I'm looking at some code from a book that details uses the heliocentric position and velocity to compute an orbit of a meteor. See attached pages. At the top of the section at mid-page, page 37, he gives a source, Herget, 1953, Solar Coordinates 1800-2000. The book was written in the late 60s, and uses a real example, but does not provide the vectors for CE 1955 October 20 07:53:32.6 UT. From my distant past, I have some minor understanding of what's going on. To get matters moving, I need to find the two vectors. Well, one is easy. I happened to have the solar position vector for 1955 from a 1955 Nautical Almanac, USNO publisher. A possibility exists that the velocity vector may be derived from the cross product of the position vector and the pole of the ecliptic. The latter should be expressed in earth centric coordinates. The only clue I have to possibly pull that off is in Jean Meeus's Astro Formulae for Calcs, fourth edition, pf 43. Maybe eqs 8.3 and 8.4 might do the trick, if I assume some appropriate lambda and beta. Comments? Note that r-bar-prime_m, r'-bar_m, is known from eq 79 on page 37 of the book. I've provided several relevant pages from the book. For the curious, I've provided 38 to 40 for those who might be interested in knowing how the orbit was calculated from these vectors. The method is that of Herget. Note that items like r-bar are vectors, r-bar-prime are velocity vectors, and notation like a b sin(theta) mean a*b*sin(theta). I see I can only upload 3 files, so I'll do page 60 next.