[Editors] MIT Lincoln Laboratory detectors seek asteroid, comet threats

[Teresa Herbert]

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Early warning of dangerous asteroids and comets
--Detectors developed at MIT Lincoln Laboratory deployed in powerful  
telescope
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For Immediate Release
TUESDAY, NOV. 18, 2008

Contact: Teresa Herbert, MIT News Office
E: therbert at mit.edu, T: 617-258-5403


David R. Granchelli, MIT Lincoln Laboratory
E: granchelli at ll.mit.edu, T: 781-981-4204

CAMBRIDGE, Mass. — Silicon chips developed at MIT Lincoln Laboratory  
are at the heart of a new survey telescope that will soon provide a  
more than fivefold improvement in scientists’ ability to detect  
asteroids and comets that could someday pose a threat to the planet.

The prototype telescope installed on Haleakala mountain, Maui, will  
begin operation this December. It will feature the world’s largest and  
most advanced digital camera, using the Lincoln Laboratory silicon  
chips. This telescope is the first of four that will be housed  
together in one dome. The system, called Pan-STARRS (for Panoramic  
Survey Telescope and Rapid Response System), is being developed at the  
University of Hawaii’s Institute for Astronomy.

“This is a truly giant instrument,” said University of Hawaii  
astronomer John Tonry, who led the team developing the new 1.4- 
gigapixel camera. “We get an image that is 38,000 by 38,000 pixels in  
size, or about 200 times larger than you get in a high-end consumer  
digital camera.”

Pan-STARRS, whose cameras cover an area of sky six times the width of  
the full moon and can detect stars 10 million times fainter than those  
visible to the naked eye, is also unique in its ability to find moving  
or variable objects.

Lincoln Laboratory’s charge-coupled device (CCD) technology is a key  
enabling technology for the telescope’s camera. In the mid-1990s,  
Lincoln Laboratory researchers Barry Burke and Dick Savoye of the  
Advanced Imaging Technology Group, in collaboration with Tonry, who  
was then working at MIT, developed the orthogonal-transfer charge- 
coupled device (OTCCD), a CCD that can shift its pixels to cancel the  
effects of random image motion. Many consumer digital cameras use a  
moving lens or chip mount to provide camera-motion compensation and  
thus reduce blur, but the OTCCD does this electronically at the pixel  
level and at much higher speeds.

The challenge presented by the Pan-STARRS camera is its exceptionally  
wide field of view. For wide fields of view, jitter in the stars  
begins to vary across the image, and an OTCCD with its single shift  
pattern for all the pixels begins to lose its effectiveness. The  
solution for Pan-STARRS, proposed by Tonry and developed in  
collaboration with Lincoln Laboratory, was to make an array of 60  
small, separate OTCCDs on a single silicon chip. This architecture  
enabled independent shifts optimized for tracking the varied image  
motion across a wide scene.

“Not only was Lincoln the only place where the OTCCD had been  
demonstrated, but the added features that Pan-STARRS needed made the  
design much more complicated,” said Burke, who has been working on the  
Pan-STARRS project. “It is fair to say that Lincoln was, and is,  
uniquely equipped in chip design, wafer processing, packaging, and  
testing to deliver such technology.”

The primary mission of Pan-STARRS is to detect Earth-approaching  
asteroids and comets that could be dangerous to the planet. When the  
system becomes fully operational, the entire sky visible from Hawaii  
(about three-quarters of the total sky) will be photographed at least  
once a week, and all images will be entered into powerful computers at  
the Maui High Performance Computer Center. Scientists at the center  
will analyze the images for changes that could reveal a previously  
unknown asteroid. They will also combine data from several images to  
calculate the orbits of asteroids, looking for indications that an  
asteroid may be on a collision course with Earth.

Pan-STARRS will also be used to catalog 99 percent of stars in the  
northern hemisphere that have ever been observed by visible light,  
including stars from nearby galaxies. In addition, the Pan-STARRS  
survey of the whole sky will present astronomers with the opportunity  
to discover, and monitor, planets around other stars, as well as rare  
explosive objects in other galaxies.

Detailed information about the Pan-STARRS design and its science  
applications can be found at http://pan-starrs.ifa.hawaii.edu/public/.  
The project was funded by the U.S. Air Force Research Laboratory.

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