What is the Visible Emission Line Coronagraph (VELC)?

Jan. 27, 2023

The handover ceremony of the Visible Emission Line Coronagraph (VELC) which is the primary payload of Aditya-L1 Mission was held recently.

About Visible Emission Line Coronagraph (VELC) on board Aditya-L1:

  • What is it?It is the largest payload that would fly on the Aditya-L1 mission. It is an internally occulted solar coronagraph capable of simultaneous imaging, spectroscopy and spectro-polarimetry close to the solar limb.
  • The VELC consists of a coronagraph, spectrograph, polarimetry module and detectors, aside from auxiliary optics.
  • It is built by the Indian Institute of Astrophysics (IIA) at its CREST (Centre for Research and Education in Science and Technology) campus at Hosakote, Karnataka.
  • Purpose:
    • It will observe the solar corona, which is the tenuous, outermost layer of the solar atmosphere.
    • It will analyze the coronal temperature, plasma velocity, density, etc.
    • It will also study Coronal Mass Ejections (CMEs) and the solar wind.

 What is Aditya-L1 Mission:

  • It is India's first dedicated scientific mission to study the Sun.
  • The spacecraft will be placed in a halo orbit around the first Lagrange point, L1, which is 1.5 million km from the Earth towards the Sun.
  • A satellite around the L1 point has the major advantage of continuously viewing the Sun without occultation/eclipses.
  • Aditya-L1 carries seven payloads to observe the photosphere, chromosphere, and the outermost layers of the Sun (the corona) using electromagnetic and particle detectors.
  • The satellite will be launched by PSLV-XL launch vehicle from Sriharikota.

 What are Coronal Mass Ejections (CMEs):

  • (CMEs) are large expulsions of plasma and magnetic fields from the Sun’s corona.
  • The blast of a CME carries about a billion tons of material out from the Sun at very high speeds of hundreds of kilometers per second.
  • A CME contains particle radiation (mostly protons and electrons) and powerful magnetic fields stronger than what is normally present in the solar wind.
  • The resulting shocks ripple through the solar system and can interrupt satellites and power grids on Earth.