THE TREATMENT OF ATTITUDE ERRORS IN SATELLITE GEOMAGNETIC DATA

Vector magnetic field measurements from magnetic field satellites are contaminated by errors from multiple sources. Previously, the effect o f these errors has been treated as isotropic, in other words as affect ing the components of the vector field independently. This is incorrec t. Here we develop a more complete formalism for dealing with attitude uncertainty, the main source of non-isotropic data errors, both for t he case where the orientation is equally well known in all directions, and also for when the attitude determination is itself anisotropic. W e demonstrate that the new method can be implemented at essentially no computational cost, and produces a small improvement in field models for Magsat-like data. Preliminary estimates of the error budget for th e Orsted satellite indicate that in this case correct treatment of att itude errors could be extremely important, particularly in studies of short-wavelength lithospheric fields, and of field-aligned currents.