Aditya-L1, to be launched aboard ISRO's Polar Satellite Launch Vehicle (PSLV) on September 2, from the Satish Dhawan Space Centre, Sriharikota, is the first space-based observatory-class Indian solar mission to study the Sun. Imagine a spacecraft, stationed in a halo orbit around the Lagrange Point 1 (L1) of the Sun-Earth system, a staggering 1.5 million kilometers away from our planet. This unique orbit offers Aditya-L1 the remarkable privilege of an unobstructed, continuous gaze at the Sun. Shielded from the shadows of eclipses, it becomes the ultimate observatory, capturing the Sun's dynamic activities.
Space experts say this ability to observe the Sun without interruptions is particularly crucial when it comes to understanding the nature of solar flares. Solar flares are sudden and intense bursts of energy and radiation that emanate from the Sun's surface. These eruptions release colossal amounts of energy, equivalent to millions of atomic bombs, and their impact on Earth's technology and communication systems can be profound.
“Solar flares are known to cause disruptions in radio communications, GPS systems, and power grids. The energy released during a solar flare can interfere with the Earth's magnetic field, leading to geomagnetic storms that affect our technological infrastructure. For instance, in 1859, a solar flare known as the Carrington Event caused a geomagnetic storm that disrupted telegraph systems across Europe and North America, leading to telegraph lines catching fire and operators receiving electric shocks,” explained Srimathy Kesan, founder and CEO of Space Kidz India, which is into design, fabrication and launch of small satellites, spacecraft and ground systems.
By continuously observing the Sun from the vantage point of Aditya-L1, scientists hope to gain deeper insights into the mechanisms behind solar flares. “The real-time data collected by Aditya-L1's instruments can help us understand the triggers of solar flares, the processes that lead to their eruption, and the patterns they follow. This knowledge is invaluable for developing better models for predicting and mitigating the effects of solar flares on Earth's technology,” added Kesan.
The Aditya L-1 spacecraft is a 1,500 kg-class satellite and represents a specialised scientific mission by the Indian Space Research Organisation (ISRO). It aims to investigate the Sun’s characteristics from a halo orbit situated around L1 within the Sun-Earth system. This unique orbit at L1 ensures uninterrupted solar observations, unaffected by eclipses or occultation. Moreover, it offers a vantage point beyond Earth’s magnetic field, allowing for direct measurements of incoming charged particles.
The Lagrange Point 1 of the Sun-Earth system is located about 1.5 million kilometers away from Earth. It is expected to take more than 120 days for the spacecraft to reach L1.
A Lagrange Point is a location in space where the gravitational forces of two celestial bodies (in this case, Earth and the Sun) are perfectly balanced by the centripetal force needed for a small-sized object to move in unison with them. Positioning a satellite within the halo orbit encircling the L1 point offers a significant benefit: unobstructed and continuous access to sunlight, free from any occurrences of occultation or eclipses. This advantage translates into an enhanced ability to monitor solar activities and their impact on space weather in real time.
Within four months, Aditya-L1 endeavors to traverse this cosmic expanse to reach its resplendent target, the Sun itself. In vivid contrast, the Parker Solar Probe, a creation of NASA, embarked on its odyssey in 2018 with an audacious goal – to "touch the Sun." With cutting-edge instruments and a remarkable carbon-composite shield, this intrepid spacecraft defies the inferno, venturing within 3.9 million miles of the Sun's blistering surface.
Space experts point out that Parker Solar Probe's sojourn through the corona—an area more scorching than the Sun's own surface—unravels enigmatic solar dynamics, delves into space weather, and deciphers the Sun's intricate dance with Earth. The divergent nature of these missions also extends to their proximity to the Sun. Aditya-L1 maintains a strategic distance, optimising uninterrupted observation, while NASA's Parker Solar Probe audaciously delves into the fiery corona, amassing invaluable insights.
Experts further point out that the Sun is divided into seven distinct regions. Internally, it comprises the core, the radiative zone, and the convection zone. As one moves outward, one encounters the visible surface, known as the photosphere, succeeded by the chromosphere, the transition zone and, finally, the corona, which is the Sun’s extensive outer atmosphere. Aditya L-1 aims to offer important understandings about the Sun, including its outermost layer, the corona.
“The Sun, our closest star, serves as a valuable plasma laboratory. Within the solar corona, plasma behaves like a fluid, while the solar wind plasma near Earth can be seen as particles. The outer solar atmosphere, stretching thousands of kilometres above the photosphere (Sun disc), is called the solar corona. Despite the photosphere’s temperature being around 5,000°C, the corona’s temperature exceeds a million degrees centigrade. The process behind the corona’s heating to these extreme temperatures remains an unsolved puzzle in solar physics,” space and aerospace expert Girish Linganna, told THE WEEK.
Explaining further, he said the material departing from the corona at supersonic speeds transforms into the solar wind, creating a significant magnetic presence, known as the heliosphere, which envelops the Sun. This magnetic influence extends beyond the orbits of the planets in our solar system.
The primary scientific goal of the Aditya L-1 mission is to uncover the secrets of the Sun’s influence on space weather dynamics and Earth’s climate by observing solar phenomena in real time. This understanding will lead to more precise forecasts of space weather and offer important perspectives on reducing their potential effects on space missions and technologies on Earth. Environmental conditions in space have the potential to impact satellites, communication networks and power grids here on Earth.
“Space weather events caused by actions on the Sun can also pose risks to astronauts in space and affect the ionosphere around Earth. The ionosphere is a layer in Earth’s upper atmosphere that contains ions and free electrons. It plays a crucial role in reflecting radio signals and influencing global communication and navigation systems,” pointed out Linganna.
There are different critical payloads on Aditya L-1 to perform different tests and research, addressing specific questions and deepening our knowledge of the Sun. Four tools look right at the sun from the special L-1 spot, while the other three tools examine particles and fields around L-1. This Aditya L-1 mission will give crucial insights into how solar activities happen throughout space. The seven payloads aboard the satellite are Visible Emission Line Coronagraph, Solar Ultraviolet Imaging Telescope, Solar Low-Energy X-ray Spectrometer, High-Energy L-1 Orbiting X-ray Spectrometer, Aditya Solar Wind Particle Experiment, Plasma Analyser Package For Aditya and Advanced Tri-axial High-Resolution Digital Magnetometers.