The Indian Space Research Organisation (ISRO) launched India’s first solar observatory mission, Adity-L1, on September 2, 2023. In its 59th flight with the Aditya-L1 on-board, the Polar Satellite Launch Vehicle (PSLV)-C57, took off from the Satish Dhawan Space Centre in Sriharikota for its voyage towards the Sun lasting for about 109 to 125 days. The Aditya-L1 spacecraft has been indigenously designed by ISRO, which has developed the liquid propulsion systems for propelling it. The total cost of this mission is estimated to be around Rs 400 crore.
About Aditya-L1
Aditya-L1 is the first space-based Indian mission to study the Sun. After the take-off, the separation of spacecraft from the satellite took place with the PSLV launching the spacecraft in the orbit around the Earth.
The spacecraft Aditya-L1 has been placed in a halo orbit around the Lagrange point 1 (L1) of the Sun-Earth system. (The Lagrange point refers to the 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. This is about 150 million kilometres (93,000,000 miles) from the Earth, which is only one per cent of the vast distance between the Earth and the Sun. The gravitational forces of both the celestial bodies cancel each other out at that point.) This would allow the mission to remain in a stable halo orbit near the Sun. According to ISRO, a spacecraft placed in the halo orbit around the L1 point has the major advantage of continuously observing the Sun without any occultation/eclipses. In other words, it would revolve around the Sun with the same relative position and hence could see the Sun continuously.
Aditya-L1 would be staying in obtain the required velocity for its long journey of about four and half the orbit around the Earth for about 16 days. In the course of time, it would undergo five manoeuvres to months towards the Sun. After that, the spacecraft would undergo a Trans-Lagrangian1 insertion manoeuvre. This would mark the onset of its 110-day trajectory to the destination around L1 Lagrange point. Once Aditya-L1 reaches this point, it would be able to orbit the Sun at the same rate as the Earth. This means that it would require very little fuel to operate.
Aditya-L1 has mission life of five years. The payloads that the spacecraft is carrying are expected to come up with much information about the Sun. They would help in understanding the problem of coronal heating, coronal mass ejection, pre-flare, and flare activities and their characteristic dynamics of space weather and propagation of particles and fields.
Payloads onboard Aditya L1
Aditya L-1 is carrying seven payloads on-board with four of them carrying out remote sensing of the Sun and three of them carrying out in-situ observation of particles and fields at the Lagrange point 1. Sensing of the Sun includes the observance of the various layers of the Sun—photosphere, chromosphere, and the corona. The seven payloads include: Remote sensing payloads: (i) Visible Emission Line Coronagraph (VELC) which is designed to observe corona imaging and spectroscopy; (ii) Solar Ultraviolet Imaging Telescope (SUIT) which would image the solar photosphere and chromosphere in near Ultra-violet (UV) and would also measure the solar irradiance variations in near UV; (iii) Solar Low Energy X-ray Spectrometer (SoLEXS) designed to measure the solar soft X-ray flux to study solar fares; (iv) High Energy L1 Orbiting X-ray Spectrometer (HEL1OS), a hard X-ray spectrometer which would observe the Sun as a star; and in-situ payloads: (v) Aditya Solar wind Particle Experiment (ASPEX) which would analyse protons and heavier ions with directions; (vi) Plasma Analyser Package for Aditya (PAPA) which would analyse Electrons and heavier ions with directions, and (vii) Advanced Tri-axial High Resolution Digital Magnetometers which would analyse the in-situ magnetic field.
Reason for Studying the Sun
The Sun is the closest star to the Earth. Thus, it offers an opportunity for in-depth examination of functioning of stars. The Sun is filled with powerful activities that are more than what is visible from the surface. The Sun periodically releases monumental bursts of energy and demonstrates various eruptive phenomena.
These solar outbursts could potentially impact our technologically dependent world by causing disruptions in our near-Earth space environment. To avoid any such disruptions, early detection and interventions of Sun’s activities is critical. The Sun, acting as a natural laboratory has been providing an invaluable arena to study these elusive phenomena. This could not be replicated directly in any controlled laboratory environment.
Along with numerous energetic particles and magnetic field, the Sun emits radiation/light in nearly all wavelengths. The atmosphere of the Earth as well as its magnetic field blocks the various harmful wavelength radiations including particles and fields. Due to this, all the radiations from the Sun do not reach the surface of the Earth. Hence, the instruments from the Earth are not able to detect and study such radiations. However, such studies could be carried out by making observations from the outer space. Further, to understand how the solar wind particles and magnetic field from the Sun travel through the interplanetary space, measurements are to be performed from a point which is far away from the influence of the Earth’s magnetic field.
Additionally, the solar system has always been affected by solar weather. The weather changes in the solar system could change the orbits of the satellites or shorten the lives of the satellites. This could also lead to power blackouts and other disturbances on the Earth. The knowledge of the solar events has always been the key to understanding space weather. Hence, to learn about and track Earth-directed storms, and to predict their impact, there has to be continuous observation of the Sun.
Aditya-L1 would provide important scientific studies of the propagatory effect of solar dynamics in the interplanetary medium.
Solar Missions by Other Countries
The National Aeronautics and Space Administration (NASA), USA, had launched the Parker Solar Probe in August 2018. In December 2021, it flew through the corona of the Sun and studied the sampled particles and magnetic fields on the Sun’s upper atmosphere.
The European Space Agency (ESA) and NASA, in a joint venture, launched the Solar Orbiter in February 2020 to collect data to find out how the Sun created and controlled the constantly changing space environment throughout the solar system.
Japan’s JAXA space agency, too, has launched various solar observation satellites to study the impact of the Sun on the Earth.
The ESA launched Ulysses in October 1990 to study the environment of space above and below the poles of the Sun. In collaboration with NASA and JAXA, the ESA launched Proba-2 in 2001. Upcoming solar missions of the ESA include Proba-3 which is scheduled to be launched in 2024, and Smile which is scheduled to be launched in 2025.
In October 2022, the National Space Science Centre, Chinese Academy of Sciences (CAS) successfully launched the Advanced Space-based Solar Observatory (ASO-S).
However, if successful, the latest mission by ISRO would be the first by any Asian nation to be placed in an orbit around the Sun.
India’s Space Programme
India has been steadily matching achievements of other spacefaring powerful nations but in an economical way. India has a comparatively low-budget space programme. However, it has grown considerably in size and momentum since it had sent a probe to orbit the Moon in 2008. Space experts from across the world say that India has the capability to keep the costs low by copying and adapting existing technology with its highly skilled engineers.
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