Spacecraft Laser Retroreflector Array (LRA) Offset

Spacecraft Laser Retroreflector Array (LRA) Offset:
"Satellite Center of Mass Measurement Correction"

To compute accurate values for the SLR center-of-mass offset measurement correction for each satellite, several pieces of information are necessary.

cartoon of vectors required for retroreflector offset

Accurate 3-dimensional knowledge of each of the vectors in the diagram above from pre-launch measurements as documented in the Interface Control Documents (ICD).
Accurate characterization of the corner-cube response for all incident geometries and wavelengths.
Accurate characterization of the detector response for all operating conditions.
Accurate knowledge of the satellite attitude in its orbit.

These CoM correction webpage shows components of the vectors from the satellite center of mass to the array phase center (the red vector in the diagram above). For very precise work, this vector should be computed by subtracting the CoM offset vector from the LRA offset vector. The CoM offset vector varies slightly with time, as it is propellant use dependent. When available, the components of this time dependent vector are given, along with the fixed components of the LRA offset vector. The "location" of the LRA phase center may also vary; it is the locus of points from which the return came as a result of a particular satellite-station geometry and station characteristics (single or multiple photon, receiver type, et cetera).

Some information on the attitude regimes of the altimetry satellites is given on the International DORIS Service website.