UFO analyzes missile site.In autumn, 1968, I had been working Minuteman Missile Security, USAF, about 60 mi.E. of Rapid City, S. Dak. I'd been chosen for TDY training. Finishing early one day, my former crew of Security Police returned from 3 days afield. They were buying all the binoculars & cameras they could afford. It seems a ball of light was hovering up & down over a missile site in "India" Flt.(White Owl/Plainview area). The Strike Team was sent to check unusual alarms & reported it. The dayshift crews(SP)and cook went up to the roof of the LCF & watched this action in the distance for several hours. The "Capsule Crew" officers reported strange readings on their monitoring instrumentation. The Missile Wing Hdqrs. back at Ellsworth called the LCF Security NCO, saying: "You DO have something out there, don't you?" The object was never seen again.This event occurred about 2 months after Rapid City newspapers reprinted accounts from papers in Wyoming and Colo. about USAF Security Police Strike Teams (2-man, in a pickup truck)had been "chased" from missile sites all the way back to Base, not just the LCF, at full speed, in those states.Since I read the newspaper accounts and had worked with these peers, I'd have expected some report of this to be on-file. Apparently, such is not the case.I was NOT a witness to the object, itself. If my peers had been joking, they would not have purchased the items mentioned. All of us had SECRET clearances at the time.To my knowledge, none of my peers were "warned" at all, about keeping this "quiet."