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首页> 外文期刊>Geoscience and Remote Sensing Letters, IEEE >Relative Ionospheric Ranging Delay in LEO GNSS Oceanic Reflections
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Relative Ionospheric Ranging Delay in LEO GNSS Oceanic Reflections

机译：LEO GNSS海洋反射中的相对电离层测距延迟

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Global Navigation Satellite System (GNSS) reflectometry leverages signals of opportunity to remotely sense the Earth's surface for a variety of science investigations. However, ionospheric refraction affects GNSS reflections detected at low Earth orbit (LEO). While multifrequency GNSS enables the elimination of most of the ionospheric error, single-frequency missions are still susceptible to this ranging delay. Motivated by the planned launch of Cyclone GNSS (CYGNSS) in 2016, a single-frequency reflectometry mission, this letter presents a simulation of the relative ionospheric delay that will shift the Delay-Doppler Map (DDM) data product. A mathematical model is presented that defines and characterizes signal propagation delay in the DDM. The model differentiates direct and reflected signals as a sum of path lengths, atmospheric refraction effects, and noise. We simulate representative ionospheric delays from the model associated with the direct and reflected ray paths as a function of satellite elevation angle, latitude, and solar activity. Simulation using the International Reference Ionosphere 2007 shows that differential ionospheric content is inversely proportional to satellite elevation angle and that low latitudes present larger ionospheric impacts on the reflected signals. Finally, high solar activity conditions lift the ionospheric density profile to and possibly above the CYGNSS orbit altitude of 500 km. The ionospheric delay will not generally affect the estimation of wind speed but may affect the CYGNSS signal acquisition and open loop tracking process. Implications of the ionospheric delay in other GNSS reflectometry applications are also discussed.
机译：全球导航卫星系统（GNSS）反射测量法利用各种机会信号来遥感地球表面，以进行各种科学研究。但是，电离层折射会影响在低地球轨道（LEO）处检测到的GNSS反射。尽管多频GNSS可以消除大多数电离层误差，但单频任务仍然容易受到这种测距延迟的影响。受到2016年计划推出的单频反射法任务Cyclone GNSS（CYGNSS）的推动，这封信提出了相对电离层延迟的模拟，这将改变延迟多普勒地图（DDM）数据产品。提出了定义和表征DDM中信号传播延迟的数学模型。该模型将直接信号和反射信号区分为路径长度，大气折射效应和噪声的总和。我们根据与卫星直角，纬度和太阳活动有关的函数，从与直接和反射射线路径相关的模型中模拟代表性的电离层延迟。使用国际参考电离层2007进行的模拟表明，电离层的差异与卫星仰角成反比，低纬度对电离层的反射信号影响更大。最后，高太阳活动条件将电离层的密度剖面提升至500 km的CYGNSS轨道高度，甚至可能更高。电离层延迟通常不会影响风速的估计，但会影响CYGNSS信号的采集和开环跟踪过程。还讨论了电离层延迟在其他GNSS反射仪应用中的含义。

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