The Mission Accessible Near-Earth Objects Survey: Four years of photometry

TL;DR

This four-year survey of Near-Earth Objects (NEOs) provided extensive lightcurve data, revealing ultra-rapid rotators, insights into shape distributions, and identifying suitable targets for future missions.

Contribution

The study presents the largest dataset of NEO lightcurves, uncovers ultra-rapid rotators, and models shape distributions, advancing understanding of NEO physical properties and mission target selection.

Findings

Discovered two ultra-rapid rotators with periods below 20 seconds.

Modeled shape distribution suggesting a balance between spherical and elongated NEOs.

Identified two NEOs as optimal targets for future robotic or human missions.

Abstract

Over 4.5 years, the Mission Accessible Near-Earth Object Survey (MANOS) assembled 228 Near-Earth Object (NEO) lightcurves. We report rotational lightcurves for 82 NEOs, constraints on amplitudes and periods for 21 NEOs, lightcurves with no detected variability within the image signal to noise and length of our observing block for 30 NEOs, and 10 tumblers. We uncovered 2 ultra-rapid rotators with periods below 20s; 2016MA with a potential rotational periodicity of 18.4s, and 2017QG$_{18}$ rotating in 11.9s, and estimate 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 morphologies distribution using the measured distribution of lightcurve amplitudes. This model suggests 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 2 NEOs as appropriate targets for a potential robotic/human mission: 2013YS$_{2}$ and 2014FA$_{7}$ due to their moderate spin periods and low $\Delta v$.