YORP torques with 1D thermal model

TL;DR

This paper presents a numerical 1D thermal model for the YORP effect on irregularly shaped objects, revealing new insights into seasonal effects and independence from conductivity.

Contribution

It introduces a novel FFT-based iterative solver for nonlinear boundary conditions in a 1D thermal model of the YORP effect on triangular mesh objects.

Findings

YORP effect in rotation rate is independent of conductivity.

Seasonal YORP effect in attitude is observed for elliptic orbits.

The model efficiently handles complex shapes with independent surface triangles.

Abstract

A numerical model of the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect for objects defined in terms of a triangular mesh is described. The algorithm requires that each surface triangle can be handled independently, which implies the use of a 1D thermal model. Insolation of each triangle is determined by an optimized ray-triangle intersection search. Surface temperature is modeled with a spectral approach; imposing a quasi-periodic solution we replace heat conduction equation by the Helmholtz equation. Nonlinear boundary conditions are handled by an iterative, FFT based solver. The results resolve the question of the YORP effect in rotation rate independence on conductivity within the nonlinear 1D thermal model regardless of the accuracy issues and homogeneity assumptions. A seasonal YORP effect in attitude is revealed for objects moving on elliptic orbits when a nonlinear thermal model is used.