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) 是一项先进技术，用于空间大地测量领域的精确轨道确定。最近，SLR 证明了其适用于地面站和近地轨道 Jason 2 卫星之间的精确时间传输。虽然多个 SLR 系统通常可以实现小于 15 ps 的单次发射精度，但各自获得的卫星轨道重建精度并不优于 20 – 45 ps，这是由一些基本缺点造成的。由于测量是在光域中完成的，并且时间标记是在微波范围内完成的，因此为了通过将系统误差降低到小于10 ps来提高光时间传递的精度。建议使用延迟补偿飞秒脉冲激光器（天文台提供）将激光测距技术的完整时间标记过程完全移入光域，并利用锁模飞秒脉冲激光器具有超低噪声的事实在光学方面这将显着提高地面韦茨尔激光测距系统与为国际空间站（ISS）运行准备的太空原子钟系统（ACES）之间的时间传输精度和准确度。类似的考虑也适用于超长基线干涉测量 (VLBI)，当天线运动时，长电缆会受到挤压和拉伸，并且温度敏感放大器和混频器延迟会导致系统误差，这些误差只能被时钟部分吸收。因此，我们建议对 VLBI 使用相同的双向光延迟补偿时间和频率分布概念，以获得稳定的明确系统参考以及超宽带飞秒脉冲激光器。基于新 VGOS 系统的相位校准，也涵盖 Ka 频段 最后但并非最不重要的一点是，我们将展示基于通用主动稳定时基的闭合测量概念中系统测量误差的减少。