The Indian programme to study the Sun and the region between the Sun and the Earth from space – Aditya-L1 is due to be launched next year.
It will carry seven payloads which have been developed by various institutions across the country.
Once the mission is launched, there will be a need for a ground support centre to monitor and coordinate the work on its various payloads.
This role will be played by the ARIES facility (short for Aryabhata Research Institute for observational Sciences) which is situated near Nainital.
In January 2021, an agreement was signed to this effect based on the proposal submitted by the ARIES team of the science working group of the Aditya-L1 mission.
Aditya – L1 First Indian mission to study the Sun:
- The Aditya-1 mission was conceived as a 400kg class satellite carrying one payload, the Visible Emission Line Coronagraph (VELC) and was planned to launch in a 800 km low earth orbit.
- A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system has the major advantage of continuously viewing the Sun without any occultation/ eclipses.
- Therefore, the Aditya-1 mission has now been revised to “Aditya-L1 mission” and will be inserted in a halo orbit around the L1, which is 1.5 million km from the Earth.
- The satellite carries additional six payloads with enhanced science scope and objectives.
Why is studying the Sun important?
- Every planet, including Earth and the exoplanets beyond the Solar System, evolves and this evolution is governed by its parent star.
- The solar weather and environment, which is determined by the processes taking place inside and around the sun, affects the weather of the entire system.
- Variations in this weather can change the orbits of satellites or shorten their lives, interfere with or damage onboard electronics, and cause power blackouts and other disturbances on Earth. Knowledge of solar events is key to understanding space weather.
- To learn about and track Earth-directed storms, and to predict their impact, continuous solar observations are needed.
- Every storm that emerges from the Sun and heads towards Earth passes through L1, and a satellite placed in the halo orbit around L1 of the Sun-Earth system has the major advantage of continuously viewing the Sun without any occultation/eclipses.
Halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system:
- Lagrange Points, named after Italian-French mathematician Josephy-Louis Lagrange, are positions in space where the gravitational forces of a two-body system (like the Sun and the Earth) produce enhanced regions of attraction and repulsion.
- The L1 point is about 1.5 million km from Earth, or about 1/100th of the way to the Sun.
- L1 refers to Lagrangian/Lagrange Point 1, one of 5 points in the orbital plane of the Earth-Sun system.
- These can be used by spacecraft to reduce fuel consumption needed to remain in position.
- A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) has the major advantage of continuously viewing the Sun without any occultation/ eclipses.
- The L1 point is home to the Solar and Heliospheric Observatory Satellite (SOHO), an international collaboration project of National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA).
The satellite will be launched during 2019 – 2020 timeframe by PSLV-XL from Sriharikota:
- Aditya-1 was meant to observe only the solar corona. The outer layers of the Sun, extending to thousands of km above the disc (photosphere) is termed as the corona.
- It has a temperature of more than a million degree Kelvin which is much higher than the solar disc temperature of around 6000K.
- In addition, particle payloads will study the particle flux emanating from the Sun and reaching the L1 orbit, and the magnetometer payload will measure the variation in magnetic field strength at the halo orbit around L1.
- These payloads have to be placed outside the interference from the Earth’s magnetic field and could not have been useful in the low earth orbit.
Studying lower corona:
- The Aditya-L1 Support Centre (ASC) will provide training through regular workshops for the guest users.
- Apart from this, it will provide ready-to-use Python and Java apps for the satellite data and demos and handouts to facilitate the guest users.
- An ARIES team has recently developed an algorithm to study the accelerating solar eruptions in the lower corona called CMEs Identification in Inner Solar Corona (in short, CIISCO), where CME stands for coronal mass ejection.
- The group has also developed several advanced image processing algorithms to detect fine-scale structures in the solar atmosphere.
- Such techniques are important to capture dynamics at different spatial and temporal scales.
Challenges in launching the mission:
- The distance of the Sun from Earth (approximately 15 crore kms on average, compared to the only 3.84 lakh kms to the Moon). This huge distance poses a scientific challenge.
- Due to the risks involved, payloads in earlier ISRO missions have largely remained stationary in space.
- However, Aditya L1 will have some moving components which increases the risks of collision.
- Other issues are the super hot temperatures and radiation in the solar atmosphere.
- However, Aditya L1 will stay much farther away, and the heat is not expected to be a major concern for the instruments on board.
How the corona gets heated to such high temperatures is still an unanswered question in solar physics.
The closest any space mission has been to the sun is NASA’s Parker Solar Probe mission which hovered at a distance of 18.6 million kilometres from the sun at a jaw-dropping speed of 3.93 lakh km per hour.
The Aditya L1 mission, unlike the Parker Solar Probe, won’t actually go anywhere near the Sun. However, unlike other satellites, it’s not going to be stuck in Earth’s lower atmosphere either.
Instead, the plan is to launch it in a halo orbit around Lagrangian Point 1 (L1).
At L1, the ISRO satellite will still be moving in orbit but its position relative to the Sun and the Earth will be stable.
Aditya-L1 with additional experiments can now provide observations of Sun’s Corona (soft and hard X-ray, Emission lines in the visible and NIR), Chromosphere (UV) and photosphere (broadband filters).