Aditya L1 Mission (The Sun Mission)

Aditya L1 Mission: Exploring the Sun from a Unique Perspective


In the wake of the historic success of Chandrayaan-3, ISRO (Indian Space Research Organization) is once again poised to create history with the Aditya L1 Mission. While it’s only been a mere two weeks since the triumph of Chandrayaan-3, ISRO’s eyes are now set on a different celestial body—the sun. In this article, we will delve deep into the Aditya L1 Mission, India’s first-ever dedicated mission to study the sun.

Aditya L1 Mission: A Sun-Observing Marvel

Unlike Chandrayaan which landed on the moon, Aditya L1  will not touch down on the sun. Instead, it will meticulously observe the sun from a significant distance. To be precise, this spacecraft will position itself closer to Earth than to the sun during its mission. After its launch, Aditya L1 will journey approximately 1.5 million kilometers away from Earth, eventually orbiting from the Lagrange point L1 in a halo orbit. It will take roughly four months to reach this point, and once it does, it will remain there for five years, tirelessly observing the sun. This unique positioning transforms Aditya L1 into not just a spacecraft but a space observatory, enabling groundbreaking scientific observations. 

Understanding Lagrange Points

To comprehend the significance of the L1 point, it’s essential to grasp the concept of Lagrange points. These are distinct locations in space where the gravitational forces of two celestial bodies, in this case, the sun and the Earth, are perfectly balanced. In the case of the sun and Earth, there exist five Lagrange points. These points offer a multitude of benefits, the most notable being stability. A spacecraft positioned at a Lagrange point requires minimal effort to maintain its position, conserving precious fuel. Furthermore, due to Earth’s orbital motion around the sun, the spacecraft naturally maintains its position, allowing for extended missions.

The second crucial benefit is continuous observation. For instance, Lagrange Point L1 offers an unobstructed view of both the Earth and the sun. This means that the sun and Earth never eclipse each other from this vantage point. In contrast, when spacecraft orbit Earth or the moon, there are periodic moments when one celestial body obscures the other. Therefore, Lagrange points, particularly L1, are highly prized in space exploration. Aditya L1’s strategic placement at the L1 point underscores its importance. Other space agencies, such as NASA and the European Space Agency, have previously positioned solar observatories at L1, exemplified by the Solar and Heliosphere Observatory (SOHO).

Unveiling the Sun’s Complexity

The sun, the radiant heart of our solar system, boasts a diameter 109 times greater than that of Earth and a mass exceeding Earth’s by a staggering 333,000 times. Similar to Earth, the sun consists of distinct layers. At its core, nuclear fusion reactions generate incomprehensible amounts of energy. Hydrogen and helium gases within the core meld together, producing the sunlight and heat that bathe our planet. The core’s temperature soars to a scorching 15 million degrees Celsius.

Beyond the core lies the radiative zone, constituting approximately 70% of the sun’s radius. Adjacent to it is the convective zone, responsible for energy transfer through convection. These layers collectively create the sun’s internal dynamics. As we move outward, we encounter the photosphere, which, though termed the “surface,” differs significantly from Earth’s. The photosphere consists of scorching-hot gases and plasma and is regarded as the lowest layer of the sun’s atmosphere. Its temperature hovers at a comparatively cooler 5,500 degrees Celsius.

Continuing our journey outward, we arrive at the chromosphere, where temperatures begin to rise, ranging from 6,000 to 20,000 degrees Celsius. Above this layer lies the transition region, followed by the outermost layer, the corona. The corona is home to extremely hot plasma, with temperatures soaring to an astonishing 1-3 million degrees Celsius.

Solar Phenomena and Aditya L1’s Mission

When we observe the sun from Earth, we primarily see the photosphere. However, during a solar eclipse, a reddish glow, known as the chromosphere, becomes visible. During a total solar eclipse, even the chromosphere is obscured, revealing only the corona as it forms a faint halo around the sun. Aditya L1’s mission centers on studying the sun’s topmost layers—the photosphere, chromosphere, and corona—from millions of kilometers away.

Solar Radiation and Phenomena

The sun emits not only heat and visible light but also a wide spectrum of electromagnetic radiation. This includes ultraviolet radiation (UV rays), which can have harmful effects on human skin, as well as infrared radiation, radio waves, X-rays, S-rays, and even gamma rays. Fortunately, Earth’s atmosphere acts as a protective shield against most of these radiations. However, the sun also releases solar wind, a torrent of charged electrons and protons. When this solar wind interacts with Earth’s magnetic field, it gives rise to the captivating Northern Lights, witnessed in countries like Sweden, Finland, and Iceland.

In addition to solar wind, the sun occasionally produces coronal mass ejections (CMEs)—enormous bursts of solar wind and magnetic fields. Furthermore, solar flares, intense flashes of light and energy, are emitted by the sun from time to time, as depicted in various science fiction movies.

To facilitate these comprehensive observations, Aditya L1 is equipped with seven cutting-edge instruments, collectively referred to as payloads:

  1. VELC (Visible Emission Line Coronagraph): VELC, short for Visible Emission Line Coronagraph, is a powerful instrument dedicated to studying the sun’s corona layer. It plays a pivotal role in observing coronal mass ejections (CMEs). By capturing visible emissions from the corona, VELC provides critical insights into the sun’s outermost atmosphere and its dynamic processes.
  2. SUIT (Solar Ultraviolet Imaging Telescope): SUIT, which stands for Solar Ultraviolet Imaging Telescope, is tasked with imaging the sun’s photosphere and chromosphere in the ultraviolet spectrum. This instrument allows scientists to peer into the sun’s inner layers, unveiling intricate details that would otherwise remain hidden. SUIT’s ultraviolet observations contribute significantly to our understanding of the sun’s composition and activity.
  3. SOLEXS (Solar Low Energy X-ray Spectrometer): SOLEXS, the Solar Low Energy X-ray Spectrometer, is designed to scrutinize the sun’s emissions in the low-energy X-ray range. It specializes in studying X-rays emitted by the sun, with a particular focus on those generated during solar flares. These observations help unravel the mechanisms behind these intense bursts of energy and radiation.
  4. HEL1OS (High Energy L1 Orbiting X-ray Spectrometer): HEL1OS, or High Energy L1 Orbiting X-ray Spectrometer, complements SOLEXS by studying high-energy X-rays emitted by the sun. This instrument is vital for analyzing the more energetic aspects of solar flares and other high-energy solar events. Together with SOLEXS, HEL1OS provides a comprehensive view of the sun’s X-ray emissions.
  5. ASPEX (Aditya Solar Wind Particle Experiment): ASPEX, short for Aditya Solar Wind Particle Experiment, is dedicated to the study of solar wind. Solar wind consists of charged electrons and protons ejected by the sun. ASPEX allows scientists to directly measure and analyze these particles, shedding light on the sun’s influence on the solar system and its interaction with Earth’s magnetic field.
  6. PAPA (Plasma Analyzer Package for Aditya): PAPA, or Plasma Analyzer Package for Aditya, works in tandem with ASPEX to explore the intricacies of the solar wind. It specializes in analyzing the plasma within the solar wind, providing valuable data on its composition and behavior. Together with ASPEX, PAPA enhances our understanding of this fundamental solar phenomenon.
  7. MAG (Magnetometer): The MAG instrument, short for Magnetometer, serves a crucial role in measuring magnetic fields at the L1 point. By monitoring these magnetic fields, MAG contributes to our comprehension of the sun’s magnetic activity and its impact on space weather. Understanding these fields is vital for predicting and mitigating potential disturbances in Earth’s magnetosphere.

“Four of the seven payloads on board the Aditya L1 spacecraft are specifically designed for direct observation and study of the sun. The remaining three payloads, on the other hand, are tasked with collecting measurements in the vicinity of the L1 Point. It’s crucial to emphasize that the need to position these instruments beyond Earth’s atmosphere arises from the fact that Earth’s protective atmosphere serves as a natural filter, blocking a significant portion of radiation, including X-rays, and other celestial emissions. While this atmospheric shielding is essential for safeguarding human life, it poses limitations when it comes to studying these phenomena in their purest form.”

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