Effect of solar protons on the orbit of geostationary satellites
Abstract
The forces acting on geostationary satellites are accurately modeled in operational orbit determination programs. The residuals of good-quality range data are typically 1 - 2 m over an interval of 2 days. In this paper, mission results from several three-axis-stabilized satellites are reported where, during periods of enhanced solar activity, the deviations between model and measurements increased by an order of magnitude or more. The causes and consequences for station keeping are analyzed. It is shown that there is a direct correlation between the disturbances in the orbit and the flux of energetic protons from the Sun. No energy dependence could be deduced, but all protons with energies greater than or equal to 4 MeV appear to trigger the disturbances. A quantitative analysis demonstrates that enhanced activity of the attitude thrusters is responsible for the unmodeled force. The protons primarily disturb the infrared earth sensors and the spurious attitude offset then causes unnecessary thruster firings. On the investigated spacecraft, the roll-thrusters are directed radially inwards, towards the Earth, with an orbit-tangential component of about 15%. From the amount of change in the eccentricity and in the semi-major axis over a disturbance, the expected ration between tangential- and radial-velocity components is verified. Finally, the extra fuel consumption during a period of high solar activity (such as the entire year 1991) is estimated.
- Publication:
-
NASA STI/Recon Technical Report A
- Pub Date:
- 1993
- Bibcode:
- 1993STIA...9585752H
- Keywords:
-
- Fuel Consumption;
- Jet Flow;
- Loads (Forces);
- Mathematical Models;
- Orbit Calculation;
- Solar Protons;
- Stationkeeping;
- Synchronous Satellites;
- Correlation;
- Optical Measuring Instruments;
- Rangefinding;
- Solar Activity;
- Three Axis Stabilization;
- Spacecraft Design, Testing and Performance