{
  "@type": "dcat:Dataset",
  "accessLevel": "public",
  "bureauCode": [
    "026:00"
  ],
  "contactPoint": {
    "@type": "vcard:Contact",
    "fn": "HEASARC Help Desk",
    "hasEmail": "mailto:andrew.ptak@nasa.gov"
  },
  "description": "The UCSD/MIT Hard X-Ray and Low-Energy Gamma-Ray Instrument, A4, was flown on the HEAO 1 satellite, between August 1977 until January 1979. The experiment consisted of a collection of collimated sodium iodide scintillators, two of which the Low Energy detectors (LED, LED-3 and LED-6), were optimized for the lower energy part of the hard X-ray range between 13 to 180 keV. The first 6-months of mission were dedicated to an all-sky scan after which a pointing phase started. In pointing mode the A4-LED instrument look axis was kept in a 1 deg dead band centered on the target position. Instead in the "ping-pong" mode the look axis was regularly alternated with a secondary target a few degrees away, usually for background determination. This database table accesses the spectra (and associated files) obtained from the A4-LED detectors in the ping-pong mode. This is a service provided by NASA HEASARC .",
  "distribution": [
    {
      "@type": "dcat:Distribution",
      "downloadURL": "https://heasarc.gsfc.nasa.gov/W3Browse/all/a4spectra.html",
      "format": "HTML",
      "mediaType": "text/html"
    },
    {
      "@type": "dcat:Distribution",
      "downloadURL": "https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=a4spectra&",
      "format": "BIN",
      "mediaType": "application/octet-stream"
    }
  ],
  "identifier": "ivo://nasa.heasarc/a4spectra",
  "keyword": [
    "__"
  ],
  "landingPage": "ivo://nasa.heasarc/a4spectra",
  "license": "https://www.usa.gov/government-works",
  "modified": "2026-09-22",
  "programCode": [
    "026:000"
  ],
  "publisher": {
    "@type": "org:Organization",
    "name": "High Energy Astrophysics Science Archive Research Center"
  },
  "theme": [
    "Astrophysics"
  ],
  "title": "HEAO 1 A4 Spectra"
}