Global Navigation Satellite System (GNSS) IGS Ultra-Rapid Orbit Solution Comparison Summary Product from NASA CDDIS

This derived product set consists of Global Navigation Satellite System Rapid Orbit/Reference Frame Product Summary from the NASA Crustal Dynamics Data Information System (CDDIS). GNSS provide autonomous geo-spatial positioning with global coverage. GNSS data sets from ground receivers at the CDDIS consist primarily of the data from the U.S. Global Positioning System (GPS) and the Russian GLObal NAvigation Satellite System (GLONASS). Since 2011, the CDDIS GNSS archive includes data from other GNSS (Europe’s Galileo, China’s Beidou, Japan’s Quasi-Zenith Satellite System/QZSS, the Indian Regional Navigation Satellite System/IRNSS, and worldwide Satellite Based Augmentation Systems/SBASs), which are similar to the U.S. GPS in terms of the satellite constellation, orbits, and signal structure. Analysis Centers (ACs) of the International GNSS Service (IGS) retrieve GNSS data on regular schedules to produce GNSS derived products. The IGS Analysis Center Coordinator (ACC) uses these individual AC solutions to generate the official IGS ultra-rapid combined orbit and ERP products. The ultra-rapid orbit and ERP is a sub-daily solution, released four times per day, at 03:00, 09:00, 15:00, and 21:00 UTC (prior to GPS week 1267 they were released twice daily). The solution summary file details information about the generation of the ultra-rapid products and comparison with the individual AC solutions. The reduced latency on availability of these products allows for significantly improved orbit predictions and reduced errors for user applications.

本衍生产品集源自美国国家航空航天局（NASA）地壳动力学数据信息系统（CDDIS）的全球导航卫星系统（Global Navigation Satellite System，GNSS）快速轨道/参考框架产品摘要。全球导航卫星系统可实现全球覆盖的自主地理空间定位。
CDDIS收录的来自地面接收机的GNSS数据集，主要包含美国全球定位系统（GPS）与俄罗斯全球导航卫星系统（GLONASS）的数据。
自2011年起，CDDIS的GNSS档案库还纳入了其他GNSS数据：包括欧洲伽利略卫星导航系统（Galileo）、中国北斗卫星导航系统（Beidou）、日本准天顶卫星系统（Quasi-Zenith Satellite System，QZSS）、印度区域导航卫星系统（Indian Regional Navigation Satellite System，IRNSS）以及全球星基增强系统（Satellite Based Augmentation Systems，SBAS），上述系统的卫星星座、轨道与信号架构均与美国GPS类似。
国际GNSS服务（International GNSS Service，IGS）的分析中心（Analysis Centers，ACs）会按固定周期获取GNSS数据，以生成GNSS衍生产品。
国际GNSS服务分析中心协调组（IGS Analysis Center Coordinator，ACC）将整合各分析中心的单独解算结果，生成官方的IGS超快速联合轨道与地球自转参数（Earth Rotation Parameters，ERP）产品。
该超快速轨道与地球自转参数产品为亚日解算成果，每日分四次于协调世界时（UTC）03:00、09:00、15:00及21:00发布；在GPS第1267周之前，该产品每日仅发布两次。
解算摘要文件详细阐述了超快速产品的生成流程，以及与各分析中心单独解算结果的对比情况。
该类产品的发布时延显著降低，可有效提升轨道预报精度，并缩减用户应用中的误差。