Analysis of Orbit Prediction Sensitivity to Thermal Emissions Acceleration Modeling for High Area-to-mass Ratio (HAMR) Objects

High area-to-mass ratio (HAMR) inactive resident space objects (RSOs) in the geosynchronous orbit (GEO) regime pose a hazard to active GEO RSOs. The combination of solar radiation pressure (SRP), and solar and lunar gravitational perturbations causes perturbations in the orbits of these HAMR RSOs. The HAMR nature of these RSOs results in greater sensitivity to SRP forces resulting in the perturbation of mean motion, inclination and eccentricity. The subsequent drift with respect to the Earth, combined with time varying orientation with respect to the sun and transitions into and out of Earth’s shadow, results in many of these RSOs being “lost” after initial acquisition as they transition through periods of days to weeks out of view of observing sites. This work examines the sensitivity of the prediction accuracies to inadequate modeling of the thermal emissions component of the SRP acceleration in the force models. The simplest models treat the thermal emission term either implicitly, or as a term that is a function of a fixed surface temperature and area. In reality, the temperature can vary with time for inert objects (e.g. orbital debris) transitioning in to and out of Earth shadow. Additionally, the orientation dynamics result in thermal acceleration components that vary relative to the inertial reference frame, and in general, have components orthogonal to the sun-object line. The prediction uncertainties associated with thermal modeling, orientation dynamics and materials uncertainties are examined in terms of the SRP acceleration perturbations for a range of representative HAMR object characteristics. Results indicate that significant prediction errors result from inadequate accounting for the thermal emissions component when compared to the standard SRP models used. These errors need to be addressed in the orbit determination and prediction to allow for more accurate re-acquisition and tracking