Satellite Drag Estimation Using Retrospective Cost Input Estimation

Orbit estimation is of increasing interest due to need to avoid close encounters between operational satellites and space debris. This paper uses input estimation to estimate the drag on a satellite, where the drag is modeled as an unknown input forcing. Retrospective cost input estimation is applied to simulated satellite data under three scenarios, namely, 1) indirect estimation of the drag acceleration in the inertial frame (that is, estimation of the total inertial acceleration), 2) direct estimation of the drag acceleration in the inertial frame (that is, estimation of only the inertial drag acceleration), and 3) estimation of the magnitude of the drag acceleration.