The Orbit Determination Process#

Last revised by M. Pugliatti on 2025 FEB 4

The Deep Whale Network (DWN) pre-process the actual radiometric quantities that are observed by a network of ground-stations (e.g. Deep Space Network or DSN, ESTRACK, etc.) and OpNav data. In doing so, the DWN also generate auxiliary data needed by computed models (e.g. for tropo/iono corrections, frequency data, turn-around ratios, etc.) These former quantities are referred to as the “observed” ones , while the latter as “auxiliary” data. These “auxiliary” data is feeded to SCB measurement models, which implement the computed formulations from [Moyer2000] for the available measurement types.

The estimation programs of SCB set fit the computed values of the observables to the observed values of the observables in a least squares (or lKF, SRIF, batch SRIF) sense by differentially correcting the values of the solve-for parameters. This process uses the observed -minus- computed residuals (R = O-C) and the partial derivatives of the computed values of the observables with respect to the solve-for parameter vector q calculated in SCB. The resulting estimated values of the solve-for parameters determine the trajectory of the spacecraft.

For this process to work correctly, a variety of tasks need to be performed to provide the filters with the necessary data in an accurate and efficient manner. This is represented by the schematic below.

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More details about the OD process can be found in the following sources:

  • [Moyer2000] T.D. Moyer, Formulation for Observed and Computed Values of Deep Space Network Data Types for Navigation, JPL/NASA, 2000.

  • [Thornton2000] C.L. Thornton and J.S. Border, Radiometric Tracking Techniques for Deep-Space Navigation, Wiley, 2000.

  • [Montenbruck2000] O. Montenbruck and E. Gill, Satellite Orbits: Models, Methods, and Applications, Springer, 2000.

  • [Tapley2004] B.D. Tapley, B.E. Schutz, and G.H. Born, Statistical Orbit Determination, Elsevier, 2004.

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