2016-10-24 10:24:14
Trilobites: A Wider-Eyed Watchdog of the Clutter Surrounding Earth

10:24, October 24 188 0

You might think that “space situational awareness” is what a football player needs when he goes up for a pass in a crowd of 300-pound helmeted assassins. But to the Department of Defense, it has a more precise and chilling meaning: namely the need to identify and track the untold hundreds of thousands of objects inhabiting the not-so-empty space around our planet – space junk, missile tests, dead rocket parts, foreign satellites of unknown intent and uncharted asteroids coming in for the kill.

The Air Force operates a globe-girdling network of telescopes, radars and even two satellites to keep track of all this stuff.

Last Tuesday, the latest addition to this sky patrol was unveiled at the White Sands Missile Range in New Mexico: the Space Surveillance Telescope, a 90-ton telescope powered by a 38,000-horsepower engine. Swiveling swiftly and almost silently like a ballerina, it can follow objects as small as a softball as they fly through the sky.

The new telescope, with an innovative mirror and detector array, represents a hundredfold improvement in the ability to see and track small objects in geosynchronous orbit and beyond, according to the Defense Advanced Projects Agency, famous for its blue-sky efforts like the internet and GPS, which developed the telescope and is handing it over to the Air Force.

After five years of testing in New Mexico, during which time it discovered 3,600 new asteroids — including four that could eventually hit Earth — the telescope will be installed next year in Australia, where it will fill a gap in surveillance of the Southern sky.

At the telescope’s heart is a 138-inch-diameter highly curved mirror, which has a wider field of view than previous surveillance telescopes. It moves the game, as Darpa said in a statement, “from seeing only a few large objects at a time through the equivalent of a drinking straw, to a ‘windshield’ view with 10,000 objects at a time.”

The result will be an avalanche of data, a terabyte a night, the agency said.

The key to this prodigious capability is a revolutionary curved detector, which could change the way astronomical telescopes are built in the future, astronomers say. Emmanuel Hugot of the Laboratory for Astrophysics in Marseille, France, called the Darpa telescope “a real breakthrough.”

The electronic detectors used in modern cameras and telescopes are imprinted on flat, rigid chips of silicon. When images from wide-field mirrors like the one in the new Darpa telescope are projected on such flat devices, however, they wind up distorted, the way Greenland looks too big on some maps of the Earth.

To get rid of such distortions and “flatten” the light for conventional flat detectors, astronomers have traditionally had to add complicated optical systems to the back ends of their telescopes, making them more expensive to build and operate.

The detectors in the Darpa telescope, developed by the Lincoln Laboratory at M.I.T., are bendable, demonstrating a way for astronomers to simplify the design and operation of their telescopes, according to Dr. Hugot, the lead author of a paper on recent attempts to make them.

Dr. Hugot said European astronomers would be meeting this month to talk about how to incorporate curved detectors into the European Extremely Large Telescope, a behemoth under construction in Chile that will be the world’s largest ground-based telescope.

What remains to be seen is when the technologies developed by Darpa will spread to civilian astronomers. The main obstacles, Dr. Hugot and his colleagues said in their paper, were manufacturing costs and the need for a parallel commercial market that would make it worthwhile for big companies to invest.