their general stability.

• Additionally, helium has an extremely low boiling point of -268.9°C, which allows it to remain in a gaseous state even in the extremely cold environments where rocket fuels are stored.

Importance in rocketry:

• Achieving the requisite speeds and altitudes for rockets to reach and maintain orbit, demands highly precise and efficient fuel management.
• Heavier rockets necessitate significantly more energy to achieve and sustain their trajectories. This increased energy demand leads to higher fuel consumption and requires more powerful engines.
• The development, testing, and maintenance of these advanced engines are not only more complex but also more costly.
• Helium is crucial in addressing these challenges due to its unique properties and essential functions:
  • Helium is used to pressurize fuel tanks, ensuring that fuel flows continuously and smoothly to the rocket’s engines throughout the mission. As the rocket’s fuel is consumed during flight, helium replaces the volume left behind, maintaining consistent pressure and preventing any interruptions in fuel delivery.
  • In addition to pressurizing fuel tanks, helium is integral to cooling systems, especially in environments where rocket fuels and oxidizers are stored at extremely low temperatures. Helium’s low boiling point ensures it remains a gas even in these frigid conditions, facilitating effective cooling and temperature management.
  • As fuel and oxidizers are depleted, helium fills the resulting voids in the tanks. This ongoing replenishment of helium helps maintain stable internal pressure, which is crucial for the efficient operation of the rocket’s fuel systems and overall performance.

Usage and safety: 

• Helium’s non-reactive nature makes it suitable for interacting safely with the residual contents in fuel tanks.
• It is also employed in cooling systems to manage temperatures and prevent overheating. 
• Despite being non-toxic, helium can displace oxygen, making it unsuitable for breathing in high concentrations.

Prone to leaks: 

• Helium’s small atomic size and low molecular weight make it prone to escaping through small gaps or seals in storage tanks and fuel systems.
• But because there is very little helium in the Earth’s atmosphere, leaks can be easily detected-making the gas important for spotting potential faults in a rocket or spacecraft’s fuel systems.
• For instance, in May, shortly before Boeing’s Starliner was set to launch its first crewed mission, sensors detected a minor helium leak in one of the spacecraft’s thrusters. NASA assessed this leak as low-risk but it contributed to subsequent issues.
• Additional leaks were detected in space after Starliner launched in June, contributing to NASA’s decision to bring Starliner back to Earth without its crew.
• The frequency of helium leaks across space-related systems, have highlighted an industry-wide need for innovation in valve design and more precise valve-tightening mechanisms.

Alternatives and industry trends; 

• In response to helium-related challenges, some space missions have explored alternative gases such as argon and nitrogen, which are also inert and potentially less expensive. 
• However, helium remains the dominant choice due to its specific advantages.
• A notable attempt to move away from helium was Europe’s new Ariane 6 rocket, which replaced the helium system of its predecessor, Ariane 5, with a novel pressurization system.
  • This system converts a small portion of its primary liquid oxygen and hydrogen propellants into gas for pressurizing these fluids.
  • Despite this innovation, the system experienced failure during the final phase of Ariane 6’s inaugural launch, illustrating the ongoing difficulties in achieving reliable pressurization systems without helium.

Missions mentioned in the news: 

Boeing Starliner:

• The Boeing Starliner, also known as CST-100, is a spacecraft developed to transport crew members to and from the International Space Station (ISS) and other low-Earth orbit destinations.
• Designed under NASA's Commercial Crew Program (CCP), the spacecraft comprises a reusable crew capsule and an expendable service module.
• Slightly larger than the Apollo command module or the SpaceX Crew Dragon, but smaller than the Orion capsule, the Starliner is capable of carrying up to seven astronauts.
• The Starliner can remain docked to the ISS for up to seven months and is launched aboard an Atlas V N22 rocket. 
• The Crew Flight Test (CFT), launched in June 2024, encountered multiple malfunctions, including helium leaks and failures in five of the eight aft-facing reaction control system thrusters during its approach to the ISS.
• Consequently, NASA deemed it too risky for returning astronauts to Earth on Starliner.
• The uncrewed Starliner CFT-1 ultimately landed in September 2024.

Polaris Dawn:

• Polaris Dawn is an upcoming private human spaceflight mission operated by SpaceX, commissioned by Shift4 CEO Jared Isaacman.
• It is the first of three planned missions in the Polaris program, marking the 14th crewed orbital flight of a SpaceX Crew Dragon spacecraft.
• The mission will carry a four-member crew. 
• The crew will be launched into a highly elliptical orbit, reaching up to 1,400 kilometers (870 miles) from Earth-the farthest human distance from Earth since NASA's Apollo program.
• This trajectory will allow the crew to pass through portions of the Van Allen radiation belts, providing a unique opportunity to study the effects of space radiation and spaceflight on human health.

• The Van Allen radiation belts are zones of energetic charged particles, primarily from the solar wind, trapped by Earth's magnetic field.
• They form a barrier that prevents the most energetic electrons from reaching Earth. 
• The belts consist of two main regions: 
  • Outer Belt: Contains high-energy particles from the Sun, trapped within Earth's magnetosphere.
  • Inner Belt: Formed by interactions between cosmic rays and Earth's atmosphere.
• The belts were discovered in 1958 by American physicist James A. Van Allen using instruments on Explorer 1, the first U.S. spacecraft.
• This discovery marked the beginning of space physics, as it revealed previously unknown radiation zones around Earth.

• One of the key objectives of Polaris Dawn is to conduct the first-ever commercial spacewalk.
• This mission not only aims to push the boundaries of private space exploration but also to advance scientific understanding of how the human body is affected by the unique conditions of deep space.

Chandrayaan-2:

• Chandrayaan-2, is India's second lunar exploration mission, developed by the Indian Space Research Organisation (ISRO) after Chandrayaan-1.
• The mission includes three components: a lunar orbiter, the Vikram lander, and the Pragyan rover, all designed and developed in India.
• Its primary objective was to map the lunar surface, study its composition, and locate lunar water deposits.
• The mission was launched in July 2019 from the Satish Dhawan Space Centre in Andhra Pradesh using a LVM3-M1 rocket.
• Chandrayaan-2 entered in August 2019. An attempted landing by the Vikram lander in September 2019 failed due to a software error.
• Despite the crash, the lunar orbiter continues to function in orbit around the Moon. 
• A subsequent mission, Chandrayaan-3, was launched in 2023 and achieved a successful lunar landing.

Also read: Pragyan rover reveals signs of magma ocean on ancient moon

Ariane 6: 

• Ariane 6 is a European expendable launch vehicle developed by ArianeGroup for the European Space Agency (ESA) and operated by Arianespace.
• It serves as the successor to the Ariane 5 within the Ariane launch vehicle family.
  • Ariane-5 Rocket has been used to launch ISRO’s communication satellites like GSAT-11, GSAT-30, GSAT-31, ESA’s Juice mission and NASA’s James Webb Space Telescope (JWST).
• The rocket is a two-stage design that employs liquid hydrogen and liquid oxygen (hydrolox) as fuel.
• The first stage is powered by an upgraded Vulcain engine from the Ariane 5, while the second stage is driven by the Vinci engine, created specifically for Ariane 6.
• The rocket is available in two variants: Ariane 62, which includes two P120 solid rocket boosters, and Ariane 64, which uses four. 
• Chosen in 2014 over an all-solid-fuel alternative, Ariane 6 was finally launched in 2024. 
  • The flight of Ariane 6 successfully placed nine cube-sats into orbit, including NASA's CubeSat Radio Interferometry Experiment (CURIE) and other satellites focused on studying Earth's climate and weather patterns.
  • The Vinci engine is capable of multiple restarts, enabling the deployment of payloads into several distinct orbits.