The Intercosmos-19 satellite was designed for investigations of the topside ionosphere structure and electromagnetic processes in it. It was launched on February 27, 1979 and worked until April, 1982. The distance between consecutive crossings of the equator was about 25 degrees in longitude. The local time of these crossings changed roughly by 1 hour every 5 days.
The instruments installed on board Intercosmos-19 were designed and manufactured by scientists of Bulgaria, Hungary, Poland, Czechoslovakia and USSR. The Intercosmos-19 scientific equipment included the topside sounder IS-338 (USSR), Langmuire probe P-4 (Bulgaria, USSR), local temperature probe KM-3 (USSR, Czechoslovakia), photometer EMO-1 (Bulgaria), soft particle spectrometer SF-3 (USSR), differential high energy spectrometer Perot-3 (USSR), VLF analyser ANCh-2ME (USSR, Czechoslovakia), HF wideband receiver with wideband telemetry transmitte r AVCh-2 (USSR), coherent 3-frequency beacon transmitter M4K-3 (Czechoslovakia).
The digital topside sounder IS-338 worked from March 5, 1979 to April 8, 1982. It had the frequency band 0.3 to 15.95 MHz. The sounding data could be directly transmitted to a receiving station (direct mode) or be stored in the onboard memory device for a certain period and then sent to the Earth (recording mode). Three recording modes were used: 2, 3, and 4. At mode 2 the time between two consecutive ionograms (sampling period) was 8 s and the data storage period was near 30 min, at modes 3 and 4 the sampling periods were 16 and 64 s, and the storage periods were near 2 and 16 hours correspondingly.