The LRA optical reference point (intersection of the optical axes of all 4 prisms within the array) in body-fixed satellite system coordinates:
O is satellite-based origin, and PC the phase center.
Vector L is from the satellite-based origin to the LRA mass center.
Vector PC is from the satellite center of gravity to the phase center of retroreflector array.
L = (-0.34, 381.92, 310.98)mm The plane of the front faces of the cubes is +35.52mm in the Z direction from the LRA mass center.
The cubes' phase centers are -h x n in the Z direction from the plane of the front faces of the cubes.
For the STSAT-2 cubes, h=22.3mm and n=1.464. So the phase centers are -32.65mm in Z direction. So Z-component of array phase center is +2.87mm from LRA mass center. So, defining vector L' as the vector from the satellite-based origin to the phase center of the retroreflector array, we have
L' = (-0.34, 381.92, 313.85)mm Finally, the vector PC from the satellite center of gravity to the phase center of the retroreflector array is PC=L' -C.
So PC = (7.26, 0.52, 311.95)mm in the STSAT-2A and (-0.16, -30.24, 313.82)mm in the STSAT-2B in satellite fixed frame.