ISIS-2 Topside Sounder Average Ionogram over Winkfield, United Kingdom: WNK, Latitude 51, Longitude 359

These Ionograms were digitized from the original ISIS-2 7-Track Analog Telemetry Tapes using the Facilities of the former Data Evaluation Laboratory at the NASA/GSFC. This Data Restoration Project is headed by Dr. R.F. Benson (NASA/GSFC). Ionograms were digitized at the Rate of 40,000 16-bit samples/s. This Sample Rate is higher than the Nyquist Frequency of 30 kHz. The Sample Frequency of 40 kHz provides a Measurement every 25 µs corresponding to an Apparent Range Interval equal to 3.75 km from c*t/2, where c is the Speed of Light. Ionograms with this Sample Rate are designated as 'Full' Ionograms because they have the full 3.75 km Apparent-Range Resolution. The Ionograms used for most Analyses, and those available from CDAWeb, were produced by averaging every four Samples of the Sounder-Receiver Video Amplitude Output to yield an average Value every 100 µs corresponding to an Apparent-Range Resolution of 15 km. These Ionogram Files are referred to as 'Average' Files with Standard Resolution. Each Ionogram consists of a Fixed-Frequency Portion and a Swept-Frequency Portion. The Time Resolution between Ionograms is typically 14 or 22 s depending on the Frequency Sweep Range.

这些电离层图是通过利用前NASA/GSFC数据评估实验室的设施，从原始的ISIS-2 7轨模拟遥测磁带进行数字化处理的。该数据恢复项目由R.F. Benson博士（NASA/GSFC）领导。电离层图以40,000 16位样本/秒的速率进行数字化。此采样率高于30 kHz的奈奎斯特频率。40 kHz的采样频率提供了每25毫秒一次的测量，对应于从c*t/2得到的3.75公里的视距间隔，其中c为光速。具有此采样率的电离层图被指定为‘完整’电离层图，因为它们具有完整的3.75公里视距分辨率。用于大多数分析和可从CDAWeb获取的电离层图，是通过平均声纳接收器视频幅度输出的每四个样本，以产生每100毫秒一个的平均值，对应于15公里的视距分辨率。这些电离层文件被称为具有标准分辨率的‘平均’文件。每个电离层图由一个固定频率部分和一个扫描频率部分组成。电离层图之间的时间分辨率通常为14秒或22秒，具体取决于频率扫描范围。