Global Navigation Satellite System (GNSS) Radio Occultation (RO) is a highly valuable remote sensing technique for probing the Earth’s atmosphere, due to its global coverage, high accuracy, long-term stability, and essentially all-weather capability. In order to ensure the highest quality of essential climate variables (ECVs), derived from GNSS signal tracking by RO satellites in low Earth orbit (LEO), the orbit positions and velocities of the GNSS transmitter and LEO receiver satellites need to be determined with high and proven accuracy and reliability. Wegener Center’s new Reference Occultation Processing System (rOPS) hence aims to integrate uncertainty estimation at all stages of the processing. Here we present a novel setup for precise orbit determination (POD) within the rOPS, which routinely and in parallel performs the LEO POD with the two independent software packages Bernese GNSS software (v5.2) and NAPEOS (v3.3.1), employing two different GNSS orbit data products. This POD setup enables mutual consistency checks of the calculated orbit solutions and is used for position and velocity uncertainty estimation, including estimated systematic and random uncertainties. For LEOs enabling laser tracking we involve position uncertainty estimates from satellite laser ranging. Furthermore, we intercompare the LEO orbit solutions with solutions from other leading orbit processing centers for cross-validation. We carefully analyze multi-month, multi-satellite POD result statistics and find a strong overall consistency of estimates within LEO orbit uncertainty target specifications of 5 cm in position and 0.05 mm/s in velocity for the CHAMP, GRACE-A, and Metop-A/B missions. In 92% of the days investigated over two representative 3-month periods (July to September in 2008 and 2013) these POD uncertainty targets, which enable highly accurate climate-quality RO processing, are satisfied. The moderately higher uncertainty estimates found for the remaining 8% of days (∼5–15 cm) result in increased uncertainties of RO-retrieved ECVs. This allows identification of RO profiles of somewhat reduced quality, a potential benefit for adequate further use in climate monitoring and research.

中文翻译：

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GNSS无线电掩星气候应用的精确轨道确定，包括不确定性估计

全球导航卫星系统（GNSS）无线电掩星技术（RO）是探测地球大气的一种非常有价值的遥感技术，因为它具有全球覆盖范围，高精度，长期稳定性以及基本上全天候的能力。为了确保从低地球轨道（LEO）中的RO卫星从GNSS信号跟踪获得的基本气候变量（ECV）的最高质量，需要确定GNSS发射器和LEO接收器卫星的轨道位置和速度以及经过验证的准确性和可靠性。因此，韦格纳中心的新参考掩星处理系统（rOPS）旨在在处理的所有阶段集成不确定性估计。在这里，我们提出了一种新颖的装置，用于在rOPS内进行精确的轨道确定（POD），它使用两个不同的GNSS轨道数据产品，通过两个独立的软件包Bernese GNSS软件（v5.2）和NAPEOS（v3.3.1）例行并行地执行LEO POD。这种POD设置可以对计算出的轨道解进行相互一致性检查，并用于位置和速度不确定性估计，包括估计的系统和随机不确定性。对于启用激光跟踪的LEO，我们需要根据卫星激光测距估算位置不确定性。此外，我们将LEO轨道解决方案与其他领先轨道处理中心的解决方案进行交叉验证。我们仔细分析了数月，多卫星的POD结果统计数据，发现在LEO轨道不确定性目标指标（位置5 cm和0）中，估算值具有很强的整体一致性。CHAMP，GRACE-A和Metop-A / B任务的速度为05毫米/秒。在两个代表性的3个月期间（2008年和2013年7月至9月）中，有92％的天数满足了这些POD不确定性目标，这些目标可以实现高度精确的气候质量RO处理。在剩余的8％的天数（约5–15厘米）中发现不确定性估计值偏高，导致RO回收ECV的不确定性增加。这样可以识别质量略有下降的反渗透剖面，这是在气候监测和研究中进一步充分利用的潜在益处。在剩余的8％的天数（约5–15厘米）中发现不确定性估计值偏高，导致RO回收ECV的不确定性增加。这样可以识别质量略有下降的反渗透剖面，这是在气候监测和研究中进一步充分利用的潜在益处。在剩余的8％的天数（约5–15厘米）中发现不确定性估计值偏高，导致RO回收ECV的不确定性增加。这样可以识别质量略有下降的反渗透剖面，这是在气候监测和研究中进一步充分利用的潜在益处。