Fast asteroidal period inversion by parallel acceleration-based three-step reduced voting

Abstract

Asteroids, especially near-Earth asteroids, have become a popular focus of research in the field of deep space exploration because they retain historical relics of the early formation and evolution of the Solar System. Rotational periods play an important role in elucidating the characteristics of asteroids, such as the rubble-pile internal structure and the spin barrier. Generally, commonly used periodogram methods, such as Fourier-type methods, can produce only a rough estimate of the rotational period, and it is difficult to obtain other essential parameters, such as the pole, shape, and scattering parameters. To alleviate this problem, this article presents a three-step reduced voting (TRV) algorithm based on the Cellinoid model to accurately and efficiently invert asteroidal periods from lightcurves. The proposed TRV algorithm can realize this inversion process to derive the high-precision period, as well as a roughly estimated pole orientation and overall shape of an asteroid. Numerical experiments confirm that the TRV algorithm can obtain accurate periods and near-accurate poles from synthetic lightcurves. Besides, this algorithm is applied to invert the rotational periods of the 61 real asteroids, and the derived periods are consistent with those reported in other publications. It is also demonstrated that more observations collected in various viewing geometries can improve the accuracy in searching the pole orientation of an asteroid. For further improving the efficiency of TRV, parallel versions of this algorithm implemented with OpenMP and CUDA C schemes are provided with environments of Hygon C86 7185 CPUs and a Tesla V100-SXM3 GPU, respectively. The maximum speedup ratio of the OpenMP scheme is 79.567x, while that of the CUDA C scheme is 110.906x. The results show that the proposed parallel acceleration schemes can greatly improve the inversion efficiency of the TRV algorithm, and can be widely used in searching the parameters of a large number of asteroids.