EYE ON THE SKIES
Hanle is hard to reach. It’s 10 hours or 270 km from the nearest city, Leh. It’s too cold at the best of times and home to 300-odd people. But to astrophysicists, it’s a stairway to heaven. The village houses the Indian Astronomical Observatory (IAO), which at 4,500 metres above sea level, is one of the world’s highest, with some of the clearest views of the skies. Since June 12, it’s also been home to India’s first robotic telescope, a device that networks with 17 others across the Northern Hemisphere to form GROWTH, a Global Relay of Observatories Watching Transients Happen.
What happens when 18 telescopes combine forces? They form an exclusive, otherworldly club where it’s always night. Earth’s rotation means that any observatory will experience downtime – daylight obliterates the view of the beyond. But GROWTH’s connected telescopes, in the US, UK, Germany, Israel, India, Taiwan and Japan, let you still watch the same patch of sky from another part of the world; one where the sun hasn’t risen yet.
WORKING FAST
For astronomers tracking transient events (short-lived cosmic occurrences that can last mere hours or days), this is a bonanza. When a survey telescope detects the start of something interesting, all GROWTH telescopes respond, says GC Anupama, an astrophysicist with the Indian Institute of Astrophysics (IIAp), who heads the project. “Rapid, constant communication within the network ensures a quick follow-up by facilities that are suitably located.” It allows researchers to gather data in the first 24 hours of an event to understand, on a physics level, what’s happening and why.
Anupama operates the telescope from the IIAp centre near Bengaluru, 3,000 km away. A pre-programmed sequence of operations can open the dome, aim the telescope towards the desired object, configure the instrument to observe what’s happening and record data. “An observer can eavesdrop periodically, from a remote location, via the internet,” she says.
The bots are especially helpful for sudden, urgent bursts of activity, says Varun Bhalerao, a physicist at the Indian Institute of Technology-Bombay, and principal investigator in the project. “When LIGO [a large-scale American observatory] detects gravitational waves somewhere in the universe, we’re usually scrambling,” he says. “Precious time is lost setting the telescope up. A robotic telescope outsources the drudgery of calibration to the machine.”
LOOKING AHEAD
It will be a couple of months of fine-tuning before the bot takes over the Hanle telescope completely, leaving scientists to spend their time on interpreting readings.
The global network aims to find electromagnetic counterparts to gravitational wave force – supporting proof of violent, energetic events in the universe. It could help understand how heavy elements combine to form a star and what happens when die. It also hopes to detect young starbursts and asteroids closer to Earth. So a system of small, linked telescopes is useful. GROWTH-India’s has a 70-cm lens.
“Think of the view from a moving train,” Bhalerao says. “Poles and closer objects appear to move by faster, trees in the distance are easier to observe. A large telescope is designed for long-range, precise focus. A small one covers a wider field. So instead of a sniper rifle, the smaller telescopes work like Rambo’s machine guns, covering a larger, closer area for longer.”
The GROWTH-India telescope cost ₹3.5 crore, funded by the Science and Engineering Research Board of India’s Department of Science and Technology. The the American institute Caltech leads the network and in India, IIAp and IIT-B run it.
At Hanle, IIAp engineer Angchuk Dorje has been keeping one eye on the telescopes and the other on the skies. It’s so remote, he says, that “a scientist needs to set aside at least five to seven days to spend a night or two here for observations”. It is however, largely cloud-free, with long nights and dark, pollution free skies – a delight for stargazers. “Whenever an astronomer or scientist visits, our faces glow at the latest astronomy news,” he says.
The IAO’s next telescope, the world’s largest at this altitude, will be ready next year. India is building a large one in Ladakh to study the sun. In 2016 in Nainital, ARIES, Asia’s largest optical telescope, was activated. In South Africa, we’ve co-funded the largest single optical telescope in the southern hemisphere and are helping build the world’s largest radio telescope. “What India needs is more eyes on the skies; at least 10 times more astronomers than we have,” Bhalerao says.