Melhem R.M., Fedoskin O.I.

The attitude determination of spacecraft based on using Earth magnetic field measurements is discussed. It is supposed thе space craft one is in the inertial stabilization mode. The basis for solution of the problem is the magnetic field measurements prediction based on a priori spacecraft-s ballistic trajectory and known magnetic field model (WMM2005 is taken). The principle of attitude determination is based on the fitting of onboard magnetic field measurements (made in body frame) to their predicted values (stated in inertial frame). The attitude vector as the task decision is to be found on the basis of the penalty function method. Penalty function to be used takes into account all differences between onboard measurements transformed to inertial frame and those predicted values along a certain ballistic curve. The decision will have some errors stipulated by measurements errors, magnetic field model inaccuracy, and a priori ballistic trajectory errors. The attitude determination errors stipulated by a priori ballistic trajectory inaccuracy are evaluated.