Abstract:

The Sun, our nearest star, is an excellent plasma laboratory where the plasma behaves as a fluid near the solar corona whereas the solar wind plasma near the Earth can be considered as a particle. The outer layers of the Sun’s atmosphere extending to thousands of km above the disc (photosphere) are known as solar corona. It has a temperature of more than a million degrees Kelvin while the photosphere temperature is around 6,000 K. How the solar corona gets heated to such a high temperature is still an unsolved mystery in solar physics.

Aditya-L1 spacecraft is a dedicated space science mission of the Indian Space Research Organization (ISRO) to study the Sun from the halo orbit around the Lagrangian point (L1) of the Sun-Earth system. The orbit around L1 provides continuous solar observations without any eclipse/occultation and is an excellent outpost outside Earth's magnetic field to make in-situ measurements of incoming charged particles. Aditya-L1 Mission is planned for a launch by a PSLV-XL rocket into an elliptical Earth Parking Orbit of 245 km by 21,000 km. The onboard satellite propulsion will be utilized to raise the orbit, transfer to the L1 point and maintain the L1 halo orbit. The transfer period is planned to be around 100 days and the mission has a nominal lifetime of five years.

Aditya-L1 is a 1500 kg-class satellite carrying seven payloads. The payloads cover the Sun’s photosphere (ultraviolet (UV) and soft and hard X-rays), chromosphere (UV) and corona (visible and NIR). The main science payloads are the 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), and three in-situ instruments, Magnetometer (MAG), Aditya Solar wind Particle Experiment (ASPEX) and Plasma Analyzer Package for Aditya (PAPA).

This paper presents an overview of the space system architecture and science objectives of India’s Aditya-L1 Mission to study the photosphere, chromosphere and corona of the Sun, detailing spacecraft architecture, science instruments, launch vehicle, mission design and ground segment through value-driven design model and tradespace exploration methods.