Current and future gravitational-wave observatories. [Image: LIGO]
Less than a week after the path-breaking report of the detection of gravitational waves by the international Laser Interferometer Gravitational-wave Observatory (LIGO) scientific team, the Indian government announced that it has approved, in principle, a project to build a new Advanced-LIGO-scale facility in India. The new facility could conceivably become operational as early as the end of 2023.
When completed, the Indian facility will join five other globally distributed observatories expected to be on line. Those will include the two Advanced LIGO facilities in the U.S. states of Washington and Louisiana; the GEO600 facility in Germany; Advanced Virgo, an observatory in Italy currently undergoing an upgrade that’s expected to go on line in 2016; and KAGRA, a Japanese project expected to begin in 2018.
Geographical advantages
The geographical spread offers significant advantages in the search for gravitational waves, and could ultimately materially expand the number of sources detected. LIGO Chief Scientist and OSA Fellow Stanley Whitcomb told OPN in a recent interview that having multiple facilities with large geographical separation helps not only with respect to capturing the very-long-wavelength signal of gravitational waves—on the order of 3,000 km—but also in ensuring good coverage of the strong polarization of these waves from the LIGO detectors, which hug the surface of the Earth and are inherently 2-D in nature.
“For every direction on the sky, for any one of these L-shaped detectors, there’s one linear polarization that we’re completely insensitive to,” Whitcomb notes. The way to get independent orientations that can capture that additional polarization, he says, is to “go a quarter of the way around the world, and on a detector that's built parallel to the Earth's surface you naturally get those other orientations.”
“Technically feasible” by 2023
Quite apart from its value in sniffing out gravitational waves, the new observatory could, in the view of the Indian Cabinet, carry some larger economic and societal benefits for the country. “LIGO-India will … bring considerable opportunities in cutting edge technology for the Indian industry,” according to the Cabinet’s statement announcing the green-light on the project. And, the statement continues, “The project will motivate Indian students and young scientists to explore newer frontiers of knowledge, and will add further impetus to scientific research in the country.”
To get the Indian project off the blocks as quickly as possible, scientists and technicians in the international LIGO consortium are actively collaborating with the Indian team on site selection, technology and designs for the exquisitely sensitive detectors. As a result, according to Fred Raab, who heads the Advanced LIGO facility in Hanford, Washington, and also acts as LIGO liaison with the India project, “it is technically feasible for LIGO-India to go online by the end of 2023.”