ESA's bug-eyed "fly-eye" telescope to watch for Earth-threatening asteroids
One aggravating property of the housefly is that swatting one is harder than it looks. One of the reasons for this is flies have eyes designed for avoiding such a day-ruining event by detecting motion over a wide field of vision. Since asteroids have the potential to do to Earth what rolled newspapers do to flies, ESA is developing a telescope based on a fly’s eye as a new asteroid-hunting tool that could be the basis for a new asteroid defense network.
The prospect of a rogue asteroid slamming into the Earth is certainly an unsettling one, so its small wonder that ESA, NASA and others are keen on identifying any potential candidates that might need dealing with in the future. Ideally, the solution would be to set up a telescope to repeatedly scan the entirety of the heavens, but it’s very big sky and an approaching asteroid might not give much notice. It’s a bit like a ship’s lookout. One person can’t look at the entire horizon without a good chance of missing something, but a team has a better chance.
In the case of asteroid hunting, the lookouts would need to be a global network of telescopes because the targets are far too small and faint to be seen with the naked eye. But it would be fantastically expensive just to buy all the telescopes required for such a network, and those scopes wouldn’t necessarily be the best instruments for hunting asteroids. That’s because telescopes are very good for capturing images, but what an asteroid hunter needs is the ability to track movement across the sky.
ESA’s answer to the problem is an automated telescope built along the lines of a fly’s compound eye. Like a fly’s eye, the new scope splits the field of view into 16 images. This means that the telescope won’t see very well, but like a fly’s eye, it will cover a large arc of the sky and be very good at detecting motion. That’s because the scope, and a fly’s eye, acts a bit like a low resolution video that’s a jumble of large pixels. You can’t make out what’s going on, but you can certainly tell if something is moving – often better than if the image were clear.
The telescope operates unattended, is modular, and is designed for mass production, which creates economies of scale and brings down the costs of building, maintaining, and operating the network. The resolution of the fly-eye scope is about that of a one-meter (3.3 ft) telescope and covers a field of view equivalent to about 13 times the diameter of the Moon as seen from the Earth.
With its split-image arrangement, this resolution isn’t enough to identify an asteroid or sort out its trajectory, but it is enough to alert astronomers to take a closer look. ESA doesn’t see the fly-eye network as a perfect solution against rogue asteroids, but the space agency sees it as a way of accounting for everything down to a diameter of 40 m (130 ft) that is within three weeks of impact.
Developed by a consortium led by Italy’s CGS SpA under a €1 million (US$1.3 million) contract, if the detailed design meets with ESA’s approval when completed next year, it will open the way to building a €10 million (US$13 million) prototype as part of ESA’s Space Situational Awareness (SSA) program’s full tracking network.
"The development of the first optical sensor specific to ESA’s NEO search and discovery activities is a fundamental step toward Europe’s contribution to safeguarding our planet from possible collisions by dangerous objects," says Nicolas Bobrinsky, Head of the SSA Programme.