Aditya-L1, India’s first space-based solar observatory to study the Sun, has started conducting scientific experiments. It exited Earth’s gravitational sphere of influence on September 19, 2023, after successfully performing the Trans-Lagrangian Point 1 Insertion (TL1I) manoeuvre, the spacecraft’s fifth and final Earth-bound manoeuvre. Aditya-L1 will reach its destination, which is a halo orbit around Lagrange Point 1 (L1), after about 110 days, through a manoeuvre.
Aditya-L1 has begun the cruise phase of its journey. L1 is located 1.5 million kilometres from the Earth. This is a strategic location that will not only allow Aditya-L1 to conserve energy by saving fuel, but also offer the spacecraft an uninterrupted view of the Sun, for the entirety of its mission duration, which is five years.
What are Aditya-L1’s payloads? What will the spacecraft study about the Sun?
Aditya-L1 is equipped with seven payloads, four of which are remote sensing instruments, and three are in-situ instruments.
The remote sensing payloads are: Visible Emission Line Coronagraph (VELC), Solar Low Energy X-ray Spectrometer (SoLEXS), Solar Ultraviolet Imaging Telescope (SUIT), and High Energy L1 Orbiting X-ray Spectrometer (HEL1OS).
The in-situ payloads are Aditya Solar wind Particle EXperiment (ASPEX), Plasma Analyser Package for Aditya (PAPA), and Advanced Tri-axial High Resolution Digital Magnetometers.
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VELC is the prime payload. It has been designed as a reflective coronagraph, which means that it will block the Sun’s light in a way such that only the corona is visible.
VELC is also equipped with a multi-slit spectrograph, which will disperse electromagnetic radiation from the Sun into a spectrum. It will perform imaging and spectroscopy of the solar corona, which is the outermost part of the solar atmosphere. Spectroscopy refers to the study of the absorption and emission of light and other radiation by matter.
SoLEXS, a soft X-ray spectrometer, will study solar flares by measuring the solar soft X-ray flux, or the number of low-energy X-ray lines passing through the surface of the Sun in a given amount of time. These X-rays have longer wavelengths.
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HEL1OS, a hard X-ray spectrometer, will study solar flares by measuring high-energy X-rays. It will study X-rays with shorter wavelengths emitted by the Sun.
SUIT, an ultraviolet telescope, will image the solar disk in the near-ultraviolet wavelength range. It will conduct imaging of the photosphere and the chromosphere. The photosphere is the innermost layer of the solar atmosphere, and the chromosphere is the layer between the corona and the photosphere.
ASPEX is a particle analyser which will analyse different particles in solar winds, such as protons and heavier ions, in different directions. It is made up of two subsystems: Solar Wind Ion Spectrometer (SWIS) and SupraThermal and Energetic Particle Spectrometer (STEPS).
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SWIS, a low-energy spectrometer, will measure the protons and alpha particles present in solar winds.
STEPS, which is Aditya-L1’s first payload to start scientific experiments, is a high-energy spectrometer measuring high-energy ions present in solar winds.
PAPA will understand solar winds and its composition, and also analyse solar wind ions.
PAPA is also a particle analyser, and will study electrons and heavier ions in solar winds in different directions.
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The magnetometer, which has two sets of magnetic sensors — one of them at the tip of a six-metre deployable boom, and the other set in the middle of the boom, three metres away from the spacecraft — will measure the low-intensity interplanetary magnetic field in space.
The magnetometer will study the magnetic fields at the Lagrange point, in order to understand how solar activities affect the magnetic fields in the interplanetary medium.
Aditya-L1 is expected to provide important information about the problem of coronal heating, dynamics of space weather, solar flares, and the propagation of particles and fields in the interplanetary medium.
Aditya-L1’s payloads have been tuned in such a way that they can observe the solar atmosphere, especially the chromosphere and the corona, and can conduct experiments to understand the local environment at L1.
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Aditya-L1’s major science objectives include studying the dynamics of the upper layers of the solar atmosphere, which are the chromosphere and corona; observing the in-situ particle and plasma environment around L1 in order to understand how particle dynamics from the Sun impact the surrounding regions of L1; measuring the temperature, velocity and density of plasma inside the corona; identifying the sequence of mechanisms occurring inside the different layers of the solar atmosphere, and how they lead to solar eruptive events; understanding the origin, composition and dynamics of solar wind to determine the drivers for space weather; studying the physics of partially ionised plasma, mechanisms of chromospheric and coronal heating and the initiation of coronal mass ejections and solar flares; understanding the physics of the solar corona and its heating mechanism; analysing the development, dynamics, and origin of coronal mass ejections; measuring the magnetic field in the solar corona; studying the acceleration of solar winds; and understanding solar wind distribution and anisotropy of solar energies, among other goals.
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