Sputnik 1 was the first artificial satellite to orbit Earth, launched by the Soviet Union on October 4, 1957. Its successful orbit showed that humans could place machines in space and track them as they moved around the planet. This event opened the Space Age and changed science, engineering, politics, and education around the world.
Sputnik also proved that rocket technology had become powerful enough to reach orbital speed.
Key Facts
- Sputnik 1 launched on October 4, 1957, from the Baikonur Cosmodrome.
- Sputnik 1 had a mass of about 83.6 kg and was about 58 cm in diameter.
- Orbital speed near low Earth orbit is about v = 7.8 km/s.
- Sputnik transmitted simple radio beeps at 20.005 MHz and 40.002 MHz.
- Orbital period is T = 2πr/v, where r is distance from Earth's center and v is orbital speed.
- Sputnik 1 burned up in Earth's atmosphere on January 4, 1958, after about 3 months in orbit.
Vocabulary
- Artificial satellite
- An artificial satellite is a human-made object placed in orbit around a planet, moon, or other body.
- Orbit
- An orbit is the curved path an object follows around a larger body because of gravity and forward motion.
- Telemetry
- Telemetry is data sent by radio from a spacecraft or instrument to receivers on Earth.
- Radio frequency
- Radio frequency is the number of electromagnetic wave cycles per second used for communication signals.
- Space Age
- The Space Age is the period of human history beginning with the launch of Sputnik 1, when space exploration became possible.
Common Mistakes to Avoid
- Calling Sputnik 1 a crewed spacecraft is wrong because it carried no humans, animals, cameras, or scientific crew cabin.
- Thinking Sputnik sent pictures of Earth is wrong because it transmitted simple radio beeps, not images or video.
- Assuming a satellite stays up because there is no gravity is wrong because gravity is what bends its path into orbit around Earth.
- Confusing launch speed with orbital speed is wrong because a rocket must first climb through the atmosphere and then give the satellite enough sideways speed to keep falling around Earth.
Practice Questions
- 1 Sputnik 1's radio signal was transmitted at 20.005 MHz. What is the period of one wave cycle in seconds? Use T = 1/f.
- 2 Assume Sputnik traveled in a nearly circular orbit with speed 7.8 km/s and orbital period 96 minutes. About how far did it travel in one orbit? Use distance = speed × time.
- 3 Explain why Sputnik's simple beeping signal was scientifically and politically important even though it did not carry a camera or astronaut.