Part of the book is that everything is slower, it took them weeks to get to the planet from where they met, and Rocky had already spent time retro fitting graces ship to let him live there. (they did not go to the planet with the intention of sampling it, they were just going to sample the line and orbit the planet as an easy way to get close to the line)

It’s been a long time since I read the book, but I think they considered the danger relatively low for the ship with their plan to stay high up and were more focused on “maybe we’ll lose the bucket risks” and didn’t want to go back to rocky ship until they were done because travel time and stuff.