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Aditya L-1 Mission

The launch of Aditya L-1 comes days after the space agency created history making India the fourth country to successfully land on the moon and first to land near the lunar south pole.

Aditya-L1 is the first space-based observatory-class Indian solar mission to study the Sun. The spacecraft is planned to be placed in a halo orbit around the Lagrangian point1 (L1) of the Sun-Earth system, which is about 1.5 million km from the Earth.

A satellite placed in the halo orbit around the L1 point has the major advantage of continuously viewing the Sun without any occultation/eclipse. This will provide a greater advantage of observing solar activities continuously. The spacecraft will carry seven payloads to observe the photosphere, chromosphere, and the outermost layers of the Sun (the corona) using electromagnetic and particle detectors.

Using the special vantage point of L1, four payloads will directly view the Sun and the remaining three payloads will carry out in-situ studies of particles and fields at the Lagrange point L1.

The suit of Aditya L1 payloads is expected to provide most crucial information to understand the problems of coronal heating, Coronal Mass Ejection, pre-flare and flare activities, and their characteristics, dynamics of space weather, study of the propagation of particles, fields in the interplanetary medium, etc.

The Sun

  • Our Sun is the nearest star and the largest object in the solar system.

  • The estimated age of the sun is about 4.5 billion years.

  • It is a hot glowing ball of hydrogen and helium gases.

  • The distance to the sun from the Earth is about 1.5 million kilometers, and is the source of energy for our solar system.

  • Without the solar energy the life on earth, as we know, can not exist. The gravity of the sun holds all the objects of the solar system together. At the central region of the sun, known as ‘core’, the temperature can reach as high as 15 million degree Celsius.

  • At this temperature, a process called nuclear fusion takes place in the core which powers the sun.

  • The visible surface of the sun known as photosphere is relatively cool and has temperature of about 5,500°C.

Why study Sun?

  • The sun is the nearest star and therefore can be studied in much more detail as compared to other stars.

  • By studying the sun we can learn much more about stars in our Milky Way as well as about stars in various other galaxies.

  • The sun is a very dynamic star that extends much beyond what we see. It shows several eruptive phenomena and releases immense amount of energy in the solar system. If such explosive solar phenomena is directed towards the earth, it could cause various types of disturbances in the near earth space environment.

  • Various spacecraft and communication systems are prone to such disturbances and therefore an early warning of such events is important for taking corrective measures beforehand.

  • In addition to these, if an astronaut is directly exposed to such explosive phenomena, he/she would be in danger.

  • The various thermal and magnetic phenomena on the sun are of extreme nature. Thus, the sun also provides a good natural laboratory to understand those phenomena which cannot be directly studied in the lab.

Lagrange Point

For a two-body gravitational system, the Lagrange Points are the postions in space where a small object tends to stay, if put there. These points in space for a two body systems such as Sun and Earth can be used by spacecraft to remain at these positions with reduced fuel consumption. Technically at Lagrange point, the gravitational pull of the two large bodies equals the necessary centripetal force required for a small object to move with them. For two body gravitational systems, there are total five Lagrange points denoted as L1, L2, L3, L4 and L5. The Lagrange points for Sun-Earth system are shown in the figure. The Lagrange point L1 lies between Sun-Earth line. The distance of L1 from Earth is approximately 1% of the Earth-Sun distance.

Trajectory of Aditya L-1

  • The Aditya-L1 mission will be launched by ISRO PSLV rocket from Sathish Dhawan Space Centre SHAR (SDSC SHAR), Sriharikota.

  • Initially the spacecraft will be placed in a low earth orbit. Subsequently, the orbit will be made more elliptical and later the spacecraft will be launched towards the Lagrange point L1 by using on-board propulsion.

  • As the spacecraft travels towards L1, it will exit the earths’ gravitational Sphere of Influence (SOI).

  • After exit from SOI, the cruise phase will start and subsequently the spacecraft will be injected into a large halo orbit around L1.

  • The total travel time from launch to L1 would take about four months for Aditya-L1.

Objectives of the Mission

  • Understanding the Coronal Heating and Solar Wind Acceleration.

  • Understanding initiation of Coronal Mass Ejection (CME), flares and near-earth space weather.

  • To understand the coupling and dynamics of the solar atmosphere.

  • To understand solar wind distribution and temperature anisotropy

Aditya L-1 Payloads

The spacecraft carries seven scientific payloads for systematic study of the Sun. All payloads are indigenously developed in collaboration with various ISRO Centres.

  1. Visible Emission Line Coronograph (VELC)

  2. Visible Emission Line Coronagraph is designed to study solar corona and dynamics of coronal mass ejections.

  3. The payload is developed by Indian Institute of Astrophysics, Bengaluru in close collaboration with ISRO.

  4. Solar Ultra-violet Imaging Telescope (SUIT)

  5. To image the Solar Photosphere and Chromosphere in near Ultra-violet (UV) and, to measure the solar irradiance variations in near UV.

  6. The payload is developed by Inter University Centre for Astronomy and Astrophysics, Pune in close collaboration with ISRO.

  7. Solar Low Energy X-ray Spectrometer (SoLEXS)

  8. SoLEXS is a soft X-ray spectrometer onboard Aditya-L1.

  9. The payload is designed to measure the solar soft X-ray flux to study solar flares.

  10. This payload is developed at U R Rao Satellite Centre, Bengaluru.

  11. High Energy L1 Orbiting X-ray Spectrometer (HEL1OS)

  12. HEL1OS is a hard X-ray spectrometer designed to study solar flares in the high energy X-rays

  13. Aditya Solar wind Particle Experiment (ASPEX)

  14. The ASPEX payload comprises 2 subsystems: SWIS and STEPS

  15. SWIS (Solar Wind Ion Spectrometer) is a low-energy spectrometer that is designed to measure the proton and alpha particles of the solar wind

  16. STEPS (Suprathermal and Energetic Particle Spectrometer)is a high-energy spectrometer that is designed to measure high-energy ions of the solar wind.

  17. Plasma Analyser Package for Aditya (PAPA)

  18. PAPA is designed to understand solar winds and its composition and, do mass analysis of solar wind ions.

  19. Magnetometer

  20. Magnetometer onboard Aditya-L1 is meant to measure the low intensity interplanetary magnetic field in space.

  21. It has two sets of Magnetic Sensors:one at the tip of a 6 meter deployable boom, and the other in the middle of the boom, 3 meters away from the spacecraft


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