GEODYN Software Package

GEODYN is a set of software tools used for orbit determination and geodetic parameter estimation. Users of GEODYN input estimates of orbital parameters (such as the initial satellite state and solar radiation coefficients) and geodetic parameters (such as tracking station coordinates). GEODYN then computes orbits from the input parameters and can also compute theoretical values of satellite tracking observations using the input geodetic parameters. GEODYN can compare the theoretical values of tracking observations with real tracking observations to refine the input values of orbital and geodetic parameters. The SGP version of GEODYN made available here has most of the capabilities of the standard version of GEODYN that is used within NASA, and is intended to be useful for the broader space geodesy community for applications such as the reconstruction and prediction of orbits of satellites tracked via satellite laser ranging.

GEODYN is a combination of three (3) programs: TDF, GEODYN_IIS and GEODYN_IIE

  • TDF (Tracking Data Formatter) is a program converting GEODYN input data in various types of ASCII formats, to a Binary file Format (G2B). The GEODYN program GEODYN_IIS reads input data in the G2B format.
  • GEODYN_IIS (Scheduling) is the program that reads input data, ancillary data files and the user's setup options. According to these options GEODYN_IIS prepares and outputs two files: the data file and the Interface file. Descriptions are provided in volume 5 of the web documentation.
  • GEODYN_IIE (Execution) reads the two files created by GEODYN_IIS and processes the data. Each measurement type is processed by the appropriate modeling routines and applies the models selected in GEODYN_IIS. GEODYN_II performs satellite orbit determination and creates computed observables. These are used along with the provided measured observations in a statistical least squares scheme. GEODYN_IIE then provides solutions of requested geophysical parameters or updated orbits. Large scale solutions may be performed by GEODYN by saving normal matrices and combining them later using an external program.

This SGP version of GEODYN is a modified version of the GEODYN program. It has been developed by the Geodesy and Geodynamics Laboratory (Code 61A) at NASA and the Earth System Science Interdisciplinary Center (ESSIC ) at UMD (see copyright). It is intented to be used for Orbit Determination of Earth orbiting satellites and Geophysical Parameter Estimation.

Additional support and examples are provided on the GEODYN support page.

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For more information about GEODYN, please contact