Why is Alpha so secret, and so badly hidden?

[Abion47]

In general, the people stationed at Tau stayed at Tau. They didn't ever go to Phi unless they had to, and then it was only via the well-trodden access corridor. The "access tunnel" was the result of damage, not an intentional path to Alpha. We don't know the actual route that Ross took to Alpha.

Of course, the existence of Alpha didn't really seem like all that much of a secret to people stationed at Tau. They knew what Ross was there for and what he was doing. My guess is that since they were all stationed at Tau, they were pretty well cut off from the rest of the stations that Carthage had no choice but to let them in on a few things to avoid unnecessary questions.

As far as why it was a secret in the first place, the biggest reason I can think of to conceal the existence of Alpha would be to hide the knowledge of what the WAU really was. If it was just some simple program with the sole purpose of handling life support systems, then there would be no reason to hide that fact. But if, perhaps, Carthage had bigger plans in mind for it... I mean, why else would they assign an AI psychologist to monitor it?