中文摘要：

激光时间比对T2L2（Time Transfer by Laser Link）是法国蔚蓝海岸天文台（OCA）和法国空间中心（CNES）进行的新一代的时间传递计划，将于2008年年中随Jason-2卫星发射上天，并开始观测。它利用激光脉冲在空间的传播来实现地面-卫星，地面-地面远距离时钟的同步，精度比现有的微波比对方式提高1～2个数量级。中国拥有5个固定激光测距站和2个流动激光测距站，基于良好的地理位置和中法双方比较成熟的激光测距技术，中法激光站之间的时间比对和中国内部激光站之间的时间比对是该计划的重要内容。本文系统描述了T2L2的主要内容和关键技术，初步估算了该计划的精度和稳定度，对中法之间的时间比对做出了初步的观测规划。同时，简单介绍了目前世界上精密时钟的发展现况、T2L2的应用前景及正在研究中的TIPO、ASTROD Ⅰ、ACES、EGE等探测基本物理的相关空间计划。

英文摘要：

The T2L2 （Time transfer by laser link） experiment under development at OCA and CNES, to be launched in the middle of 2008 on Jason-2, allows the synchronization of remote clocks on Earth. It is based on the propagation of light pulses in space which is better controlled than the radio wave propagation. This experiment will enhance the performances of time transfer by 1-2 orders of magnitude compared to existing microwave techniques like GPS and TWSTFT （Two-way satellite time and frequency transfer）. China possesses 5 fixed laser ranging stations and two mobile stations. The geography of these stations allows common view comparisons among one another, and non-common view comparisons between China and France. In this paper, the principle, main instruments on board the satellite, preliminary performance budgets, observation budget will be presented. In addition, this paper will review recent progresses in precision clock, and related fundamental space missions TIPO, ASTROD, ACES, EGE.