Schematic presentation of the spacecraft to illustrate the configuration without the protective multi-layer insulation and to show the definition of SAA and AA with respect to the spacecraft axes. SAA is the angle between the Sun direction vector and the Z axis of the spacecraft, while the AA (azimuth angle α) is the angle between the X axis and the projection of the Sun direction on the X-Y plane. Thermal disturbances occur whenever SAA >90°, where the Sun illuminates the bottom of the spacecraft, or AA > − $2_{\cdot }^{\circ }5$, where the Sun illuminates the micro-propulsion system (MPS) boom (yellow circle in the figure).