It may be hard to believe, but today's astronauts use an 18th century marine navigational tool as back-up technology.
Invented in the 1600s and put to wide practical use by seafarers during the 1700s, sextants have long been used for navigation by mariners as they ranged and explored the globe. This brilliant device is used to plot a course by measuring the angle between the horizon and the sun, moon, or a star to determine latitudinal position on the high seas. With today’s modern satellite based GPS navigation and electronic charts, many experienced bluewater cruisers still keep a sextant onboard and train themselves in celestial navigation in the event of electronics failures underway. Turns out they aren't the only ones.
NASA astronauts on board the International Space Station are conducting sextant observations and experiments to be used as navigational tools in the event of catastrophic electronic system failures during future long-distance space expeditions to the moon or Mars. With the observational mechanics of celestial navigation holding true whether on the high seas or on deep space missions, Apollo astronaut James Lovell first demonstrated that a sextant could be practically and successfully used to navigate a spacecraft back to Earth during the first flyby moon missions in 1968. The first demonstrational sextant sightings and tests were done in space by the early Gemini astronauts as NASA prepared to go to the moon in 1965–66.
As America and humankind leaps toward another round of deep-space exploration with the manned Orion spacecraft currently under development, there’s something inherently comforting and optimistic about our modern space mariners reaching back to this revered old technology that helped us to first explore and navigate our planet.