改善激光观测数据偏差对推动毫米级精度卫星激光测距(Satellite Laser Ranging, SLR)技术在全球大地测量观测系统中应用具有重要作用。系统时延标定误差是激光观测数据偏差产生的主要原因, 其中地面靶目标测量与卫星测量时的系统差异, 以及单光子探测中激光回波强度所引起的光子探测时间游动误差是主要因素。以上海天文台SLR系统为平台, 对上述两种测量模式下系统时延及激光回波强度差异进行了分析和修正。利用激光偏振特性, 应用半波片-偏振片组合调能技术, 实现两种测量模式下光路的“零差异”切换以及回波强度的实时控制, 有效减少光路不同和探测器时间游动效应, 激光数据偏差改善了10~20 mm, 达到了国际SLR数据质量标准要求。激光偏振技术也可用于高重复率激光测距的激光后向散射规避, 提高激光回波数, 具有很好的应用推广价值。

Improving SLR observation data deviation has an important role in promoting application of millimeter precision satellite laser ranging technology in global geodetic observation system. The error of system time-delay calibration is the main reason of producing SLR observation data deviation. In the affecting factors, the system difference between target measurement and satellite laser ranging and time walk effects of detector for echo intensity in single photon detection are the mainly ones. On the platform of SLR system in Shanghai Astronomical Observatory, the differences of system delay and laser echo intensity in two measurement modes were analyzed and corrected. Laser polarization property was made use of, polarization technology of half wave plate-polarizer combination for energy regulation was applied, and optical path "zero difference" switch and echo intensity of real-time control in two measurement modes were implemented. The technology effectively reduces the light path difference and time walk effects of detector, and data improvement was about 10-20 mm which has met SLR international quality standard. The technology can also be used for backscatter avoidance in high repetition rate laser ranging, improve the echo numbers and have the good value for popularization and application.