What satellite series was known as "fellow traveler"?

What satellite series was known as “fellow traveler”? Sputnik was the Soviet satellite series. The Russian word спутник (sputnik) literally means “fellow traveler” or “traveling companion,” and in an astronomical context it means “satellite.”

Sputnik 1, launched by the Soviet Union on October 4, 1957, became the first artificial satellite to orbit Earth. The polished, radio-transmitting sphere was small but historically enormous: its launch opened the Space Age and startled the United States during the Cold War. Its regular radio beeps could be detected by radio operators around the world.

Sputnik 2 followed on November 3, 1957, carrying Laika, a dog and the first living creature to orbit Earth, although the mission was not designed to return her safely. Later Sputnik missions expanded the program’s scientific work. A common mix-up is treating Sputnik as only the name of the first spacecraft; it also identifies a broader series and, in Russian, is the ordinary word for a satellite.