Damage to antennae stalls reopening of giant telescope

A day after the Giant Metrewave Radio Telescope (GMRT) at the National Centre for Radio Astrophysics (NCRA), Pune was shut as a precautionary measure in view of

A day after the Giant Metrewave Radio Telescope (GMRT) at the National Centre for Radio Astrophysics (NCRA), Pune was shut as a precautionary measure in view of high wind speeds due to Cyclone Nisarga, the observatory could not restore operations on Thursday owing to power disruption and minor damage to few antennas.

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On Wednesday, the world’s largest radio telescope facility operating at low radio frequencies was temporarily shut down since Cyclone Nisarga’s predicted trajectory was close to its array of 30 fully steerable parabolic dishes of 45-metre diameter antennas, spread out over a 30km region about 10km east of Narayangaon town on Maharashtra’s Pune-Nashik highway. All GMRT antennas were parked in the default safe mode pointing vertically upwards with brakes on.

As the severe cyclonic storm made landfall, high wind speeds brought trees down on the main power line from Narayangaon, thereby cutting electricity to the centre and far away antennas.

A team at NCRA on Thursday assessed that telescopes were damaged.

“Our wind recording metres showed wind speeds peaking to 80-90kmph, which is fairly high. There is some damage to the sheds where equipment is housed. While 20 out of 30 antennas seem to be fine (rotating with local power from DG sets), there is a little bit of damage to the mesh attached to a couple of antennas,” said Yashwant Gupta, director, NCRA, adding that the mesh on antennas is used for reflection of radio signals.

Gupta said observations were to restart at 8pm on Thursday but have been put off till Friday evening. “Those who were scheduled for observations tonight have been rescheduled for tomorrow afternoon since they requires as many antennas,” said Gupta. “While there is no major damage, a final confirmation will be when we start operating the whole array.”

Though the antennas have been designed to withstand wind speed of 100-120 kmph, the maximum operating speed limit for the antennas is 45kmph. The last time when GMRT operations were suspended temporarily was during the pre-monsoon season in 2016 when gusty winds travelled at 80kmph speed.

Of the 30 parabolic dishes, 14 are located in a central array in a region of about 1sqkm while the remaining 16 dishes are spread out in Y shape over a much larger region up to 25kms.

Built and operated since 2002 by NCRA of the Tata Institute of Fundamental Research, the GMRT facility is used to by astronomers from more than 25 countries to study a wide range of subjects in modern astronomy including the origin and evolution of the universe, pulsars, quasars, radio galaxies.