Description
The spacecraft reports its orientation (i.e., attitude) and time on a regular basis. These tasks record the information, for use by other tasks. The slave tasks are responsible for distributing the data.
The master task receives seven messages per second from the spacecraft: 5 attitude, 1 time-tone, 1 ancillary (containing orbit information and status info). The master task redistributes these messages to slave tasks on all CPUs.
The slave tasks use these messages to build time and attitude tables for interrogation by other tasks/functions. Attitude tables can be interpolated to give spacecraft attitude at a requested time.
Time tone messages, combined with time hacks (also distributed to all CPUs) provide wall clock time throughout the system, accurate to ~200 nanoseconds.
See also: annotated data flow animation
Role: Master
CPU(s): SIU only
Input
-
The 1553 Receive Service task sends spacecraft telecommand packets to this task.
The LCB Receive Service task sends LAT internal-protocol packets to this task.
Output
The Master task sends time and attitude messages to its slave tasks.
Package(s)
Role: Slaves
CPU(s): all CPUs
Input
-
The LCB Receive Service task sends LAT internal-protocol packets to this task.
The Spacecraft Attitude/Time Master task sends time and attitude messages to this task.
The Watchdog Slave tasks send status interrogation requests to this task.
Output
The task sends time and attitude tables to the Solid State Recorder.
Package(s)