高重复率激光时间比对激光发射时序精确控制

Precise control of laser emission epoch in laser time transfer with high repetition rate

我国空间站即将首次开展高重复率(~kHz)星地激光时间比对,搭载的星载探测器拟采用固定门控开启模式,对地面激光发射时序的控制提出了高实时、高重复率和高精度等要求。基于卫星激光测距(SLR)的距离门控原理,提出高重复率激光时间比对地面激光点火信号精确产生方法,以使上行激光脉冲能在门控信号之后短时间内到达星载探测器,极大减少噪声干扰。该方法可在单片可编程门阵列FPGA中实现,具有重复率大于10 kHz、控制精度5 ns以及软件交互简单等优势,结合方法计算精度和半导体泵浦激光器的纳秒级触发抖动,预计地面激光发射时刻精度最终控制在10 ns以内,满足空间站激光时间比对激光发射时序的控制需求,并可为其他激光时间比对工程的实施提供技术支持。

A satellite-ground laser time transfer(LTT) with high repetition rate will be carried out in the China’s space station. The onboard laser detector intends to adopt a fixed gated opening mode, which puts forward the control requirements of high repetition rate, high precision and high real time for laser emission epoch on the ground station. Based on the principle of range gate in satellite laser ranging(SLR), a precise control method of laser firing signal in satellite-ground LTT with high repetition rate was proposed, so that the uplink laser pulse could reach the detector within a short time after the onboard gate signal, which greatly reduced the background noise interference. This method could be implemented in a field programmable gate array(FPGA), which had the advantages of repetition rate greater than 10 kHz, control accuracy of 5 ns(200 MHz clock) and simple software interaction, etc. Combined its theoretical calculation accuracy and nanosecond jitter of the diode-pumped picosecond laser, the final realization accuracy of laser emission epoch was expected to be within 10 ns. It could meet control requirements of the laser emission epoch of the China ’s space station LTT project and provide technical support for other LTT projects.