John Glenn

John Glenn was born in 1921 in Ohio. He became a Marine Corps aviator, flew combat missions, and later worked as a test pilot.

His experience with high-performance aircraft helped prepare him for selection as one of NASA's original Mercury Seven astronauts.

On February 20, 1962, Glenn launched aboard Friendship 7 and became the first American to orbit Earth.

He completed three orbits before reentry and splashdown, demonstrating that the United States could sustain a human orbital mission.

Katherine Johnson worked on trajectory calculations connected to early NASA missions, and Glenn famously asked for the computer-generated numbers for his flight to be checked by her.

The story captures an important transition in spaceflight: electronic computers were becoming essential, but human mathematical verification still carried enormous trust.

A spacecraft in orbit moves quickly relative to the ground and repeatedly passes in and out of range of different tracking stations.

Knowing its position and velocity is critical for communications, orbital prediction, and determining the correct time to begin reentry.

The same broad concepts used to follow satellites—position, velocity, ground track, prediction, and timing—also apply to human spacecraft.

Glenn's mission makes those ideas easier to understand because the tracked object carried a person.

Friendship 7 depended on launch hardware, spacecraft systems, precise calculations, and real-time tracking.

Glenn's story shows how orbital flight is both a mathematical prediction and a continuously observed mission.