Solar wind particle experiment payload onboard Aditya-L1 starts operations, says ISRO

The Aditya Solar Wind Particle Experiment payload onboard India’s Aditya-L1 satellite has commenced its operations and is performing normally, ISRO said on Saturday.

Aditya-L1 Mission:

The Solar Wind Ion Spectrometer (SWIS), the second instrument in the Aditya Solar wind Particle Experiment (ASPEX) payload is operational.

The histogram illustrates the energy variations in proton and alpha particle counts captured by SWIS over 2-days.… pic.twitter.com/I5BRBgeYY5

— ISRO (@isro) December 2, 2023

Aditya L1, India’s first space-based mission to study the Sun, was successfully launched on September 2 from the Satish Dhawan Space Centre (SDSC) in Sriharikota. Aditya-L1 is the first Indian space-based observatory to study the Sun from a halo orbit around the first Sun-earth Lagrangian point (L1), which is located roughly 1.5 million km from Earth.

In a statement, ISRO said the Aditya Solar Wind Particle Experiment (ASPEX) comprises two cutting-edge instruments ‘the Solar Wind Ion Spectrometer (SWIS) and the SupraThermal and Energetic Particle Spectrometer (STEPS). The STEPS instrument was operational on September 10, 2023. The SWIS instrument was activated on November 2, 2023, and has exhibited optimal performance.

“SWIS, utilising two sensor units with a remarkable 360 field of view each, operates in planes perpendicular to one another,” the statement read.

According to ISRO, the instrument has successfully measured solar wind ions, primarily protons and alpha particles. A sample energy histogram acquired from one of the sensors over two days in November 2023 illustrates variations in proton and alpha particle (doubly ionized helium, He2+) counts, the agency said.

“These variations were recorded with nominal integration time, providing a comprehensive snapshot of solar wind behaviour,” ISRO said. The directional capabilities of SWIS enable precise measurements of solar wind protons and alphas, contributing significantly to addressing longstanding questions about solar wind properties, underlying processes, and their impact on Earth, the space agency explained.

“The change in the proton and alpha particle number ratio, as observed by SWIS, holds the potential to provide indirect information about the arrival of Coronal Mass Ejections (CMEs) at the Sun-Earth Lagrange Point L1,” ISRO said.

The enhanced alpha-to-proton ratio is often regarded as one of the sensitive markers of the passage of interplanetary coronal mass ejections (ICMEs) at the L1 and hence considered crucial for space weather studies.

What is the Aditya-L1 mission?

The Aditya-L1 is an ‘observatory’ or spacecraft that will monitor the Sun 24×7. This will be the first time that India will put a spacecraft on a Lagrange point – a position in space where, as per NASA, “the gravitational forces of a two-body system like the Sun and Earth produce enhanced regions of attraction and repulsion”.

There are five Lagrange points in the Sun-Earth system; India’s solar mission will be placed in a halo orbit around Lagrange point 1, or L1, which is about 1.5 million km from the Earth, according to ISRO.

L1, Aditya’s parking spot, has been housing Solar and Heliospheric Observatory, a project by America’s NASA and the European Space Agency (ESA) since 1996, reported Space.com.

The Aditya-L1 mission will carry seven payloads, out of which four will directly observe the Sun. These seven payloads or scientific instruments include Visible Emission Line Coronagraph(VELC), Solar Ultraviolet Imaging Telescope (SUIT), Solar Low Energy X-ray Spectrometer (SoLEXS), High Energy L1 Orbiting X-ray Spectrometer (HEL1OS), Aditya Solar wind Particle Experiment (ASPEX), Plasma Analyser Package For Aditya (PAPA) and Advanced Tri-axial High Resolution Digital Magnetometers.

These instruments will study the photosphere or the Sun’s visible surface; the layer above the photosphere known as the chromosphere; and the corona – the outermost part of the Sun’s atmosphere.

Objectives of Aditya-L1 mission

As per ISRO, the spacecraft will examine the dynamics of the chromosphere and corona; in-situ particle and plasma environment; the heating mechanism of the corona; magnetic field topology and magnetic field measurements in corona; temperature, velocity and density of coronal and coronal loops plasma; and development, dynamics and origin of coronal mass ejections (CMEs).

It will also study chromospheric and coronal heating, space weather, the physics of the partially ionized plasma, what leads to solar eruptive events, and how CMEs and solar flares start.

Why is studying the Sun important?

Before that, here are some facts about the centre of our solar system. The Sun, which sustains most life on Earth, is a 4.5 billion-year-old star. Located 150 million kilometres away from the Earth, the Sun’s gravity holds the solar system together. Unlike Earth, the Sun’s surface is not solid but made of “super-hot, electrically charged gas called plasma”, noted NASA.

According to the US Space Agency, “The Sun’s activity, from its powerful eruptions to the steady stream of charged particles it sends out, influences the nature of space throughout the solar system.”

The solar activity constitutes solar flares, CMEs or huge plasma clouds, high-speed solar wind, and solar energetic particles.

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Chandan Prakash