ISRO Missions and Discoveries

Aditya-L1: India’s first mission to Sun to be launched soon


From UPSC perspective, the following things are important :

Prelims level: Aditya L1 mission

Mains level: Read the attached story


The Indian Space Research Organisation (ISRO) is planning to launch the Aditya-L1 mission by June or July this year.

What is Aditya-L1 Mission?

  • ISRO categorizes Aditya L1 as a 400 kg-class satellite that will be launched using the Polar Satellite Launch Vehicle (PSLV) in XL configuration.
  • It will observe the Sun from a close distance, and try to obtain information about its atmosphere and magnetic field.
  • The space-based observatory will have seven payloads (instruments) on board to study the Sun’s corona, solar emissions, solar winds and flares, and Coronal Mass Ejections (CMEs), and will carry out round-the-clock imaging of the Sun.

L1: Behind the name

  • L1 refers to Lagrangian/Lagrange Point 1, one of five points in the orbital plane of the Earth-Sun system.
  • 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 one-hundredth of the way to the Sun.

Major payloads

  • In total Aditya-L1 has seven payloads, of which the primary payload is the Visible Emission Line Coronagraph (VELC), designed and fabricated by the Indian Institute of Astrophysics, Bengaluru.
  • The satellite carries additional six payloads-
  1. SUIT, the solar ultraviolet imaging telescope
  2. ASPEX (Aditya Solar Wind Particle Experiment),
  3. PAPA (Plasma Analyser Package for Aditya),
  4. SoLEXS (Solar Low Energy X-ray Spectrometer),
  5. HEL1OS (High Energy L1 Orbiting X-ray spectrometer) and
  6. Magnetometer — with enhanced science scope and objectives possible by extensive remote and in-situ observation of the sun.

Why is studying the Sun important?

(1) To understand space weather

  • To learn about and track Earth-directed storms, and to predict their impact, continuous solar observations are needed.
  • Every storm that emerges from the Sun and heads towards Earth passes through L1, and a satellite placed in the halo orbit around L1 of the Sun-Earth system has the major advantage of continuously viewing the Sun without any occultation/eclipses.

(2) Observing corona

  • The VELC payload will be able to observe the corona continuously and the data provided by it is expected to answer many outstanding problems in the field of solar astronomy.
  • No other solar coronagraph in space has the ability to image the solar corona as close to the solar disk as VELC can.
  • It can image it as close as 1.05 times the solar radius.
  • It can also do imaging, spectroscopy, and polarimetry at the same time, and can take observations at a very high resolution (level of detail) and many times a second.

Why are solar missions challenging?

  • Distance: What makes a solar mission challenging is the distance of the Sun from Earth (about 149 million km on average, compared to the only 3.84 lakh km to the Moon).
  • Heat: More importantly the super-hot temperatures and radiations in the solar atmosphere make it difficult to study.

Major missions to Sun till now

  • NASA’s Parker Solar Probe has already gone far closer — but it will be looking away from the Sun.
  • 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.


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