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D-4.2 Tracking and Navigation Data Processing

Figure D-3 depicts the data flow for the Process Tracking and Navigation Data process. Raw tracking data originates from ARTS RGFs of the Range Segment and is stored. If available, navigation data (SV crosslink and GPS position) are extracted from telemetry . After thinning, engineering unit conversion, calibration and editing, they are stored in the Screened, Edited, Observations data store for use by Orbit Determination.

Figure D-3. Process Tracking and Navigation Data data flow diagram.

The following processes are shown in Figure D-3.

Store Raw Tracking Data - Receives raw tracking and status indicators from the Range, uses status for threshold screening, then archives slant range, range rate, azimuth, and elevation raw measurements.

Thin Data - Selects raw tracking and navigation data at a sample rate that controls the amount of data subsequently processed.

EU Convert - Converts raw tracking data counts to engineering units, using appropriate conversion factors.

Calibrate Data - Using an RGF database and antenna calibration measurements (either static or obtained in real time at the RGF), RGF antenna bias corrections are applied. Tropospheric and ionospheric delay calibrations make use of real-time calibration measurements from the Range as well as orbit ephemeris information for path modeling.

Compute and Validate Residuals - Orbit ephemeris and RGF information are used to calculate the differences between actual measurements and predicted measurements at each point. Edit controls are applied to residuals to identify and reject excessively noisy or biased measurements. An Anomaly Knowledge Base provides constraints and rules used to identify corrective action needed for malfunctioning hardware or software. Residual computation is also a necessary subfunction of Orbit Determination.

Demodulate Range Rate - Antenna motion modulation of range rate from spinning SVs is filtered, using range rate residuals. The measurement corrections from filtering are then used for final residual validation and measurement editing.