The stat line just says 'heavy array'. Doesn't say anything about what it's an array of. The logical assumption is that it's a heavy version of the twin particle array, which definitely can't. It would be stupid for it not to be able to, but it would also be stupid for it not to have Shuttles, which it doesn't.
It can take the mass drivers; they're AP. On average, over two turns, you'll hit and kill twelve emplacements. If you allow the Heavy Arrays, Double, Twinlink against hull 5, that's another twelve per turn, six hits doubling up. Slow loading is the real problem.
It's also only half the job. At Battle level, say, once all the emplacements are gone that would leave twenty- five troops still alive on the planet, and the Secundus drops one a round. Does not compute.
I've never taken a planet by dropping troops, plural, on it. What has worked is bombarding the smeg out of the emplacements while simultaneously sending down every available Sentri to strafe the troops on the ground. When they are all dead or smouldering ruins, one troop unit takes posession, and that's all you need.
If you really want to make room, ditch the Octurion to begin with. Big ships are a lot easier come by in the course of the campaign than small ships are to replace; they are better got with Priority points to begin with, the biggies with RR. I always start a campaign, now, with a relatively light fleet list- 2-3 Battle, 2-3 Raid, and the rest Skirmish and Patrol.