Ties between kinematic and dynamic reference frames (D-VLBI)

D-VLBI项目的目标是实现空间探测器（如卫星或航天器）、月球和其他行星体的动态参考框架、运动学定义的国际天球参考框架（ICRF）和地球上实现的国际地球参考框架（ITRF）之间的框架联系。最好是使用差分甚长基线干涉测量法，这是一种确定校准器和目标源之间相对角度的精确方法，通常由空间机构用于航天器导航。D-VLBI数据也被广泛地纳入现代星历计算中，D-VLBI已被证明能够用于微弱射电源的相对天体测量以及光学和无线电目录的帧绑定。在这个项目的第二阶段，我们要执行证明的概念，真实的差分观测到各种卫星，以测试现代D-VLBI技术和硬件的天体测量性能，并确定限制和现实的不确定性，在最终的框架关系，目前可以实现，为特定的卫星和发射机配置。我们计划对GNSS卫星、空间VLBI卫星RadioAstron和Gaia航天器进行新的观测。通过我们的GNSS观测，我们的目标是证明差分VLBI观测到各种GNSS系统，包括伽利略和北斗，可以成功地使用IVS站进行，并且我们能够执行完整的分析链参数估计。RadioAstron在船上有一个VLBI天线，我们想展示卫星位置和框架连接可以为同时也是VLBI观测网络一部分的航天器做得多好。对于盖亚，我们的目标是确定最佳的观测策略，将盖亚的轨道与ICRF联系起来，从而改善与盖亚自身观测框架的联系。此外，我们希望与研究部门的合作伙伴分享所取得的成就，例如，改进行星和月球星历。我们将为月球SELENE和嫦娥任务提供D-VLBI分析结果，包括嫦娥三号着陆器和漫游车，以改善项目PN 1和PN 3的月球星历和月球运动学框架关系。对于这些相同的群体，我们也将提供模拟差分观测未来的任务，调查可能的星历和帧绑定的改进。我们将与PN 2项目合作，研究VLBI校准源位置的核移效应。核心移位效应限制了所有涉及ICRF源的天体测量的准确度，使其只能达到毫弧秒的相当一部分。我们将与PN 7a项目合作安排和执行观测，该项目将提供技术和观测援助。

The goal of project D-VLBI is the realization of frame ties between the dynamic reference frames of space probes like satellites or spacecraft, the Moon and other planetary bodies, the kinematically defined International Celestial Reference Frame (ICRF), and the International Terrestrial Reference Frame (ITRF) realized on Earth. This can be done best by using differential Very Long Baseline Interferometry (D-VLBI), which is a precise method for the determination of relative angles between a calibrator and a target source and is typically applied by the space agencies for spacecraft navigation. D-VLBI data are also extensively incorporated into modern ephemeris calculations and D-VLBI has been proven capable for relative astrometry of faint radio sources and for frame tying of optical and radio catalogues. In the second phase of this project we want to perform proofs of concepts of real differential observations to a variety of satellites to test the astrometric performance of modern D-VLBI techniques and hardware, and to identify limitations and realistic uncertainties in the ultimate frame ties that can currently be achieved, for specific satellite and transmitter configurations. We plan new observations of GNSS satellites, the space VLBI satellite RadioAstron, and the Gaia spacecraft. With our GNSS observations, we aim to demonstrate that differential VLBI observations to a variety of GNSS systems, including Galileo and BeiDou, can be successfully carried out using IVS stations, and that we are able to perform the complete analysis chain to parameter estimation. RadioAstron has a VLBI antenna on board and we want to show how well the satellite positions and frame ties can be made for spacecraft that are themselves simultaneously part of the VLBI observing network. And for Gaia, we aim to determine the optimum observing strategy to tie Gaia's orbit to the ICRF, leading in turn to an improvement in the tie to Gaia's own observational frame. Additionally, we want to share the acquired achievements with the partners in the Research Unit, for example, to improve the planetary and Lunar ephemerides. We will provide D-VLBI analysis results for the Lunar SELENE and Chang'e missions, including the Chang'e-3 lander and rover, to projects PN1 and PN3, to improve the Lunar ephemeris and kinematic-Lunar frame tie. For these same groups we will also provide simulations of differential observations for future missions to investigate possible ephemeris and frame-tying improvements. We will cooperate with project PN2 on core-shift affects in the positions of the VLBI calibrator sources. Core-shift effects limit the accuracy with which all astrometric measurements involving ICRF sources can be made at the level of a substantial fraction of a milliarcsecond. Scheduling and executing our observations will be done in cooperation with project PN7a, which will provide technical and observational assistance.