It has been found that spacecraft on certain flyby trajectories around the earth gain an amount of energy that is unaccounted for. The asymmetric trajectories highlight this anomaly as described here http://en.wikipedia.org/wiki/Flyby_anomaly" [Broken]. I read that the most asymmetric flyby’s produce the greatest ‘unexpected increase’ in velocity. The asymmetry refers to the fact that the spacecraft might approach at one latitude and leave by another. (I can't actually understand how this asymmetry occurs. Doesn't the earth appear gravitationally as a point source?) Anyway my main question is; Does this asymmetry equate to the spacecraft’s approach being on average further away from the earth than its average distance from the earth on the exit? In other words: Is the spacecraft further from the earth on average when the earth’s gravity is accelerating it positively just before it reaches the perigee? And following on: Is the spacecraft closer to the earth on average when the earth’s gravity is decelerating it after passing the perigee?