Print Friendly, PDF & Email





If 2019 was all about the Moon for Indian space agency ISRO, year 2020 could well be about the Sun. In his Mann Ki Baat address on Sunday, Prime Minister Narendra Modi spoke about the ISRO’s plans to launch its first Sun Mission Aditya L1. This ambitious plan of the Indian Space Research Organisation will not only put India in a very elite league, but also at the very frontier of cutting edge research. With Aditya L1, ISRO will take a huge step forward in the study of solar corona. The solar Corona is the outer most part of the Sun’s atmosphere. It is usually hidden by the bright light of the Sun’s surface. The 400 KG-Class Aditya L1 will carry six scientific payloads that will be inserted in a halo orbit around the Lagrangian point 1 or L1, Incidentally L1 is 1.5 million kilometres from the Earth.

Aditya-1 mission:

  • The Aditya-1 mission was 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 mid 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.

What are Lagrangian points and halo orbit?

Lagrangian points are the locations in space where the combined gravitational pull of two large masses roughly balance each other. Any small mass placed at that location will remain at constant distances relative to the large masses. There are five such points in Sun-Earth system and they are denoted as L1, L2, L3, L4 and L5. A halo orbit is a periodic three-dimensional orbit near the L1, L2 or L3

Why do we study the sun and the solar wind?

  • The sun is the only star we can study up close. By studying this star we live with, we learn more about stars throughout the universe.
  • The sun is a source of light and heat for life on Earth. The more we know about it, the more we can understand how life on Earth developed.
  • The sun also affects Earth in less familiar ways. It is the source of the solar wind; a flow of ionized gases from the sun that streams past Earth at speeds of more than 500 km per second (a million miles per hour).
  • Disturbances in the solar wind shake Earth’s magnetic field and pump energy into the radiation belts, part of a set of changes in near-Earth space known as space weather.
  • Space weather can change the orbits of satellites, shorten their lifetimes, or interfere with onboard electronics. The more we learn about what causes space weather – and how to predict it – the more we can protect the satellites we depend on.
  • The solar wind dominates the space environment. As we send spacecraft and astronauts further and further from home, we must understand this space environment just as early seafarers needed to understand the ocean.

Solar Missions:

  • Genesis (2001-04)- Genesis was the first spacecraft to capture a sample of the solar wind, or the constant stream of particles that emanate from our sun.
  • Solar and Heliospheric Observatory (SOHO) (1995-present)- SOHO is a collaboration between the European Space Agency (ESA) and NASA to study the sun, observing all the way from its core out to the solar wind.
  • Transition Region and Coronal Explorer (TRACE) (1998-2010)- TRACE’s major goal was to better understand how magnetic fields and plasma (superheated gas) act in the sun’s environment.
  • Ulysses (1990-2009)- Ulysses, a joint mission between NASA and ESA, was designed to look at the heliosphere, which is the part of space under the influence of the sun.
  • Yohkoh (1991-2001)- Yohkoh (also known as Solar-A) was a Japanese-led spacecraft from the Institute of Space and Astronautical Science, the former name of Japan’s space agency. The Earth-orbiting spacecraft imaged the sun in X-rays and with spectrometry.
  • Hinode (2006-present)- Japan’s Hinode satellite (also known as Solar-B) focuses on the solar corona, the extremely hot upper atmosphere of the sun.
  • Solar Terrestrial Relations Observatory (STEREO) (2006-present)- STEREO was launched with two spacecraft: STEREO-Ahead (which orbits the sun ahead of Earth in its orbit) and STEREO-Behind (which orbits the sun behind Earth). Its achievements include showing the three-dimensional structure of CMEs and showing how matter and energy flow to Earth
  • Solar Dynamics Observatory (SDO) (2010-present)- The major goal of SDO is to better understand solar activity.
  • Interface Region Imaging Spectrograph (2013-present)- IRIS focuses on the lower levels of the sun’s atmosphere, which is a region that is called the interface region.

ISRO’s Success Story: 2019

  • Microsat-RMicrosat-R, an imaging satellite was successfully injected into intended orbit of 274 km by PSLV-C44 on January 24, 2019.
  • GSAT-31India’s telecommunication satellite, GSAT-31 was successfully launched on February 06, 2019 from Kourou launch base, French Guiana by Ariane-5 VA-247.The satellite provides Indian mainland and island coverage.
  • EMISAT– EMISAT is a satellite built around ISRO’s Mini Satellite-2 bus weighing about 436 kg. The satellite was successfully placed in its intended sun-synchronous polar orbit of 748 km height by PSLV-C45 on April 01, 2019. The satellite is intended for electromagnetic spectrum measurement.
  • RISAT-2BRISAT-2B is radar imaging earth observation satellite developed by ISRO.
  • Chandrayaan 2- Chandrayaan-2 mission is a highly complex mission, which represents a significant technological leap compared to the previous missions of ISRO. It comprised an Orbiter, Lander and Rover to explore the unexplored South Pole of the Moon.
  • Cartosat-3 Cartosat-3 satellite is a third generation agile advanced satellite having high resolution imaging capability.
  • RISAT-2BR1 RISAT-2BR1 is radar imaging earth observation satellite. The satellite will provide services in the field of Agriculture, Forestry and Disaster Management.