Speaker
Description
Thousands of Near Earth Objects (NEOs) are discovered every year, but only a small number of these have their compositions determined. In fall, 2024, we have begun a new program to determine the rough taxonomies and therefore compositions of at least ~1000 very small (absolute magnitude >25, or diameters <30 meters) NEOs over a three year period using the MuSCAT3/4 simultaneous four-channel imagers on the Las Cumbres Observatory (LCO) 2-meter telescopes. We will answer two science questions: (1) To what extent does the measured compositional distribution of small NEOs match the predicted distribution based on the Granvik dynamical model? and (2) How much discrepancy is there between the compositions of the smallest NEOs and the meteorite collection? This project is highly relevant for planetary defense, in that we will determine the distribution of compositions of NEOs. We will characterize some 10% of all NEOs discovered each year with a very modest amount of telescope time (67 hours per year).
NEOs can have rotation periods from seconds to hours, and traditional single-filter NEO observations would require filter cycling (r-g-r-i-r-zs-r or similar: seven exposures) to correct for lightcurve effects before NEO color could be determined. However, because of MuSCAT's powerful technique of making simultaneous multi-filter observations, there will be no lightcurve ambiguity introduced into our measurements; there is no offset in time between measurements at different wavelengths. Furthermore, these observations could also allow the detection of rotational heterogeneity.
This is a very efficient and cost-effective program to characterize a large number of
very small NEOs that will not be characterized by any other program. NEO spectroscopy programs rarely observe targets with V>18 – a limit given by the sensitivity of IRTF/SpeX, which is the most commonly used NEO characterization facility, and which is used by MANOS and MITHNEOS to observe some 60--80 NEOs per year between the two programs – but our LCO targets will be as faint as V=22. The work proposed here is highly complementary to other NEO characterization programs.
This project could not easily be carried out with LSST data. Most moving objects will be observed hundreds of times by LSST over its ten year period, but because the observations are random in rotational phase and filter, it will take many years to provide enough measurements to resolve the lightcurve and measure the color for any given asteroid. Furthermore, many NEOs have long synodic periods and may not be observed often during the primary LSST survey, which means that their colors may never be measured from LSST data. Therefore, this project is highly relevant and even in the era of Vera C. Rubin Observatory and the Legacy Survey of Space & Time.
In this presentation we will show first results from this survey, from the 2024B and 2025A semesters.
This project is supported by the NASA YORPD program.