The Mission Accessible Near-Earth Objects Survey: Four Years of Photometry

Abstract

Over 4.5 years, the Mission Accessible Near-Earth Object Survey assembled 228 near-Earth object (NEO) light curves. We report rotational light curves for 82 NEOs, constraints on amplitudes and periods for 21 NEOs, light curves with no detected variability within the image signal-to-noise and length of our observing block for 30 NEOs, and 10 tumblers. We uncovered two ultra-rapid rotators with periods below 20 s, - 2016 MA with a potential rotational periodicity of 18.4 s, and 2017 QG₁₈ rotating in 11.9 s - and estimated the fraction of fast/ultra-rapid rotators undetected in our project plus the percentage of NEOs with a moderate/long periodicity undetectable during our typical observing blocks. We summarize the findings of a simple model of synthetic NEOs to infer the object's morphology distribution using the measured distribution of light curve amplitudes. This model suggests that a uniform distribution of axis ratio can reproduce the observed sample. This suggests that the quantity of spherical NEOs (e.g., Bennu) is almost equivalent to the quantity of highly elongated objects (e.g., Itokawa), a result that can be directly tested thanks to shape models from Doppler delay radar imaging analysis. Finally, we fully characterized two NEOs - 2013 YS₂ and 2014 FA₇ - as appropriate targets for a potential robotic/human mission due to their moderate spin periods and low Δv. Keywords: minor planets; asteroids; general