Comet/Asteroid Planetary Defense System - Abstract
Comet/Asteroid Planetary Defense System
Allen Brown, et. all
December 9, 1994
Over the last few years, it has been realized that near-Earth objects pose a definite hazard to human life on Earth. The impact of cosmic objects are thought to be linked to the extinction of the dinosaurs and up to 60% of all other known extinctions. Technology now exists to find, track, and catalog these Near Earth Objects (NEOs) in order to determine the risk of an Earth impact. Technology also exists that could alter the paths of hazardous NEOs so that they pass harmlessly by Earth, provided that steps are taken to implement a defense system. Experimental procedures, such as precursor missions, and practice interception missions, will also be needed.
Aegis Systems, LTD. has developed a plan, using current technologies, to provide planetary defense against a wide variety of NEO threats. The system consist of a detection, a tracking/prediction, and a deflection sub-system. These sub-systems will interact with a central database and command center.
Detection of NEOs is the first step in providing an adequate defense. Current technology allows us to discover nearly all asteroids or short-period comets larger than 1 km in diameter, and more than 75% of the 0.5 km asteroids in a 25 year survey. To do this, six telescopes equipped with 3 CCD detectors per telescope with apertures of 3.0 m will be used. The telescopes, having a limiting stellar magnitude of V=22, will be search approximately 6000 square degrees per month centered on opposition, observing + 60¡ celestial latitude and + 30¡ celestial longitude. To ensure maximum coverage, three telescopes must be located in the Southern Hemisphere and three in the Northern Hemisphere. Although the required amount of sky could be covered with four 3 meter telescopes, by using six we will have redundancy in each of the hemispheres. Also along with the telescopes a central database must also be constructed in order to coordinate the observing programs.
The Tracking System obtains the position of initially detected NEOs and position updates on catalogued NEOs from the central database. Optical telescopes provide the approximate orbits within several days for newly detected objects, and refinement of existing orbits is ongoing. If the closest approach of an NEO is within 0.05 AU of the Earth, radar could be used to determine the precise orbit within 10 km. The orbit can be predicted years or even decades into the future to determine the long-term potential threat. The orbit parameters are then returned to the central database. Any hazards identified are communicated to the decision-making group.
Once the decision-making group is convinced of an incoming projectile, the deflection system is engaged. An appropriate deterrence system needs to be employed which can effectively deter most types of incoming threats. Innovative as well as current technologies were evaluated in determining an appropriate deterrence system option.
When choosing a system to respond to an incoming NEO threat, many constraints exist because of our present state of technology, the possible lack of forewarning, the sometimes massive amounts of deflection energies required, and the lack of hard facts about the NEOs themselves. Ultimately, the only available tools to work with are nuclear fusion devices with chemical rocket propulsion. However, these tools are limited at the present time to stand-off applications where the lack of detailed NEO knowledge will not adversely affect the deflection maneuver. While the pulverization or destruction of a NEO is not beyond technical means for certain sizes, the penetration and asteroid fracture parameters are directly influenced by knowledge of NEOs which is not available without a detailed precursor or reconnaissance mission.
With the energies available and the slow flight rates of chemical rockets, it seems that only far-out intercepts stand a great chance for deflection. Close-in intercepts are more difficult in terms of energy required, which directly increases the payload size. Thus, close-in intercepts, if possible, allow little or no chance for a second attempt, should the first attempt fail.
Last Modified: July 3, 1998
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