It's like The Girls of Atomic City.
That's a terrific nonfiction book about women who worked in Oak Ridge, Tennessee during WWII doing Uranium enrichment work to aid the Manhattan Project.
Very deliberately, the people in charge of the project made sure that no one except some top-level people knew anything beyond the very specific job they had. While the book is about women (because their stories are less often told), this idea extended to all workers.
If your job was to perform a specific test on rocks and then report the numbers, that's all you did. You didn't know what the rocks were or which numbers were good or bad or what happened before and after your tests.
Even the town the workers lived in was more or less a secret. They weren't allowed to talk to anyone outside the project about what they were doing, even though they didn't really know what they were doing. Nor could they share information with co-workers outside of specific work tasks. They could give a mailing address to far flung family (and white workers could bring their families with them to the town, which had schools and etc) but that was about it. People got fired for small infractions.
It wasn't until the end of the war, or even after the war, that the workers knew what they had been doing and what the final product was.
So if your space station is owned by a government or private entity and serves a purpose they need to keep secret, it's very possible that they'd tell their workers absolutely nothing beyond what they need to do their jobs and keep the station running properly. If the purpose is secret, the lack of satellite imagery, drones, and so forth is a given. The workers don't need that information for their work, so why would they have it?
The scientists may know more about the purpose of the space station, or they at least can give some educated guesses, but that doesn't tell them what is really going on. It will be obvious to most that the planet they're orbiting has something important hidden on it, and that may make them even more eager to explore, but they won't know what it is.
The years between expeditions is because the government/company chose that timing. They needed to get people they trust in place. Plus they had to get the equipment there. Since expeditions weren't part of the regular schedule, the station didn't have enough equipment to run another expedition.
There are going to be consequences if the workers break the rules. Depending on how isolated they are and what they find out, being fired and removed from the station might not even be possible. The risks of disobeying orders might be quite grave indeed.