Areas where there is virtually no population or if there is they wouldn't know what they were seeing, anyway. That would make the visible missions a show for the public. Then, suppose what the Apollo astronauts saw on the moon, was not alien. Cape Canaveral having way to much visibility. Different types of radiation are identified by discoloration of film, waves, etc.
Photos taken with lead shields intensify the radiation penetration.
One of the cameras uses a lead shield film packet. The film is stored in a container made of depleted uranium, completely shielding all radiation so that the film advanced through the iris is the only piece exposed. It's been within the last 4 years. USSR supplied technical information only. I worked with all sorts of radiation sources for 40 years at Monsanto and lead shielding was used in every one of them.