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Connecting atmospheric science and atmospheric models for aerocapture at Titan and the outer planets

机译：连接大气科学和大气模型以进行土卫六和外行星的航空捕获

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Many atmospheric measurement systems, such as the sounding instruments on Voyager, gather atmospheric information in the form of temperature versus pressure level. In these terms, there is considerable consistency among the mean atmospheric profiles of the outer planets Jupiter through Neptune, including Titan. On a given planet or on Titan, the range of variability of temperature versus pressure level due to seasonal, latitudinal, and diurnal variations is also not large. However, many engineering needs for atmospheric models relate not to temperature versus pressure level but atmospheric density versus geometric altitude. This need is especially true for design and analysis of aerocapture systems. Drag force available for aerocapture is directly proportional to atmospheric density. Available aerocapture "corridor width" (allowable range of atmospheric entry angle) also depends on height rate of change of atmospheric density, as characterized by density scale height. Characteristics of hydrostatics and the gas law equation mean that relatively small systematic differences in temperature versus pressure profiles can integrate at high altitudes to very large differences in density versus altitude profiles. Thus, a given periapsis density required to accomplish successful aerocapture can occur at substantially different altitudes (～150-300 km) on the various outer planets, and significantly different density scale heights (～20-50 km) can occur at these periapsis altitudes. This paper will illustrate these effects and discuss implications for improvements in atmospheric measurements to yield significant impact on design of aerocapture systems for future missions to Titan and the outer planets. Relatively small-scale atmospheric perturbations, such as gravity waves, tides, and other atmospheric variations can also have significant effect on design details for aerocapture guidance and control systems. This paper will discuss benefits that would result from improved understanding of Titan and outer planetary atmospheric perturbation characteristics. Details of recent engineering-level atmospheric models for Titan and Neptune will be presented, and effects of present and future levels of atmospheric uncertainty and variability characteristics will be examined.
机译：许多大气测量系统（例如Voyager上的测深仪）以温度对压力水平的形式收集大气信息。用这些术语来说，木星到海王星外的木星，包括泰坦在内的平均大气廓线之间有相当大的一致性。在给定的行星或土卫六上，由于季节，纬度和昼夜变化而引起的温度对压力水平的变化范围也不大。但是，大气模型的许多工程需求与温度与压力水平无关，而与大气密度与几何高度有关。对于航空捕获系统的设计和分析，这一需求尤其如此。用于航空捕捉的阻力与空气密度成正比。可用的航空捕获“走廊宽度”（大气进入角的允许范围）还取决于以密度标尺高度为特征的大气密度变化的高度。流体静力学的特性和气体定律方程意味着，温度与压力曲线相对较小的系统差异可以在高海拔时积分为密度与高度曲线的非常大差异。因此，在不同的外行星上，成功完成航空捕获所需的给定的围泻密度可能会发生在不同的高度（〜150-300 km）上，并且在这些围解高度上会出现明显不同的密度标高（〜20-50 km）。本文将说明这些影响，并讨论改善大气测量的意义，从而对未来的土卫六和外行星飞行任务的航空捕获系统的设计产生重大影响。相对较小的大气扰动（例如重力波，潮汐和其他大气变化）也会对航空制导和控制系统的设计细节产生重大影响。本文将讨论通过更好地了解土卫六和外部行星大气扰动特性而带来的好处。将介绍有关泰坦和海王星的最新工程水平大气模型的详细信息，并将检查当前和未来大气不确定性和变异性特征水平的影响。

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