The radio occultation technique provides stable atmospheric measurements that can work as a benchmark for calibrating and validating satellite-sounding data. Launched on 25 June 2019, the Constellation Observing System for Meteorology, Ionosphere, and Climate 2 and Formosa Satellite Mission 7 (COSMIC-2/FORMOSAT-7) are expected to produce about 5000 high-quality RO observations daily over the tropics and subtropics. COSMIC-2 constellation consists of 6 Low Earth Orbit (LEO) satellites in 24° inclination orbits at 720 km altitude and distributed mainly between 45°N to 45°S. The COSMIC-2 observations have uniform temporal coverage between 30°N to 30°S. This paper presents an independent inversion algorithm to invert COSMIC-2 geometry and phase data to bending angle and refractivity. We also investigate the quality of Global Navigation Satellite System (GNSS) and LEO position vectors derived from the UCAR COSMIC Data Analysis and Archive Center (CDAAC). The GNSS and LEO position vectors are stable with LEO position variations < 1.4 mm/s. The signal-to-noise ratio (SNR) on the L1 band ranges from 300–2600 v/v with a mean of 1600 v/v. The inversion algorithm developed at NOAA Center for Satellite Applications and Research (STAR) uses the Full Spectrum Inversion (FSI) method to invert COSMIC-2 geometry and phase data to bending angle and refractivity profiles. The STAR COSMIC-2 bending angle and refractivity profiles are compared with in situ radiosonde, the current COSMIC-2 products derived from CDAAC, and the collocated European Center for Medium-Range Weather Forecasts (ECMWF) climate reanalysis data ERA5. The mean bias at 8–40 km altitude among the UCAR, ERA5, and STAR is <0.1% for both bending and refractivity, with a standard deviation in the range of 1.4–2.3 and 0.9–1.1% for bending angles refractivity, respectively. In the lowest 2 km, the RO bias relative to ERA-5 shows a strong latitudinal and SNR dependence.

中文翻译：

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使用全光谱反演方法将COSMIC-2相数据转换为弯曲角度和折射率分布

无线电掩星技术可提供稳定的大气测量结果，可作为校准和验证卫星声音数据的基准。气象，电离层和气候2号星座观测系统和台塑7号任务（COSMIC-2 / FORMOSAT-7）于2019年6月25日启动，预计每天将在热带和亚热带产生约5000份高质量的反渗透观测资料。COSMIC-2星座由6个低地球轨道（LEO）卫星组成，它们在720公里的高度以24°的倾角轨道运行，并且主要分布在45°N至45°S之间。COSMIC-2观测值在30°N到30°S之间具有均匀的时间覆盖范围。本文提出了一种独立的反演算法，可将COSMIC-2几何形状和相位数据反演为弯曲角度和折射率。我们还将调查从UCAR COSMIC数据分析和存档中心（CDAAC）派生的全球导航卫星系统（GNSS）和LEO位置向量的质量。GNSS和LEO位置矢量在LEO位置变化<1.4 mm / s时是稳定的。L1频段的信噪比（SNR）为300–2600v / v，平均值为1600 v / v。由NOAA卫星应用和研究中心（STAR）开发的反演算法使用全光谱反演（FSI）方法将COSMIC-2几何形状和相位数据反演为弯曲角度和折射率分布图。将STAR COSMIC-2的弯曲角度和折射率曲线与原位无线电探空仪，源自CDAAC的当前COSMIC-2产品以及并置的欧洲中型天气预报中心（ECMWF）气候再分析数据ERA5进行了比较。在UCAR，ERA5和STAR中，弯曲和折射率在8-40 km高度的平均偏差均<0.1％，弯曲角折射率的标准偏差分别在1.4-2.3和0.9-1.1％的范围内。在最低的2 km中，相对于ERA-5的RO偏置表现出很强的纬度和SNR依赖性。