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  • Satellite Effects of Space Weather
  • Satellites and spacecrafts
  • Spacecraft Orientation Effects

Spacecraft Orientation Effects

  • Some spacecraft use Earth's magnetic field as an aid in orientation or as a force to work against to dump momentum and slow down reaction wheels. During geomagnetic storms, dramatic unexpected changes in the magnetic field observed by the satellite can lead to mis-orientation of the spacecraft. Some effects have been reported at Kp values as low as Kp=4. Usually, problems are not experienced until Kp>=6 occurs. GEO spacecraft also experience a unique occurrence termed a Magnetopause Crossing. The sunward boundary of Earth's magnetic field magnetopause) is usually located approximately 10 Earth radii from Earth center. Variations in the pressure (due to changes in the velocity, density, and magnetic field) of the incoming solar wind change the location of that boundary. Under solar wind conditions of high velocity and density and strongly southward magnetic field, this boundary can be rammed to inside the altitude of GEO orbit at 6.6 Earth radii. A GEO spacecraft on the sunward side of Earth can be outside the (compressed) magnetopause and in the (modified) solar wind magnetic field for minutes to hours. When the magnetopause is inside 6.6 radii, GEO spacecraft are within the magnetosheath between the bow shock and the magnetopause. Magnetic sensors on board become confused as the detected magnetic field drops from ~200 nanoTesla to near zero and its sign changes erratically. The GOES spacecraft have magnetometers on board that unambiguously identify crossings at their positions. (See GOES Magnetometer plots). However, since magnetopause compression is time varying, and different spacecraft are at different longitudes, a GOES satellite may not observe a crossing experienced by others, and conversely.

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