EXEC has two main roles: executing the plan and recovering from failures that prevent proper execution. To execute the plan, first EXEC retrieves the current plan, usually spanning about a week, from PS. The plan is made up of tasks which have relatively large windows of time within which they can be accomplished. Examining the plan, EXEC figures out what smaller steps must be done, in order to accomplish each task in the plan. Then EXEC sends commands to the necessary parts of the spacecraft to carry out the steps. For example, if MICAS should be turned on, EXEC sends a command to MICAS to flip the power switch to "on." When it finds out that a task has been accomplished, EXEC moves on to the next task.
EXEC is able to help the spacecraft recover from many failures. EXEC may receive information that the commanded tasks are not being properly carried out. EXEC will command that the task be attempted again or will command a new method for carrying out a task. Sometimes MIR reports to EXEC that there is a failure with one of the spacecraft parts. EXEC asks MIR to suggest a recovery action and then will execute the recovery plan. If the failure is extremely serious, like lack of power, EXEC will put the spacecraft on "standby", shutting down all activities but the ones necessary for the spacecraft's survival. It will then wait for instructions from Mission Control.
How does Remote Agent improve space exploration?
Is Remote Agent like the robots in science fiction movies?
How are remote agents used?
What makes DS1 send distress signals?
How does the planner/scheduler work?
What is an example of planning and scheduling in everyday life?
What is MICAS?
How is NASA overseeing the DS1 mission?
How does PS really work?
How does MIR really work?
How does the EXEC really work?