The Indian Space Research Organization (ISRO) is preparing for its first scientific expedition to study the Sun, Aditya-L1. It would be placed into a point in space known as the L1 Lagrange point.
- Aditya L1 will be ISRO’s 2nd space-based astronomy mission after AstroSat, which was launched in 2015.
- Aditya 1 was renamed as Aditya-L1. The Aditya 1 was meant to observe only the solar corona.
- AstroSat, was launched in September, 2015, by PSLV-C30 from Sriharikota (Andhra Pradesh).
- It is the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, optical and UV spectral bands simultaneously.
- Launch Vehicle: Aditya L1 will be launched using the Polar Satellite Launch Vehicle (PSLV) XL with 7 payloads (instruments) on board.
- Objective: Aditya L1 will study the Sun’s corona (Visible and Near infrared rays), Sun’s photosphere (soft and hard X-ray), chromosphere (Ultra Violet ), solar emissions, solar winds and flares, and Coronal Mass Ejections(CMEs), and will carry out round-the-clock imaging of the Sun.
- Challenges: The distance of the Sun from Earth ( approximately 15 crore kms on average, compared to the only 3.84 lakh kms to the Moon).This huge distance poses a scientific challenge.
- Due to the risks involved, payloads in earlier ISRO missions have largely remained stationary in space; however, Aditya L1 will have some moving components which increases the risks of collision.
- Other issues are the super hot temperatures and radiation in the solar atmosphere. However, Aditya L1 will stay much farther away, and the heat is not expected to be a major concern for the instruments on board.
- Evolution of every planet, including Earth and the exoplanets beyond the Solar System, is governed by its parent star i.e the Sun in our case. The Solar weather and environment affects the weather of the entire system. Therefore, it is important to study the Sun.
- Effects of Variation in Solar Weather System: Variations in this weather can change the orbits of satellites or shorten their lives, interfere with or damage onboard electronics, and cause power blackouts and other disturbances on Earth.
- Knowledge of solar events is key to understanding space weather.
- To learn about and track Earth-directed storms, and to predict their impact, continuous solar observations are needed.
- Many of the instruments and their components for this mission are being manufactured for the first time in the country.
Lagrange Point 1
- Lagrange Points, named after Italian-French mathematician Josephy-Louis Lagrange, are positions in space where the gravitational forces of a two-body system (like the Sun and the Earth) produce enhanced regions of attraction and repulsion.
- The L1 point is about 1.5 million km from Earth, or about 1/100th of the way to the Sun.
- L1 refers to Lagrangian/Lagrange Point 1, one of 5 points in the orbital plane of the Earth-Sun system.
- These can be used by spacecraft to reduce fuel consumption needed to remain in position.
- A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) has the major advantage of continuously viewing the Sun without any occultation/ eclipses.
- The L1 point is home to the Solar and Heliospheric Observatory Satellite (SOHO), an international collaboration project of National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA).
Aditya L1 Mission
The Aditya-1 mission has conceived as a 400kg class satellite carrying one payload, the Visible Emission Line Coronagraph (VELC) and was planned to launch in a 800 km low earth orbit. A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system has the major advantage of continuously viewing the Sun without any occultation/ eclipses. Therefore, the Aditya-1 mission has now been revised to “Aditya-L1 mission” and will be inserted in a halo orbit around the L1, which is 1.5 million km from the Earth. The satellite carries additional six payloads with enhanced science scope and objectives.
The project is approved and the satellite will be launched during 2019 – 2020 timeframe by PSLV-XL from Sriharikota.
Aditya-1 was meant to observe only the solar corona. The outer layers of the Sun, extending to thousands of km above the disc (photosphere) is termed as the corona. It has a temperature of more than a million degree Kelvin which 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 additional experiments can now provide observations of Sun’s Corona (soft and hard X-ray, Emission lines in the visible and NIR), Chromosphere (UV) and photosphere (broadband filters). In addition, particle payloads will study the particle flux emanating from the Sun and reaching the L1 orbit, and 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 and could 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 remains the same. The complete list of payloads, their science objective and lead institute for developing the payload is provided below:
- Visible Emission Line Coronagraph (VELC): To study the diagnostic parameters 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 monitor 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 observe the dynamic events in the solar corona and provide 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 magnitude 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 to solar scientists from multiple institutions within the country to participate in space based instrumentation and observations. Thus the enhanced Aditya-L1 project will enable a comprehensive understanding of the dynamical processes of the sun and address some of the outstanding problems in solar physics.
Other Missions to the Sun
- NASA’s Parker Solar Probe’s aim is to trace how energy and heat move through the Sun’s corona and to study the source of the solar wind acceleration.
- It is part of NASA’s ‘Living With a Star’ programme that explores different aspects of the Sun-Earth system.
- The earlier Helios 2 solar probe, a joint venture between NASA and space agency of erstwhile West Germany, went within 43 million km of the Sun’s surface in 1976.
A more recent technical report on this topic by Dr. Angel, in which the idea is taken to another stage in development using only electromagnetic launch from Earth and no construction on the Moon or at L1
So we hope these mission will able to unveiled the secret of Sun’s Atmosphere and its Corona. Aditya L1 mission will create history for Indian Space Program and proved to be landmark as expected.