Remote GPS measurements to improve SAR ice monitoring

星载合成孔径雷达(SAR)观测可以用来测量南极冰盖内的结构和速度。到目前为止，大多数搜救任务都使用L波段(1-2 GHz)，但现在人们的兴趣转向更低频率的P波段信号(约430 MHz)，因为它们对冰的穿透能力更强。巴斯大学和BAS目前都参与了与未来欧空局卫星的P波段合成孔径雷达设计有关的可行性研究。极地轨道上的P波段SARS，如定于2014年发射的欧空局生物量卫星，有可能绘制出冰盖的三维结构图。然而，它们的信号将受到显著的电离层效应的影响，包括法拉第旋转、距离散焦、距离延迟和干涉相位偏差。在系统设计中必须考虑电离层，但目前还不存在这样做所需的电离层测量。该项目将提供南极地区的测量结果，并为成功的P波段合成孔径雷达任务奠定基础。该项目涉及设备开发、现场工作和分析。实地工作的目标是部署改装的GPS接收设备，首次测量整个南极偏远地点的总电子含量(TEC)、等离子体速度和电离层闪烁。为实现这一目标，将部署8个新的全球定位系统接收器，在两年期间对极光和极冠区域进行长期测量。国际合作伙伴将提供南极低纬度地区的更多数据。这些测量将用于开发南极电离层的多尺度模型。这一模型将是对合成孔径雷达设计的关键投入，它将最大限度地减少电离层对未来卫星飞行任务冰测量的影响。

Space-borne synthetic aperture radar (SAR) observations can be used to measure structure and velocity within the Antarctic ice sheet. Most SAR missions to date have used L-band frequencies (1-2 GHz) but interest is now turning to lower-frequency P-band signals (around 430 MHz) because they have greater penetration of the ice. Both the University of Bath and BAS are currently involved in feasibility studies relating to P-band SAR design for future ESA satellites. P-band SARs in polar orbits such as the ESA BIOMASS satellite due to launch in 2014, have the potential to map out the three-dimensional structure of ice sheets. However, their signals will suffer from significant ionospheric effects including Faraday rotation, range defocusing, range delay and interferometric phase bias. The ionosphere must be taken into account in the system design but the necessary ionospheric measurements to do this do not currently exist. This project will deliver the measurements for the Antarctic region and lay the foundation for successful P-band SAR missions. This project involves equipment development, fieldwork and analysis. The objective of the fieldwork is to deploy modified GPS receiving equipment that will for the first time take measurements of total electron content (TEC), plasma velocity and ionospheric scintillation at remote locations across the Antarctic. To achieve this, eight new GPS receivers will be deployed to undertake long-term measurements in the auroral and polar-cap regions over a two year period. Additional data from lower Antarctic latitudes will be provided by international partners. The measurements will be used to develop a multi-scale model of the Antarctic ionosphere. This model will be a critical input to SAR design that will minimize the impact of the ionosphere on ice measurements for future satellite missions.