Not the rank -- there are loads of ensigns on board that are 'junior officers' (for example, Ensign Jenkins in Warhead is a member of the 'junior staff' and in the same episode Harry explicitly mentions he is a 'senior officer'. ) .
Not the experience - no-one came fresher from the Acadamy than he and his position didn't change in 7 years, so I'll have to assume he was considered a 'senior officer' right from the start.
Or did it just come with his position perhaps? In that case, what exactly is the position that makes him 'senior'? 'First operations officer' or something like that?
For that matter, what exactly is a 'senior officer', if it isn't tied to rank or experience?
Not the experience - no-one came fresher from the Acadamy than he and his position didn't change in 7 years, so I'll have to assume he was considered a 'senior officer' right from the start.
Or did it just come with his position perhaps? In that case, what exactly is the position that makes him 'senior'? 'First operations officer' or something like that?
For that matter, what exactly is a 'senior officer', if it isn't tied to rank or experience?