Spin States of Near-Earth Asteroids From Radar Speckle Tracking

Grant #: NNX13AQ44G
Senior Scientist: Michael Busch

The spin states of near-Earth asteroids (NEAs) are fundamental physical properties of the objects. Understanding the pole directions and spin rates of a representative sample of NEAs is essential to understanding the near-Earth population as a whole. Knowing the spin states of individual objects is also necessary to characterize their shapes, to predict their long-term trajectories, and for planning both human and robotic spacecraft missions. However, measurements of NEA spins – particularly pole directions, rather than spin periods – are frequently ambiguous. Currently, pole directions are known for only about 40 NEAs. 

We have developed a new technique, radar speckle tracking, using the Arecibo and Goldstone radars and elements of the Very Long Baseline Array and the Jansky Very Large Array to rapidly and uniquely determine asteroid pole directions and spin rates. We propose to make speckle tracking a routine part of the current NEA radar observing campaign, to measure the spin states, including the pole directions, of roughly 20 more NEAs over a two-year period. 

We will improve our understanding of the near-Earth asteroid spin state distribution, increase the number of objects for which we can provide shape models, and provide better size constraints and trajectory predictions for those targets, particularly for potential mission targets and objects with potential Earth impacts.