It would be perfectly acceptable for a character to do this. There are docks and shuttles that are used for ferrying supplies back and forth from the planet station, and Hypatia monitors everything that comes or goes (for the most part), but she isn't going to take great offense to a PC that likes to take a walk outside her walls. If he happened to go past a certain distance from the station Hypatia might treat him like a ship trying to make a break for open space, and she would probably try to laser him, but it ought to be clear anyway that floating off to freedom isn't an option. There is Sacrosanct and there is Asphodel and there is the space in between them.

As for surviving on the planet surface, characters are more than welcome to go down to Asphodel any time they choose. There's just not much draw, aside from the Resistance being down there. The surface is inhospitable and the tunnels not that much better, and the magmaworms have a tendency to eat anything that causes vibrations from sound or motion. But yes, a determined character could do it, and it would be allowed.