|M.Sc Student||Brack Daniel|
|Subject||In-orbit Tracking of High Area-to-Mass Ratio|
|Department||Department of Aerospace Engineering||Supervisor||Professor Pinchas Gurfil|
|Full Thesis text|
In-orbit tracking using spacecraft on-board systems is a challenging task. It is required to be computationally simple, use limited sensors and present robustness for a variety of scenarios. This task also requires a line-of-sight control in addition to performing highly accurate real time estimation. The relative dynamics between a spacecraft and a high area-to-mass ratio space object make the task even more complicated as the solar radiation pressure perturbation needs to be considered.
In this work the design of an in-orbit on-board algorithm for the tracking of high area-to-mass ratio space objects is presented. This design includes measurement sensor arrays and pre-processing, the core estimation algorithm, line-of-sight control, and estimation post-processing intended for the extraction of additional information from the measurements. The estimation state defined for the system includes the chaser-target relative motion position and velocity as well as the target's solar radiation pressure coefficient. An underlying assumption in the algorithm design is the dominance of the solar radiation pressure perturbation, which is confirmed using an analysis of the relative motion dynamics.
The performance of several subsystem alternatives is presented and compared in a range of scenarios. The alternatives include different non-linear Kalman filter solutions with a combination of optical sensors and a range-meter. The relative motion scenarios range from very similar chaser and target geosynchronous orbits to high chaser-target eccentricity differences. Additional scenarios checked a range of target sizes and the system ability to estimate a low area-to-mass ratio target state. Good state estimation performance is observed in the simulations with estimation errors as low as 0.1%-2% of state variable for most cases. The main conclusion regarding system alternatives is that the Extended Kalman Filter and the range-meter integrated sensor array are preferred.
This work shows that a high area-to-mass ratio target can be tracked and its solar radiation pressure coefficient can be estimated efficiently from orbit using simple sensors and with low computational requirements.