There is no need to fire with perfect accuaracy, as long as it is going in the general direction of the Archivist's pretty big body, it would score a hit due to the self-destructing nature of the rockets. Fuchsia is merely pulling the trigger a second time when he realises that the spider is coming at him, before jumping.

Edit: He only has to fire straight-forward to hit the spider running at him -straight forwardly- (That is not a word, I know)

Edit edit: You also keep saying he's invisible. Am I missing something here? His CS states that he's harder to see, especially in shadows. Quote "The Data Pad allows for a rudimentary cloaking, making him harder to see especially in shadows for a total of roughly thirty seconds before it needs to recharge from a serious power source. (Can’t be recharged in battle, leaves the Data Pad with only basic function of Data access.)"