Collaborative Research: Design of a Nanosat Constellation for Measuring Internal Gravity Wave Fluxes in the Earth's Stratosphere

重力波，即由浮力提供恢复力的波，通常在池塘和湖泊的表面传播，在船只的尾迹中传播，并在海滩的冲浪区破裂。类似的波也出现在大气中，但大气重力波既可以水平传播，也可以垂直传播。垂直传播意味着地表附近的活动，如从山上吹过的风或对流云中的上升气流，可以影响平流层的环流。平流层环流反过来又能影响全球大部分地区的地表天气，是长期预报技术的潜在来源。因此，重力波对平流层的驱动是一个既有实际意义又有科学意义的课题。该项目的目标是设计一个观测大气重力波的卫星星座。该星座由9颗低成本立方体卫星组成，利用无线电掩星（RO）探测穿过对流层上层和平流层下层的温度剖面中的重力波。RO是一种测量全球导航卫星系统（GNSS，包括GPS卫星）的卫星穿过大气层时信号折射的技术。在感兴趣的水平上，折射可以用来推断大气温度，因此星座将同时产生9个温度曲线，每个温度曲线都包含表明重力波存在的摆动。这些可以结合起来确定波包的三维结构，由此可以推断其传播和对平流层环流的可能影响。该项目是一项可行性研究，其中PIs使用高分辨率大气模型，即全球非流体静力配置的跨尺度预测模型（MPAS），来产生真实的垂直传播重力波。一个虚拟星座在模型模拟上“运行”，以确定卫星对给定波场和给定一组卫星、轨道和仪器特性将产生哪些观测结果。这项工作具有社会意义，因为在用于天气预报的模型中需要更好的重力波表示，并为决策者提供指导。此外，这项工作有助于立方体技术的发展，该技术具有各种商业和科学应用。立方体卫星也提供了宝贵的教育经验，因为它们可以由大学生建造和操作。该项目为研究生提供支持和培训，从而促进该研究领域的劳动力发展。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Gravity waves, meaning waves for which buoyancy provides the restoring force, are commonly seen propagating across the surfaces of ponds and lakes, in the wakes of ships, and breaking in the surf zone at the beach. Similar waves occur in the atmosphere, but atmospheric gravity waves can propagate vertically as well as horizontally. Vertical propagation means that activity near the surface, such as winds blowing over mountains or updrafts in convective clouds, can influence the circulation at stratospheric levels. Stratospheric circulation can in turn affect surface weather over much of the globe, and is a potential source of long-range forecast skill. Thus the driving of the stratosphere by gravity waves is a topic of both practical and scientific interest.The goal of this project is to design a satellite constellation for observing atmospheric gravity waves. The constellation consists of nine low-cost cubesats using radio occultation (RO) to detect gravity waves in temperature profiles extending through the upper troposphere and lower stratosphere. RO is a technique which measures the refraction of signals from satellites of the Global Navigation Satellite System (GNSS, which includes the GPS satellites) as they pass through the atmosphere. At the levels of interest refraction can be used to deduce atmospheric temperature, thus the constellation would produce nine simultaneous temperature profiles, each containing wiggles indicating the presence of gravity waves. These could be combined to determine the three-dimensional structure of a wave packet, from which its propagation and likely influence on stratospheric circulation could be inferred. The project is a feasibility study in which the PIs use a high-resolution atmospheric model, the Model for Prediction Across Scales (MPAS, in a global nonhydrostatic configuration), to generate realistic vertically propagating gravity waves. A virtual constellation "orbits" over the model simulation to determine what observations would be produced by the satellites for a given wave field and a given set of satellite, orbit, and instrument characteristics.The work has societal relevance due to the desirability of better gravity wave representations in models used for weather prediction and to provide guidance to decision makers. In addition, the work contributes to the development of cubesat technology, which has a variety of commercial and scientific applications. Cubesats also provide valuable educational experiences, as they can be built and operated by university students. The project provides support and training to a graduate student, thereby promoting workforce development in this research area.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.