Figure E-2 describes the DFD associated with Attitude Analysis. The Space/Ground Geography Catalog contains data related to the solar, lunar, stellar and planetary ephemerides as well as models of the Earth's geomagnetic field, thermal variance, and CO2 layer. The Orbit Ephemeris data store contains orbital position information needed by Determine Attitude. The Sensor Performance and Specification data store contains information related to sensors used to collect attitude observation data. The Attitude Ephemeris data store contains the results of Determine Attitude. The data flows are discussed below as they relate to the processes involved.
Process Attitude Data - This function receives raw attitude observation data and sensor status to generate an edited and formatted observation data file for attitude determination. This process serves as a prefilter to Determine Attitude.
Determine Attitude - This process accepts the edited observation data file and extracts data regarding the location and specification of attitude sensors and astronomical bodies from the appropriate data stores. Data regarding the spacecraft's orbit is extracted from the Orbit Ephemeris data store. Data related to the attitude state is generated based upon an initial guess or a previous attitude state and is stored in the Attitude Ephemeris data store. Corrective action, if required, is diagnosed and appropriate initial conditions are passed to Mission Planning from the Timeline data store.
Generate Attitude Ephemeris and Events - Given the estimated attitude state and data from predefined data stores, this application generates a time-ordered attitude ephemeris and predicts key attitudinal events. Included in this prediction are time intervals for TT&C applications that require data from the SV Antenna Pattern data store. Resulting data is stored in the Attitude Ephemeris data store.
Define Spacecraft Sensor/Antenna Configuration- Vehicle-unique data addressing sensor specifications is used in this process to generate a data store containing sensor database items. This data store may be edited in real time to reflect on-orbit sensor conditions and/or anomaly configurations.