Some measurement was performed using two theodolites.
Step 1.
One theodolite was aligned with the surfaces of the cube and used as a transfer standard to determine the angular displacements of the second one.
Step 2.
The second theodolites was equipped with a cross-hair target at the focal point of a lens simulating a source at infinity.
Step 3.
When re-imaged by the lenses of the LAC, an image of the crosshair was formed on each of the focal planes. The image of the crosshair was ~20 pixels across, allowing the center of the crosshair to be located to ~0.1 pixel. The image of the crosshair was translated along the nominal along-track direction of each focal plane by rotating the theodolites source.
Explanation
Position measurements were made at several locations for several rows of each array. In this way, the roll and yaw angles of each array were determined to approximately 40-microradian accuracy (0.1 pixels).
Direction of using
This information was used to map the angular position of each pixel for use in geolocating the on-orbit image data.
Some measurement was performed using two theodolites.