LRO takes a closer look at Apollo sites Aug 13, 2011 0:45:20 GMT -4
Post by coelacanth on Aug 13, 2011 0:45:20 GMT -4
Not Bob B, but I'll do my best ...
Assuming a circular orbit (and also assuming I'm doing my calculations right), the velocity is inversely proportional to the square root of the radius of the orbit.
Wikipedia reports a mean radius of the not-quite-spherical moon of 1737.1 km. So if we're talking about an orbit 50km above the surface vs. one 20km above, that's only 1787.1 vs. 1757.1, after taking square roots and reciprocals, I'm getting that it should speed up by a factor of about 0.85%. Then it is 20km away instead of 50km, if it is looking straight down and ignoring the curvature of the moon's surface, the distance to the target is 60% less, and should pass out of the field of vision 2.5 times faster. So we're talking a factor of 150% because it is closer, and a factor of 0.85% because it's faster. Again, assuming I haven't made some appalling cock-up here.