arXiv subjects

Andy J. López-Oquendo

Publications and source records attributed to Andy J. López-Oquendo.

5 recordsLinked to original sources

arXiv2026

Probing the Taxonomic Diversity of the Small Near-Earth Object Population

Small near-Earth objects (NEOs) represent the immediate source population of meteors and meteorites and provide a direct window into the compositional and dynamical evolution of the inner Solar System. However, their small sizes, rapid rotation rates, and short observability windows have historically limited systematic compositional characterization. We present results from a multi-year rapid-response near-infrared spectrophotometric survey of recently discovered NEOs conducted with the UKIRT-WFCAM instrument between 2016 and 2024. Our campaign obtained 371 observation sequences, yielding reliable color measurements and probabilistic taxonomic classifications for 122 NEOs, with diameters ranging from 5 m to 150 m and a median size of 60 m. We employed lightcurve-corrected Z, J, H, and K photometry and a machine-learning-based classification framework to derive both observed and debiased taxonomic distributions as a function of object size. The observed taxonomic fractions show a population of small NEOs dominated by S-complex and CX-complex objects in nearly equal proportions. After accounting for observational selection biases, however, the inferred intrinsic population is instead dominated by dark, carbonaceous (CX-complex) bodies, with important implications for the intrinsic composition of the small NEO population. We further explore the relationship between small NEOs, meteorite fall statistics, and atmospheric filtering effects, finding that a substantial fraction of carbonaceous material likely does not survive atmospheric entry. These results highlight the importance of debiased surveys of small NEOs for interpreting the meteorite record, refining delivery models from the main belt, and informing the selection of future mission targets and planetary defense strategies.

astro-ph.EP↗

arXiv2025

Thermal and Optical Characterization of Near-Earth Objects: Science Commissioning of the Recently Upgraded Mid-Infrared Camera MIRSI on the NASA Infrared Telescope Facility

Mid-infrared (mid-IR) observations of Near-Earth Objects (NEOs) have historically been a valuable tool for understanding their physical properties. However, the current state of mid-IR instruments on ground-based telescopes places several limitations on performing thermal characterization of NEOs. The complexity of maintaining these instruments in operational conditions on telescopes has led to their decommissioning. Here, we present the first science commissioning observations out to 12.5 microns from the upgraded Mid-Infrared Spectrograph and Imager (MIRSI) at the NASA-IRTF. We obtained 42 observations of 31 NEOs and derived their diameters and albedos. Since MIRSI allows simultaneous optical observations with its MIRSI Optical Camera (MOC), we were able to determine the absolute magnitude for most of the targets at the time of the thermal acquisition. We present ejecta characterization for the Didymos system from observations made 11 hours and 9 days after the Double Asteroid Redirection Test (DART) impact. We present albedo and size measurements for (98943) Torifune 2001 CC21, the fly-by target of the Japanese Extended Hayabusa2 Mission. We also highlight several applications that the MIRSI system will provide for future airless body characterization, such as constraining thermal inertia from simultaneous optical and thermal lightcurves. This work also demonstrates the importance of having MIRSI as an available rapid-response instrument for planetary defense purposes.

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arXiv2024

Infrared Colors of Small Serendipitously-Found Asteroids in the UKIRT Hemisphere Survey

The UKIRT Hemisphere Survey covers the northern sky in the infrared from 0-60 degrees declination. Current data releases include both J and K bands, with H-band data forthcoming. Here we present a novel pipeline to recover asteroids from this survey data. We recover 26,138 reliable observations, corresponding to 23,399 unique asteroids, from these public data. We measure J-K colors for 601 asteroids. Our survey extends about two magnitudes deeper than 2MASS. We find that our small inner main belt objects are less red than larger inner belt objects, perhaps because smaller asteroids are collisionally younger, with surfaces that have been less affected by space weathering. In the middle and outer main belt, we find our small asteroids to be redder than larger objects in their same orbits, possibly due to observational bias or a disproportionate population of very red objects among these smaller asteroids. Future work on this project includes extracting moving object measurements from H and Y band data when it becomes available.

astro-ph.EP↗

arXiv2024

Laser Irradiation of Carbonaceous Chondrite Simulants: Space Weathering Implications for C-complex Asteroids

Surfaces of carbonaceous asteroids (C-complex) have shown diverse contrasting spectral variations, which may be related to space weathering. We performed laser irradiation experiments on CI and CM simulant material under vacuum to mimic the spectral alteration induced by micrometeorite impacts. We used in situ ultraviolet-visible and near-infrared reflectance spectroscopy to analyze spectral alterations in response to pulsed laser irradiation, as well as scanning electron microscopy and x-ray photoelectron spectroscopy to search for microstructural and compositional changes. Laser irradiation causes an increase in spectral slope (reddening) and a decrease in the albedo (darkening), and these changes are stronger in the ultraviolet-visible region. These spectral changes are likely driven by the excess iron found in the altered surface region, although other factors, such as the observed structural changes, may also contribute. Additionally, while the 0.27~$μm$ band appears relatively stable under laser irradiation, a broad feature at 0.6~$μm$ rapidly disappears with laser irradiation, suggesting that space weathering may inhibit the detection of any feature in this spectral region, including the 0.7~$μm$ band, which has typically been used an indicator of hydration. Comparing our laboratory results with optical spectrophotometry observations of C-complex asteroids, we find that the majority of objects are spectrally red and possess colors that are similar to our irradiated material rather than our fresh samples. Furthermore, we also find that ``younger'' and ``older'' C-complex families have similar colors, suggesting that the space weathering process is near-equal or faster than the time it takes to refresh the surfaces of these airless bodies.

astro-ph.EP↗

arXiv2022

Physical Characterization of 2015 JD1: A Possibly Inhomogeneous Near-Earth Asteroid

The surfaces of airless bodies such as asteroids are exposed to many phenomena that can alter their physical properties. Bennu, the target of the OSIRIS-REx mission, has demonstrated how complex the surface of a small body can be. In 2019 November, the potentially hazardous asteroid 2015 JD1 experienced a close approach of 0.0331 au from the Earth. We present results of the physical characterization of 2015 JD1 based on ground-based radar, spectroscopy, and photometric observations acquired during 2019 November. Radar polarimetry measurements from the Arecibo Observatory indicate a morphologically complex surface. The delay-Doppler images reveal a contact-binary asteroid with an estimated visible extent of ~150 m. Our observations suggest that 2015 JD1 is an E-type asteroid with a surface composition similar to aubrites, a class of differentiated enstatite meteorites. The dynamical properties of 2015 JD1 suggest it came from the $ν_6$ resonance with Jupiter, and spectral comparison with major E-type bodies suggest that it may have been derived from a parental body similar to the progenitor of the E-type (64) Angelina. Significantly, we find rotational spectral variation across the surface of 2015 JD1 from red to blue spectral slope. Our compositional analysis suggests that the spectral slope variation could be due to the lack of iron and sulfides in one area of the 2015 JD1 and/or differences in grain sizes.

astro-ph.EP↗