Powers That Be - McCaffrey, Anne a Scarborough, Elizabeth Ann

It was a world of ice and snow - a planet that just supported life and that had been terraformed from frozen uninhabitable rock. The people of Petaybee were hardy, self-reliant, friendly - and also very secretive. Major Yana Maddock, medically discharged from the service, was shipped to Petaybee in the hope that her burnt-out lungs might recover.