Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Eric D. Swenson, PhD.


Due to the United States' growing dependence on space based assets and the in- creasing number of resident space objects (RSO), improvement of Space Situational Awareness (SSA) capabilities is more necessary than ever. As a way to aid in this need, the Air Force Institute of Technology (AFIT) is developing the Space Object Self-Tracker (SOS) as a proof-of-concept experimental satellite for RSO precision tracking and collision avoidance system in Low Earth Orbit (LEO). Specifically, SOS will use Global Positioning System (GPS) position estimates for on-board orbit de- termination. Currently, SOS will use the Simplified General Perturbations-4 (SGP4) algorithm as its orbit determination algorithm. This research investigates the use of a modified Special Perturbations (SP) orbit determination algorithm as an alternative means for on-board orbit determination (OD) for the SOS experiment. The research is focused on evaluating performance gains and studying the effects of using GPS navigation solutions as the input observation data on the achievable accuracy of the SP algorithm. The SP OD algorithm was evaluated in testing both simulated and real world observation data. The position estimates generated by the SP algorithm from both GPS navigation solution observations and observations delivered in the J2000 inertial frame were analyzed to determine the effects of the SP algorithm's achievable performance. The accuracy of position estimates generated from the SP algorithm were also compared to those generated by SGP4 algorithm. Analysis leads to the conclusion that the SP algorithm will be beneficial in providing more accurate position estimates for observed GPS navigation solutions. However, the SP algorithm will require improvements to the dynamics modeled in the SP algorithm by specifically including more perturbations such as those due to air drag.

AFIT Designator


DTIC Accession Number