PanSTARRS: the University of Hawaii's plans to search for Asteroids. by Andrew Pickles and Klaus Hodapp, UH Institute for Astronomy Shooting stars can be seen every clear dark night, usually a few per night, sometimes as many as a few dozen. The meteorites that produce these brilliant displays are surprisingly small, the size of a grain of sand, up to maybe a small pebble. Shooting stars are completely harmless, burning up high above the ground, but much larger objects can occasionally reach the ground and cause damage. As an extreme example, the dinosaurs and many other species were wiped out by the impact of a 10 mile wide asteroid some 65 million years ago. In 1908, a small asteroid about half the size of a football field exploded a few miles above ground with the force of a large thermonuclear warhead, mercifully over sparcely populated nothern Siberia. So why should we worry? The best estimates today are that each human being has a one in 20000 chance of getting killed by asteroid impact. This is a lower chance than dying in a car accident, but is comparable to the lifetime odds of dying in a plane crash for the occasional vacation flier. Or it is about the same as your odds of ever winning the jackpot in a major lottery if you bought one ticket every week of your life. Considering how much our nation spends on airplane safety, air traffic control and crew training, it seems prudent to invest more public funds into finding potentially threatening asteroids. As things stand today, mankind has spent more money on asteroid movies (Deep Impact, Armageddon and others) than on actual asteroid searches, clearly not a good situation. This is one real-life documentary where we really don't want to see things explode. About a decade ago, the government asked NASA to find at least 90% of all asteroids that threaten civilization. Some smaller asteroid search projects are already under way and have already found a good fraction of the larger asteroids. Only one of these objects has a small chance of hitting the earth some 800 years from now, and this object is being carefully monitored to better determine its orbit. At present, the focus is on finding potentially threatening objects and monitoring them. This will likely give us enough advance warning that the government could then develop the necessary technologies to actually deflect the object well before it reaches earth. In 2000 the "decadal review" of the National Academy of Sciences called for building a large wide field survey telescope as one of its most important objectives for this first decade of the new millennium. The UH Institute for Astronomy has now received a planning grant for exactly such a telescope system called PanSTARRS: Panoramic Survey Telescope and Rapid Response System. Prof. Nick Kaiser is the principal investigator of this project, and the UH IfA Associate Director for national telescope projects. He is joined by a team of IfA faculty with expertise in telescope design, detector design, software and database management, and asteroid science. There are two basic approaches to the problem of seeing wide and faint. One is to build a single large mirror, say 8m diameter to see faint, but with complicated optics to also see a wide angle. The other is to design smaller telescopes, which see wide angles more easily, and then build several of them to be able to see sufficiently faint. This second approach has been chosen in our PanSTARRS design. There are several advantages to having multiple small telescopes for this survey rather than a single large one. The first is that it is easier to image large areas with smaller telescopes. The second is cost since even a large number of small telescopes is cheaper than a single large one with the same collecting area. Since each telescope needs its own large CCD camera this would seem to increase costs. But in fact we can save costs here because having multiple telescopes allows us to build cheaper cameras. We can tolerate each having a few defective areas, as long as they don't line up in each image. When we combine images of the sky, we can remove these camera defects. In PanSTARRS each telescope is based around a mirror of diameter 1.8 meters (about 6 feet) with a field of view of three degrees (36 times the area of the moon) imaged onto a large digital CCD camera covering about two square feet and containing one billion pixels. Our system will include four such telescopes, each looking at the same piece of sky for about one minute. The whole system will incorporate the latest advances in detector technology. It will have about 40000 times the light collecting power and 800 times the number of pixels of a professional digital camera available today. The data volume will also be enormous, about 10 Terabytes per night, requiring massive pipeline data processing to find and tag all the moving objects. We will use the Maui High Performance Computer Center, one of the largest supercomputers on earth, for this task. The idea is to image the whole sky available from Hawaii each and every week, determine orbits for everything that moves, and compare this to a database of all known objects in the Solar System. This basic method has been used for centuries. The unique capability of PanSTARRS is that it can cover large parts of the sky every night, and can detect much fainter objects than previous search projects. This added sensitivity is required to detect moving objects as small as 1000 feet, still large enough to destroy a country when they hit land, or to cause a devastating tsunami if they impact our ocean. There are several possible telescope designs that we are now exploring, including equatorial and altitude-azimuth mounts, individual mounts or combining four telescopes on a common mount. We are also looking at several possible locations for PanSTARRS, on Haleakala and Mauna Kea. One attractive option is to refurbish the old coude spectrograph extension to the UH 2.2-m telescope. Such a refurbishment of an existing structure would minimize the impact on the environment and cultural resources on Mauna Kea. Final site selection depends on the results of ongoing site testing and more detailed engineering studies. The Office of Mauna Kea Management has been informed of the PanSTARRS project. We expect to submit a formal request to build this new facility this year, after more extensive review and design studies. This proposal will, of course, go through the comprehensive environmental and cultural review process outlined in the Mauna Kea Master Plan. On Saturday February 1, at the Onizuka Visitors Center at Hale Pohaku mid-level site at 6pm, Dr. Klaus Hodapp of the UH Institute for Astronomy will discuss the probabilities of an asteroid hit, and how we at the University of Hawaii are proposing to find those objects.