Choose PRN
The Choose PRN window will list the Start and Stop time for your scenario. There is also a list of PRNs for all active GPS satellites during that specified time period.
| Option | Description |
|---|---|
| PRN | The satellite PRN number per ICD-GPS-200 (PDF). This is a required data item as it is the GPS user's primary means of identifying GPS satellites. The PRN is a transmission identifier in the GPS message. At certain times, the transmitted GPS message will not contain information for a particular PRN. This is particularly relevant during update of the GPS constellation, when a PRN will be updated from one spacecraft to another. Typically, the PRN will be unavailable during an interval in which it switches to assignment from one spacecraft (with its SVID) to another (with a new SVID). If you are operating in online mode, STK will automatically account for the assignment intervals and prevent propagation over an interval in which the PRN is unassigned or will only create ephemeris for the satellite over this reduced interval. |
| SVN | The space vehicle number as defined in the ICD-GPS-200 (PDF). Each SVN corresponds to a different spacecraft. During its operational time interval, it will transmit on one assigned PRN. When a spacecraft becomes decommissioned, it no longer transmits its PRN; instead, a new spacecraft is assigned to transmit for that PRN. |
| SSC | The SSC Number of the Satellite. |
| Span | Early - The PRN disappears earlier than the requested interval's end time. Late - The PRN appears later than the requested interval's start time. This option is only available if you select Automatic - AGI Server. |