CCSDS OEM Ephemeris File
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The Consultative Committee for Space Data Systems (CCSDS) produces an Orbit Ephemeris Message (OEM) containing a series of state vectors for a single object.
The CCSDS OEM is an ASCII text file containing a header, Metadata, explanatory information (optional comments), and ephemeris data.
The header contains information on the file itself including the format version, file creation date and time, creating agency, and optional comments. An example of the header is shown below.
The Metadata contains information about the ephemeris data including object name, object ID, reference frame of the ephemeris, time system, recommended interpolation method and interpolation degree, and start and stop times.
The body of the file contains ephemeris records. The data records store the spacecraft's orbital position and velocity for a given epoch time. The format of the body section of a CCSDS OEM Ephemeris File is:
where X, Y, Z are positions in km and Vx, Vy, and Vz are velocities in km/s. If the user chooses to include position and velocity covariance in the CCSDS OEM Ephemeris file, the covariance information will be included at the end of the file following the Ephemeris state vector data. The covariance for a given epoch time is displayed as a lower diagonal matrix as shown in the example below.