Shape Modeling of two Near Earth Asteroids: 1990 UQ and 2015 DP155, Using Radar and Optical Observations

The study of near-Earth asteroids (NEAs) is helpful for understanding the dynamics of our solar system and assessing potential impact risks to Earth. Among these, Potentially Hazardous Asteroids (PHAs) warrant particular attention due to their orbital proximity to our planet. Characterizing the physical properties of PHAs, such as their size and shape, is fundamental for hazard assessment and for planning potential mitigation strategies. Furthermore, detailed knowledge of these small bodies can offer valuable insights into the formation and evolution of the solar system. In this study we present two shape models of two distinct PHAs: 5189 (1990 UQ) and 2015 DP155.

Asteroid 5189 (1990 UQ), a potentially hazardous asteroid, was found to be an interesting case study as it helped us with characterization of a mini-moon, 2022 NX1, due to polarimetric results from observations at VLT. In August 2022, it was determined from those observations that 1990 UQ and 2022 NX1 have similar properties, indicating that they should share similar albedos. This is particularly important as 2022 NX1's orbit makes it challenging to observe. Shortly after NX1's closest approach in 2022, it became visible, leading to acquisition of a visible spectrum with GranTeCan (de la Fuente et al. 2023). However, to achieve our goals of gaining insights about NX1 characteristics, precise knowledge of 1990 UQ’s physical properties is essential. Fortunately, 1990 UQ has a much longer observational history, including radar data obtained at Goldstone in May 2021, and numerous lightcurves.

2015 DP155 is also a PHA and a potential spacecraft target. It has radar observations from both Arecibo and Goldstone in June 2018, as well as optical lightcurves from various facilities. Using these data for shape modeling, we find an average diameter of about 140 m (Repp et al. 2020), making it one of the smallest asteroids with a well-determined shape model. It looks approximately triangular when viewed along its rotation axis.

We found 3D shape models for both of these PHAs using the SHAPE software (Magri et al. 2007) with the available radar and lightcurve data. These models offer additional insight into their physical properties, which may help in evaluating potential hazards and guiding planetary defense measures.

References

[1] R. de la Fuente Marcos, J. de Léon, C. de la Fuente Marcos, J. Licandro, M. Serra-Ricart, and A. Cabrera-Lavers. Mini-moons from horseshoes: A physical characterization of 2022 NX1 with OSIRIS at the 10.4 m Gran Telescopio Canarias. Astronomy amp; Astrophysics, 670:L10, February 2023. ISSN 1432-0746. doi: 10.1051/0004-6361/202245514.

[2] Repp et al. Shape modeling of potentially hazardous asteroid 2015 DP155 from radar and lightcurve observations. LPSC, 2020.

[3] Christopher Magri, Steven J Ostro, Daniel J Scheeres, Michael C Nolan, Jon D Giorgini, Lance AM Benner, and Jean-Luc Margot. Radar observations and a physical model of Asteroid 1580 Betulia. Icarus, 186(1):152–177, 2007.