Idle mode is the ‘manager’ mode of the spacecraft. Nothing computationally heavy is happening and spacecraft is waiting for it’s System State Variables (SSVs) to tell it to move into another mode. Ideally it moves into another mode as soon as possible.

Nominal Case

Under nominal operations, the spacecraft can change into idle mode for the following reasons:

1. Finished with LEOP Operations - Will only happened once (LEOP —> Idle)
2. Finished with Downlink Mode (Downlink —> Idle)
3. Finished all tasks in Processing Mode and it is not time to enter Downlink (Processing —> Idle) [because the ground station encounter is still a long time away, for example]
4. Command sent from ground to exit safety mode (if it was entered in the first place) (Safety —> Idle)

Contingency Cases

Scheduling or power availability prevent the spacecraft from performing nominally. In this case, it may enter idle because there is:

1. Not enough power available to image (Imaging —> Idle)
2. Not enough power available to process (Processing —> Idle)

What do we do?

In Command mode the spacecraft does the following things.

1. State Decision

Here we are constantly analyzing what Mode of Operation to join. We look in the priority list of Modes. Whenever a Current Mode is finished we then look for the highest priority mode we can enter and enter that mode.

The hierarchy of Mode Priority is:

1. Imaging
2. Downlinking
3. Processing