“If you were ascending and already started to Orbit you should be fine ”
Your wording is wrong. If you are ascending to orbit
. You are already past the shield.
There are three parts to a planet. [ie; those nifty icons on some ships and vehicles that show repulsors and landing gear mean they can enter planetary levels]
Orbit - Space above. Not shieldable, but usually (always?) has a gravity well.
Atmosphere - Area just inside the planet. Can not be shielded. Repulsors needed to enter here.
Ground - City level. This is the area under a shield [if one is on]. Landing gear needed to go here.
It's tricky. I've tested it, and not really came to a conclusion. Basically, trying to trap someone, access would have to be removed near if not before ascension to atmosphere is started.
One would think, if it was removed during the one hour ascension, it would trap you. But I do not have concrete proof on that.
EDIT: changed "is" to "are" :3