Multi-epoch Spitzer Space Telescope 24 μm data is utilized from the MIPSGAL and Taurus Legacy surveys to detect asteroids based on their relative motion. Methods. Infrared detections are matched to known asteroids and average diameters and albedos are derived using the near Earth asteroid thermal model (NEATM) for 1865 asteroids ranging in size from 0.2 to 169 km. A small subsample of these objects was also detected by IRAS or MSX and the single wavelength albedo and diameter fits derived from these data are within the uncertainties of the IRAS and/or MSX derived albedos and diameters and available occultation diameters, which demonstrates the robustness of our technique. Results. The mean geometric albedo of the small Main Belt asteroids in this sample is pV = 0.134 with a sample standard deviation of 0.106. The albedo distribution of this sample is far more diverse than the IRAS or MSX samples. The cumulative size-frequency distribution of asteroids in the Main Belt at small diameters is directly derived and a 3σ deviation from the fitted size-frequency distribution slope is found near 8 km. Completeness limits of the optical and infrared surveys are discussed.
Bibliographical noteFunding Information:
E.L.R. and C.E.W. acknowledge support from National Science Foundation grant AST-0706980 to conduct this research. This research was supported by an appointment to the NASA Postdoctoral Program at Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA.This work is based, in part, on archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by an award issued by JPL/Caltech. We thank an anonymous referee for helpful comments which greatly improved this paper.
© 2015 ESO.
- Infrared: general
- Minor planets, asteroids: general