This is jumbled and out of order for the moment; I'll try to sort it out when I'm done.
security against orbital bombardment
Hmm, cool. If this colony is on the Moon, or another body with not much of an atmosphere, they might be at risk of being hit by something. With no atmosphere, the body has no natural defenses against an asteroid or a comet, so it would be nice for the colonists to figure out a way to avoid that sort of thing.
However, it's extremely unlikely that a person would be killed by an asteroid on Earth (I take it these numbers take into account disasters from asteroids, though I could be wrong), and the Moon is an even smaller target. Bigger targets, like Venus, Mars, and, or course, the gas giants have atmospheres, and so some objects will burn up upon entry. The odds are still slim for being hit. So it's clearly not worth it to have a large task force standing by. Also, this group wouldn't necessarily fall under the control of the military.
This would not be necessary on a body with no atmosphere because wings would be absolutely useless. Helicopter blades are also useless. Airships might not work in such a vacuum, and they would have to contend with extreme temperatures. There's a simple rule of thumb: No air, no air force.
On a planet with an atmosphere, perhaps a small air force would be used. The trouble is, as SJuan76 said, there's a good chance the world is pretty peaceful. You won't have rival nations mucking about, and so there wouldn't be any dogfights, or air-to-air combat. I suppose that airplanes (and helicopters) could be useful for strafing or bombing any rebels that dared to revolt, but I think the odds of that are slim, with such a small population.
We have a similar rule of thumb here: No liquids, no navy. You can't sail a boat on the lunar seas (pun intended). Also, if there are no rival nations, there's no point in having a navy. Again, perhaps it could be useful in knocking out any rebel bases if there's something like an ocean on the planet, but there probably won't be a rebellion happening any time soon.
Boat design would be interesting because any bodies of liquid might not contain water. If you have hydrocarbon lakes, you may not want to put in ships using exposed internal combustion engines! So you'd have to adapt your ships in some way so that there isn't a huge risk of an explosion. Anti-navy tactics would also be interesting. I'm not a chemist, but hydrocarbons are flammable, so . . .
You need a small standing army. Maybe it won't be large, because, once again, there aren't any rival nations, but you need some people with weapons to take down any attacks. There would be infantry, and probably some artillery. You might see tanks, as well. If there's air, guns won't have any problem functioning; a planet without oxygen in the air will not be suitable for guns. Phasers, anyone? Or lightsabers? Jokes aside, you might need some weapons that are unlike what we have on Earth.
This is crucial. What's your one way off this godforsaken rock? Outer space. What happens if some outside force blockades you in (perhaps by guarding the wormhole)? You're in pretty big trouble. You might not see Luke Skywalker flying around, but you'll need a lot of spaceships guarding the wormhole and all flight paths to it. Also, if someone takes a spaceship rogue, you may need to shoot them down. Well, there is no down in space, so perhaps you're better off just blowing them up.