Drag Coefficient Estimation using Satellite Attitude and Orbit Data

Open Access
Author:
Hassa, Christopher Louis
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 13, 2013
Committee Members:
  • David Bradley Spencer, Thesis Advisor
  • Sven G Bilen, Thesis Advisor
Keywords:
  • Swift
  • coefficient of drag
  • spacecraft drag coefficient
Abstract:
The coefficient of drag for spacecraft in a variety of orbits and solar cycle conditions is generally assumed to be a constant value of 2.2. The research herein revisits the validity of this assumption and chooses to directly calculate the coefficient of drag using orbital data gathered from NASA’s Swift spacecraft. In order to accomplish this task, an accurate cross-sectional area calculation algorithm is generated and an atmospheric model is utilized. The area algorithm accurately predicts the operational cross-sectional area of Swift at any given orientation. The density model used is the NRLMSISE-00 atmospheric model, which, when compared to the internally calculated density values assuming the coefficient of drag is 2.2, show large amounts of error. The uncertainty of the density at the altitude of Swift leads to an extended analysis of its orbital decay, giving the best estimate of a no-earlier-than deorbit date of mid-2022 to early 2023. This analysis proved inconclusive, however, as no single model followed the actual decay of Swift, implying that the coefficient of drag may change over the mission’s duration. The results of the calculation of the coefficient of drag clearly show that no single value can be assumed as correct. However, some of these results also fall outside of the expected bounds of the coefficient of drag, implying that additional research is required to incorporate additional variables to properly determine what values of the coefficient of drag to use and when.