The Analysis Centers (ACs) of the International GNSS Service (IGS) have reprocessed a large global network of GPS tracking data from 1994.0 until 2014.0 or later. Each AC product time series was extended uniformly till early 2015 using their weekly operational IGS contributions so that the complete combined product set covers GPS weeks 730 through 1831. Three ACs also included GLONASS data from as early as 2002 but that was insufficient to permit combined GLONASS products. The reprocessed terrestrial frame combination procedures and results have been reported already, and those were incorporated into the ITRF2014 multi-technique global frame released in 2016. This paper describes the orbit and clock submissions and their multi-AC combinations and assessments. These were released to users in early 2017 in time for the adoption of IGS14 for generating the operational IGS products. While the reprocessing goal was to enable homogeneous modeling, consistent with the current operational procedures, to be applied retrospectively to the full history of observation data in order to achieve a more suitable reference for geophysical studies, that objective has only been partially achieved. Ongoing AC analysis changes and a lack of full participation limit the consistency and precision of the finished IG2 products. Quantitative internal measures indicate that the reprocessed orbits are somewhat less precise than current operational orbits or even the later orbits from the first IGS reprocessing campaign. That is even more apparent for the clocks where a lack of robust AC participation means that it was only possible to form combined 5-min clocks but not the 30-s satellite clocks published operationally. Therefore, retrospective precise point positioning solutions by users are not recommended using the orbits and clocks. Nevertheless, the orbits do support long-term stable user solutions when used with network processing with either double differencing or explicit clock estimation. Among the main benefits of the reprocessing effort is a more consistent long product set to analyze for sources of systematic error and accuracy. Work to do that is underway but the reprocessing experience already points to a number of ways future IGS performance and reprocessing campaigns can be improved.

中文翻译：

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来自 IGS 二次再处理的组合轨道和时钟

国际 GNSS 服务 (IGS) 的分析中心 (AC) 重新处理了从 1994.0 到 2014.0 或之后的大型 GPS 跟踪数据全球网络。每个 AC 产品时间序列均使用其每周运营 IGS 贡献统一延长至 2015 年初，以便完整的组合产品集涵盖 GPS 周 730 至 1831。三个 AC 还包括早在 2002 年的 GLONASS 数据，但这不足以允许组合 GLONASS产品。重新处理的地面坐标系组合程序和结果已经报道，并被纳入2016年发布的ITRF2014多技术全球坐标系。本文描述了轨道和时钟提交及其多AC组合和评估。这些是在 2017 年初及时向用户发布的，以便采用 IGS14 来生成可操作的 IGS 产品。虽然再处理的目标是使与当前操作程序一致的均匀建模能够追溯应用于观测数据的完整历史，以便为地球物理研究提供更合适的参考，但该目标仅部分实现。持续的 AC 分析变化和缺乏充分参与限制了成品 IG2 产品的一致性和精度。定量的内部测量表明，再处理的轨道比当前的运行轨道或什至是第一次 IGS 再处理活动的后期轨道精度稍低。对于缺乏强大的交流参与的时钟而言，这一点更加明显，这意味着只能形成组合的 5 分钟时钟，而不能形成可运行的 30 秒卫星时钟。因此，不建议用户使用轨道和时钟进行追溯性精确点定位解决方案。然而，当与具有双差分或显式时钟估计的网络处理一起使用时，轨道确实支持长期稳定的用户解决方案。再处理工作的主要好处之一是更一致的长产品集，用于分析系统误差和准确性的来源。这样做的工作正在进行中，但后处理经验已经指出了可以改进未来 IGS 性能和后处理活动的多种方法。