Two radio transmitters were installed in the satellite, constantly emitting "beep, beep" signals on frequencies of 20.005 MHz and 40.002 MHz that could be picked up by amateur radio operators throughout the world. The scientific instruments on board carried out the first measurement of atmospheric density and the first investigation into the transmission of electromagnetic waves through the ionosphere.
The radio transmissions from Sputnik 1 ceased on 26 October 1957 when its batteries were exhausted. After spending 3 months in space and circling the Earth for about 60 million km, Sputnik 1 was destroyed upon re-entering the Earth's atmosphere on January 4 1958 due to the natural decay of orbit.
Russian Sputnik 1 stamp (indigo color on bluish colored paper, designed by Ye. Gundobin) on FDC issued on 4 November 1957 to commemorate the launching of the world's first artificial satellite, Sputnik 1, on 4 October 1957. The stamp design shows an orbit circling the Earth. Near the top of the orbit just above the Earth's globe is a white ball representing the Sputnik spacecraft with four white antennae. The date in the upper-left side is 4 October 1957, Sputnik 1 launch date. The text in the lower-right side reads "First in the World, Soviet Artificial Sputnik of the Earth" in Russian.
Russian Sputnik 1 overprint stamp (bright-blue color on white paper) on FDC issued on 28 December 1957.
Sputnik 1 stamps used on a registered mail to USA.