ADAM: a general method for using various data types in asteroid reconstruction

Abstract

We introduce ADAM, the All-Data Asteroid Modelling algorithm. ADAM is simple and universal since it handles all disk-resolved data types (adaptive optics or other images, interferometry, and range-Doppler radar data) in a uniform manner via the 2D Fourier transform, enabling fast convergence in model optimization. The resolved data can be combined with disk-integrated data (photometry). In the reconstruction process, the difference between each data type is only a few code lines defining the particular generalized projection from 3D onto a 2D image plane. Occultation timings can be included as sparse silhouettes, and thermal infrared data are efficiently handled with an approximate algorithm that is sufficient in practice because of the dominance of the high-contrast (boundary) pixels over the low-contrast (interior) pixels. This is of particular importance to the raw ALMA data that can be directly handled by ADAM without having to construct the standard image. We study the reliability of the inversion, using the independent shape supports of function series and control-point surfaces. When other data are lacking, one can carry out fast non-convex lightcurve-only inversions, but any shape models resulting from it should only be taken as illustrative large-scale models.

Photometric survey, modelling, and scaling of long-period and low-amplitude asteroids

“…Although main belt asteroids can only be observed at relatively small phase angles (up to 30 • at most), it has been shown that their lightcurves contain signatures of non-convex topographic features, so that these features can be successfully reproduced in the shape models (Bartczak & Dudziński, MNRAS, accepted). When modelling on lightcurves is a priori complemented by auxiliary data like adaptive optics or occultation contours in one multi-data inversion process, such non-concavities gain more support (as in models created using ADAM algorithm, Viikinkoski et al 2015;Hanuš et al 2017). However, when SAGE non-convex models based exclusively on lightcurves are a posteriori compared to multi-chord occultations, their topographic features are confirmed, as has been shown in the case of binary asteroid (90) Antiope (Bartczak et al 2014), but also in simulations and real-case studies performed recently by Bartczak & Dudziński (MNRAS, accepted).…”

VLT/SPHERE- and ALMA-based shape reconstruction of asteroid (3) Juno

“…We used the ADAM algorithm (Viikinkoski & Kaasalainen 2014;Viikinkoski et al 2015) for the shape and spin reconstruction. ADAM enables an easy combining and weighting of various data types.…”

“…We used both subdivision surfaces and octantoid parametrization for shape representations (Viikinkoski et al 2015). Based on a global parametrization by spherical harmonics, octantoids produce smooth curved surfaces, while the subdivision surfaces, together with the regularization we use, are characterized by sharper local features.…”

“…However, recovering nonconvex features reliably is seldom possible with lightcurves alone (Ďurech & Kaasalainen 2003). On the other hand, lightcurves are crucial for enabling and completing the reconstruction when only a few disk-resolved observations are available (Viikinkoski & Kaasalainen 2014;Viikinkoski et al 2015). For Juno, 37 relative-magnitude lightcurves were obtained in the years 1954-1991.…”

“…Keck Foundation. 1 https://almascience.eso.org/alma-data/ science-verification package (Viikinkoski et al 2015) and present a model based on ALMA data, lightcurves, AO images, and stellar occultations.…”