Calculation of quasi-steady accelerations occurring onboard the International Space Station

We describe the method for calculation of quasi-steady accelerations occurring onboard the Service Module of the International Space Station and give a few examples of its application. We calculated the accelerations basing on telemetry information about station attitude motion. The information contains values of the station angular rate and the quaternion of the station attitude with respect to an inertial coordinate system at some instants. Both kinds of values are given with the step 1 s in time. We calculated accelerations by two ways. The first way started with smoothing each component of the quaternion data by discrete Fourier series. Then the station angular rates and angular accelerations were calculated by differentiation of the series. Finally, acceleration at a given point of the station was calculated. The angular rate data were used to choose the number of harmonics in the smoothing series. In the second way, we used separate series to smooth components of the angular rate data. The differentiation of these series gave the components of the station angular acceleration. The agreement of series for different kinds of data was carried out by finding approximation of station attitude motion by solutions of kinematic equations. The comparison was given for accelerations calculated by these ways.