The Indian Institute of Astrophysics (IIA) has successfully completed the assembly, testing, and calibration of the Visible Line Emission Coronagraph (VELC), the primary payload on board Aditya-L1, India's first dedicated scientific mission to study the sun. The VELC, which is the largest and one of the most technically challenging of the seven payloads/telescopes that will fly on Aditya-L1, was handed over to the Indian Space Research Organisation (ISRO) in a ceremony at the Centre for Research and Education in Science and Technology (CREST) campus of IIA.
Aditya-L1 is the first space-based Indian mission to study the sun from a halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system. This mission, with seven payloads on board to observe the photosphere, chromosphere, and the outermost layers of the sun (the corona), will provide greater advantage of observing solar activities and its effect on space weather, according to officials of ISRO.
ISRO Chairman S Somanath said that the launch of Aditya-L1 is expected to be around June or July. He noted that understanding the effect of the sun on Earth and its surroundings has become very important now and Aditya-L1 aims to shed light on this topic. Somanath also mentioned that it has taken 15 years for VELC from concept to completion and that this period was needed for a complex system like this. He said, "The VELC has been the finest collaboration between IIA and ISRO."
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The mission was initially conceived as Aditya-1 with a 400 kg class satellite carrying one payload (VELC) and was planned to be launched in an 800 km low earth orbit. But since a satellite placed in a halo orbit around the L1 of the Sun-Earth system has the major advantage of continuously viewing the sun without any occultation/eclipses, the mission was revised to Aditya-L1 and it would now be inserted in a halo orbit around the L1, which is 1.5 million km from the Earth towards the sun.
The other six payloads are: Solar Ultraviolet Imaging Telescope, Aditya Solar Wind Particle Experiment, Plasma Analyser Package for Aditya, Solar Low Energy X-ray Spectrometer, High Energy L1 Orbiting X-ray Spectrometer, and Magnetometer. The scientific studies by the satellite will enhance our current understanding of the Solar Corona and also provide vital data for space weather studies, ISRO officials said.
The Principal Investigator of the VELC payload, Prof Raghavendra Prasad, explained that no other solar coronagraph in space has the ability to image the solar corona as close to the solar disk as VELC can. He said, "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." He added that this capability will revolutionize solar astronomy around the world and the data is expected to answer many outstanding problems in the field.
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Former Chairman of ISRO A S Kiran Kumar said that VELC is not a trivial piece of engineering and it has taken 15 years to produce such a complex system. He said, "This augurs well for future space missions and I look forward to more such novel space science missions in the future."