SCIENTISTS have worked out that WT1190F will plunge to Earth above the Indian Ocean on November 13, 2015, making it one of the very few space objects whose impact can be accurately predicted. More unusual still, WT1190F was a “lost” piece of space debris orbiting far beyond the Moon, ignored and unidentified, before being glimpsed by a telescope in early October.

An observing campaign is now taking shape to follow the object as it dives through Earth’s atmosphere, says Gerhard Drolshagen, co-manager of the European Space Agency’s Near-Earth Object office in Noordwijk, the Netherlands. The event offers not just a scientific opportunity, but also tests the plans that astronomers have put in place to coordinate their efforts when a potentially dangerous space object shows up. “What we planned to do seems to work,” Drolshagen says. “But it’s still three weeks to go.”

WT1190F was detected by the Catalina Sky Survey, a program aimed at discovering asteroids and comets that swing close to Earth. At first scientists didn’t know what to make of this weird body. But they quickly computed its trajectory, after collecting more observations and unearthing 2012 and 2013 sightings from telescope archives, says independent astronomy software developer Bill Gray, who has been working to track the debris with NASA’s Jet Propulsion Laboratory in Pasadena, California.

WT1190F travels a highly elliptical orbit, swinging out twice as far as the Earth-Moon distance, Gray says. Gray’s calculations show that it will hit the Earth at 6:20 UTC, falling about 65 kilometres off the southern tip of Sri Lanka. Much if not all of it will burn up in the atmosphere, but “I would not necessarily want to be going fishing directly underneath it,” Gray says.

The object is only one to two metres in size, and its trajectory shows it is low-density, perhaps hollow. That suggests an artificial object, “a lost piece of space history that’s come back to haunt us”, says Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. It could be a spent rocket stage or paneling shed by a recent Moon mission. It is also possible that the debris dates back decades, perhaps even to the Apollo era. An object seen orbiting the Earth in 2002 was eventually determined to be a discarded segment of the Saturn V rocket that launched the first men to land on the Moon.

WT1190F is a rare breed. Researchers currently track only 20 or so artificial objects in distant orbits, says Gareth Williams, an astronomer at the Minor Planet Center in Cambridge, Massachusetts. There are likely many more such pieces of space junk in orbit around the Earth-Moon system, but it is impossible to say how many. The disruptive presence of the Sun and Moon must have kicked WT1190F onto a path that will soon lead it to self-destruct in the atmosphere. No others are known to have made the return trip to Earth, though it’s likely some have done so without anyone noticing, McDowell says.
Drolshagen plans to get spectral information on the object, which may help identify it, and he hopes to coordinate impact observations conducted on board ships or planes.

But that may be the end of the concerted effort to study this class of objects. Unlike near-Earth asteroids, space debris that flies well away from Earth has not commanded significant amounts of funding and attention. And the US military, which tracks space debris, says it lacks the ability to identify WT1190F or predict its path.
“There is no official, funded effort to do tracking of deep-Earth orbits the way we track low-Earth orbit,” McDowell says. “I think that has to change”.
*Adapted from Nature