Context: ISRO’s Aditya L1 mission was successfully launched from Satish Dhawan Space Centre on 2 September 2023. 

About Aditya L1:

• Aditya L1 is the first space-based observatory class to study the Sun.
• It was launched to the low earth orbit using ISRO’s reliable Polar Satellite Launch Vehicle (PSLV).
  • Aditya-L1 will undergo multiple apogee-raising orbital manoeuvres and is expected to exit the Earth’s orbit on the fifth day after launch.
  • After leaving Earth’s gravity, it will get into a heliocentric path. Later, getting into the orbit around L1 is the most crucial aspect. L1 is not an object, just a location in space, which also co-moves with Earth around the Sun.
• Once launched, it will take 125 days to travel to its destination at L1. 

Objectives:

• Study of Solar upper atmospheric (chromosphere and corona) dynamics.
• Study of chromospheric and coronal heating, physics of the partially ionized plasma, initiation of the coronal mass ejections, and flares
• Observe the in-situ particle and plasma environment providing data for the study of particle dynamics from the Sun.
• Physics of solar corona and its heating mechanism.
• Diagnostics of the coronal and coronal loops plasma: Temperature, velocity and density.
• Development, dynamics and origin of CMEs.
• Identify the sequence of processes that occur at multiple layers (chromosphere, base and extended corona) which eventually leads to solar eruptive events.
• Magnetic field topology and magnetic field measurements in the solar corona.
• Drivers for space weather (origin, composition and dynamics of solar wind.

Payloads: 

• Weighing 1,475 kg, it will carry seven payloads. The payloads include-
  • Solar Ultraviolet Imaging Telescope (SUIT) is designed to image the Sun in the 200-400 nanometre (nm) of the ultraviolet band. SUIT’s imager will continuously record the entire disk of the Sun through 11 filters. The images of these layers could help improve our understanding of the Sun’s immediate atmosphere.

• Visible Line Emission Coronagraph (VELC) is the Corona/Imaging and Spectroscopy payload that Aditya-L1 will use to focus on the Sun’s Corona. 
• Solar Low Energy X-ray Spectrometer (SoLEXS) and High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) payloads will study the X-ray flares emitted by the Sun over a wide range of X-ray energy range.
• Aditya Solar wind Particle Experiment (ASPEX), during the cruise phase, will turn on and start performing in situ measurements of solar particles and ions. 
• Plasma Analyser Package for Aditya (PAPA) will study the solar wind and energetic ions. 
• Magnetometer (MAG) payload is meant to measure the low-intensity interplanetary magnetic field in space.

Significance of the mission:

• Aditya-L1 would help in understanding the effect of the Sun on the Earth and its surroundings. The mission hopes to generate user-friendly informationto issue space weather alerts that can help safeguard a range of satellite-dependent operations such as telecommunications, mobile-based Internet services, navigation, power grids, etc.
  • Disturbances in the form of solar flares, Coronal Mass Ejection, or solar winds directed towards Earth, can adversely impact space weather; studying the Sun is, therefore, of paramount importance.
• It would study solar upper atmospheric (chromosphere and corona) dynamics and understand the physics of the solar corona and its heating mechanism.
  • The difference between the Sun’s upper atmosphere’s temperature of 1-3 million degrees Celsius and its lower temperature of 5500 degree Celsius is one of the most significant unresolved problems in the study of solar physics.
  • To understand this issue, it will capture near-simultaneous photos of the many layers of the Sun’s atmosphere, revealing how energy is routed and transported from one layer to the next.
• Aditya-L1 can potentially pave the way for future Indian astronomy missions. After the launch, India entered into an elite group of nations that have sent probes to study the Sun.
  • Aditya-L1 is ISRO’s second astronomy observatory-class mission after AstroSat.
  • AstroSat, weighing 1,515 kg, lifted off with five in situ instruments, is India’s first dedicated astronomy mission aimed at studying celestial sources in X-ray, optical, and UV spectral bands simultaneously, and remains operational almost eight years after its launch in 2015. 

Lagrange points:

• Lagrange points, named after mathematician Josephy-Louis Lagrange who discovered them, are positions in a moving two-body system where forces acting on a third body of smaller mass cancel each other out. 
• At these special locations in space, the combined gravitational forces of two large bodies (such as the Sun and Earth or Earth and the Moon) equal the centrifugal force felt by a much smaller third body. The interaction of the forces creates a point of equilibrium (net of all forces is zero) where a spacecraft may be “parked” to make observations.
• There are five Lagrangian points, denoted L1 to L5, which are located along the line connecting the two larger celestial bodies. Of these, three are unstable and two are stable.
  • Unstable Lagrange points are labelled L1, L2 and L3. Unstable means that if an object/satellite located at these points is nudged, it will break out from the orbit and drift off into interplanetary space.
  • Stable Lagrange points are labelled as L4 and L5. This means that if a small object at L4 or L5 is nudged, there would be an effective restoring force to bring a satellite back to the stable point.

1. L1 point: L1 is located roughly 1.5 million kilometres from Earth, where the Sun and Earth’s combined gravitational pull permits a spacecraft to remain nearly stationary to the Sun. The L1 point provides an uninterrupted view of the Sun as the satellite can continuously view solar activities without eclipses. 
2. L2 point: L2 point is used as a location for space-based observatories, as it provides an unobstructed view of the Universe and is stable enough to allow long-duration observations. James Webb Space Telescope is placed at the L2 Lagrange point. 
3. L3 point: L3 point lies behind the Sun, opposite to Earth. Objects in L3 cannot be seen from Earth and offers the potential to observe the far side of the Sun. There is no known natural object at the L3 point, but it is sometimes discussed as a possible location for a future space-based observatory.
4. L4 and L5 point:  L4 and L5 are good and stable locations, but are much farther from Earth compared to L1, which is directly between the Sun and the Earth.