Determination of a spacecraft attitude motion in the astrocorecction mode by measurements of the star sensor BOKZ-M

We consider the problem of determining a spacecraft attitude motion formed for the astrocorrection purpose. This motion is very slow and smooth. It continues for a few minutes. The parameters of the motion are determined by measurements of the star sensor BOKZ-M. The sensor determines the quaternion of the spacecraft attitude every 3 seconds with very high accuracy and negligible lag time. We have to estimate very precisely the spacecraft attitude and the angular rate at an instant in the motion time interval or the spacecraft attitude at two spaced instants in the interval. We propose the statistical method for solving this problem. It uses the convenient representation of the measurement data and their polynomial smoothing. The method allows also smoothing the measurements basing on the model of Euler’s rotation of a spacecraft. The use of this model increases the accuracy of the solution, when Euler’s rotation is used for the astrocorrection purpose. We test the method using the BOKZ-M measurements produced in ground-based testbed.