{"@type": "dcat:Dataset", "accessLevel": "public", "bureauCode": ["026:00"], "contactPoint": {"@type": "vcard:Contact", "fn": "NASA Space Physics Data Facility", "hasEmail": "mailto:NASA-SPDF-Support@nasa.onmicrosoft.com"}, "description": "These ionograms were digitized from the original ISIS-1 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. Each ionogram consists of a fixed-frequency and and a swept-frequency portion. The time resolution between ionograms is typically 29 seconds.", "distribution": [{"@type": "dcat:Distribution", "downloadURL": "https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1969-009A-01", "format": "BIN", "mediaType": "application/octet-stream"}, {"@type": "dcat:Distribution", "downloadURL": "https://nssdc.gsfc.nasa.gov/space/isis/isis-status.html", "format": "HTML", "mediaType": "text/html"}], "identifier": "/SDE/SPASE_JSON/|82aa1971bbe95a07ef892eb3df5d4403", "keyword": ["akr", "ducted-echoes", "fai", "field-aligned-irregularities", "fixed-and-swept-frequency-sounder", "ground-echoes", "ground-reflections", "ionospheric-echoes", "ionospheric-reflections", "plasma-resonance", "plasma-waves", "solar-type-iii-bursts", "spectrum-ionogram", "topside-ionosphere", "topside-sounder", "upper-hybrid-noise-band", "wave-scattering", "waves-active"], "license": "https://www.usa.gov/government-works", "modified": "2026-04-20", "programCode": ["026:000"], "publisher": {"@type": "org:Organization", "name": "NASA Space Physics Data Facility (SPDF) Data Services"}, "theme": ["Heliophysics"], "title": "ISIS 1 Topside Sounder Ionograms"}