After the missions you can get better officers for your team.div>
I got the Admiral Beverly Crusher hologram after a mission.
In the year 2364: Crusher becomes Chief Medical Officer aboard the U.S.S. Enterprise-D.
Beverly Crusher is a doctor in the Terran Empire, and mother to Emperor Crusher.
When I tried to add it, I got the following message:
You have reached the limit of officers that you can have of this type ...
What you have to do is to check that you have a free slot in the team.
Go to the station, dismiss a candidate and then choose the one you want to add to the team.
Here's where you should do these steps, I've already added it to the team so it doesn't appear in the list:
Here is the added hologram, it can be improved.