Simulations of VLBI observations of a geodetic satellite providing co-location in space
Simulations of VLBI observations of a geodetic satellite providing co-location in space
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DOI：
10.1007/s00190-018-1115-5
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发表时间：
2018-09-01
影响因子：
4.4
通讯作者：
Schuh, Harald
中科院分区：
文献类型：
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作者：
Anderson, James M.;Beyerle, Georg;Schuh, Harald
我们进行了Monte Carlo模拟甚长基线干涉测量（VLBI）的地球轨道卫星的观测，将共同定位的空间大地测量仪器，以研究如何以及VLBI框架和航天器框架可以绑在一起使用这样的测量。我们模拟观测的航天器VLBI观测，飞行时间（TOF）测量使用的时间编码的信号在航天器的传输，类似的概念，精确的点定位，差分VLBI（D-VLBI）观测使用角附近的类星体校准，比较它们的相对性能。我们使用拟议的欧洲大地测量参考天线在空间（E-GRASP）使命作为我们的软件的初始测试用例。我们发现，标准的VLBI技术是有限的，在一定程度上，目前缺乏知识的绝对偏移的VLBI时间协调世界时在微秒的水平。飞行时间测量能够更好地克服这个问题，并提供框架纽带的不确定性，在平移和规模近三个因素小于VLBI测量产生的。如果绝对时间偏移问题可以通过外部手段解决，VLBI结果可以得到显着改善，并可以接近提供1毫米精度的帧连接参数。D-VLBI观测与最佳性能的假设提供了大约两个更高的不确定性的E-GRASP轨道的一个因素。我们还模拟了空间站和航天器位置偏移如何影响框架连接性能。
We performed Monte Carlo simulations of very-long-baseline interferometry (VLBI) observations of Earth-orbiting satellites incorporating co-located space-geodetic instruments in order to study how well the VLBI frame and the spacecraft frame can be tied using such measurements. We simulated observations of spacecraft by VLBI observations, time-of-flight (TOF) measurements using a time-encoded signal in the spacecraft transmission, similar in concept to precise point positioning, and differential VLBI (D-VLBI) observations using angularly nearby quasar calibrators to compare their relative performance. We used the proposed European Geodetic Reference Antenna in Space (E-GRASP) mission as an initial test case for our software. We found that the standard VLBI technique is limited, in part, by the present lack of knowledge of the absolute offset of VLBI time to Coordinated Universal Time at the level of microseconds. TOF measurements are better able to overcome this problem and provide frame ties with uncertainties in translation and scale nearly a factor of three smaller than those yielded from VLBI measurements. If the absolute time offset issue can be resolved by external means, the VLBI results can be significantly improved and can come close to providing 1 mm accuracy in the frame tie parameters. D-VLBI observations with optimum performance assumptions provide roughly a factor of two higher uncertainties for the E-GRASP orbit. We additionally simulated how station and spacecraft position offsets affect the frame tie performance.