Aditya-L1: ISRO’s First Space-Based Solar Observatory Reaches Home. Know 20 Interesting Facts

Aditya-L1, India’s first space-based solar observatory to study the Sun, reached its final destination today (January 6, 2024). The Indian Space Research Organisation (ISRO) inserted its maiden solar mission into a halo orbit around the Sun-Earth Lagrange Point 1 (L1). Aditya-L1 reached L1 at around 4 pm IST on January 6, Prime Minister Narendra Modi announced on X (formerly Twitter).

Now that Aditya-L1 has reached its home, it will not stop. It will perform a slow and graceful dance around that point, Manish Purohit, a former ISRO scientist, told ABP Live.

Here are 20 interesting facts about Aditya-L1

1. L1, located 1.5 million kilometres from the Earth, is a special vantage and strategic location in space because not only will it provide the Aditya-L1 spacecraft an uninterrupted view of the Sun’s outer atmosphere or corona for the entirety of its mission duration, but will also enable the vehicle to conserve energy and save fuel. 
2. The reason behind this is that at L1, the gravitational forces exerted by the Sun and the Earth on Aditya-L1 will balance the centripetal force required by the spacecraft to keep moving around the location, in the vicinity of the Sun and Earth. 
3. At L1, no eclipses or occultations occur. 
4. Since the forces will be balanced at L1, Aditya-L1 will be in an equilibrium state and a stable position, and will simply hover in the halo orbit without spending much fuel.
5. The distance between the Sun and the Earth is about 150 million kilometres, and that between the Aditya-L1 spacecraft and the Earth is 1.5 million kilometres. This means that the distance between Aditya-L1 and the Sun is about 148.5 million kilometres. 
6. The strategic location will also allow Aditya-L1 to view the Sun without coming in contact with the star’s scorching heat, for it is situated 148.5 million kilometres from the Sun. 
7. Launched on September 2, 2023, it took Aditya-L1 127 days to reach its final destination. 
8. On September 19, 2023, Aditya-L1 performed a manoeuvre called ‘Trans-Lagrangian Point 1 Insertion’, following which the spacecraft entered the trajectory that will take it to Sun-Earth L1. Aditya-L1 exited Earth’s gravitational sphere of influence that day. It is India’s second spacecraft to exit Earth’s gravitational sphere of influence, after Mangalyaan-1. 
9. Aditya-L1 has a mission duration of five years. 
10. The spacecraft is equipped with seven payloads, four of which are remote sensing instruments, and three are in-situ instruments. The remote sensing payloads are: Visible Emission Line Coronagraph (VELC), Solar Low Energy X-ray Spectrometer (SoLEXS), Solar Ultraviolet Imaging Telescope (SUIT), and High Energy L1 Orbiting X-ray Spectrometer (HEL1OS). The in-situ payloads are Aditya Solar wind Particle EXperiment (ASPEX), Plasma Analyser Package for Aditya (PAPA), and Advanced Tri-axial High Resolution Digital Magnetometers.
11. So far, Aditya-L1 has conducted scientific experiments such as measuring high-energy particles, capturing its first high-energy X-rays from solar flares, measuring energy variations in protons and alpha particles, and capturing full-disk images of the Sun in near-ultraviolet wavelengths.
12. Aditya-L1 is expected to provide important information about the problem of coronal heating, dynamics of space weather, solar flares, and the propagation of particles and fields in the interplanetary medium.
13. Aditya-L1’s payloads have been tuned in such a way that they can observe the solar atmosphere, especially the chromosphere and the corona, and can conduct experiments to understand the local environment at L1.
14. Inside the 4.5-billion-year-old star, nuclear fusion reactions occur. Aditya-L1’s findings may help scientists understand these reactions better, and how they power the Sun. The temperature of the central region of the Sun, or the core, is about 15 million degrees Celsius, and that of the photosphere is about 5,500 degrees Celsius. Aditya-L1 will also study the reasons behind this difference in temperature.
15. By studying the changing environmental conditions in space, Aditya-L1 can provide insights into how solar activities impact space weather in real time.
16. The charged particle environment and the nature of magnetic fields near the Earth change when particles and magnetic fields from the Sun are directed towards the planet. Since these explosive phenomena can affect space assets, it is essential to send spacecraft that will perform experiments to understand the impact of solar activities on space weather in real time. Aditya-L1 is one such solar mission.
17. The distance between Aditya-L1 and the Sun will not negatively affect the spacecraft’s ability to study high-energy particles originating from the Sun. High-energy particles emitted by the Sun include protons and electrons. These particles can give scientists important information about the dynamic behaviour of the Sun.
18. Aditya-L1 is the first spacecraft which will spatially resolve the solar disk in the near-ultraviolet band. The solar disk is the circular visible surface of the Sun. Spatial resolution refers to a measure of the smallest object that can be resolved by a sensor, and allows two neighbouring structures to be distinguished as separate.
19. Aditya-L1 will study solar coupling, which refers to the firm connection between the solar magnetic field and the Sun formed by the highly conducting solar atmosphere.
20. Halo orbits are special paths that are not perfect circles or ovals. They are more like lopsided shapes called lissajous figures. These orbits are extremely huge – there is a 13 lakh kilometre-distance between the farthest points.