| 
| 
 |  
| 
   N.V. Pushkov
 
 |  
|   
 
 
31/10/2025 04:19 MSK
 |  |  | 
	
	| 
  
    |  |  |  |  
    |  | The experimental base of the investigations is the topside sounding data obtained on board of the Intercosmos-19 and Cosmos-1809 satellites. The Intercosmos-19 satellite was active during the high solar activity period from March 1979 to February 1981. It carried on board the following scientific payload: satellite ionospheric station for radio sounding of ionosphere (IS-338) and apparatus for the measurements of low-frequency electromagnetic field (VLF-2ME), electric component of high-frequency field (AHF-2K), electron temperature (KM-3), and spectrometer of photoelectrons (SF3-M). The Intercosmos-19 characteristics are given in the Table. 
 
 
  
    | Parameter | Интеркосмос-19 | Космос-1809 |  
    | Period of active processing | from February, 1979 till February, 1981 | from February, 1986 till December, 1990 |  
    | Orbit Heights | 500-1000 km | ~1000 km |  
    | Orbit Inclination | 74° | 80° |  
    | Period between sounding | 8 s, 16 s, 32 s, 64 s | 16 s, 32 s |  
    | Duration of one telemetric data record | ~15 m, 1 h, 2 h, 17 h | 1 h, 2 h |  
 The Cosmos-1809 satellite was launched on December 18, 1986 and failed on May 23, 1993. The scientific apparatus consisted of topside radiosound (IS-338) and set of the instruments for the measurements of the local parameters of the space plasma: low-frequency electromagnetic field (VLF-2ME), quasistationary electric field (DCEF), electric component of high-frequency field (AHF-2K), electron density and its irregularities (inhomogeneities) (IZ-2), electron temperature (KM-9), mass-spectrometer (NAM-4) and spectrometer of photoelectrons (SF-EM).
 
 The N(h)-profiles of the electron density in the topside ionosphere were calculated from the ionograms obtained by means of IS-338. The example of such ionogram obtained on board of the Intercosmos-19 on November 28, 1979 is shown in Figure 1.
 
 Figure 1. Ionogram obtained from topside sounding onboard Intercosmos-19
 
   
 Figure 2. N(h)-profile of the mid-latitude ionosphere
 
 
   
 The N(h)-profile of the topside ionosphere calculated from this ionogram is shown in Figure 2. It is a typical profile for the daytime mid-latitude ionosphere for high solar activity.
 
 |  |  |  |  |