Determination of Atmospheric Density in Low-Earth Orbit Using GPS Data

Abstract : The objective of this project was to develop an algorithm to accurately determine atmospheric density using simulated GPS data. This algorithm is designed to Support a future USNA Small Satellite mission. Atmospheric density is the most variable factor in orbit propagation. Thus, the uncertainty in density generates the most error when predicting a satellite=s future position. Numerous models have been developed to account for the variations, but more accurate models are needed. In developing the algorithm, Satellite Tool Kit (STK), Analytical Graphics Inc.=s orbit propagation software, was used to generate data using one of several atmospheric models. By measuring the changes in the satellite=s orbit due to atmospheric drag, the density was accurately calculated to within 1% of the 1976 Standard Atmospheric Model. To validate the algorithm, the density Output was compared to that of the model used in STK. The USNA Small Satellite Program has planned to design and place a satellite in low-Earth orbit (LEO) with a GPS receiver on board. The primary mission of the satellite is to determine density in the upper atmosphere. Once the USNA satellite is on orbit, the algorithm can be used to create a database of densities. Other small satellite programs will launch similar satellites to generate sufficient data. With the new atmospheric density data, scientists can create an improved atmospheric model.