the_newsbeagle writes "Chinese aerospace engineers have revealed, for the first time, details about their Chang'e-2 spacecraft's encounter with the asteroid Toutatis last month. They have plenty to boast: The asteroid flyby wasn't part of the original flight plan, but engineers adapted the mission and navigated the satellite through deep space (PDF). Exactly how close Chang'e-2 came to Toutatis is still unclear. The article states that the first reports 'placed the flyby range at 3.2 km, which was astonishingly—even recklessly—tight. Passing within a few kilometers of an asteroid only 2 to 3 km in diameter at a speed of 10,730 meters per second could be described as either superb shooting or a near disaster.' If the Chinese spacecraft did pass that near, it could provide a "scientific bonanza" with data about the asteroid's mass and composition."
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"