India’s first space-based solar observatory, Aditya-L1, has successfully reached its final destination orbit around the Sun-Earth Lagrange point 1 (L1) on Saturday, January 6, 2024. The Indian Space Research Organisation (ISRO) performed the final manoeuvre to inject the spacecraft into a halo orbit around L1, where it will study the Sun’s corona, photosphere, chromosphere, and solar wind.
Aditya-L1 mission overview
Aditya-L1 is a 400-kg spacecraft that carries seven scientific payloads to observe various aspects of the Sun. It was launched on September 2, 2023, aboard the Polar Satellite Launch Vehicle (PSLV-C57) from the Satish Dhawan Space Centre in Sriharikota. The spacecraft travelled about 1.5 million kilometres from the Earth over 125 days to reach the L1 point, where the gravitational forces of the Sun and the Earth are balanced.
The L1 point is a vantage point for observing the Sun, as it offers a continuous view of the solar disc without any occultation by the Earth or the Moon. Aditya-L1 will be the first Indian spacecraft to be placed in a halo orbit around L1, which is a circular orbit with a radius of about 50,000 km. The spacecraft will orbit L1 once every six months, while maintaining its orientation towards the Sun.
Aditya-L1 scientific objectives and payloads
The main objective of Aditya-L1 is to study the Sun’s corona, which is the outermost layer of the solar atmosphere that extends millions of kilometres into space. The corona is the source of the solar wind, which is a stream of charged particles that affects the Earth’s magnetosphere and climate. The corona also produces coronal mass ejections (CMEs), which are huge eruptions of plasma and magnetic fields that can cause geomagnetic storms and disrupt communication and navigation systems on Earth.
Aditya-L1 will also study the Sun’s photosphere and chromosphere, which are the inner layers of the solar atmosphere that emit visible and ultraviolet light, respectively. The photosphere and chromosphere are the regions where the Sun’s magnetic fields emerge and interact, creating sunspots, flares, and other phenomena. Aditya-L1 will also measure the solar wind and the magnetic field in the vicinity of the spacecraft.
The seven scientific payloads on board Aditya-L1 are:
- Visible Emission Line Coronagraph (VELC): This is the main payload of the mission, which will image the corona in visible light and perform spectroscopy and polarimetry to measure the temperature, density, velocity, and magnetic field of the coronal plasma.
- Solar Ultraviolet Imaging Telescope (SUIT): This payload will image the photosphere and chromosphere in ultraviolet wavelengths, and monitor the variations in solar irradiance that affect the Earth’s climate.
- Solar Low Energy X-ray Spectrometer (SoLEXS): This payload will measure the soft X-ray emission from the Sun, which is an indicator of the solar activity and flares.
- High Energy L1 Orbiting X-ray Spectrometer (HEL1OS): This payload will measure the hard X-ray emission from the Sun, which is associated with high-energy processes and CMEs.
- Aditya Solar wind Particle Experiment (ASPEX): This payload will measure the solar wind protons and heavier ions with their directions, and study their origin and acceleration mechanisms.
- Plasma Analyser Package for Aditya (PAPA): This payload will measure the solar wind electrons and heavier ions with their directions, and study their distribution and dynamics.
- Advanced Tri-axial High Resolution Digital Magnetometers: This payload will measure the in-situ magnetic field in three directions, and study its variations and interactions with the solar wind.
Aditya-L1 mission significance and challenges
Aditya-L1 is a milestone mission for India, as it will provide valuable data and insights into the Sun and its influence on the Earth and the solar system. The mission will also contribute to the international efforts to understand the Sun and its variability, and to improve the space weather forecasting capabilities. Aditya-L1 will also demonstrate India’s technological prowess and scientific potential in the field of solar physics.
The mission, however, is not without challenges. The spacecraft will have to withstand the harsh environment of space, especially the intense radiation and thermal fluctuations near the Sun. The spacecraft will also have to maintain its orientation and communication with the Earth, while orbiting L1. The mission will also require a high level of coordination and collaboration among the various ISRO centres and institutes involved in the design, development, launch, and operation of the spacecraft and its payloads.
ISRO Chairman S. Somanath congratulated the Aditya-L1 team for achieving the final orbit insertion and said that the mission is a proud moment for the country. He said that the spacecraft is in good health and that the payloads will be switched on and calibrated in the coming days. He also thanked the scientific community and the public for their support and interest in the mission.