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.
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).
Title: NEA discovery, orbit calculation and impact probability assessment
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.