Package org.orekit.estimation.iod

Class IodLambert

java.lang.Object

org.orekit.estimation.iod.IodLambert

public class IodLambert
extends Object

Lambert initial orbit determination, assuming Keplerian motion. An orbit is determined from two position vectors. References: Battin, R.H., An Introduction to the Mathematics and Methods of Astrodynamics, AIAA Education, 1999. Lancaster, E.R. and Blanchard, R.C., A Unified Form of Lambert’s Theorem, Goddard Space Flight Center, 1968.

Since:

8.0

Author:

Joris Olympio

Constructor Summary

Constructors

Constructor	Description
IodLambert(double mu)	Creator.

Method Summary

Modifier and Type	Method	Description
KeplerianOrbit	estimate(Frame frame, boolean posigrade, int nRev, Vector3D p1, AbsoluteDate t1, Vector3D p2, AbsoluteDate t2)	Estimate a Keplerian orbit given two position vectors and a duration.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

IodLambert

public IodLambert(double mu)

Creator.

Parameters:

mu - gravitational constant

Method Detail

estimate

public KeplerianOrbit estimate(Frame frame,
                               boolean posigrade,
                               int nRev,
                               Vector3D p1,
                               AbsoluteDate t1,
                               Vector3D p2,
                               AbsoluteDate t2)

Estimate a Keplerian orbit given two position vectors and a duration.

The logic for setting posigrade and nRev is that the sweep angle Δυ travelled by the object between t1 and t2 is 2π nRev - α if posigrade is false and 2π nRev + α if posigrade is true, where α is the separation angle between p1 and p2, which is always computed between 0 and π (because in 3D without a normal reference, vector angles cannot go past π).

This implies that posigrade should be set to true if p2 is located in the half orbit starting at p1 and it should be set to false if p2 is located in the half orbit ending at p1, regardless of the number of periods between t1 and t2, and nRev should be set accordingly.

As an example, if t2 is less than half a period after t1, then posigrade should be true and nRev should be 0. If t2 is more than half a period after t1 but less than one period after t1, posigrade should be false and nRev should be 1.

Parameters:

frame - frame

posigrade - flag indicating the direction of motion

nRev - number of revolutions

p1 - position vector 1

t1 - date of observation 1

p2 - position vector 2

t2 - date of observation 2

Returns:

an initial Keplerian orbit estimate