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    "fn": "NASA Space Physics Data Facility",
    "hasEmail": "mailto:NASA-SPDF-Support@nasa.onmicrosoft.com"
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  "description": "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/sec. This sample rate is higher than the Nyquist frequency of 30 kHz. The sample frequency of 40 kHz provides a measurement every 25 microseconds corresponding to an apparent range (c*t/2) interval of 3.75 km. 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 analysis, 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 microseconds 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 and and a swept-frequency portion. The time resolution between ionograms is typically 14 or 22 seconds depending on the frequency sweep range.",
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  ],
  "identifier": "https://doi.org/10.48322/v11k-e045",
  "keyword": [
    "akr",
    "ducted-echoes",
    "fai",
    "field-aligned-irregularities",
    "fixed-and-swept-frequency-sounder",
    "ground-echoes",
    "ground-reflections",
    "ionogram",
    "ionospheric-echoes",
    "ionospheric-reflections",
    "plasma-resonance",
    "plasma-waves",
    "solar-type-iii-bursts",
    "spectrum",
    "topside-ionosphere",
    "topside-sounder",
    "upper-hybrid-noise-band",
    "wave-scattering",
    "waves-active"
  ],
  "landingPage": "https://doi.org/10.48322/v11k-e045",
  "license": "https://www.usa.gov/government-works",
  "modified": "2026-09-21",
  "programCode": [
    "026:000"
  ],
  "publisher": {
    "@type": "org:Organization",
    "name": "SPDF"
  },
  "theme": [
    "Heliophysics"
  ],
  "title": "ISIS 2 Topside Sounder Ionograms"
}