Boisits Janina, Landskron Daniel, Böhm Johannes
Department of Geodesy and Geoinformation, TU Wien, Vienna, Austria.
Present Address: Federal Office of Metrology and Surveying (BEV), Vienna, Austria.
J Geod. 2020;94(6):57. doi: 10.1007/s00190-020-01385-5. Epub 2020 Jun 17.
The troposphere is considered as one of the major error sources in space geodetic techniques. Thus, accurate troposphere delay models are essential to provide high-quality products, such as reference frames, satellite orbits, or Earth rotation parameters. In this paper, a new troposphere delay model for satellite laser ranging, the Vienna Mapping Functions 3 for optical frequencies (VMF3o), is introduced. The model parameters are derived from ray-traced delays generated by an in-house ray-tracing software. VMF3o comprises not only zenith delays and mapping functions, but also linear horizontal gradients, which are not part of the standard SLR analysis yet. The model parameters are dedicated to a signal wavelength of 532 nm. Since some SLR stations operate also with other wavelengths, VMF3o provides a correction formula to transform the model parameters to any requested wavelength between 350 and 1064 nm. A test demonstrates that the correction formula approximates slant delays calculated at different wavelengths very accurately. The remaining error for slant delays at a wavelength of 1064 nm adds up to only a few millimetres at elevation angle. A comparison study of the modelled delays that are derived from VMF3o and ray-traced delays was carried out to examine the quality of the model approach. The remaining differences of modelled and ray-traced delays are expressed as mean absolute error. At elevation angle, the mean absolute error is only a few millimetres. At elevation angle, it is at the 1 mm level. The results of the comparison also reveal that introducing linear horizontal gradients reduces the mean absolute error by more than 80% for low elevation angles.
对流层被视为空间大地测量技术中的主要误差源之一。因此，精确的对流层延迟模型对于提供高质量的产品至关重要，例如参考框架、卫星轨道或地球自转参数。本文介绍了一种用于卫星激光测距的新对流层延迟模型——光学频率维也纳映射函数3（VMF3o）。该模型参数源自内部光线追踪软件生成的光线追踪延迟。VMF3o不仅包括天顶延迟和映射函数，还包括线性水平梯度，而线性水平梯度尚未成为标准卫星激光测距分析的一部分。该模型参数适用于532纳米的信号波长。由于一些卫星激光测距站也使用其他波长进行观测，VMF3o提供了一个校正公式，可将模型参数转换为350至1064纳米之间的任何所需波长。一项测试表明，该校正公式能非常精确地近似不同波长下计算出的斜距延迟。在仰角为 时，1064纳米波长下斜距延迟的剩余误差总计仅为几毫米。对源自VMF3o的建模延迟和光线追踪延迟进行了比较研究，以检验模型方法的质量。建模延迟与光线追踪延迟的剩余差异以平均绝对误差表示。在仰角为 时，平均绝对误差仅为几毫米。在仰角为 时，平均绝对误差处于1毫米水平。比较结果还表明，对于低仰角，引入线性水平梯度可使平均绝对误差降低80%以上。
