What is the Visible Emission Line Coronagraph (VELC)?

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

• It is the largest payload that would fly on the Aditya-L1 mission.
• What is it? 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.

 

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Q1) What is a spectrograph?

A spectrograph — sometimes called a spectroscope or spectrometer — breaks the light from a single material into its component colors the way a prism splits white light into a rainbow. It records this spectrum, which allows scientists to analyze the light and discover properties of the material interacting with it.

Source: India’s first mission to study the Sun will be launched by June-July: ISRO chairman