Context : The Yarkovsky effect , which causes orbital drift , and the YORP effect , which causes changes in rotation rate and pole orientation , play important roles in the dynamical and physical evolution of asteroids .
Near-Earth asteroid ( 1862 ) Apollo has strong detections of both orbital semimajor axis drift and rotational acceleration .

Aims : We produce a unified model that can accurately match both observed effects using a single set of thermophysical properties derived from ground-based observations , and we determine Apollo ’ s long term evolution .

Methods : We use light-curve shape inversion techniques and the advanced thermophysical model ( ATPM ) on published light-curve , thermal-infrared , and radar observations to constrain Apollo ’ s thermophysical properties .
The derived properties are used to make detailed predictions of Apollo ’ s Yarkovsky and YORP effects , which are then compared with published measurements of orbital drift and rotational acceleration .
The ATPM explicitly incorporates 1D heat conduction , shadowing , multiple scattering of sunlight , global self-heating , and rough surface thermal-infrared beaming in the model predictions .

Results : We find that ATPM can accurately reproduce the light-curve , thermal-infrared , and radar observations of Apollo , and simultaneously match the observed orbital drift and rotational acceleration using : a shape model with axis ratios of 1.94:1.65:1.00 , an effective diameter of 1.55 \pm 0.07 km , a geometric albedo of 0.20 \pm 0.02 , a thermal inertia of 140 _ { -100 } ^ { +140 } J m ^ { -2 } K ^ { -1 } s ^ { -1 / 2 } , a highly rough surface , and a bulk density of 2850 _ { -680 } ^ { +480 } kg m ^ { -3 } .
Using these properties we predict that Apollo ’ s obliquity is increasing towards the 180° YORP asymptotic state at a rate of 1.5 _ { -0.5 } ^ { +0.3 } degrees per 10 ^ { 5 } yr .

Conclusions : The derived thermal inertia suggests that Apollo has loose regolith material resting on its surface , which is consistent with Apollo undergoing a recent resurfacing event based on its observed Q-type spectrum .
The inferred bulk density is consistent with those determined for other S-type asteroids , and suggests that Apollo has a fractured interior .
The YORP effect is acting on a much faster timescale than the Yarkovsky effect and will dominate Apollo ’ s long term evolution .
The ATPM can readily be applied to other asteroids with similar observational data sets .