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Debris objects such as rocket bodies can pose a threat to active space assets in orbit and to assets and humans on the ground through reentry. Orbit and reentry predictions for low-perigee resident space objects are strongly influenced by atmospheric drag. Such predictions are typically performed using fixed or fitted drag/ballistic coefficients that can result in large prediction errors. Accurate drag coefficients require, among other things, knowledge of the attitude. This paper develops an approach to compute accurate drag coefficients for debris objects toward accurate orbit and reentry predictions. The method uses a nonlinear least-squares estimator to estimate the attitude and angular velocities using light curves for debris objects with known shape models. This paper focuses on rocket bodies in particular. The estimated attitude and angular velocities are then used to compute the drag coefficients using a flat-plate panel method. The technique is validated using simulated data scenarios with a number of representative rocket body models. Good performance is observed for the developed approach. Results show that neglecting attitude variations for resident space objects in highly elliptic orbits can result in orbit errors of more than 100 km after just ten brief passes through the atmosphere. [ABSTRACT FROM AUTHOR]

Drag coefficient is a major source of uncertainty in calculating the aerodynamic forces on satellites in low Earth orbit. Closed-form solutions are available for simple geometries under the assumption of free molecular flow; however, most satellites have complex geometries, and a more sophisticated method of calculating the drag coefficient is needed. This work builds toward modeling physical drag coefficients using the direct simulation Monte Carlo method capable of accurately modeling flow shadowing and concave geometries. The direct simulation three-dimensional visual program and the direct simulation Monte Carlo analysis code are used to compare the effects of two separate gas-surface interaction models: diffuse reflection with incomplete accommodation and quasi-specular Cercignani-Lampis-Lord models. Results show that the two gas-surface interaction models compare well at altitudes below ~500 km during solar maximum conditions and below ~400 km during solar minimum conditions. The difference in drag coefficient of a sphere at ~800 km calculated using the two gas-surface interaction models is ~6% during solar maximum and increases to ~10% during solar minimum. The difference in drag coefficient of the GRACE satellite computed using the two gas-surface interaction models at ~500 km differs by ~15% during solar minimum conditions and by ~2-3 % during solar maximum conditions. [ABSTRACT FROM AUTHOR]