The basic analysis of spacecraft tracking data requires 
relating the position and velocity of the spacecraft to the 
position and velocity of the tracking system.  The 
coordinate system used in spacecraft navigation is shown in 
Figure 1.   The basic measurements are of r and its time 
derivative and sequences of these measurements, combined 
with knowledge of the tracking station location and 
equations of motions of the spacecraft, allow the position 
of the spacecraft denoted here by distance r, right 
ascension, a, and declination, d, and its velocity to be 
determined as a function of time.  In addition to knowing 
the coordinates of the spacecraft in an inertial coordinate 
system, the coordinates of solar system bodies are also 
needed in this frame.  Tracking data collected on 
spacecraft near planets can also be used to improve the 
ephemerides the planets through the gravitational 
perturbations of the spacecraft motions.   Large combined 
analysis of tracking data and direct measurements of 
planets (radar and optical positions) are used to generate 
planetary ephemeredes.