Collaborative Research: Cubesat--Ionospheric Scintillation Explorer (ISX)

该项目是设计、开发、建造、运行和分析名为“电离层闪烁探测器”(ISX)的立方体卫星航天器任务的结果。电离层闪烁指的是穿过电离层湍流区域的无线电信号的幅度和相位的随机波动。它影响无线电信号的功率和相位，是由沿信号路径的电离层电子密度的小尺度(公里到厘米)结构造成的。电离层闪烁影响频率高达几吉赫兹的跨电离层无线电信号，因此可能对基于卫星的通信和导航系统，如基于全球定位系统的系统，以及需要观测跨电离层无线电信号的科学仪器，如射电天文学产生不利影响。导致闪烁的等离子体不规则结构的产生背后的物理原因还没有完全被理解，这主要是由于缺乏足够的观测。这样做的一个明显后果是，也不存在可靠的能力来预测或减轻闪烁对无线电波的影响。ISX将生成一个广泛的数据集，用于应用衍射无线电成像，这使得能够预测从成像结构确定的任何频率的闪烁，并可能通过抵消相位波动来缓解失真信号。拟议项目的另一个更广泛的影响是，它是一项试点工作，目的是利用世界各地现有的机会信号，对电离层无线电波失真进行全球天基监测。虽然单个航天器不能提供实时监测，但它可以为未来航天器星座提供这样的空间气象服务指明方向。在称为赤道扩展F(ESF)的电离层密度结构中，闪烁效应主要发生在赤道区域。该项目的主要目标是对与ESF有关的闪烁尺度电离层不规则的结构提供新的观测。具体地说，ISX将同时记录多个地面数字电视(DTV)载波信号的闪烁模式。一组独特的实验几何图形的闪烁模式将被比较，以确定湍流图沿磁场的距离，这是关于这些亚公里结构的三维电动力学的关键观测数据。在该项目的生命周期中，它将提供广泛的学生培训机会，包括学生参与加州理工大学的航天器设计课程和资助研究生。每年，20-40名学生将参与这一任务的设计、制造和飞行。Cal Poly已经飞行了许多学生卫星任务；拟议的努力将利用所有这些任务的传统和经验。这个项目解决了科学问题：某些横向尺度的不规则性沿着通量管延伸到多远？由于很难在短时间内对多个位置的通量管进行采样，因此很难测量闪烁尺度湍流结构的磁场取向。这种测量现在是可能的，因为全世界正在向数字电视过渡，这为从许多有利位置遥感电离层不规则性提供了独特的机会。各种格式的DTV频谱包含同时传输的相位稳定的窄带导频分量。一个4通道雷达接收器将同时记录最多4个从地面分离的空间传输。对于大多数实验几何，相应的发射机-卫星视线将在1-10 S内穿过相同的磁通管，这对于假设“冻结”的不规则性来说是相当短的时间。对应于同一通量管上的多个点的幅度和相位闪烁图案的相关性将是结构沿磁场的空间范围的量度。将使用其中两个或更多发射器与轨道路径对准的几何子集来推断结构的时间发展。无线电接收器是基于在先前的无线电极光探测器(RAX)国家科学基金会立方体卫星项目上开发并成功演示的仪器。

This project is to design, develop, construct, operate and analyze the results of a spacecraft CubeSat mission named "Ionospheric Scintillation eXplorer" (ISX). Ionospheric scintillation refers to random fluctuations in amplitude and phase of radio signals traversing a region of turbulence in the ionosphere. It impacts the power and phase of the radio signal and is caused by small-scale (kilometer to centimeters) structure in the ionospheric electron density along the signal path. Ionospheric scintillation affects trans-ionospheric radio signals up to a few GHz in frequency and, thus, can have detrimental impacts on satellite-based communication and navigation systems, such as GPS-based systems, and also on scientific instruments requiring observations of trans-ionospheric radio signals, e.g. for radio astronomy. The physics behind the generation of the plasma irregularity structures that cause scintillation is not fully understood, largely due to a lack of adequate observations. An obvious consequence of this is that neither does a reliable capability exist for the prediction or mitigation of the effects of scintillations on radio waves. ISX will generate an extensive dataset for applying diffraction radio imaging, which enables the prediction of scintillations at any frequency determined from the imaged structure, and potentially the mitigation of distorted signals by canceling phase fluctuations. Another broader impact of the proposed project is that it is a pilot effort to provide global, space-based monitoring of ionospheric radio wave distortion using signals of opportunity available worldwide. While a single spacecraft cannot provide real-time monitoring, it can show the way for a constellation of spacecraft to provide such a space weather service in the future. Scintillation effects occur predominantly in the equatorial region in ionospheric density structures termed Equatorial Spread F (ESF). The main goal of this project is to provide new observations on the structure of scintillation-scale ionospheric irregularities associated with ESF. Specifically, ISX will simultaneously record scintillation patterns of multiple ground-based digital television (DTV) carrier signals. Scintillation patterns for a unique set of experimental geometries will be compared to determine how far along the magnetic field the turbulence maps, which is crucial observational data on the three-dimensional electrodynamics of these sub-km structures.During the lifecycle of the project, it will provide extensive student training opportunities, including student involvement through Cal Poly spacecraft design classes and funded graduate students. Each year, 20-40 students will be involved in the design, fabrication, and flight of this mission. Cal Poly has flown many student satellite missions; the proposed effort will leverage the heritage and experience from all of these.This project addresses the science question: To what distance along a flux tube does an irregularity of certain transverse-scale extend? It has been difficult to measure the magnetic field-alignment of scintillation-scale turbulent structures because of the difficulty of sampling a flux tube at multiple locations within a short time. This measurement is now possible due to the worldwide transition to DTV, which presents unique signals of opportunity for remote sensing of ionospheric irregularities from numerous vantage points. DTV spectra, in various formats, contain phase-stable, narrowband pilot carrier components that are transmitted simultaneously. A 4-channel radar receiver will simultaneously record up to 4 spatially separated transmissions from the ground. For most experimental geometries, the corresponding transmitter-satellite lines-of-sight will cross the same magnetic flux tube within 1-10 s, a reasonably short time to assume "frozen" irregularities. Correlations of amplitude and phase scintillation patterns corresponding to multiple points on the same flux tube will be a measure of the spatial extent of the structures along the magnetic field. A subset of geometries where two or more transmitters are aligned with the orbital path will be used to infer the temporal development of the structures. The radio receiver is based on the instrument developed and successfully demonstrated on the previous Radio Aurora eXplorer (RAX) NSF CubeSat project.