How to Succeed at "Protect Resupply Operation in the Kuras Drift"

In the game X-wing versus Tie-Fighter: Balance of Power, there is a Rebel campaign mission titled "Protect Resupply Operation in the Kuras Drift". In this mission you are tasked with protecting an asteroid within which is a research and development lab, in addition to some freighters intended to transfer some warheads from a 3rd party to the Rebels.

The mission begins with some T-wings flying around and eventually attacking the asteroid base you are to defend. Once a few wings of T-wings are shot down, two things happen. First, some Imperial Gunboats begin warping in, two at a time, and attacking the asteroid base. Second, an Imperial capital ship (Star Destroyer?) warps in from a different angle and sends out a bunch of Tie-Interceptors and seems to attack whatever ships are closest. The ships attacked by this latter group seem to be a corvette and a ship resembling the Millennium Falcon (I can't recall the classification of that ship type.)

The problem is, whether I go to intercept the Gunboats OR if I deal with the interceptors, I receive a message after a couple of minutes stating that we've encountered unacceptable losses and the mission is a failure. The real trouble is that I don't even know which ship or ships were destroyed!

Does anyone know how to complete this mission, what I am doing wrong, or what friendly ships seem to be destroyed quickly? I am stuck in the Rebel campaign until I figure this out. (It is pretty annoying to repeat because the T-wing portion of the mission involves a lot of waiting.)