About "new stuff", I think explorers experience shouldn't depend on fights,
maybe on time on deep space or something else.
Or .. their exploration skill shouldn't depend on fight skill (experience).
You explore the universe most at beginning, before the first fight. When your
explorers fight (if you make they fight, and don't use fighters), the universe
will be quite well known, likely. So you dont need anymore their skill:
By now, there are following ways of increase the experience:
New useful way for explorers can be for discover a new planet, enemy or empty.
(it will be added)
Now the explore skills depending of the ship's level: