Delta-T: All Optical Time Tagging in Satellite Laser Ranging And Optical Delay Compensation For Very Long Baseline Interferometry Based On Ultra-Short Mode-Locked Laser

Delta-T：卫星激光测距中的全光时间标记和基于超短锁模激光器的超长基线干涉测量的光延迟补偿

• 批准号: 423159159
• 负责人: Professor Dr.-Ing. Ulrich Schreiber
• 金额: --
• 依托单位: Lehrstuhl für Geodäsie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/423159159?language=en
• 关键词: Delta; Optical; Time; Tagging; Satellite

Satellite Laser Ranging (SLR) is an advanced technology, which is used in the field of space geodesy for precise orbit determination. More recently SLR demonstrated its suitability for accurate time transfer between a ground station and the Jason 2 satellite in a low Earth orbit. While a single shot precision of less than 15 ps is typically achieved by several SLR systems, the respective obtained accuracy for the reconstruction of the satellite orbit is not better than 20 – 45 ps. This is caused by some fundamental short-comings of the current realization of the SLR technique, since the measurement is done in the optical domain and the time tagging in the microwave regime. In order to improve the accuracy of optical time transfer by reducing systematic errors to less than 10 ps, we propose to use a delay compensated fs-pulse laser (available on the observatory) to move the complete time tagging process of the laser ranging technique entirely into the optical domain and exploit the fact that mode-locked fs-pulse lasers have ultra-low noise in the optical and microwave regime simultaneously. This will significantly improve the time transfer precision and accuracy between the Wettzell Laser Ranging System on the ground and the Atomic Clock Ensemble in Space (ACES), which is prepared for the operation on the International Space Station (ISS). Similar considerations apply for the Very Long Baseline Interferometry (VLBI). Long cables, subject to squeezing and stretching when the antenna is in motion and temperature sensitive amplifier and mixer delays are causing systematic errors. These can only partially be absorbed by clock adjust-ments and modeling tropospheric delay corrections. Therefore we propose to use the same two-way optical delay compensated time and frequency distribution concept also for the VLBI in order to obtain a stable unambiguous system reference as well as an ultra-wideband fs pulse laser based phase calibration for the new VGOS systems, covering also the Ka band. Last but not least we shall demonstrate the reduction of systematic measurement errors in a closure measurement concept based on a common actively stabilized timebase.

卫星激光测距（SLR）是一种用于空间大地测量的精密定轨技术。最近，SLR证明了它适合于在地面站和低地球轨道上的Jason 2号卫星之间进行精确的时间传递。虽然小于15 ps的单次发射精度通常由几个SLR系统实现，但是用于卫星轨道的重建的相应获得的精度不优于20 - 45 ps。这是由于目前实现的SLR技术的一些基本的缺点所造成的，因为测量是在光域中进行的，而时间标记是在微波区域中进行的。为了提高光学时间传递的精度，减少系统误差小于10 ps，我们建议使用延迟补偿的fs脉冲激光器（可在天文台上）移动的激光测距技术的完整的时间标记过程完全进入光域，并利用锁模fs脉冲激光器具有超低噪声的事实，同时在光学和微波制度。这将大大提高地面上的Wettzell激光测距系统与准备在国际空间站上运行的空间原子钟之间的时间传递精度和准确度。类似的考虑也适用于甚长基线干涉测量（VLBI）。长电缆，受到挤压和拉伸时，天线是在运动和温度敏感的放大器和混频器延迟是造成系统误差。这些误差只能通过钟差和对流层延迟改正模型来部分吸收。因此，我们建议使用相同的双向光学延迟补偿的时间和频率分布的概念，也为VLBI，以获得一个稳定的明确的系统参考，以及一个超宽带飞秒脉冲激光为基础的相位校准的新的VGOS系统，也涵盖了Ka波段。最后但并非最不重要的是，我们将证明在一个共同的积极稳定的时基的基础上关闭测量概念的系统测量误差的减少。