Determination of the spacecraft Foton M-2 attitude motion on measurements of the Earth magnetic field

The preprint presents the results of reconstruction of the Foton M-2 attitude motion during its uncontrolled flight 31.5 – 16.06.2005. The reconstruction was carried out by processing onboard measurements of the Earth magnetic field strength. The measurement data were accumulated continually during the most part of the flight, but the processing procedure dealt with data segments, which had length 270 min. The measurement data on each such segment were processed simultaneously by means of the least squares method and integration of the spacecraft attitude motion equations. The estimates of the mathematical model parameters and initial conditions of the attitude motion were obtained as a result of such processing. The results of processing several segments above made clear the motion during the flight. The motion began with very small angular rates, but then it became faster and proved to be close to Euler's regular precession of an axially symmetric rigid body. In the last day of magnetic filed measurements 09.06.2005, the spacecraft angular rate around its longitudinal axis was equal 1.1 deg./s, projection of the angular rate vector onto the plane perpendicular to that axis was equal 0.11 deg./s. Deflections of the longitudinal axis from the normal to the spacecraft orbital plane did not exceed 60$^\circ$. The estimations of real quasi-steady acceleration component on board the spacecraft were obtained.