reference frame fixed with respect to the sensor external optical cube where the origin of the ARF is defined unambiguously with reference to the sensor external optical cube
NOTE 1 The X-, Y- and Z-axes of the ARF are a right-handed orthogonal set of axes which are defined unambiguously with respect to the normal of the faces of the external optical cube. Figure 3-2 schematically illustrates the definition of the ARF.
NOTE 2 The ARF is the frame used to align the sensor during integration.
NOTE 3 This definition does not attempt to prescribe a definition of the ARF, other than it is a frame fixed relative to the physical geometry of the sensor optical cube.
NOTE 4 If the optical cube’s faces are not perfectly orthogonal, the X-axis can be defined as the projection of the normal of the X-face in the plane orthogonal to the Z-axis, and the Y-axis completes the RHS.