Know all about ISRO’s Aditya-L1, the space detective trying to solve solar puzzle

Aditya-L1 will be the first dedicated Indian space mission to observe the Sun. It is likely to be launched on 2 September.

BySumit Jha

Published Aug 28, 2023 | 9:30 AMUpdatedAug 28, 2023 | 8:45 PM

Know all about ISRO’s Aditya-L1, the space detective trying to solve solar puzzle

After scripting history with Chandrayaan-3, the Indian Space Research Organisation (ISRO) is gearing up for its solar mission, Aditya-L1.

Though an official launch date is yet to be announced, the Aditya-L1 launch vehicle, PSLV-XL, is likely to blast off from the ISRO’s spaceport at Sriharikota in Andhra Pradesh on 2 September. It will be India’s first dedicated space mission to observe the Sun.

Developed at the UR Rao Satellite Centre in Bengaluru, Aditya-L1 reached the Satish Dhawan Space Centre two weeks ago and has since been resting on the launch pad.

“The launch will most likely be on 2 September,” an ISRO official said.

Aditya-L1 is designed for remotely observing the solar corona and in situ observations (made from the instrument’s location) of the solar wind at L1 (Sun-Earth Lagrangian point), about 1.5 million km from the Earth.

What is Lagrangian Point?

Imagine a small object, like a satellite, that has to put at a specific spot in space where it can stay balanced under the gravitational influence of two larger objects, like the Earth and the Sun. This spot is called a “Lagrangian point.”

Different Lagrangian Points (ISRO)

There are five Lagrangian points — L1 to L5 — in the Earth-Sun system. They are named after mathematician Joseph-Louis Lagrange, who found these points.

L1 is located between the Earth and the Sun, a bit closer to the Sun, 1.5 million km from the Earth. It is like a point where the gravitational forces of the Earth and the Sun balance the third object in such a way that the third object will not move towards either the Earth or the Sun. Instead, it hovers due to the gravitational forces of the bigger bodies cancelling each other.

L1 Lagrangian Point distance. (ISRO)

Scientists and engineers use Lagrangian points to position satellites and space observatories because these points allow them to get a stable view of either the Sun or the Earth without using much fuel to constantly adjust positions.

Aditya-L1 at L1 can continuously observe the Sun without being blocked by the Earth.

In simple terms, a Lagrangian point is a sort of cosmic “sweet spot” where an object can stay balanced between two larger objects’ gravitational forces.

A satellite placed in the halo orbit around the L1 point has the major advantage of continuously viewing the Sun without any occultation/eclipses, ISRO noted.

“This will provide a greater advantage of observing the solar activities and its effect on space weather in real-time,” it said.

Also Read: Capable of launching more interplanetary missions: ISRO chairman

What is Aditya-L1 carrying?

The Aditya-L1 mission, aimed at studying the Sun from an orbit around the L1, would carry seven payloads to observe the photosphere (the visible surface of a star like the Sun, where light is emitted), chromosphere (a layer above the Sun’s visible surface where the temperature increases, and it appears as a reddish glow during solar eclipses and the outermost layers of the Sun), the corona (extending far beyond the visible surface, very hot and creates the Sun’s halo-like glow during total solar eclipses, in different wavebands).

Aditya-L1 is a fully indigenous effort with the participation of national institutions, ISRO said.

The Bengaluru-based Indian Institute of Astrophysics (IIA) is the lead institute for the development of the Visible Emission Line Coronagraph payload. While Inter-University Centre for Astronomy and Astrophysics, Pune, developed the Solar Ultraviolet Imager payload for the mission.

Aditya-L1 can provide observations on the corona, and on the solar chromosphere using the UV and the X-ray payloads. The particle detectors and the magnetometer payload can provide information on charged particles and the magnetic field reaching the halo orbit around L1.

Aditya-L1 payloads (ISRO)

The work of payloads

Using the vantage point L1, four payloads directly view the Sun and the remaining three payloads carry out in situ studies of particles and fields at L1, thus providing important scientific studies of the propagation effects of solar dynamics in the interplanetary medium.

“The suits of Aditya L1 payloads are expected to provide the most crucial information to understand the problem of coronal heating, coronal mass ejection, pre-flare and flare activities, their characteristics, dynamics of space weather, propagation of particle and fields,” the ISRO said.

The seven payloads, or high-tech tools, Aditya takes to the space will help in learning more about the Sun and its behaviour.

Also Read: ISRO eyes 2 September for launch of Aditya L1 solar mission

What are the ‘tools’?

1. Visible Emission Line Coronagraph (VELC): This is a special camera that can click pictures of the Sun’s outer atmosphere, the corona. It’s like capturing images of the Sun’s crown for a better understanding of its composition and dynamics.

2. Solar Ultraviolet Imaging Telescope (SUIT): This tool is also like a camera that focuses on the Sun’s surface and outer layers, specifically those that emit ultraviolet rays. Images from SUIT help in gathering information about different layers of the Sun’s atmosphere.

3. Solar Low Energy X-ray Spectrometer (SoLEXS): Imagine an X-ray machine for the Sun. It looks at the Sun’s X-rays to learn about its composition and activity, similar to how a medical X-ray helps physicians.

4. High-Energy L1 Orbiting X-ray Spectrometer (HEL1OS): This is another X-ray tool, but it focuses more on energetic X-rays from the Sun. It is like studying the Sun’s powerful X-ray emissions to get insights about its energetic processes.

Now, these are the tools that go closer to the Sun:

5. Aditya Solar Wind Particle Experiment (ASPEX): A special collector that grabs tiny particles coming from the Sun, like a cosmic dustpan. These particles help in studying the Sun’s composition and the materials it sends into space.

6. Plasma Analyser Package For Aditya (PAPA): This tool is like a net that captures speedy, charged particles that the Sun releases. These particles are like a “solar wind,” and by analysing them, the Sun’s magnetic activity and its influence on space could be understood.

7. Advanced Tri-axial High-Resolution Digital Magnetometers: It is like a super-precise compass that indicates how the Sun’s magnetic fields are oriented in space. These magnetic fields play a crucial role in solar activity, and studying them helps in predicting the space weather.

Also Read: Why did ISRO choose South Pole of Moon for Chandrayaan-3?

What are Aditya-L1’s objectives?

The Aditya-L1 mission aims to study the Sun and its behaviour in a closer and more detailed way.  By positioning the spacecraft near the Sun, scientists can make close observations of the Sun’s outer layers, its activity, and the environment around it.

1. Study of Solar upper atmospheric (chromosphere and corona) dynamics: The Sun has different layers above its visible surface, its special atmosphere. Aditya-L1 will learn more about how these layers move and change, like clouds moving in the sky.

2. Study of chromospheric and coronal heating, physics of the partially ionized plasma, initiation of the coronal mass ejections, and flares: Scientists are curious why the outer parts of the Sun are hotter than the inner parts, like figuring out why the outside of a campfire is hotter than the firewood. Aditya-L1 also wants to understand sudden outbursts of energy — huge bursts of light and heat — from the Sun.

3. Observe in situ particle and plasma environment providing data for the study of particle dynamics from the Sun: Think of the Sun as a giant particle factory, always sending out tiny bits and charged stuff into space. Aditya-L1 plans to collect and study these particles.

4. Physics of solar corona and its heating mechanism: The Sun has a ‘cool’ outer glow around it called the corona. But it is hotter than the rest of the Sun’s surface, which is puzzling. Aditya-L1 wants to know why the Sun’s “halo” is super hot and why it behaves the way it does.

5. Diagnostics of the coronal and coronal loops plasma: Temperature, velocity and density.: Plasma is like a super-hot soup of charged particles. Aditya-L1 will measure how hot and fast this soup is moving in different parts of the Sun. It is also like using a special compass to understand how the Sun’s invisible magnetic fields work.

6. Development, dynamics and origin of CMEs (Coronal Mass Ejections): The Sun sometimes has these huge outbursts called coronal mass ejections (CMEs), where it throws out a bunch of stuff into space. Aditya-L1 wants to know how these explosive events happen and what causes them. It is like understanding why a balloon pops.

7. Identify the sequence of processes that occur at multiple layers (chromosphere, base and extended corona) which eventually leads to solar eruptive events: Imagine the Sun is like a big, layered onion. Aditya-L1 wants to peel and look into these layers — from the surface to the outer edges —  and understand the sequence of events that happen in each layer before a solar eruption.

8. Magnetic field topology and magnetic field measurements in the solar corona: The Sun has invisible lines of magnetism that affect its behaviour and influence things around it. Aditya-L1 will help us see and understand these magnetic forces, like studying invisible magic strings.

9. Drivers for space weather (origin, composition and dynamics of solar wind): Just like Earth has weather, space has its weather caused by the Sun’s behaviour. Aditya-L1 will help in understanding the origins of space weather and how it impacts satellites and communication systems.

In short, Aditya-L1 is like a space detective, on a mission to uncover the Sun’s secrets, learn about its different layers and behaviours, and understand how it interacts with the space around it.

It is like solving a cosmic puzzle to know the Sun better than ever before.

Also Read: ISRO chief credits Chandrayaan-3 success to ‘incremental progress’, ‘contribution of a generation of leadership’