A4SPECTRA ivo://nasa.heasarc/a4spectra NASA/GSFC HEASARC Gruber; HEASARC 2026-08-07 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Spectrum 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 . https://heasarc.gsfc.nasa.gov/W3Browse/all/a4spectra.html Archive Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=a4spectra& GET text/xml 180 99999 true 100.3814269 -79.7522458 1 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=a4spectra GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_a4spectra&Action=More+Options&Action=Parameter+Search&ConeAdd=1 HEAO1 1 X-ray public a4spectra HEAO 1 A4 Spectra name Object Name meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable start_time Time of Observation Start mjd time.start;obs int nullable d3_count_rate Detector 3 count rate ct/s float nullable d3_count_rate_error Detector 3 count rate error ct/s float nullable d6_count_rate Detector 6 count rate ct/s float nullable d6_count_rate_error Detector 6 count rate error ct/s float nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable lii Galactic Longitude degree pos.galactic.lon double nullable d6_filename Detector 6 file name char nullable d6_respfile Detector 6 response matrix file name char nullable d3_exposure Detector 3 exposure s float nullable bii Galactic Latitude degree pos.galactic.lat double nullable alt_name Alternative Object name meta.id char nullable start_date Time of Observation Start in dd/mm/yy hh:mm:ss format char nullable gif_file GIF file showing the spectra of detectors 3 & 6 char nullable class Browse Object Classification src.class int nullable stop_date Time of Observation End in dd/mm/yy hh:mm:ss format char nullable d6_exposure Detector 6 exposure s float nullable d3_respfile Detector 3 response matrix file name char nullable d3_filename Detector 3 file name char nullable stop_time Time of Observation End mjd int nullable