基于多望远镜接收回波信号的空间目标激光测距技术研究

The way of using a single telescope to receive laser echo signals is usually adopted in the field of laser ranging to space targets and the system ability of laser measurement is limited to the aperture of telescope. Large aperture of telescope has the strong ability of receiving laser echo signals, but it has the characteristics of development difficulty, system complexity and limited expansibility. Based on the mode of laser ranging which depends on the number of laser photon detection, the ability of laser measurement to space targets can be enhanced as the number of laser echo signals is increased within the certain time interval. The distributions of laser echo signals from the targets cover with the certain area and by using the number of telescopes locating at the different positions to receive laser echo signals simultaneously, the number of laser echo signals can be markedly increased to enhance the ability of laser measurement. The proposal of adopting a number of relatively small aperture of telescopes to receive laser echo signals at the same time are put forward in order to realize the equivalent receiving ability produced by the one large aperture of telescope and the laser measurement system has good flexibility, maintainability and expansibility. By using the 60cm SLR telescope, 35cm SLR telescope and 1.56m astronomical observation telescope at Shanghai Astronomical Observatory the experimental platform of multi-receiving telescopes will be established to perform the measurement and validate the equivalent measuring ability and the researches on control of multi-receiving telescopes, laser data processing, calibration of measurement system delay, are also implemented to provide alternative technical approach and solution for laser measurement to far distance space targets with weak laser echo signals.

空间目标激光测距通常采用单台望远镜接收激光信号，系统测量能力受限于望远镜口径。大口径望远镜具有强接收能力，但其具有研制难度大、系统复杂及扩展性有限等特点。基于光子数探测的激光测距模式，增加单位时间内回波数可提升目标测量能力，而从目标返回的激光信号具有一定覆盖区域，多个不同位置望远镜同时接收激光回波信号，可增加单位时间内回波数，提升目标测量能力。本项目提出采用多个相对较小口径望远镜同时接收激光信号测距方法，以实现单台大口径望远镜等效测量能力，且系统具有较好灵活性、维护性和扩展性。基于上海天文台60cm SLR望远镜、1.56m天文望远镜和35cm SLR望远镜，进行多望远镜接收激光回波信号试验研究，验证其等效测量能力，并开展多望远镜测量控制方法、激光数据处理方法、测距系统时延标定等研究，以期为今后对远距离弱回波信号空间目标激光探测提供一种技术途径和方案。

空间目标激光测距通常采用测量激光脉冲信号往返于地面站与空间目标飞行时间获取目标距离测量信息。激光回波信号强度随传输距离四次方衰减。对于远距离目标、激光漫反射目标，返回激光信号弱探测难度大，地面测量系统需大口径望远镜系统的支持。激光测距从目标返回的激光信号可覆盖一定范围，在此范围内均可对回波信号进行接收和探测。通过设置多台望远镜同时接收探测激光回波信号，可有效增加地面系统单位时间内激光回波数，十分有利于提升对目标测量能力。.本项目开展多望远镜信号接收激光测距技术研究。依托中科院上海天文台现有1.56m口径天体测量光学望远镜和60cm口径激光测距光学望远镜(两者相距约60米)，建立了双望远镜信号接收激光测距试验系统，进行了空间目标激光观测试验及数据处理分析，开展了多望远镜系统激光测量方法验证，包括测距控制、距离门同步控制、回波信号接收等。基于激光测距雷达方程理论分析了多望远镜信号接收等效测量能力并进行了演示验证。采用光纤时间传递方法进行了多望远镜系统时间同步方法验证，并进行了多望远镜系统时延标定试验。通过空间目标观测数据处理分析，进行了测量系统误差分析（达厘米级精度）。根据对多台望远镜接收的回波数据处理分析，体现了多望远镜测量技术优势，完成了多望远镜测量技术可行性的试验验证。.在此基础上，对位于上海天文台佘山科技园区内60cm口径激光测距望远镜系统进行适应性改造，使之具备对空间碎片目标跟踪和回波信号接收能力，配合上海天文台佘山激光测距望远镜系统（相距约3公里），建立远距离双望远镜激光回波信号接收试验系统。在国内首次实现远距离双望远镜系统接收空间碎片激光回波信号，获得了多圈次激光观测数据，验证了远距离多站望远镜共视观测非合作目标的可行性。该观测试验成功开展为后续实施更远距离多望远镜激光信号接收和目标测量奠定了基础，将在空间目标定位测量中发挥重要作用。