The PCs are hear because they've been stranded here by the Orion pirates, or to investigate the Orion pirate safe-house, or maybe just as a routine part of their system survey.
The Orions will fight to the death rather than face capture--they fear their superiors more than the Federation justice system. The safe-house will be protected by ECM and Traps--the ultimate of which is a self-destruct which fortunately announces its intentions.