[Top] | [Previous] | [Next]

D-4.4 Orbit Ephemeris and Events Generation

Figure D-5 depicts the Generate Ephemeris and Events function, including the following processes:

Generate Orbit Ephemeris - When indicated in the Timeline data store, this function performs a numerical integration of the trajectory indicated by the latest orbit state in the Orbit Ephemeris data store. This state is used to generate a time-ordered set of states, which will be used by several other SSCS processes. This ephemeris is then placed back in the Orbit Ephemeris data store.

Compute Orbital Events - This process uses the Orbit Ephemeris data store and a set of physical parameters to generate orbital events such as nodal crossings, eclipses, perigee, and apogee. Resulting events are then associated with (possibly new) orbit ephemeris points and returned to the Orbit Ephemeris data store.

Compute Point-to-Point Viewing Periods - This process uses the Orbit Ephemeris (possible from several vehicles), RGF data, and a set of physical parameters to generate viewing events such as satellite rise and set times relative to an RGF and satellite-to-satellite viewing periods. Resulting events are then associated with (possibly new) orbit ephemeris points and returned to the Orbit Ephemeris data store.

Diagnose Orbit Conditions - Evaluates the future orbit state based on the Orbit Ephemeris data store for possible anomalies using constraints and rules from the Anomaly Resolution Knowledge Base. If a problem is found, an Orbit Maintenance activity is requested through the Timeline data store.

Figure D-5. Generate Orbit Ephemeris and Events data flow diagram.