VISSRSMS1L1EHT is the Visible Infrared Spin-Scan Radiometer (VISSR) Level 1 Experimenter History Tape (EHT) data product from the first Synchronous Meteorological Satellite (SMS-1). Each data file contains a segment of the Earth with radiances that were measured in the visible (0.55 to 0.70 micrometer) and/or IR (10.5 to 12.6 micrometer) wavelengths with a spatial resolution of 0.9 and 8 km, respectively. Files also include time, geolocation, orbit, attitude, and telemetry information. A data file is structured with a header, followed by an IR scan line and then 8 visible scan lines (although some files only contain IR scans). Visible scans are at full resolution of 15288 pixels and a file will contain several hundred scan lines. IR scans are at 3822 pixels and up to a hundred scan lines. A full scan of the Earth was made every 20 minutes.Data for this product are only available for 9 days: 1974/08/23 (IR only), 1974/08/27 (IR only), 1974/08/31, 1974/09/01, 1974/09/02, 1974/09/05, 1974/09/24 (IR only), 1975/01/10, and 1975/02/17. The SMS-1 satellite was initially parked over the equator at longitude 45W on June 7, 1974 viewing the hemisphere below the satellite to support the GARP Atlantic Tropical Experiment (GATE). It was moved to its operational position at 75W on Nov 15, 1974 where it remained until GOES-1 was launched, after which SMS 1 was moved to 105W and placed in stand-by-mode as a backup to GOES-1 or SMS-2. The VISSR experiment was operated by the NOAA National Environmental Satellite Data and Information Service (NESDIS), as well as scientists from NASA Goddard Space Flight Center.This product was previously available from the NSSDC with the identifier ESAD-00126 (old ID 74-033A-01A).