Simpler trajectories such as basic orbits could once be calculated by hand, at least if you were Richard Feynman [1]: >"The process of orbit determination is f

Simpler trajectories such as basic orbits could once be calculated by hand, at least if you were Richard Feynman [1]: >"The process of orbit determination is fairly taken for granted today. During the effort to launch America's first artificial Earth satellites, the JPL craft Explorers 1 and 2, a room-sized IBM computer was employed to figure a new satellite's trajectory using Doppler data acquired from Cape Canaveral and a few other tracking sites. The late Caltech physics professor Richard Feynman was asked to come to the Lab and assist with difficulties encountered in processing the data. He accomplished all of the calculations by hand, revealing the fact that Explorer 2 had failed to achieve orbit and had come down in the Atlantic ocean. The IBM mainframe was eventually coaxed to reach the same result, hours after Professor Feynman had departed for the weekend." For more complicated paths such as the Rosetta mission, my understanding is that since the 3 body problem remains unsolved for general initial conditions, a numerical solution has to be derived. This numerical solution, at least until recently, seems to have required some fine tuning and intelligent guessing of initial mission parameters [2]: > “It took only two days of computing time on an ordinary desktop computer and no other user input to reproduce the Cassini mission configuration — a trajectory that originally took extremely talented designers many months to develop.” Since this mission launched before the development of the software in the above reference, it's likely that a team of experienced engineers spent some time fine tuning it from an initial guess. [1] http://www2.jpl.nasa.gov/basics/bsf13-1.php http://www2.jpl.nasa.gov/basics/bsf13-1.php [2] http://www.nasa.gov/content/goddard/nasa-technologist-makes-traveling-to-hard-to-reach-destinations-easier/#.U-DmWfkRDmY http://www.nasa.gov/content/goddard/nasa-technologist-makes-...