Aditya L-1’s journey to its celestial destination is on schedule, with the ISRO Chairman S. Somanath confirming its anticipated arrival at L-1 Lagrange Point 1, at 4pm on January 6, 2024. Launched on September 2, 2023, Aditya-L1, aboard the PSLV-C57 rocket, is on a path to profoundly enhance our understanding of the Sun, including its outermost layer, the corona. The Aditya L-1 mission’s duration is estimated to be approximately 5.2 years, offering an extended period for solar research.
When positioned at the Lagrange Point 1 (L-1), Aditya L-1 will be about 1.5 million kilometres from Earth, around 1 per cent of the Earth-Sun distance. This key location is critical for its mission as it enables in-depth studies of the Sun’s outer layers, including the photosphere, chromosphere and corona. Located in a region where the gravitational forces of both Earth and the Sun balance, L-1 provides a stable point for uninterrupted solar observation.
“The Sun’s structure is fascinating, starting with the photosphere, its visible surface, which is about 500 kilometres thick and the primary source of sunlight. Above this is the chromosphere, approximately 2,000 kilometres to 3,000 kilometres deep, emitting a red glow during eclipses. The outermost corona, extending millions of kilometres into space, is visible as a glowing aura during total eclipses and is significantly hotter than the inner layers,” explained space expert Girish Linganna.
Interestingly, Aditya L-1’s journey to launch spans over 15 years, starting as a concept in January 2008 by the Advisory Committee for Space Sciences (AdCoS). Initially envisioned as a small 400-kilogram satellite in low-Earth orbit, the mission’s scope expanded significantly over the years. Reflecting its evolved scale and objectives, the mission was named ‘Aditya L-1’ in July 2019.
The primary scientific goal of the Aditya L-1 mission is to unravel the secrets of the Sun’s influence on space weather dynamics and Earth’s climate by observing solar phenomena in real-time. The results derived from the observations will help us more precisely forecast space weather and offer solutions for 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.
“The Aditya-L1 mission, positioned near Earth, will not only study the Sun, but also Earth’s magnetic field and the magnetosphere. It aims to observe how these are affected by solar winds and coronal mass ejections (CMEs) from the Sun. Solar winds are streams of charged particles flowing outward from the Sun, while CMEs are significant bursts of solar material and magnetic field rising from the Sun’s surface, the photosphere. These phenomena can impact Earth’s space environment, making their study crucial. The mission intends to investigate the photosphere and corona to find out why the corona’s temperature is higher, despite being around 1,609 kilometres further from the Sun’s core, a heat-producing source where actual intense nuclear fusion occurs. This research may resolve some of the Sun’s enigmatic features,” remarked Linganna.
Aditya-L1, with a launch mass of 1,475 kilograms is designed as a cube-shaped satellite featuring a honeycomb sandwich structure. The dimensions of its main body measure approximately 89 centimetres x 89 cm x 61.5 cm (2.9 feet x 2.9 feet x 2 feet). The satellite, carrying about 244 kilograms of scientific instruments on its top deck, has been developed by ISRO in collaboration with Indian academic institutions. These seven instruments are split into two categories – Four are for direct solar observation, and three focus on studying particles and fields at the L-1 Point. This suite of instruments aims to deepen our knowledge of solar activities and their impact on space weather.
Initially launched in a compact, folded state, Aditya L-1 unfolded in space, revealing two wings, each equipped with a solar panel measuring 120 cm x 81 cm (3.9 feet x 2.7 feet). These panels, alongside a lithium-ion battery, power the spacecraft. Additionally, Aditya L-1 uses a miniaturized GPS receiver to track its position, velocity and time data accurately in real-time.