Aditya – L1 First Indian mission to study the Sun
The Aditya-1 mission was conceived as a 400kg class satellite carrying one payload. This payload is the Visible Emission Line Coronagraph (VELC). The satellite was planned to launch in an 800 km low earth orbit. A satellite placed in the halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system has a major advantage. It can continuously view the Sun. There are no occultations or eclipses. This is a significant help. So, the Aditya-1 mission has now been revised to “Aditya-L1 mission.” It will be inserted in a halo orbit around the L1, which is 1.5 million km from the Earth. The satellite carries more than six payloads with enhanced science scope and objectives.
The project is approved and the satellite will be launched during the 2019–2020 timeframe by PSLV-XL from Sriharikota.
Aditya-1 was meant to see only the solar corona. The outer layers of the Sun, extending to thousands of km above the disc (photosphere) are termed the corona. It has a temperature of more than a million degrees Kelvin. This is much higher than the solar disc temperature of around 6000K. How the corona gets heated to such high temperatures is still an unanswered question in solar physics.
Aditya-L1 with more experiments can now give observations of the Sun’s Corona (soft and hard X-ray). It can also see emission lines in the visible and NIR, Chromosphere (UV), and photosphere (broadband filters). Also, particle payloads will study the particle flux emanating from the Sun and reaching the L1 orbit. The magnetometer payload will measure the variation in magnetic field strength at the halo orbit around L1. These payloads have to be placed outside the interference from the Earth’s magnetic field. They not have been useful in the low earth orbit.
The main payload continues to be the coronagraph with improved capabilities. The main optics for this experiment stay the same. The finished list of payloads, their scientific aim and the lead institute for developing the payload are provided below:
- Visible Emission Line Coronagraph (VELC): To study the diagnostic limits of solar corona and dynamics and origin of Coronal Mass Ejections (3 visible and 1 Infra-Red channels); magnetic field measurement of solar corona down to tens of Gauss – Indian Institute of Astrophysics (IIA)
- Solar Ultraviolet Imaging Telescope (SUIT): To image the spatially resolved Solar Photosphere and Chromosphere in near Ultraviolet (200-400 nm) and measure solar irradiance variations – Inter-University Centre for Astronomy & Astrophysics (IUCAA)
- Aditya Solar Wind Particle Experiment (ASPEX): To study the variation of solar wind properties as well as its distribution and spectral characteristics – Physical Research Laboratory (PRL)
- Plasma Analyser Package for Aditya (PAPA): To understand the composition of solar wind and its energy distribution – Space Physics Laboratory (SPL), VSSC
- Solar Low Energy X-ray Spectrometer (SoLEXS): To check the X-ray flares for studying the heating mechanism of the solar corona – ISRO Satellite Centre (ISAC)
- High Energy L1 Orbiting X-ray Spectrometer (HEL1OS): To see the dynamic events in the solar corona and give an estimate of the energy used to accelerate the particles during the eruptive events – ISRO Satellite Centre (ISAC)and Udaipur Solar Observatory (USO), PRL
- Magnetometer: To measure the size and nature of the Interplanetary Magnetic Field – Laboratory for Electro-optic Systems (LEOS) and ISAC.
With the inclusion of multiple payloads, this project also provides an opportunity for solar scientists. They come from multiple institutions within the country. They can now take part in space-based instrumentation and observations. Thus, the enhanced Aditya-L1 project will turn on a comprehensive understanding of the dynamic processes of the sun. It will discuss some of the outstanding problems in solar physics.
Reference- https://www.isro.gov.in/ and https://www.sac.gov.in
