Speaker
Description
Photometric observations of near-Earth asteroids (NEAs) using the TRAPPIST telescopes are regularly performed notably to support shape modeling using radar data as well as an effort to calibrate the relation between the albedo and the polarization displayed by NEAs. These two methods allow to obtain accurate size determination for these objects.
The TRAPPIST telescopes are two twin 60-cm robotic telescopes operated by the Liège University (Jehin+2011). TRAPPIST-North (Z53) is located at Oukaïmeden Observatory in Morocco, while TRAPPIST-South (I40) is based at the ESO La Silla Observatory in Chile. About 25% of their observation time is dedicated to asteroid observations.
Photometry is a necessary complement to radar data, allowing for extended observation times and at a wider range of phase angles than in radar, which is of great importance for spin axis determination and shape modeling purposes. We are supporting shape modeling efforts using archive radar data from the Arecibo Observatory and/or observations from the Goldstone Observatory.
The degree of linear polarization of the light scattered by an asteroid surface is dependent on its albedo at first order (Belskaya+2015). High albedo results in low polarization and vice versa. To calibrate this relationship for the first time for NEAs at high phase angles, polarimetric observations of NEAs are ongoing which will provide a strong tool to determine the albedo of a given NEA, thus its size, from a single polarimetric observation at phase angle > 40°. To refine or determine the albedo of our targets, we use photometric lightcurves to help determine the spin axis orientation, thus the size of the objects thanks to the radar data. Additionally, observations at low phase angles are used to construct phase curves that allow to refine the absolute magnitude H.
To date, we have observed over 60 NEAs with available radar data from Arecibo and/or Goldstone and we possess polarimetric data for about 30 of them. Since 2017, we have acquired a dense lightcurve for each of these objects during one or several apparitions, complemented with color data using the B, V, R, and I Cousins filters. Finally, dedicated short observations at low solar phase angles can be acquired. Notable Examples of shape modeling using the TRAPPIST data include NEAs 2005 UD (Kueny+2023) and 1998 OR2 (Devogèle+2024).
In this presentation, we will highlight the capabilities of the TRAPPIST telescopes, the current dataset of NEA observations, and planned observations of NEAs with existing radar data but remaining to be analyzed.
Belskaya, I. et al. (2015) Asteroids IV, 151–163. Devogèle, M. et al. (2024) PSJ, 5, 44..
Jehin, E. et al. (2011) The Messenger, 145, 2–6. Kueny, J. K. et al (2023) PSJ, 4, 56.
