Space optical and low-frequency radio searches for earth-crossing asteroids and comets
Earth-crossing asteroids (ECAs) are small and backscatter strongly, so they are usually discovered near opposition during dose approaches to Earth. This opposition effect produces strong biases in Earth-based searches for ECAS, particularly for Atens. An observing site much closer to the sun than the orbit of Earth, such as a satellite orbiting Venus or telescopes on Mercury, would not suffer this bias. All Atens that cross the orbit of Earth would be observable near opposition from these sites, so a survey from them would not systematically miss any large ECAS. A satellite at the Lagrangian point between the Earth and the sun would be effective in detecting objects in the final day before they hit Earth including asteroids and long-period comets that approach Earth from the sunward side. Outgassing comets present large cross sections to the solar wind. Spacecraft have observed low-frequency radio emission produced by the wiggling of the magnetic field in the solar wind as it sweeps past comets. Asteroids axe expected to emit similar radio emission at lower power. This radiation may be observable by a radio array in space or on the moon. A satellite at the Lagrangian point could also detect the downstream solar wind wakes of comets and asteroids that approach Earth from the direction of the sun. Military surveillance satellites may be used to observe the fragmentation of large meteoroids in the atmosphere. Because it observes the entire atmosphere of Earth and is not affected by local weather conditions, such a surveillance network has a much larger cross section than a ground survey for observing the rare, large meteors that more closely approach the size of those that cause economic damage.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10140003
- Report Number(s):
- LA-UR-93-599; CONF-930185-1; ON: DE93008716
- Resource Relation:
- Conference: Hazards due to comets and asteroids,Tucson, AZ (United States),Jan 1993; Other Information: PBD: [1993]
- Country of Publication:
- United States
- Language:
- English
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