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Curious about the NASA Asteroid Grand Challenge to “discover all asteroids that could threaten human populations and find out how to deal with them”? NASA is sponsoring a series of virtual seminars on the properties of Near Earth Asteroids (NEAs) and what is being done to learn more about the hazards and the opportunities they may pose for us here on Earth. The purpose is to inform interested astronomers (both amateur and professional), students, teachers, and others who are potentially interested in contributing to studies of NEAs. Each seminar will focus on some aspect of the asteroid population, how we discover and track NEAs, and what we need to know about them if we are ever required to change the orbit of a NEA that is an impact threat.

The seminar format will be a 40-minute talk by an asteroid expert followed by 20 minutes for questions from the audience. They will be broadcast over the Internet. The audience will watch, listen and post questions by Adobe Connect using an Internet connection and a web browser.

The seminars will be held on the second and fourth Fridays of each month beginning on February 14. The time is 11:00 am Eastern, which will allow live audience participation over most of the United States, Europe, and Africa.

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Speakers & Recordings:

Feb. 14th: David Morrison (NASA Ames & SSERVI)

Title: The Asteroid Impact Hazard: Historical Perspective

Click here to download David’s presentation


Feb. 28th: Lindley Johnson (NASA Headquarters)

Title: NASA’s NEA programs

Click here to download Lindley’s presentation


Mar. 14th: Paul Chodas (NEO Program Office at JPL)

Title: NEA Discovery, Orbit Calculation and Impact Probability Assessment

Click here to download Paul’s presentation


Abstract: Two rare but unrelated asteroid encounters occurred on the same day a year ago: a 20-meter asteroid impacted the Earth’s atmosphere unannounced over Chelyabinsk, Russia, and a 40-meter asteroid called 2012 DA14 came so close to the Earth that it passed inside the ring of geosynchronous satellites. Since that day, several more asteroids have made the news for less dramatic close approaches, including two which passed within the distance of the moon just last week. Why does it seem like there are suddenly so many space rocks heading our way? If we’re getting better at finding Near-Earth Asteroids, why was the Russian impactor not detected before it started burning up in the atmosphere? How could we be so sure that 2012 DA14 was not headed for an impact? This seminar will discuss issues such as how asteroids are discovered and tracked, how scientists compute their trajectories, and how we assess the probabilities that they might impact the Earth. Last week’s two asteroid encounters will be used as examples in some of these discussions, and a few other notable asteroid encounters will also be described.


About Paul: Paul Chodas is a senior scientist at JPL, computing orbits for asteroids and comets for over 30 years. He is the principal architect of the core small body algorithms and software for: propagating trajectories, determining orbits, and computing uncertainties, close approaches, impact probabilities and warning times. He computed the times and locations for the Jupiter impacts of Comet Shoemaker-Levy 9 and the Earth impact of 2008 TC3. Paul coined the useful term “keyhole” to describe the potential gateway that leads from a close approach to a later impact. He has analyzed keyhole locations and widths for well known asteroids like Apophis and Bennu and studied the role of keyholes in asteroid deflection. He has analyzed trajectories of objects in Earth-like orbits, and in 2002 demonstrated that a recently discovered unidentified object was likely the Apollo 12 third stage returning after 30 years in heliocentric orbit. Over the last year Paul has coordinated the search for and characterization of possible candidate targets for the proposed Asteroid Redirect Mission (ARM).


Mar. 28th: Alan Harris (JPL retired)

Title: Title: NEA populations and impact frequency

Click here to download a copy of Alan’s slides


Abstract: An accurate estimate of the population versus size of NEAs is needed both to determine the frequency of impacts and attendant risk, and to assess the progress of surveys. I will describe the method of estimating survey completion by the ratio of new discoveries by a survey to the total number of detections. This “re-detection ratio” must be corrected to allow for the fact that not all NEAs are equally easy to detect. This requires a model of the orbit distribution of NEAs, and computer simulations of surveys to relate the raw re-detection ratio at a given size of objects to an actual completion estimate. Once an actual survey has been “calibrated” with respect to the computer model, it is possible to extrapolate to even smaller sizes where there are essentially no re-detections by the survey, thus we can make completion estimates down to the smallest sizes observed at all by the surveys. I will apply these methods to two special cases of current interest: the population and impact frequency of “Chelyabinsk” sized objects, and the population of “ARM target” asteroids that may be discoverable.


About Al: Alan Harris received his PhD in Earth and Space Sciences at UCLA in 1975, and spent 28 years at JPL, for some time in the tracking and navigation group and then in the Earth and Space Sciences Division, as a Senior Research Scientist. His specialty has been small body dynamics and evolution, both orbital and rotational, of asteroids, comets, satellites, and ring particles. For more than two decades he has participated in numerous studies by NASA, NRC, and international bodies evaluating all aspects of the NEO impact hazard (impact probabilities and consequences, survey design and progress, mitigation strategies, and even social and political aspects). Now retired from JPL, Harris continues an active research program sponsored by NASA and NSF, and serves as a frequent consultant to NASA and JPL on the NEO Program.


Apr. 11th: Dan Britt (University of Central Florida)

Title: Title:Physical properties of NEAs

Click here to download a copy of Dan’s slides


Abstract: What we know about the physical properties of NEAs depends not only on observations of these objects, but also the study of meteorites and meteors. Taken together, these sources are telling us a story of how NEAs formed, how they evolved over the age of the solar system, and what their current state and structure may be as we continue robotic, and potentially human, exploration of these objects. Asteroids in general and NEAs in particular, have turned out to be far more complex and interesting then the cold lumps of rock that many of us originally expected. These objects have complex collisional histories, varied structures, and a surprising range of physical properties that provide data about the early solar system as well as insight into the hazards of asteroid impacts and the challenges we will face during exploration. I will review what is known from our varied sources and paint a picture about what to expect in future asteroid encounters.


About Dan: Daniel Britt is a Professor of Astronomy and Planetary Sciences at the Department of Physics, University of Central Florida (UCF). He was educated at the University of Washington and Brown University, receiving a Ph.D. in Geology from Brown in 1991. He has had a varied career including service in the US Air Force as an ICBM missile launch officer and an economist before going into geology and planetary sciences. He has served on the science teams of two NASA missions, Mars Pathfinder and Deep Space 1. He was the project manager for the camera on Mars Pathfinder and has built hardware for all the NASA Mars landers. He currently does research on asteroids, comets, Mars, and climate change under several NASA grants. Honors include 5 NASA Achievement Awards, election as a Fellow of the Meteoritical Society, and an asteroid; 4395 DanBritt. He has recently served as President of the Division for Planetary Sciences of the American Astronomical Society and is currently the Director of the Center for Lunar and Asteroid Surface Science based at UCF.


Apr. 25th: David Kring (Lunar and Planetary Institute)

Title: Title: Examples and consequences of NEA impacts

Click here to download a copy of David’s slides


Abstract: Local, regional, and global consequences of impact cratering events will be outlined and illustrated with several examples (e.g., Odessa, Meteor Crater, and Chicxulub). The consequences of those events in the geologic past will be examined and the implications for future impacts of similar sizes will be explored.


About David: David Kring received his Ph.D. in earth and planetary sciences from Harvard University. He specializes in impact cratering processes produced when asteroids and comets collide with planetary surfaces. He has worked extensively at Meteor Crater, which is one of the world’s most spectacular NEA impact sites. Kring is perhaps best known, however, for his work with the discovery of the Chicxulub impact crater, which he linked to the K-T boundary mass extinction of dinosaurs and over half of the plants and animals that existed on Earth 65 million years ago. He has also studied the environmental effects of impact cratering and shown how impact processes can affect both the geological and biological evolution of a planet. Dr. Kring has led a decade-long campaign to test the lunar cataclysm hypothesis, which is one of the great intellectual legacies of the Apollo program. Kring has suggested that the impact bombardment created vast subsurface hydrothermal systems that were crucibles for pre-biotic chemistry and provided habitats for the early evolution of life. He calls this concept the impact-origin of life hypothesis.


May 9th: Tim Spahr (Minor Planet Center, CFA)

Title: Title: MPC and the International Warning Network

Click here to download a copy of Tim’s slides


Abstract: The Minor Planet Center, or MPC, is the world’s data collection and distribution center for all positional measurements of minor planets and comets. The MPC is operated at the Harvard-Smithsonian Center for Astrophysics, granted authority for operation by the International Astronomical Union, and fully funded by NASA. While the MPC is tasked with processing and distributing all minor planet observations, the MPC specializes in rapid handling of observations of Near-Earth Objects, or NEOs. For each new NEO submitted, the MPC computes the short-term impact probability and is the first line of warning for impacts that will happen in the near future. As impacts are an international concern, the United Nations has become involved and suggested an International Asteroid Warning Network, or IAWN. While some elements of the IAWN are functioning and growing, there are many more pieces yet to be formed. This talk will discuss the operation of the MPC, and its role as a functioning key node of the IAWN.


About Tim: Timothy Spahr (b. 1970), has been interested in astronomy, particularly comets, since about 1976. Both of Tim’s science-inclined parents supported his astronomical hobby, including driving him to dark skies to see Comet Halley in 1986. He attended the University of Arizona for physics and astronomy degrees, and while there he worked with Stephen Larson and Carl Hergenrother to found the Catalina Sky Survey. During graduate school, Tim studied celestial mechanics with Stanley Dermot at the University of Florida. As a graduate student, Tim co-discovered 1996 JA_1, a 200 meter diameter NEO that passed between the Earth and Moon; this event solidified his scientific interest in NEOs. After graduating with his Ph.D. in 1998, Tim returned to the University of Arizona to write software for the Catalina Sky Survey. In 2 short years, he moved on to the Minor Planet Center, under the direction of Brian Marsden. Tim was eventually promoted to Director during the infamous Prague IAU meeting, where the fate of Pluto as a planet was debated.


May 23rd: Dan Mazanek (NASA Langley)

Title: Title: NEA deflection strategies

Click here to download a copy of Dan’s slides

Abstract: A variety of strategies have been proposed to deflect a near-Earth asteroid (NEA) from impacting the Earth, ranging from slow-push techniques (e.g., gravity tractor, ion beam deflection, and laser ablation) to impulsive techniques that impart a rapid momentum change (e.g., high-speed kinetic impactors and nuclear detonations). Altering the NEA’s trajectory early minimizes the required change in velocity (ΔV). This is particularly true for NEAs that are an immediate threat because the required ΔV can increase by several orders of magnitude during the final months before impact. Additionally, deflection strategies need to be effective against a wide range of physical characteristics. NEAs can range from friable carbonaceous objects to stony or mostly metallic, with vastly different porosity and structural integrity. Additionally, their surfaces may have regolith that can affect deflection efforts, particularly contacting and attaching to the object. Depending on the warning time available, techniques that do not require detailed knowledge of the NEAs physical characteristics are desirable, and methods that can deflect a NEA without contacting the surface may be advantageous. Ultimately, spacecraft capable of rapidly engaging a threat and/or delivering significant payloads are extremely beneficial, and several approaches for modifying the NEA’s orbit could be incorporated into a deflection strategy.


About Dan: Dan Mazanek is a Senior Space Systems Engineer at NASA’s Langley Research Center (LaRC) with 25 years of experience in space mission and architecture formulation and conceptual design and sizing of human and robotic spacecraft. He graduated with a B.S. degree in Aerospace Engineering from Virginia Tech in 1989. He was the Comet/Asteroid Protection System (CAPS) Study lead under NASA’s Revolutionary Aerospace Systems Concepts (RASC) program in 2001-2002 and led the LaRC technical analyses and independent technical review of NASA’s 2006 Near-Earth Object Survey and Deflection Study. He is a technical expert and a leader in the field of human and robotic missions to small planetary bodies and has led multiple study efforts to investigate sending humans beyond low-Earth orbit, including the development of a Near-Earth Object (NEO) crewed mission concept in 2005 and the Mars-Phobos-Deimos Preliminary Destination Mission Concept Study in 2012. He is the NEO mission lead analyst at LaRC and serves as the Near-Earth Asteroid Destination Lead for NASA’s Human Spaceflight Architecture Team. He is currently leading analysis efforts for the Agency’s Asteroid Redirect Mission (ARM) option of robotically capturing a boulder from a large asteroid and returning it to cislunar space.


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How to Join:

This seminar series can be viewed online by clicking hereor by going to the following URL:


Please “Enter as a Guest” and use your full name. Audio will be heard through your computer speakers, while questions will be accepted in the room’s chat window. If you have any technical difficulties or questions, please contact one of our Technical Systems Specialists: [Ricky Guest] or [Ashcon Nejad]

System requirements for viewing this seminar series are:
1. An up-to-date web browser (e.g. Safari, Firefox, Internet Explorer).
2. The latest version of Adobe Flash Player [Click here for the latest version]

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Posted by: Soderman/SSERVI Staff
Source: NASA

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