The tracking software consists of two parts on-board software and ground segment. For a detailed description - STR/STM users guide

The on-board software could operate in a number of modes and with different settings. All settings and different modes are controlled & displayed in the ground segment. The communication is performed by transferring UDP blocks.

The tracking mode is designed to be fast and uses a minimal amount of calculations. The simplest possible form only localizes highest pixel value within a sub window and sends the x,y value to the ACS system. The ACS systems tries to minimize the dx=x_calculated-x_measured dy=y_calculated-y_measured.

The ground segment could perform a number of extensive calculations for monitoring the tracking and safeguarding the pointing is performed directly. If the on-board software is in monitoring mode stars are identified (in accordance with certain criteria’s) and send down as individual ,positions to the ground segment. The ground segment gives a representation of the actual sky seen by the star tracker (yellow dots). A wanted sky is calculated based on the position of the gondola (latitude,longitude), time (UT)  and the desired astronomical coordinates RA and DEC. The calculated sky is displayed as red dots in the same display. This gives a good feedback and could easily be used to verify that the pointing is correct.