On February 4, 1995, astronauts aboard the space shuttle Discovery launched an itty bitty satellite called an Orbital Debris Calibration Sphere into orbit around the Earth.
The satellite measured just 6 inches across, and it was one of six spheres that the astronauts deployed on mission STS-63. The spheres helped NASA calibrate equipment like telescopes and radars that were designed to track and measure space junk floating around in Earth's orbit. The spheres came in different sizes, and knowing the size of the spheres as they observed them from the ground allowed NASA scientists to calibrate their instruments so they could calculate the size of other objects floating around in space.
