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.