* Astronomy

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RE: NEO

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Title: Orbital Simulations on Deflecting Near-Earth Objects by Directed Energy
Author: Qicheng Zhang, Kevin J. Walsh, Carl Melis, Gary B. Hughes, Philip M. Lubin

Laser ablation of a Near-Earth Object (NEO) on a collision course with Earth produces a cloud of ejecta which exerts a thrust on the NEO, deflecting it from its original trajectory. Ablation may be performed from afar by illuminating an Earth-targeting asteroid or comet with a stand-off "DE- STAR" system consisting of a large phased-array laser in Earth orbit. Alternatively, a much smaller stand-on "DE-STARLITE" system may travel alongside the target, slowly deflecting it from nearby over a long period. This paper presents orbital simulations comparing the effectiveness of both systems across a range of laser and NEO parameters. Simulated parameters include magnitude, duration and, for the stand-on system, direction of the thrust, as well as the type, size and orbital characteristics of the target NEO. These simulations indicate that deflection distance is approximately proportional to the magnitude of thrust and to the square of the duration of ablation, and is inversely proportional to the mass. Furthermore, deflection distance shows strong dependence on thrust direction with the optimal direction of thrust varying with the duration of laser activity. As one example, consider a typical 325 m asteroid: beginning 15 yr in advance, just 2 N of thrust from a ~20 kW stand-on DE-STARLITE system is sufficient to deflect the asteroid by 2 R_e. Numerous scenarios are discussed as is a practical implementation of such a system consistent with current launch vehicle capabilities.

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After Chelyabinsk European experts assess asteroid options

This week, Deimos Space, an industrial partner working for ESA on SSA, has invited top researchers from universities, research institutes, national space agencies and industry in Europe and the USA to discuss the state of the art in NEO impact effects and threat mitigation.
The meeting is taking place in Tres Cantos, Spain, near Madrid.
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Scientists unveil new detectors in race to save Earth from next asteroid

The extraterrestrial double whammy that Earth only partially avoided on Friday has triggered an immediate response from astronomers. Several have announced plans to create state-of-the-art detection systems to give warning of incoming asteroids and meteoroids. These include projects backed by Nasa as well as proposals put forward by private space contractors.
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Explained: Near-miss asteroids

On May 29, an asteroid the size of a bus came whizzing past Earth at 10 times the speed of a fired bullet. The near-miss asteroid, named 2012 KT42 - streaked across the orbits of weather and television satellites, 22,000 miles above Earth's surface, making it the sixth-closest asteroid approach on record. While the object had little chance of colliding with Earth, its approach gave scientists an opportunity to run a rapid-response program - or as MITs Richard Binzel calls it, an asteroid-tracking "fire drill" - to gain as much information as possible from the incoming space rock.
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Near Earth Objects

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Spaceguard survey

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RE: NEO

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Title: NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results
Authors: A. Mainzer, T. Grav, J. Masiero, J. Bauer, E. Hand, D. Tholen, R. S. McMillan, T. Spahr, R. M. Cutri, E. Wright, J. Watkins, W. Mo, C. Maleszewski

The NEOWISE dataset offers the opportunity to study the variations in albedo for asteroid classification schemes based on visible and near-infrared observations for a large sample of minor planets. We have determined the albedos for nearly 1900 asteroids classified by the Tholen, Bus and Bus-DeMeo taxonomic classification schemes. We find that the S-complex spans a broad range of bright albedos, partially overlapping the low albedo C-complex at small sizes. As expected, the X-complex covers a wide range of albedos. The multi-wavelength infrared coverage provided by NEOWISE allows determination of the reflectivity at 3.4 and 4.6 \mu m relative to the visible albedo. The direct computation of the reflectivity at 3.4 and 4.6 \mu m enables a new means of comparing the various taxonomic classes. Although C, B, D and T asteroids all have similarly low visible albedos, the D and T types can be distinguished from the C and B types by examining their relative reflectance at 3.4 and 4.6 \mu m. All of the albedo distributions are strongly affected by selection biases against small, low albedo objects, as all objects selected for taxonomic classification were chosen according to their visible light brightness. Due to these strong selection biases, we are unable to determine whether or not there are correlations between size, albedo and space weathering. We argue that the current set of classified asteroids makes any such correlations difficult to verify. A sample of taxonomically classified asteroids drawn without significant albedo bias is needed in order to perform such an analysis.

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NASA Space Telescope Finds Fewer Asteroids Near Earth

New observations by NASA's Wide-field Infrared Survey Explorer, or WISE, show there are significantly fewer near-Earth asteroids in the mid-size range than previously thought. The findings also indicate NASA has found more than 90 percent of the largest near-Earth asteroids, meeting a goal agreed to with Congress in 1998.
Astronomers now estimate there are roughly 19,500 -- not 35,000 -- mid-size near-Earth asteroids. Scientists say this improved understanding of the population may indicate the hazard to Earth could be somewhat less than previously thought. However, the majority of these mid-size asteroids remain to be discovered. More research also is needed to determine if fewer mid-size objects (between 100 and 1,000-metre wide) also mean fewer potentially hazardous asteroids, those that come closest to Earth.
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