State Vector Warping Routine

Suppose you have ECI coordinates corresponding to a specific time (JDi), and you want to keep the relative orientation with respect to Earth at a different time (JDf). This function will calculate new ECI vectors corresponding to the desired time with a fixed position relative to the earth. In effect, this will hold the earth and the satellite orientation in the same place while allowing for time to elapse.

Example function call is shown below:
>> [rf,vf,af] = FixedECI(t0,tf,r0,v0,a0);

Where:

Inputs:
t0 is the initial julian date in days corresponding to the ECI coordinates provided below [1xN]
tf is the julian date in days in which the ECI coordinates are needed [1xN]
r0 is the initial position vectors in the ECI coordinate frame of reference (km) [3xN]
v0 is the initial velocity vectors in ECI coordinate frame of reference (km/s) [3xN]
a0 is the initial acceleration vectors in ECI coordinate frame of reference (km/s^2) [3xN]

Outputs:
rf is the warped position vector in the ECI coordinate frame of reference (km) [3xN]
vf is the warped velocity vector in ECI coordinate frame of reference (km/s) [3xN]
af is the warped acceleration vector in ECI coordinate frame of reference (km/s^2) [3xN]