ISIS-1 Topside Sounder Average Ionogram over Fairbanks, AK: ULA, Latitude 65, Longitude 212

This Ionogram was digitized from the original ISIS 1 Analog Telemetry Data on 7-Track Tape using the Facilities of the Data Evaluation Laboratory at NASA GSFC, Code 500. This Data Restoration Project is headed by Dr. R.F. Benson, NASA GSFC, Code 692. 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 ms corresponding to an Apparent Range Interval of c*t/2, where c is the Speed of Light, or 3.747 km. Each Ionogram consists of a Fixed Frequency Portion and a Swept Frequency Portion. The Time Resolution is typically 29 s.

本电离层图系由原ISIS 1模拟遥测数据（存储于7轨磁带上）通过美国国家航空航天局戈达德太空飞行中心数据评估实验室（代码500）的设备进行数字化处理所得。此次数据恢复项目由NASA GSFC的R.F. Benson博士（代码692）负责领导。电离层图的数字化速度为每秒40,000个16位样本。此采样率高于30 kHz的奈奎斯特频率。40 kHz的采样频率使得每25毫秒进行一次测量，相当于光速c乘以时间t的一半，即3.747公里。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。时间分辨率通常为29秒。