MIT engineers have developed silicon chips that will be at the heart of a telescope installed on Haleakala mountain, Maui, Hawaii, which will begin operation next month. 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. 'The primary mission of Pan-STARRS is to detect Earth-approaching asteroids and comets that could be dangerous to the planet.' Apparently, it will be able to give us early warnings about dangerous asteroids and comets. The lead researcher says that they '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.' In fact, this telescope will be able to detect 'stars 10 million times fainter than those visible to the naked eye' and other moving objects near the Earth. But read more...
You can see above the "schematic of one of the four Pan-STARRS gigapixel cameras. About half of the 60 Orthogonal Transfer Array (OTA) devices can be seen through the 56-cm diameter window, which also comprises the final corrector lens in the optical path of the telescope. The four grey boxes on each side of the camera contain the readout electronics for the OTA devices. The overall length of the camera is about 1.5 meters." (Credit: Pan-STARRS project) Here is a link to a larger version of this diagram and another one to other pictures about this camera. You also might want to take a peek at this page about the camera design.
You can see above an image captured "in early 2008 while the PS1 telescope and its camera were undergoing commissioning and debugging. At this stage of commissioning, the system 'image quality' was about a factor of 2 worse than what will be achieved by the end of commissioning and the beginning of science operations." This is a picture of the galaxy M51 and its companion NGC5195. "In the full resolution version each pixel represents the native resolution of 0.26 arcsec. In the binned version on this page each pixel is 1.3 arcsec." (Credit: Pan-STARRS) Here are two links to other early images and to a bigger photo gallery.
The chips inside this gigapixel camera have been developed at MIT Lincoln Laboratory by astronomer John Tonry and colleagues at MIT. While Tonry now works for the University of Hawaii, he still is very present at MIT. For example, read Lincoln Laboratory supplies detectors for world's most advanced digital camera (September 2008).
But why are these chips so unique? "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."
As one goal of Pan-STARRS is to detect as many as 99% of "stars in the northern hemisphere that have ever been observed by visible light," the gigapixel camera has a very wide field of view, which presents some challenges. "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."
But the primary goal of Pan-STARRS is to detect Earth-approaching asteroids and comets that could be dangerous to us. "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."
For more information about this aspect of the Pan-STARRS mission, you should read The Threat to Earth from Asteroids and Comets. Here is an excerpt. "Since it formed over 4.5 billion years ago, Earth has been hit many times by asteroids and comets whose orbits bring them into the inner solar system. These objects, collectively known as Near Earth Objects or NEOs, still pose a danger to Earth today. Depending on the size of the impacting object, such a collision can cause massive damage on local to global scales. There is no doubt that sometime in the future Earth will suffer another cosmic impact; the only question is "when?". There is strong scientific evidence that cosmic collisions have played a major role in the mass extinctions documented in Earth's fossil record. That such cosmic collisions can still occur today was demonstrated graphically in 1994 when Comet Shoemaker-Levy 9 broke apart and 21 fragments, some as large as 2 km in diameter, crashed into the atmosphere of Jupiter."
Sources: David Chandler, MIT News Office, November 17, 2008; and various websites
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