Newly developed methods for SLR observation at Simosato hydrographic observatory

In satellite laser ranging (SLR) observation the distance to an artificial satellite is measured from round-trip travel time of a laser pulse which is transmitted from the station, reflected at the corner cube reflectors on the surface of the satellite and then received back at the station. The ranging accuracy depends on how accurately the specific point of returned pulse is identified. A simple method to identify such a point by detecting the leading edge of a transmitted and a received pulse has been degrading the ranging accuracy because of 'time walk' caused by variation of signal intensity. In order to reduce the time walk, two new techniques were introduced at Simosato Hydrographic Observatory in 2006: namely, the methods named Triple Threshold Screening (TTS) and Constant Mid-signal Detection (CMD). The authors intend to verify both of them are effective in improvement of ranging accuracy in this paper. The principle of these techniques and some examples of their effectiveness are given.