When is the RNG for Astra rolled when attacking?

[Whisky]

With Crits, you need to hit first before you roll for a Crit. You roll to Hit and then if you hit you roll for a Crit.

Does Astra work the same way as a Crit, only rolling after the Hit has already been confirmed? Or do you roll for Astra before the Hit and then each attack of Astra has a separate chance of hitting, missing, or critting?

[Seafarer]

Astra kinda has to be rolled before anything else, because it's a chance to turn one attack into 5. Each of the 5 attacks has a separate chance of hitting or critting, and it'd be a bit weird if the first attack always hit because you had to hit before you could proc Astra.