Physical properties of near-Earth asteroids manually recovered from NEOWISE data

<p class="p1"><span class="s1">The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) </span><span class="s1">spacecraft was reactivated in December 2013 and since then has been </span><span class="s1">conducting an all-sky survey at 3.4 and 4.6 microns to discover and </span><span class="s1">characterize asteroids and comets that come close to the Earth.&#160; </span><span class="s1">NEOWISE employs an automated pipeline for the detection of moving </span><span class="s1">objects, recording their astrometry and photometry and reporting </span><span class="s1">positions to the Minor Planet Center for archiving.<span class="Apple-converted-space">&#160; </span>However, there </span><span class="s1">are a subset of near-Earth objects that are not found by the automated </span><span class="s1">system due to rates of motion or acceleration outside the pipeline </span><span class="s1">limits, an insufficient number of detections, or confusion with </span><span class="s1">background sources.<span class="Apple-converted-space">&#160; </span>Because NEOWISE archives every full-frame image </span><span class="s1">obtained during the survey, detections of these objects can be </span><span class="s1">recovered by manually searching the expected positions for coincident </span><span class="s1">sources.</span></p> <p class="p1"><span class="s1">We have performed searches for near-Earth objects in the NEOWISE </span><span class="s1">archives from 2013 to 2019, recovering detections for over 400 objects </span><span class="s1">and enabling fitting of their diameters and albedos (Masiero et </span><span class="s1">al. 2018, Masiero et al. 2020).<span class="Apple-converted-space">&#160; </span>This builds on earlier work that </span><span class="s1">searched the data from the cryogenic phase of the original WISE </span><span class="s1">mission (Mainzer et al. 2014).<span class="Apple-converted-space">&#160; </span>Objects found through this technique </span><span class="s1">tend to be smaller than those detected by the automated processing. </span><span class="s1">The distribution of albedos for these objects is skewed to high </span><span class="s1">reflectivities, as is expected for a population that is </span><span class="s1">optically-selected.</span></p> <p class="p1"><span class="s1">Here we present the results of our searches along with the physical </span><span class="s1">properties of the recovered objects.<span class="Apple-converted-space">&#160; </span>We also will discuss the reasons </span><span class="s1">these objects were missed by the automated processing, and what the </span><span class="s1">observed physical property distribution implies about any remaining </span><span class="s1">objects still waiting to be found in the data.</span></p>