Subject: Fwd: NEO News (10/09/02) Dawn & small NEO searches
From: David Morrison
Submitted: Thu, 10 Oct 2002 08:07:58 -0700
Message number: 12
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Sent to the full LSST list at the suggestion of Mike Strauss
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>Date: Wed, 9 Oct 2002 13:35:35 -0700
>To: david.morrison@arc.nasa.gov
>From: David Morrison <dmorrison@arc.nasa.gov>
>Subject: NEO News (10/09/02) Dawn & small NEO searches
>
>
>NEO News (10/09/02) Dawn & small NEO searches
>
>====================================
>
>OFFER TO JOIN THE DAWN MISSION MAILING LIST
>
>The Dawn mission has been selected as NASA's ninth Discovery mission to
>be launched in May 2006 to orbit both Vesta and Ceres. Achieving Dawn's
>goal of understanding the origin and early evolution of the solar system
>through the study of these two very complementary bodies requires close
>coordination with the small body and meteorite communities. The Dawn
>science team places high importance on maintaining close collaboration
>with their colleagues and as a first step would like to establish a
>mailing list of those who wish to be kept informed of the status of
>the Dawn investigation, and opportunities for collaboration with the
>team. Our current plan is to do this by issuing an occasional, brief
>electronic newsletter.
>
>If you would like to be on the Dawn email list, please send email to
>majordomo@igpp.ucla.edu with the following in the body of the message:
>
> subscribe dawn
>
>Once on the list, you may unsubscribe from the list by sending the
>following to majordomo@igpp.ucla.edu:
>
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>Looking forward to your joining us in this exciting adventure,
>
> The Dawn Science Team
>
>=======================================
>
>Statement from the U.S. National Optical Astronomy Observatories to
>the House Science Committee in support of its recent hearings on The
>Threat of Near-Earth Asteroids.
>
>THE HAZARD PRESENTED BY SMALL ASTEROIDS AND STRATEGIES FOR DETECTING THEM
>
>Programs are currently in place to discover potentially hazardous
>Earth-crossing asteroids (PHAs) larger than one kilometer in
>diameter. The census should reach its goal of being approximately
>90 percent complete by 2008.
>
>Two surveys of scientific priorities for the next decade conducted
>by the National Research Council (Astronomy and Astrophysics in the
>New Millennium and New Frontiers in the Solar System) have
>recommended that discovery be extended to asteroids of smaller size.
>
>The following statement summarizes the reasons for this extended
>survey and a potential strategy for carrying it out.
>
>Hazard Presented by Asteroids Less than One Kilometer in Diameter
>
>Asteroids with sizes smaller than one kilometer in diameter present
>a significant hazard. While larger asteroids cause more damage per
>event, they also occur much less frequently. Somewhere in a size
>range above 1 km (0.6 miles), impacts cause global environmental
>effects that can put the entire population of the Earth at risk,
>even those a hemisphere away from the impact site. Such events may
>occur only once in a million years. In contrast, a "Tunguska-sized"
>impact, like the one that occurred over Siberia in 1908, occurs
>perhaps once per 1,000 years. The quantitative assessment of the
>hazard presented by smaller asteroids is currently in progress. The
>actual damage that will occur depends on a number of factors,
>including not only the size of the asteroid and the frequency of
>occurrence but also on modeling of such effects as the blast damage,
>earthquakes, fire, and tsunamis. The extent of the damage also
>depends on the composition of the asteroid and the angle at which it
>impacts the atmosphere.
>
>The large damage that would be caused by the impact of an asteroid
>larger than 1 km in diameter is the concern of the present
>"Spaceguard Survey." With the technology at hand a decade ago, when
>Congress first called for a study of the impact hazard, the cost to
>conduct a survey of these most hazardous large NEOs was found to be
>worth the projected savings in terms of the risk posed by such large
>impacts. That task is now well underway, and much improved
>technology has become available. Accordingly, it is appropriate to
>ask whether it is worth implementing a next generation survey to
>find smaller and less hazardous, but more frequent impactors.
>
>The smallest asteroid that can penetrate the atmosphere to or near
>enough to the ground to cause damage is about 50 meters (150 ft) in
>diameter. Smaller objects generally explode high in the atmosphere,
>at most dropping a few small fragments (meteorites) to the ground
>nearly without harm. There is no recommendation from studies by the
>National Research Council at the present time to search for
>asteroids smaller than 200-300 meters because of the limited
>potential for damage and because most of the time such small
>asteroids are too far away and therefore too faint to be detected
>with current techniques. Systematic searches for larger objects will
>continue to discover asteroids in this small size range when they
>venture close to the Earth.
>
>Accordingly, the appropriate size range for a new survey for
>potentially hazardous asteroids is 200-300 meters to one kilometer
>
>Strategy for Discovering and Cataloguing Asteroids in the Size Range
>200-300 Meters to 1 Kilometer
>
>In order to extend the "Spaceguard Goal" (90% completion in about 10
>years of surveying) to a smaller size of ~300 meters it is necessary
>to meet three requirements. First, it must be possible to reach a
>limiting visual magnitude of 24 according to the NRC report.
>Second, this limiting magnitude must be reached with a short
>exposure time (ideally less than 20 seconds). For fixed objects, it
>is possible to lengthen the exposure time in order to reach fainter
>limiting magnitudes; moving objects, such as PHAs, however, will
>move significantly during long exposures and will be more difficult
>to detect when their images are elongated. Third, it is necessary
>to survey a large area of the sky (several thousand square degrees)
>six times during each lunation in order to link the observations of
>any single asteroid and to derive a preliminary orbit.
>
>Unlike the present Spaceguard survey to about magnitude 19.5, this
>more ambitious survey cannot rely on amateur astronomers or other
>smaller observatories to follow up detections. Not only are such
>faint objects beyond the range of most other telescopes, but the
>sheer number of objects to be tracked becomes so great that every
>field imaged contains multiple objects requiring follow-up. Thus
>the only practical scheme is for the survey telescope to cover the
>entire sky multiple times per month, thereby providing the data both
>for discovery and for tracking and orbit determination. The
>National Optical Astronomy Observatory has funded a study to model
>the cadence required, optimum exposure times, and methods of prompt
>data processing.
>
>The Large Synoptic Survey Telescope (LSST), recommended by name by
>the two NRC reports, is being designed to achieve these goals. It
>has a large aperture (8.3 m) and will reach V = 24 in 20 seconds; it
>has a wide field of view and can survey the entire visible sky in a
>few days; and it will be able to slew and settle quickly in order to
>maximize throughput. The community of interested scientists is
>developing a costed conceptual design for the LSST that will meet
>the goal of creating, over about a decade of observing, a catalog of
>PHAs that is about 90 percent complete down to diameters of 200-300
>meters, with the exact details of completeness and limiting size to
>be determined after more detailed modeling of the predicted
>population of PHAs and of LSST performance.
>
>=======================================
>
>UNIVERSITY OF HAWAII ASTRONOMERS TO DEVELOP NEW TELESCOPES FOR
>"KILLER ASTEROID" SEARCH
>
>For Immediate Release, Tuesday, October 8, 2002
>University of Hawaii
>
>Dr. Nicholas Kaiser 808-956-6898 kaiser@ifa.hawaii.edu
>Dr. Rolf-Peter Kudritzki 808-956-8566 kudritzki@ifa.hawaii.edu
>Mrs. Karen Rehbock 808-956-8566 rehbock@ifa.hawaii.edu
>
>Astronomers at the University of Hawaii Institute for Astronomy
>(IfA) have been awarded a $3.4 million grant by the Air Force
>Research Laboratories to design a new observatory to survey the
>entire sky and detect very faint objects. The Panoramic Survey
>Telescope and Rapid Response System (Pan-STARRS) is currently
>conceived of as an array of small telescopes, and sites on either
>the Big Island or on Maui are being considered. Planned to become
>operational in 2006, Pan-STARRS will be more powerful for survey
>work than all existing telescopes combined. A major goal of the
>project is to identify and track asteroids that might collide with
>Earth.
>
>Commenting on the project, IfA Director Rolf Kudritzki said, "I am
>pleased that the Institute will be able to play an important role in
>finding these hazardous asteroids that threaten humanity."
>
>Exploiting recent advances in electronic detector technology,
>Pan-STARRS will have revolutionary optical sensors with billions of
>pixels, or picture elements. The IfA is collaborating with Lincoln
>Laboratories of the Massachusetts Institute of Technology (MIT) to
>develop the advanced detectors.
>
>The telescopes will have a very large field of view, allowing them
>to image an area about 30-40 times that of the full moon in a single
>exposure. The system will rapidly survey large areas of the sky,
>making it uniquely powerful for detecting transient objects such as
>supernovae, and for detecting moving objects, such as asteroids.
>
>Once operational, Pan-STARRS will generate huge quantities of data.
>To process these, the IfA astronomers have teamed up with the Maui
>High Performance Computer Center (MHPCC), and with Science
>Applications International Corporation (SAIC), a leader in the field
>of massive databases.
>
>The huge database generated by Pan-STARRS will be made available
>over the Internet so that others may use it for education and
>research. Kudritzki commented that the Pan-STARRS database will be
>"a unique opportunity for education."
>
>The currently favored design is an array of four relatively small
>telescopes. This would permit rapid construction, and would have a
>small environmental impact, because the system would be very
>compact. In fact, one possibility being explored is to house the
>system within the university's existing telescope building on Mauna
>Kea.
>
>The IfA is working closely with the Office of Mauna Kea Management,
>and in accord with the design review process set out in the Mauna
>Kea Science Reserve Master Plan, to develop a design that minimizes
>environmental and cultural impacts.
>
>The data from Pan-STARRS will be used to address many scientific
>questions, ranging from the origin of the Solar System to the
>properties of the Universe on the largest scales. However, a major
>goal of the project is to make an inventory of potentially dangerous
>asteroids.
>
>It is now widely recognized that a collision with a large asteroid
>was responsible for the mass extinction of the dinosaurs 65 million
>years ago, and that more frequent collisions with smaller asteroids
>present a real hazard. Fatal asteroid collisions are rare, but when
>they happen they can be very destructive. In fact, experts have
>determined that, averaged over time, the risk of dying from an
>asteroid strike is approximately that of dying in a plane crash. A
>number of recent widely publicized close encounters with asteroids
>have highlighted the risk.
>
>Congress has charged NASA to support searches for "killer
>asteroids." These surveys determine the orbits of the asteroids that
>they discover, and then project them forward to see if they will
>impact Earth. Pan-STARRS principal investigator Nick Kaiser comments
>that "current surveys have detected roughly half of the objects
>bigger than a mile in diameter. Impacts of this size cause
>global-scale catastrophes. Pan-STARRS will help complete this task
>and will extend the search to much smaller objects."
>
>The Institute for Astronomy at the University of Hawaii conducts
>research into galaxies, cosmology, stars, planets, and the Sun. Its
>faculty and staff are also involved in astronomy education, deep
>space missions, and in the development and management of the
>observatories on Haleakala and Mauna Kea. Refer to
>http://www.ifa.hawaii.edu/ for more information about the Institute.
>--
>+++++++++++++++++++++++++++++++++++++++++++
>
>NEO News is an informal compilation of news and opinion dealing with
>Near Earth Objects (NEOs) and their impacts. These opinions are the
>responsibility of the individual authors and do not represent the
>positions of NASA, the International Astronomical Union, or any
>other organization. To subscribe (or unsubscribe) contact
>dmorrison@arc.nasa.gov. For additional information, please see the
>website: http://impact.arc.nasa.gov. If anyone wishes to copy or
>redistribute original material from these notes, fully or in part,
>please include this disclaimer.
--
+++++++++++++++++++++++++++++++++++++++++++
David Morrison, NASA Ames Research Center 240-1
Tel 650 604 5094; Fax 650 604 4251
david.morrison@arc.nasa.gov or dmorrison@arc.nasa.gov
website: http://astrobiology.arc.nasa.gov
website: http://nai.arc.nasa.gov
website: http://impact.arc.nasa.gov
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