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D-4. Orbit Analysis Data Flow Diagrams

D-4.1 Orbit Analysis - Top Level

Figure D-2 depicts the top-level Orbit Analysis reference architecture. The Physical Parameters data store contains geopotential information, SLP ephemeris, and certain physical constants and the RGF Database contains Remote Ground Facility (RGF) information such as locations, measurement uncertainties, and biases. Determine Orbit uses the Screened and Edited Observations data store, which consists of processed RGF tracking and navigation data. Navigation data consists of vehicle crosslink measurements and processed measurements, such as GPS position measurements. Navigation data are Quality Assessed Engineering Unit (EU) Measurand data from telemetry.

Figure D-2. Overall data flow diagram for Orbit Analysis.

The following processes are identified in Figure D-2.

Task Antennas - When a tracking activity (i.e., a pass) is indicated by the Timeline data store, this process computes the data needed to point the network ground antennas for SV tracking. These data consist either of pointing angles generated from an orbit ephemeris and sent to the Range in real-time, or a NORAD 2LMES, used by the antenna operator to generate pointing data.

Process Tracking and Navigation Data - The tracking and navigation data are received by this function along with possible real-time calibration data from the Range and are combined, thinned, calibrated, edited, and stored in preparation for being used by Orbit Determination.

Determine Orbit - Tracking and navigation data are processed here in an estimation procedure to update the SV orbit estimate. The output to Orbit Ephemeris is an updated state vector consisting of orbital elements and any other estimated parameters at an epoch time.

Generate Ephemeris and Events - This process uses a state vector from the Orbit Ephemeris data store and generates orbital positions and velocities at uniform, discrete time intervals. Orbital events (node crossings, perigees, apogees, eclipses, maneuvers, etc.), view periods, and orbital anomaly conditions are tabulated and placed back in the Orbit Ephemeris data store.

Orbit Deconfliction - Ephemeris information from all available space objects is analyzed for Radio Frequency Interference (RFI) and directed energy beam hazards. The output of this analysis is written to the Orbit Ephemeris data store to be used by Mission Planning to ensure that no conflicts are present in the final Timeline.

Define Mission Vehicle Data - This function defines the Mission Vehicle Database from the SV Properties data supplied by the contractor or engineer.