Date of Award

January 2012

Document Type


Degree Name

Master of Science (MS)


Space Studies

First Advisor

Ronald A. Fevig


NASA seeks to reliably detect potential Earth Impactors (EI) in time to defend the planet by deflecting them. Congress has given an unfunded mandate to NASA to lead Spaceguard, a coalition of worldwide observatories and scientists who find, track, and determine impact probabilities for potential EIs (Udall, 2007). This effort fits within the first stages of a typical military targeting cycle, which begins by detecting and characterizing targets. In the first half of this analysis, military targeting is applied to the EI challenge through the development of a methodology to characterize early warning times for different size objects. In the second half, recommendations for acting on different warning time scenarios are presented, to include augmentation of observation technology and use of a precursor transponder implantation mission.

An interdisciplinary approach is taken to measure the success of the Spaceguard efforts in increasing the warning times for approaches of variously sized bodies. A multi-step method is developed, beginning with determining past and present warning times for asteroids entering the 0.05 AU Astronomical Unit (AU) Minimum Orbit Intersection Distance (MOID) of Earth. Using source data from NASA's NEO Program database of close approaches, JPL's Small Body Database, and the IAU Minor Planet Center, the differences between the dates of first discovery of these Potentially Hazardous Asteroids (PHA) and the dates of 7300 penetrations of the MOID to graph warning times for known PHAs' penetration of the MOID were aggregated. The method also includes the estimate of PHA discovery, rates of objects with high orbital uncertainties, and missed approach rates. A discussion of potential sources for error and directions to take for further development of the model is included. Finally, recommendations for campaigns against EIs are provided, given different warning time and size scenarios.

The most significant of the conclusions is that, given current technology, and given the limitations of the model used, the 100-300 m size range appears to contain the most likely EI Spaceguard will discover with enough warning time (over 30 years) to take some form of action. A counterintuitive additional conclusion is that this size range also may yield an object that will strike with no warning time. Another conclusion is that EIs smaller than 100 m will provide negligible warning time for centuries.

Targeting campaigns against the most-likely EI warning-time and size scenarios are discussed. These campaigns include first, additional observation technology; second, an inexpensive short-termed precursor transponder mission; third, a long-term observation mission; fourth, a suite of simultaneous observation and mitigation missions, and finally, evacuation and recovery operations. The overall conclusion is that additional resources should be allocated toward more robust survey technology, the first layer of defense, with continued development of precursor characterization transponder mission technology, the second layer of defense.