Orbital Mechanics

"..besides the science, Cassini is state of the art in the arcane discipline of orbital mechanics — how to get from one place to another in space to fulfill a mission’s science requirements without running out of fuel. The plans are for Cassini to keep working for seven more years, but it currently has only 22 percent of the maneuvering propellant it had when it started.

Figuring out how to more than double the duration of the mission with less than a quarter of the fuel is hard. Cassini’s orbital mechanics present an astonishingly complex exercise in Keplerian physics and geometry. The enormous array of science objectives and targets — moons, rings, Saturn itself — makes it one of the most complex missions ever flown. "

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Source©right: NYTimes