# Orbital Elements-Identification of method

1. Jan 13, 2012

### solarblast

Orbital Elements--Identification of method

I'm looking at a book that has a method for calculating the six orbital elements. I'm attaching the relevant pages. My knowledge about orbits is limited to knowing the meaning of the six elements. What I'd like to know is where did these equations come from, and is the author right when he says, "e from (87) and (88)" at the bottom of page 39. I suspect he meant 86 and 87.

I've heard of Gauss' and LaPlace's methods for determining orbits. Is the approach given one of those? He notes Herget as a source at the top of page 40. I have access to it, but is not a simple matter to browse through to find the approach on page 40.

2. Jan 13, 2012

### solarblast

Re: Orbital Elements--Identification of method

Well, for all practical purposes, it looked like I attached 4 jpg files. Guess not, so I'll do it now.

Ah, they were tif files. Invalid. Not quite. I had posted these before with a similar question, and apparently cannot post them again. It's a different question this time.

3. Jan 13, 2012

### Drakkith

Staff Emeritus
Re: Orbital Elements--Identification of method

I think it's saying that you need to find p before you can find e, so you would have to do 88 first then do 87. Not sure really.

4. Jan 14, 2012

### solarblast

Re: Orbital Elements--Identification of method

As it turns out, after really following the text onto page 40, the equations there at the top of the page transform x,y,z in equatorial coordinates to ecliptic coordinates. That paves the way to get omega, capital omega, and the inclination. These are all related to the ecliptic, while the six on the previous page are orbital. If the author had mentioned ecliptic that would have made it clearer. There actually seven orbital elements. q, perihelion distance is mentioned above eq (85), and in (92). We are now getting proper results.

It appears the math here is from the La Place method.