NASA image of Pioneer 10's famed Pioneer plaque, a pictorial message to any extraterrestrial being that may intercept the probe. It features a design engraved into a gold-anodized aluminum plate, 152 by 229 millimeters (6 by 9 inches), attached to the spacecraft's antenna support struts to help shield it from erosion by interstellar dust.
In a LOR mission a main spacecraft and a smaller lunar module travel together into lunar orbit. The lunar module then independently descends to the lunar surface. After completion of the mission there, it returns to lunar orbit and conducts a rendezvous with the main spacecraft. The main spacecraft then returns to Earth.
First mention of LOR dates back to 1916. It was proposed by Yuri Kondratyuk, a self-educated Russian, who calculated that LOR was the most economical way of landing a human on the Moon.
O'Neill began researching high-energy particle physics at Princeton in 1954 after he received his doctorate from Cornell University. Two years later, he published his theory for a particle storage ring. This invention allowed particle physics experiments at much higher energies than had previously been possible. In 1965 at Stanford University, he performed the first colliding beam physics experiment.
While teaching physics at Princeton, O'Neill became interested in the possibility that humans could live in outer space. He researched and proposed a futuristic idea for human settlement in space, the O'Neill cylinder, in "The Colonization of Space", his first paper on the subject. He held a conference on space manufacturing at Princeton in 1975. Many who became post-Apollo-era space activists attended. O'Neill built his first mass driver prototype with professor Henry Kolm in 1976. He considered mass drivers critical for extracting the mineral resources of the Moon and asteroids. His award-winning book The High Frontier: Human Colonies in Space inspired a generation of space exploration advocates. He died of leukemia in 1992.