Physical Characterization of Small Near-Earth Asteroids

Impacts due to near-Earth Objects (NEOs) can have a devastating effect on life here on the Earth. The most recent testament to this is the Chelyabinsk meteor, which on February 15, 2013, disintegrated in an airburst with an energy of ~ 500 kilotons of TNT, injuring hundreds of people and causing widespread property damage in several Russian cities. While ground-based asteroid surveys have been prolific in finding new NEOs and creating an up-to-date inventory, physical characterization of these objects has lagged behind.

The goal of the proposed research is to continue our survey of physically characterizing small near-Earth Asteroids (NEAs) (less than 150 meters in diameter) to constrain their surface composition, rotation state, albedo and size. Our sample population would include low-delta V targets that are accessible to future robotic and human exploration. The proposed research has three main objectives:

2) To compositionally characterize small NEAs, i.e., determine mineral abundances and chemistry, and find meteorite analogs using spectral data from the SpeX instrument on the NASA IRTF. (Technique: Spectroscopy; Wavelength: 0.7-2.5 microns; No. of Objects: 144; V. Magnitude Limit: brighter than 19.5)

3) To physically characterize small NEAs and constrain their albedo and diameter using spectral data from the SpeX instrument on the NASA IRTF (Technique: Thermal Modeling; Wavelength: 2.0-2.5 microns; No. of Objects: 40-50; V. Magnitude Limit: brighter than 18.0).

Our proposed research effort (Objective 1) will increase the number of objects that have accurate rotation periods in this size range by 50% compared to existing studies (e.g., Statler et al. 2013; Warner pers. comm.) and a five-fold increase in the number of small NEAs with accurate surface composition, albedo and meteorite analogs (Objectives 2 and 3).

The phase A of the survey that is currently in progress (ending in June 2017) would characterize 95 of our 239-object sample size and we are requesting five additional years of funding to obtain rotational period and composition of the remaining 144 objects (32 NEOs/year) . We used the method by Cochran (1963) to estimate the number of NEAs that need to be observed in this size range (absolute magnitude H greater than 20) to obtain a statistically significant result with ~95 percent confidence level.

The proposed research work will involve observing NEAs using ground-based telescopes to obtain photometric and spectroscopic data. All observations will be made remotely and no funding is being requested for travel to observing sites. The PI and his team have more than a decade of a successful track record observing and characterizing NEAs with the NASA IRTF. The photometric data will be reduced and analyzed using an IDL-based code and spectroscopic data will be reduced and analyzed using the Spextools package. The resulting data products will be archived on the PDS Small Bodies Node and the results will be published as DPS conference abstracts and papers in peer-reviewed journals (Icarus/ApJ).