Convergence of the predicted Yarkovsky semimajor axis drift (solid line plotted on primary y-axis) and thermal component of the YORP obliquity shift (dashed line plotted on secondary y-axis) with number of depth steps used to solve the 1D heat conduction equation. The horizontal grey lines represent the convergence limits estimated by Aitken’s delta-squared process. The example convergence series shown here are calculated for the “new” shape model variant of (1862) Apollo assuming a thermal inertia of 140 J m^-2 K^-1 s^−1/2 and a roughness fraction of 60%.