Notes

• NOTE 1 The Z-axis of any SRF is defined to be the direction from the SRF origin to the true position of the selected star Figure 3-6 schematically illustrates the definition of the SRF. Figure 3-7 gives a schematic representation of the reference frames.
• NOTE 2 The X- and Y- axes of the SRF are obtained under the assumption that the BRF can be brought into coincidence with the SRF by two rotations, the first around the BRF X-axis and the second around the new BRF Y-axis (which is coincident with the SRF Y-axis).