IIA hands over key Aditya-L1 payload to study corona to Isro | India News


BENGALURU: The Indian Institute of Astrophysics (IIA), which has built the Visible Line Emission Coronagraph (VELC) payload for Isro’s Aditya-L1 mission at its CREST (Centre for Research and Education in Science and Technology) campus in Hoskote, on Thursday handover the same to the space agency.
Aditya-L1 is India’s first dedicated scientific mission to study the Sun, and is expected to be launched by Isro in the second half of this year. It is an observatory-class space-based solar mission wherein the spacecraft will be placed in a halo orbit around the first Lagrange point (L1) of the Sun-Earth system.
According to Isro, a satellite around L1 point has the major advantage of continuously viewing the Sun without occultation/eclipses as the position provides a greater advantage of observing solar activities continuously.
Aditya-L1 will carry seven payloads to observe the photosphere, chromosphere, and the outermost layers of the Sun (the corona) using electromagnetic and particle detectors. While four payloads directly view the Sun from L1, the remaining three carry out in-situ studies of particles and fields at L1.
IIA said on Thursday: “VELC is the largest and one or the most technically challenging of the seven payloads that Aditya-L1 will carry. The payload is designed as an internally occulted reflective coronagraph and has been assembled, tested and calibrated at CREST campus.”
To Study What
Pointing out that one of the main puzzles in solar astrophysics was that the atmosphere of the Sun (Corona) is at a temperature of about a million degrees whereas the surface of the Sun is only at about 6,000 Kelvin, IIA said, answering this needs continuous observations of the Corona.
“…Such observation needs to be done right from the surface of the Sun (its disk) and the lower Corona. VELC, which weighs 90kg, has an internal occulter which separates the light from the disk and discards it. The remaining light which is from the Corona, from 1.05Ro to 3Ro (Ro is the radius of the Sun) is sent for further processing,” it said.
What’s unique:
■ It can image solar corona down to as close as 1.05Ro (that is, starting from 1.05 times the solar radius). That would be the closest that any coronagraph on a space mission will be able to image the corona ever
■ It can take observations roughly 3 times every second and with a high pixel resolution of 2.5 arcseconds per pixel
■ Its instruments will have to be kept at a temperature of 22°C while also radiating away enormous amount of heat and light from the solar surface
■ VELC has 40 optical elements with an internally occulted coronagraph with a scatter of just 50 parts per million.

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