Meeting orbit determination requirements for a small satellite mission

A study is conducted with the goal of utilizing estimation techniques on measurements obtained from various onboard resources such as a Sun sensor, a magnetometer and a commercial GPS unit in order to approximate the true trajectory of the vehicle in realtime and minimize the error associated with the process. This carries significant relevance to the field of orbit determination, where a small mission could operate a relatively cheap system for tracking purposes. This paper models a GPS sensor to become available only 5 minutes each day, which approximates a worst-case scenario where sparse pseudorange data is only possible due to suboptimal operating conditions for commercial GPS receivers taken to the space environment. Using a dynamic propagation model, which includes effects of Earth’s gravity, J2 zonal harmonics, and atmospheric drag, a sequential filtering method is used in order to estimate the states (position and velocity) of the vehicle with respect to time. This study demonstrates the capability of this system to achieve an error of approximately 15 meters, which is greatly influenced by the inclusion of a low-cost GPS module as an alternative to high end units that may be unaffordable for low-budget small satellite missions.