Good luck, SynFlood, to you and your co-workers. My wife is in charge of a 3.5 meter optical telescope, and the hours are brutal in the winter but much nicer in the summer: a typical shift is an hour or so before sundown to an hour or so after sunrise. Employees are expected to have side-projects (maintaining wikis, writing training materials, etc) to fill out a 40 hr week because no one works exactly 40 hours a week. People work blocks of time: three days on, ten days off (very roughly) because in the winter, those are very tough days. But we're at 9200' and no where near as cold as Chile, it's regularly below freezing in the winter but the telescopes are never open when the temperature drops below 0f (we had -20f for a few days two or three years ago). My wife's telescope has the advantage that they normally don't do post-observation work, that's the job of the scientist's team, the other telescope on-site does their own data reduction but has a much larger team.
US law does not allow changing contracts, at least while the contract is in force. After the contract expires or is being renegotiated, then changes can be made but have to be agreed to by the parties involved.
