Solar position and velocity vectors -- Use? What are the solar position and velocity vectors used for? A program I'm working with requires them to help construct the trajectory of a meteor. Do they somehow become useful in calculating the orbit of the meteor? Aside from their use, I'm looking at an old astronomy almanac for 1991, and found them in a table. I would like to know them for CE 1955 October 20 07:53:32.6 UT for three dates either side of that date. The USNO probably has them on a web site, but a msg I sent to them early last week has gone unanswered so far.