Word: orbitals
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Dates: during 2000-2009
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...rovers were launched atop separate boosters. Spirit left Earth on June 10, 2003, and Opportunity followed on July 7, taking advantage of the biannual close approach Mars and Earth make as they orbit the sun. On solar system scales, a close approach is still a goodly distance - 35 million miles in 2003 - which means that the rovers needed seven months to get where they were going. Spirit landed first, bouncing down in a swaddle of air bags in Mars' Gusev Crater. Opportunity followed three weeks later, landing on the other side of the planet in what is now known...
...Apollo 8 did go. On the morning of Saturday, Dec. 21, 1968, the crew blasted off aboard the 36-story, seven-million-pound Saturn V rocket into Earth orbit. Five hours later, the crew fired the Saturn's upper stage engine and Apollo 8 peeled out for the moon...
...Christmas Eve the crew got busy. Settling Apollo 8 into orbit around the moon was a high-wire maneuver that involved turning the ship backward and firing its powerful service propulsion engine for precisely four and a half minutes - an eternity in a business in which barely a breath from a thruster is enough to set a ship spinning off course. The engine burn was designed to slow the spacecraft down just enough to ease it into a lunar orbit without losing so much altitude that it crashed into the moon instead. Orbital mechanics also demanded that the maneuver occur...
...Lovell typed the instructions for the engine burn into the on-board computer, and the computer flashed back "99:40," which was code for "Are you sure?" Lovell hit the Proceed button. The engine lit and the burn worked exactly as scripted, inserting Apollo 8 into an initial lunar orbit 169.1 miles high at its peak and just 60.5 miles above the lunar craters at its nadir. Even before the crew re-emerged around the other side of the moon and back into radio contact with Houston, Anders snapped what is surely the most iconic photo of the space...
...crew circled the moon 10 times over the next 20 hours. On their final orbit, once again alone behind the moon, the crew re-lit the engine that was their only ticket home. If it had failed to burn, they would have been stranded forever in lunar orbit. The flight controllers - to say nothing of the families - waited anxiously for the astronauts to emerge from radio blackout. When they did, it was Lovell's voice that broke the silence...