GOES-13 Propulsion Modeling

Abstract

The Geostationary Operational Environmental Satellite (GOES) 13 is the first in a new series of weather satellites. Compared to previous GOES satellites, GOES-13 has improved Image Navigation and Registration (INR) accuracy, can continue imaging during eclipse periods, periodically yaw-flips to provide better instrument cooling, and uses daily momentum dumping maneuvers to offset solar torque generated by the single solar array. Post launch testing showed that GOES-13 met all INR requirements, but post-maneuver orbit predictions, particularly longitude drift, were not nearly as accurate as desired. Ground software computes the maneuver velocity change ( v) for the predictions using firing data (telemetry if available, or predicted firing if not) and a propulsion model for the twelve 9.25 N bi-propellant thrusters. Investigations verified that the propulsion model met flowdown requirements on maneuver v accuracy, but several problems were uncovered. In particular, the effect of plume impingement on the solar array was not modeled, the propulsion model was not accurate for pulsed firing with short off-times, and prelaunch calibrations of jet thrust and direction were slightly in error. A plume impingement model was developed using detailed models of plume momentum flux and plate reflection. Corrections to calibrations of jet thrust and direction were computed using a thruster calibration algorithm that fits maneuver v estimates (obtained from orbit determination), angular momentum change ( h) telemetry data, and prior information. Thruster mass and energy flow was analyzed to understand factors affecting pulsed firing. Problems in modeling short off-time pulsed firing were eventually traced to the effects of liquid propellant remaining between the jet valves and thrust chamber after valve closure. A new propulsion model was developed and validated using data for hundreds of test firings. With these changes, the ground system can accurately predict GOES-13 maneuver performance for all maneuver types.

Geostationary Satellite Station Keeping Robustness to Loss of Ground Control

“…An important contributor to NS maneuver cross-coupling is impingement of the thruster plumes on the solar array of the satellite, which deflects some of the thruster exhaust, and thereby thrust, in an unintended direction (see, e.g., Gibbs et al 2008). The magnitude and direction of the deflected thrust depends on the orientation of the solar array with respect to the thrusters at the time of firing.…”

GOES-13 Orbit and Attitude Determination Analysis

“…NEWOAD also solved for an EW ISEC parameter, but inclusion of ISEC did not have a significant effect on other parameter estimates. NEWOAD used values for the daily momentum-dumping v that were determined after applying post-PLT modifications to the propulsion model and thruster calibration 18 by the operational OATS during PLT are slightly biased compared to the calibrated values, but the effect on the range and landmark residuals is barely noticeable in the 24-hour predictive plots. This is verified by the similarity in the predictive range residuals of Fig.…”

“…Investigation revealed that North jet plume impingement on the solar array produced a force sufficient to cause this longitude drift error. A plume impingement model was developed and with minor adjustment to thruster force and cant angles 4 3 remained when the spacecraft was upright, but not when inverted. Additional maneuver modeling errors were eliminated as a potential source of the problem because changes in angular momentum across the maneuvers were well modeled using existing propulsion and plume impingement models.…”