Achieving and maintaining sub-centimetre accuracy for the Herstmonceux single-photon SLR Facility

To maintain high accuracy for the Herstmonceux SLR system, we have carried out a detailed study of the potential for observational bias from two key elements of the system: range-dependent bias induced by the time-of-flight measurement process; and satellite signature effects which are ranging-system dependent. We have carried out tests on our cluster of four Stanford SR620 counters and find that range-dependent bias introduced by any one of the timers can approach a level of up to one centimetre at the distance of the prime geodetic satellite Lageos. At the single-photon level of return the characteristics of the satellites' retroreflector arrays affect the distribution of the observations, and consequently corrections to be applied to the data to refer them to the centre of mass of the satellites depend upon the processing technique.