Cyclone shuts global facility to study cosmos
Built and operated since 2002 by the National Centre for Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research, the GMRT facility studies a wide range of subjects in modern astronomy including the origin and evolution of the universe, pulsars, quasars, radio galaxies.Updated: Jun 04, 2020 01:23 IST
The Giant Metrewave Radio Telescope (GMRT), which is the world’s largest radio telescope facility operating at low radio frequencies, was shut down for a day on Wednesday since cyclone Nisarga’s predicted trajectory was close to its array of 30 fully steerable parabolic dishes of 45m-diameter antennas, spread out over a 30km region about 10km east of Narayangaon town on Maharashtra’s Pune-Nasik highway.
Built and operated since 2002 by the National Centre for Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research, the GMRT facility studies a wide range of subjects in modern astronomy including the origin and evolution of the universe, pulsars, quasars, radio galaxies. The facility, used by astronomers from more than 25 countries, is equipped to investigate a span ranging from nearby solar systems to the edge of the observable universe. In May, it was instrumental in helping a team of international scientists discover a new class of powerful astronomical explosions caused by a Fast Blue Optical Transient, which simply put, is a super powerful explosion of a star.
A team at NCRA was tracking the storm’s path since Tuesday. “Going by the wind speed from various climate models, we decided to shut down the observatory, and all antennas have been parked in safe mode since morning, till the track of Cyclone Nisarga passes over GMRT,” said Yashwant Gupta, director, NCRA.
Gupta added that though antennas have been designed to withstand wind speed of 100-120 kmph, the maximum operating speed limit for the antennas is 45kmph. The safe position with antennae pointing straight up ensures minimum cross section for the wind. Also, the wire mesh design of GMRT helps reduce loading of the wind. The last time that GMRT operations were suspended temporarily was during the pre-monsoon season in 2016.
“It was an extreme episode of gusty winds travelling at 80kmph. High winds usually prevail during the pre-monsoon months of April to mid May over the area where GMRT is located,” said Gupta. “While the antennas survived at that speed, wind speed from Cyclone Nisarga was predicted to be 50-60kmph and could have been higher. For a major cyclone activity, we shut operations for the first time.”
Having decided on Tuesday evening to suspend regular observations from Wednesday morning, the public outreach team at NCRA tweeted that antennas have been parked in the default safe position with brakes on, on both the axes.
“In the park position, all GMRT antennas point vertically upwards, towards the zenith. The elevation axis is locked with a mechanical arrangement which is meant for this purpose. This will remain in force till tomorrow morning or until the conditions are declared safe,” the tweet said.
Of the 30 parabolic dishes, 14 are located in a central array in a region of about one kmsq while the remaining 16 dishes are spread out in Y shape over a much larger region up to 25km.
“We would like to normalise operations tomorrow (Thursday) but that will depend whether or not power lines trip since 16 antennas are powered with electricity lines that cross farms lands, while power lines for 14 run underground on our land,” said Gupta.