## Help in determining orbital parameters

## Help in determining orbital parameters

(OP)

I have a Keplerian problem:

Given two points in space that an elliptical orbit travels through, and the time that it takes for the satellite to travel between them, how do you determine the orbit?

Specifically, I'm thinking of the equation of the ellipse as

r0

r = -----------------------------

1 - e * cos (theta - theta0)

But any other method of describing the orbit is just fine.

(I'm only worried about a 2D orbit for now, I'm pretty sure I could extend it on my own)

Can this be done analytically?

Given two points in space that an elliptical orbit travels through, and the time that it takes for the satellite to travel between them, how do you determine the orbit?

Specifically, I'm thinking of the equation of the ellipse as

r0

r = -----------------------------

1 - e * cos (theta - theta0)

But any other method of describing the orbit is just fine.

(I'm only worried about a 2D orbit for now, I'm pretty sure I could extend it on my own)

Can this be done analytically?

## RE: Help in determining orbital parameters

T

## RE: Help in determining orbital parameters

I have not, however, convinced myself of this other question's intractablity:

Given two points in an orbit and the time it takes to transverse them (and whether you're going more or less than pi radians around the ellipse), what is your velocity at the initial point?

Using the methods in these books, I can solve my problem numerically. Battin almost implies that there is an analytic solution (see section 6.8, "Terminal Velocity Vector Diagrams") but I"m not seeing it. Does anyone know if it exists?

## RE: Help in determining orbital parameters

Brian Lewis

The Aerospace Corporation

http://www.aero.org/

## RE: Help in determining orbital parameters

With Lambert or Gauss, first you solve for the orbit, then you determine v at a point.

T

## RE: Help in determining orbital parameters

i have to find out a transfer-ellipse between earth and any other object in space. I know the orbit of all objects. So i have startpoint at starttime and the goalpoint at arrivaltime so i habe the ime also.

I've checked out Valado and Bate,Mueller,White and it works but only with low dt or TOF (Time of Flight). The Example which is given in Bate,Mueller,White works (here: TOF 780s)

but a TOF about 3 or 4 month the orbit is far away from goalorbit(i've checked the earthorbit with TOF=1,2,3 Month and all was right but....

short TOF for better Orbitcalculation but why?