The exploitation of a mode locked train laser pulse for satellite ranging has been used. The Nd YAG oscillator/amplifier/frequency doubler/laser generates a mode locked train at 0.53um, most of the energy is contained in three pulses, the individual pulse duration is 70psec. During the 1963 Merit Campaign, within 4 months, 10 low satellite passes and 31 Lageos passes have been ranged. When tho mode locked substructure has been resolved for the received signal (50 % of passes), the BMS was 6-8 cm.
The method of processing of laser ranging data collected using the passively mode locked YAG train laser is described. The algorithm for resolving of individual peaks in measured ranges histogram and system internal noise determination is explained together with the crosscorrelation methods for system calibration constant evaluation. The low/Lageos satellite and calibration ranging results are included.
One of the limiting factors in decreasing the systematic error of laser ranging is the influence of the atmospheric refraction. Two colour ranging may contribute useful information for more precise refraction factor modelling and calculation. We will describe two wavelength experiment using streak camera as a high resolution detector for ground target distance measurement.
To fulfill the requirements on the laser ranging systems, the soft/hardware package of the Helwan station was significantly modified in period 1982-84. The max. ranging reprate was increased up to 5 pps. The mount pointing accuracy was increased implementing the mechanical inaccuracies software model. The automatical comparison of the time base to the Loran C signal was put into operation.