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ISRO’s Aditya-L1: India’s first Indian mission to study Sun up close

Huma Siddiqui

ISRO Solar Mission: For the scientific community, Sun has forever generated an enigmatic interest as it is our closest Star (at the center of our Solar System), and has been the key to life on Earth, and continues to play a crucial role in Earth's circadian and annual cycles.

Sun's observational studies have been pursued in India for over a century by Kodaikanal Solar Observatory, set up in early 1900s and now run by Indian Institute of Astrophysics, Bengaluru. For last forty years, India also boasts of an exclusive lake island based Udaipur Solar Observatory, for Sun data.

Sun does not possess a fixed borderline since its density decreases exponentially with increasing height of the Solar disc, which is the visible surface of the Sun's outer shell emitting light. The outer layers of the Sun, extending to thousands of km above Photosphere is called the Corona, which is truly enigmatic since it is million degrees Kelvin higher than approx. 6000K temperature of the Solar disc.

This has intrigued the scientist to date, and whenever high magnetic fields develop within the Sun, the middle layer of Sun's three-layered atmosphere (called Chromosphere) has sudden bursts of energy. "These flares release charged particles at very high speed, which travel towards Earth’s atmosphere and this phenomenon is called Coronal Mass Ejection (CME), says Milind Kulshreshtha, Artificial Intelligence, and C4I expert.

CME radiation ionizes the Earth’s upper atmosphere (day time portion), creating the electrically conducting ionosphere which is a well-known phenomenon used for Communication and Radar systems. However, these Solar flares are unpredictable and run the risk of hindering satellites and power transformers adversely.

Sun Observation in Space

Kulshreshtha further explains: A 24/7 Solar observation from the point of measuring its influence on Earth is established when this satellite is positioned within Halo orbit around a special point, called Lagrangian Point 'L1', at a distance of 1.5million km in the Sun-Earth geometry. At this L1 point, the satellite shall be away from Earth's magnetic field to avoid its interference on Sun measurements. Aditya-L1 shall carry seven payloads for providing measurements on following solar parameters:-

(a) Particle flux originating from the Sun and the variations in the magnetic field strength

(a) Solar Corona and dynamics of Coronal Mass Ejections

(b) Solar Photosphere and Chromosphere in near Ultraviolet and measure solar irradiance variations

(c) Spectral characteristics and variation of solar wind properties

ISRO in consultation with various Astrophysics Institutes of India has worked out the payload that will be onboard Aditya L1.

"The statistics collected on the Sun shall help in advance research by various institutions within India to decipher Sun's secrets and verify various mathematical models in use in astronomy. And, overall, Aditya L1 is a 1500kg satellite carrying the seven scientific payloads for various in-situ measurements. The satellite is planned to be launched onboard PSLV-XL rocket from Sriharikota in next few months. Initially, the rocket shall place the satellite in the elliptical Earth Parking Orbit, before being raised for insertion to L1 orbit through various satellite manoeuvres. The designed life cycle of the Mission here five years," he adds.