### Instruction:

Extract the cause and effect entities from the following sentence:
Only when, during this campaign, the source fades away, the campaign can be stopped to save observing time

### Assistant:

KEYWORD: during
VARIABLE: observing time
CAUSE_1: this campaign
CONDITION: to save
CAUSE_2: the source fades away
EFFECT_1: the campaign can be stopped
EFFECT_2: to save observing time

