Why was the ship running at full capacity before any passengers were expected to be awake?

A few points. In the original script, on page 71, we see them viewing the same Stellar Fly-by of a Red Giant. No name is given to the star. And no Announcement is made. It's just Jim pulling Aurora to see it.

Now, as to why the ship may have the announcement:

1. This is not the first ship. It's likely also not the only type of ship. Before Hibernation, they likely had generation ships. And those ships would benefit from those announcements.

2. Jim, who was in control of the passenger liaison command center, could trigger it. In the original, he's rushing Aurora to see it, for her birthday. As we see, Jim does multiple things on the ship for Aurora's benefit. Having the ship announce this is just another one.

3. General software is used, and the programmers didn't see a reason to disable the announcement. Or they found disabling it introduced bugs into the code. So they left it on.

4. They have 8 nuclear or fission reactors and power is not an issue. Self repair is also possible. So no effort was spent in pairing down unnecessary features.

If you notice, when Jim wakes up, the computer tells him they're on schedule and the ship will arrive in four months and schedules him for his orientation classes, etc. So at least part of the computer was behaving as though the passengers were due to wake up - which could explain why passenger-specific areas of the ship came on line.

Some of this is simple dramatic licence. When Jim wakes up, he is able to breathe and find food. With his immediate physical needs met, the audience can focus on his confusion and loneliness. Because Arthur the bartender activates automatically, we get an interesting scene when Jim is shocked at meeting Arthur, and then shocked again when he realises Arthur is not human.

As for the Arcturus announcement, I can think of at least two possible explanations:

1) It's possible that Jim set it up himself, in order to entertain Aurora.

2) Real-world software frequently contains "Easter eggs" and whimsical hidden features. The announcement may have been left as a joke by the system designers.

As the life support pod malfunctioned, the systems may have auntomatically come online as they assumed everyone was awake.

The ship may not be “running all systems”:

• The flight crew areas remained inaccessible and inactive, at least until one of them actually was activated.
• The medical station could only be accessed by someone with credentials. It was accessed only later on when a member of the flight crew activated it.
• The ship probably had thousands of processes and/or systems. We simply don’t know how many of them stayed “asleep”.

Once we have a malfunction, we introduce several possible ways that a particular system can be activated (beyond the bartender being activated by normal motion):

• The malfunction caused a pod to take Jim out of “sleep”. This same malfunctioning process could have, in turn, activated other systems. That would explain general life support, the holograms that were trying to heard the “many people” through initial orientation, and the little clean-up crew munchkin robots.
• Other malfunctions started to appear – so there was more than someone waking up. Many of them would have been noticeable to the casual observer. One of these systems could simply be a PA announcer telling the general population orientation details like their present distance/time to destination. Under normal circumstances, it would have been an announcement stating days to destination. But since they were many years to destination, the computer systems were just trying to be accurate.