Upgrade and Operational Support for an MF Radar at Rarotonga

这项建议将为热带南太平洋拉罗汤加现有的中频雷达（21.5S, 160W）提供现代化，并提供两年的业务支助。根据这项建议，将安装一个新的数据采集系统，并将8位接收器升级为12位或16位数字化接收器。雷达的工作高度范围（目前80-98公里）将向下扩展到覆盖大部分中间层（~60-98公里），90公里以上的测量精度将得到提高。现有的8位数字化的动态范围已被证明是严重不足的中间层中频雷达回波。各种验证和技术研究表明，90公里以上的接收器饱和（这在8位操作中几乎是不可避免的）会导致风级低估。这种偏差源将被消除，升级将使雷达更可靠，提高其整体性能。拉罗汤加岛位于一个关键的纬度带，目前没有测量能力，与夏威夷考艾岛现有的中频雷达几乎精确地共轭（相同的经度和相反的纬度）。热层电离层中间层能量学和动力学（TIMED）卫星任务（开始于2000年5月）将促进卫星仪器和多个地面站点的综合数据分析。对于诸如日潮等现象的相关全球研究，必不可少的是参与雷达提供跨系统具有相似性能的无偏风。

This proposal would provide for the modernization of an existing MF radar at Rarotonga (21.5S, 160W) in the tropical southern Pacific and operational support for two years. Under this proposal, a new data acquisition system would be installed and the 8-bit receivers upgraded to 12- or 16-bit digitization. The operational height range of the radar (currently 80-98 km) will be expanded downward to span most of the mesosphere (~60-98 km), and the measurement accuracy above 90 km will be improved. The dynamic range of the existing 8-bit digitization has been shown to be grossly inadequate for mesospheric MF radar returns. A variety of validation and technical studies have demonstrated that receiver saturation above 90 km (which is nearly unavoidable with 8-bit operation) results in wind magnitude under-estimates. This source of bias will be eliminated and the upgrade will make the radar more reliable and increase its overall performance. Rarotonga is situated in a key latitude belt where there are presently no measurement capabilities and is almost precisely conjugate (same longitude and opposite latitude) to an existing MF radar at Kauai, Hawaii. The Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite mission (beginning in May 2000) will foster combined data analysis from satellite instruments and multiple ground-based sites. For correlative global studies of phenomena like the diurnal tide it is essential that the participating radars provide unbiased winds with similar performance across systems.