Like most missions, Cassian relays the information to himself on repeat, to remind him to stay focused. It's harder to do so looking at Jyn, because she looks so miserable and he relates, even if there's no sign of it.

But he's a Captain. He's equipped to deal with this. Whatever he feels is irrelevant and he's used to burying that. He's especially used to trying to bury Jyn and the deep ache in his chest over what she'd done to him. He couldn't let it hold him back, so he did his best to ignore it - always always ignoring - but it may not have prepared him fully to deal with her now, because if he's honest, he's never properly dealt with it in the first place.

"They're calling it a planetkiller. There is little else we have so far, which is why it's important we succeed on Jedha."