PUNE: For the first time, the Giant Metrewave Radio Telescope (GMRT) near Pune is all set to participate in international observations. After a series of upgrades and nearly two years of successful trial runs, the GMRT will now be integrated with global Very Long Baseline Interferometry (VLBI) networks, allowing Indian telescopes to work in sync with observatories across Europe, Australia and Japan; the National Centre for Radio Astrophysics (NCRA) confirmed.
Yashwant Gupta, director of the NCRA, said that the integration marks a significant leap in the GMRT’s observational range. “The GMRT has completed extensive groundwork to expand its reach far beyond the existing 30 km baseline. The GMRT’s 30 antennas work together as a single telescope by combining data from all antennas. The question now is: can we push this beyond 30 km — to 100 km, 500 km, even 1,000 km? In principle, it is possible. The advantage is much higher resolution, allowing us to see much finer objects in the sky,” Gupta said.
Gupta further said that India already has facilities capable of complementing the GMRT’s frequency range, enabling long-distance coordinated observations. “For example, the Ooty radio telescope works at frequencies that overlap with the GMRT. Thus, there is potential for joint observations. Beyond that, we can link up with Australia, East Asia, Japan, China and observatories in Europe,” he said.
Explaining the technique, Gupta said that such synchronised global operations fall under VLBI. “When telescopes in different regions conduct coordinated observations, it is called Very Long Baseline Interferometry. The ‘very long’ refers to distances far greater than the GMRT’s current maximum baseline of 30 km,” he said.
{{/usCountry}}Explaining the technique, Gupta said that such synchronised global operations fall under VLBI. “When telescopes in different regions conduct coordinated observations, it is called Very Long Baseline Interferometry. The ‘very long’ refers to distances far greater than the GMRT’s current maximum baseline of 30 km,” he said.
{{/usCountry}}To make the GMRT compatible with global VLBI systems, the NCRA undertook significant technical modifications. “We had to incorporate additional techniques — how we take the data, record it and transmit it to a common centre for analysis. Over the past two years, the GMRT has been running VLBI trials with observatories in Europe, Australia and Japan, and ‘all tests are now showing good results’,” Gupta said.
With these successful trials, Indian researchers are now preparing for the GMRT’s first, full-scale scientific observations in collaboration with the European VLBI Network (EVN). “Researchers are planning actual science experiments combining the GMRT with the EVN. This will be the first time an Indian telescope will participate in joint scientific observations with international observatories,” Gupta said.
The NCRA is also advancing a three-way VLBI initiative connecting the GMRT, Ooty radio telescope and Japanese observatories. “This will be the first time that Indian telescopes, together with international partners, will conduct coordinated VLBI observations. Europe and the US routinely conduct such joint work. We were not able to until now, but with the GMRT upgrade, India will join the global VLBI community,” Gupta said.
Located at Khodad village around 80 km from Pune, the GMRT is one of the world’s largest and most sensitive low-frequency radio telescope arrays. Built and operated by the NCRA–Tata Institute of Fundamental Research, it consists of 30 fully steerable, 45-metre antennas operating between 150 MHz and 1.5 GHz. The extensive upgrade project, which has been underway since 2014, is now complete — firmly placing India on the global map of collaborative radio astronomy.