<delurk>
Not canon, but my assessment of ranks would suggest occasionally a Sublieutenant (or ‘Oberleutnant’) but normally a Lieutenant (or ‘Kapitensleutnant ‘) for this role. YMMV.
Rank roles: http://sol.trisen.com/default.
asp?topic=10&page=38 Comparative ranks: http://sol.trisen.com/default.
asp?topic=10&page=41