Thermospheric mass density (TMD) measurements are invaluable to accurately estimate and predict the position and velocity of orbiting objects in Low Earth Orbit (LEO). Existing observational methods and predictive models have some problems (e.g., accuracy, resolution, coverage, cost, etc.) to describe and forecast the actual air drag variations as required for practical applications. With the increasing number of LEO satellites equipped with high‐precision Global Navigation Satellite System (GNSS) receivers, the precise orbits can be used to obtain non‐gravitational accelerations, and therefore estimate TMD variations. In this study, TMD is estimated from the precise orbits of CAScade SmallSat and IOnospheric Polar Explorer (CASSIOPE) at one‐second time step, and the TMD variations following the February 2014 geomagnetic storm are investigated. Using this method, a more detailed description than previous methods and empirical models is given with short‐term TMD variations during geomagnetic storm conditions. The empirical model NRLMSISE‐00 shows less pronounced and more averaged variations, while CASSIOPE‐derived TMD can reflect the abrupt disturbances triggered by the geomagnetic storm. CASSIOPE TMD shows a correlation of 72.4% to the merging electric field E_m index, while the NRLMSISE‐00 model shows a correlation of 42.1%.

中文翻译：

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CASSIOPE精确轨道的高大气层质量密度变化

热球质量密度（TMD）测量对于准确估计和预测低地球轨道（LEO）中绕行物体的位置和速度非常宝贵。现有的观测方法和预测模型存在一些问题（例如，准确性，分辨率，覆盖范围，成本等），以描述和预测实际风阻的实际变化，以满足实际应用的需求。随着配备高精度全球导航卫星系统（GNSS）接收机的LEO卫星的数量不断增加，精确的轨道可用于获得非重力加速度，从而估算TMD变化。在这项研究中，TMD是从CAScade SmallSat和IOnospheric Polar Explorer（CASSIOPE）的精确轨道以一秒钟的时间步长估算的，并研究了2014年2月地磁风暴后的TMD变化。使用这种方法，可以在地磁风暴条件下利用短期TMD变化给出比以前的方法和经验模型更详细的描述。经验模型NRLMSISE-00的变化较小，但平均程度较高，而CASSIOPE衍生的TMD可以反映由地磁风暴触发的突变。CASSIOPE TMD与合并电场的相关性为72.4％E _m指数，而NRLMSISE-00模型显示42.1％的相关性。