That's a great idea. I love seeing expansion on the Expedition aspect of the game.
My only concern is that these Artifacts/Relics are all very powerful. Would it be possible to make different "sizes" of these items (like a small ION Field Generator that increases Planetary Defense by only 5%)? The higher your Expedition Skill (perhaps the more Expedition experience you have, if you're still planning on incorporating experience and missions into the game) the better your odds are at not only finding an Artifact, but a bigger/better artifact. You could even introduce new Researches into the game that allows people to gain more use out of Artifacts, maybe at first level you only get 1% bonus, but as you research the Tech it increases more and more until you reach the maximum with that Artifact. Were you planning on having the effects stackable (ie, I find two Data Archives so my research is 50% faster)?
The other thing I think would be interesting is if the Artifact only affected the planet that it's on. It's an object that's being used, not a new technology that was researched for everybody. It would make people think about where the Artifact would benefit them most, and then you'd have to fly the sucker around to where you wanted it.
There's quite a bit of expanding that can go into Expeditions and Artifacts, I think you're off to a great start.