Vanguard 2

Vanguard 2

Vanguard 2 was an Earth-orbiting satellite launched on February 17, 1959, aboard a Vanguard SLV-4 rocket as part of the United States Navy's Project Vanguard. It was designed to study cloud cover and learn about the atmosphere. This mission was important because it was one of the first space missions and the first weather satellite. Vanguard 2 is still in orbit today, marking a key moment in the history of space exploration during the Space Race between the United States and the Soviet Union.

Previous satellites

Before Vanguard 2 could launch in 1959, there were four earlier tries in 1958. These were called Vanguard 2A, 2B, 2C, and 2D, but they did not reach their planned orbit around Earth.

• Vanguard 2A: launched 29 April 1958, by the Vanguard TV-5 rocket
• Vanguard 2B: launched 28 May 1958, by the Vanguard SLV-1 rocket
• Vanguard 2C: launched 26 June 1958, by the Vanguard SLV-2 rocket
• Vanguard 2D: launched 26 September 1958, by the Vanguard SLV-3 rocket

The satellite that finally succeeded was called Vanguard 2E.

Spacecraft

The spacecraft was a round sphere made of magnesium. It was 508 mm (20.0 in) wide. It had two optical telescopes with two photocells. The inside of the sphere was gold-plated. The outside had a special coating to help with thermal control.

It used radio to send messages. It had a 1 watt, 108.03 MHz telemetry transmitter and a 10 mW, 108 MHz beacon transmitter for tracking. A command receiver could turn on a tape recorder to send telescope data to the telemetry transmitter. The power came from mercury batteries.

Instruments

The optical scanner on Vanguard 2 was made to learn about clouds between the equator and halfway to the northern regions. Two special light sensors, called photocells, measured how much sunlight bounced off clouds, land, and water. As the satellite moved around Earth, these sensors scanned the surface below and sent the information back to scientists.

Vanguard 2 was also used to study the upper atmosphere. By watching how the satellite’s path changed over time, scientists learned about the air far above Earth. This helped them understand how Earth’s atmosphere fades into space. The satellite’s shape and orbit gave useful clues about these conditions.

Post mission

After its mission ended, Vanguard 2 and the top part of the rocket that launched it stayed in orbit around Earth for many years. Both are still orbiting today. Like Vanguard 1 and Vanguard 3, Vanguard 2 helps scientists study Earth’s atmosphere. These satellites have been orbiting for over 60 years and are expected to continue for about 300 years.