The International Quiet Sun Year (IQSY) was a cooperative international effort to study the effects of the sun during the quiet period of the 11 year solar activity cycle (Dec. 1964 – Dec. 1965). The IQSY was organized by the International Council of Scientific Unions to study solar events that are easier to observe during periods of lower solar activity. Observations were made using terrestrial observatories and various spacecraft.
To commemorate the IQSY, Togo issued a set of six stamps with three designs on December 12, 1964. Common to each of the stamps is a stylized sun and a globe with lines of latitude and longitude.
The 10 and 45 Franc design features a Mariner Satellite and an orbiting geo-physical observatory. The Mariner program was run by NASA and used a series of Satellites to observe and explore the planets of our solar system, I believe that it is most likely Mariner 2 or 4 depicted on these stamps. Mariner 2 and 3 are now in a Orbit around the sun. The status of Mariner 4 is unknow as it was hit by several micrometeoroids.
The 15 and 25 Franc design features the Tiros and Telestar Satellite as well as an orbiting solar observatory. The Tiros satellite was launched in April 1960 and was a weather satellite designed to take television images of weather patterns. It was operational for 78 days. Telestar was the first private satellite launched, It was a communication satellite and was used to test satellite communications over the Atlantic Ocean.
The 20 and 50 Franc design features the Nymbus, Syncom and Relay Satellites. The nymbus(nimbus) program was designed by NASA and used for meterological research. The Syncom satellites were used telecommunications. The one depicted on the stamps are either Syncom I, II or III. The Relay satellites were designed and built by RCA. They were experimental communication satellites, Relay I was the first satellite to provide television transmissions across the Pacific ocean.
McKenna Susan M P. “The International Years Of The Quiet Sun”. retrieved from : http://adsabs.harvard.edu/full/1965IrAJ….7….4M
Scott Postage Stamp Catalogue Volume 6