Ground based observations are key to accurately detecting NEOs-NASA should fully fund the Arecibo and Goldstone stations
IRWIN I. SHAPIRO et al in 10,( Harvard-Smithsonian Center for Astrophysics, Chair FAITH VILAS, MMT Observatory at Mt. Hopkins, Arizona, Vice Chair MICHAEL A’HEARN, University of Maryland, College Park, Vice Chair ANDREW F. CHENG, Johns Hopkins University Applied Physics Laboratory FRANK CULBERTSON, JR., Orbital Sciences Corporation DAVID C. JEWITT, University of California, Los Angeles STEPHEN MACKWELL, Lunar and Planetary Institute H. JAY MELOSH, Purdue University JOSEPH H. ROTHENBERG, Universal Space Network, Committee to Review Near-Earth Object Surveys and Hazard Mitigation StrategiesSpace Studies BoardAeronautics and Space Engineering BoardDivision on Engineering and Physical Sciences, THE NATIONAL ACADEMIES PRESS, http://www.fas.harvard.edu/~planets/sstewart/reprints/other/4_NEOReportDefending%20Planet%20Earth%20Prepub%202010.pdf)
On the other hand, the committee concluded that vigorous, ground-based characterization at modest cost is important for the NEO task. Modest funding could support optical observations of already-known and newly discovered asteroids and comets to obtain some types of information on this broad range of objects, such as their reflectivity as a function of color, to help infer their surface properties and mineralogy, and their rotation properties. In addition, the complementary radar systems at Arecibo and Goldstone are powerful facilities for characterization within their reach in the solar system, a maximum of about one-tenth of the Earth-Sun distance. Arecibo, which has a maximum sensitivity about 20-fold higher than Goldstone’s, but does not have nearly so good sky coverage as Goldstone, can for example, model the three-dimensional shapes of (generally very odd-shaped) asteroids, and estimate their surface characteristics, as well as determine whether the asteroid has a (smaller) satellite or satellites around it, all important to know for planning active defense. Radar can also accurately determine orbits of NEOs, from a few relatively closely spaced (in time) observations, which has the advantage of being able to quickly calm public fears (or possibly, in some cases, show that they are warranted). Finding: The Arecibo and Goldstone radar systems play a unique role in the characterization of NEOs, providing unmatched accuracy in orbit determination, and insight into size, shape, surface structure, and other properties for objects within their latitude coverage and detection range. Recommendation: Immediate action is required to ensure the continued operation of the Arecibo Observatory at a level sufficient to maintain and staff the radar facility. Additionally, NASA and NSF should support a vigorous program of radar observations of NEOs at Arecibo and NASA should support such a program at Goldstone for orbit determination and characterization of physical properties. For both Arecibo and Goldstone continued funding is far from assured, not only for the radar systems, but for the entire facilities. The incremental annual funding required to maintain and operate the radar systems even at their present relatively low levels of operation, is about $1 million at each facility (see Chapter 4). The annual funding for Arecibo is approximately $12 million. Goldstone is part of the Deep Space Network and its overall funding includes additional equipment for space communications.
Deflection – Tractor Beams
Tractor beam technology can also be used to clean up space debris.
Sinko and Schlecht in 10 (John E. Sinko, Micro-Nano Global Center of Excellence, Graduate School of Engineering, Nagoya University, and Clifford A. Schlecht, Institute for Materials and Complexity, AIP Conference Proceedings, CO2 Laser Ablation Propulsion Tractor Beams, EBSCO, DF)
One concept that is receiving significant attention as an application for laser propulsion is the removal of orbital space debris. Such debris poses a serious hazard to space stations, satellites, and spacecraft, and reduces the lifetime and functionality of in-space systems . When discussing how to approach space debris, the size of the object is a major deciding factor. For small particles, targeting a wide region of space over a long period of time may be feasible, but it does run the risk of interfering with or disabling existing satellites. For large objects (say, perhaps 10 cm or larger) these methods may not be feasible, as ablative thrust may be expected to be relatively small, due to the large masses of such objects
One possible solution for large objects is to 'tag' them with an inexpensive, cooperative thrust system that can then be targeted by an external energy source in order to allow remote control and ultimate removal of the object from orbit. Rendezvous of this kind of "cooperative target system" with actual target objects can be expected to be a significant challenge. On the other hand, once tagged, an object could be targeted over a long period of time, potentially accumulating significant thrust. It might be possible to introduce a small, cheap, rocket-propelled interceptor to bring the cooperative system into the orbit of the target object and facilitate attachment. The promise of this application appears adequate to justify research and development on methods to tag passive objects in order to support remote control. The question is whether such systems can be produced without exceptional cost. Gravity tractors can deflect asteroids if warned early
Now, two NASA scientists, both also astronauts, suggest a simpler, safer, and much more plausible way of diverting an offending asteroid. Their method relies on the gravitational tug of a massive, unmanned spacecraft to pull the rock away from a damaging rendezvous with Earth.The gravitational tractor, as the researchers call their proposed craft, would require the sustained power of a nuclear-propulsion system to reach the asteroid and perform the maneuvers that would be required to deflect it. For general space exploration, NASA has already proposed a fleet of suitable vehicles, although their funding is currently uncertain. As envisioned by Ed Lu and Stan Love of NASA's Johnson Space Center in Houston, the gravitational tractor would hover some tens of meters from a spinning asteroid. Only the force of gravity would connect the two. Careful control of the tractor's thrusters would keep the craft close to the asteroid as it slowly pulled the rock off its collision course. Given enough lead time, it would take just a year for a 20-ton spacecraft to drag a 200-meter-wide asteroid weighing about 60 million tons away from Earth's path, Lu and Love calculate in the Nov. 10 Nature. Towing would have to begin at least 20 years before the projected collision.