 Why does Captain Branson warn Ellason that he won't be able to publish his observations?
Upon the return to Earth a year later, the crew's report of suffering and chaos during the year's outgoing voyage was twisted, distorted and fragmentary. The decision of Interstellar was that the colonists started a revolution far out in space, that it was fanned by the ignorance of Captain Sessions in dealing with such matters. "We have conquered the problem of small groups in space—witness the discovery of Antheon, for example—but when there are large groups, control is more difficult." We don't think anything is going to happen, but if it does, we want to get an impersonal, unprejudiced view. Basically, it was an instrument which would open distant vistas to colonization, reducing the shoulder-to-shoulder pressure of a crowded solar system. In the tradition of newspaperman and observer, Keith Ellason tried to be as inconspicuous as possible, pressing against a bulkhead, but Captain Branson's eyes sought his several times as Branson listened to final reports from his engineers, record keepers, fuel men, computermen, and all the rest. On loan from Transworld, he will have an observer status." In Ellason's mind the incident, though insignificant from the standpoint of the ship as a whole, could very well be the cause of dissension later on. He said it was significant that all en route had passed stability tests, and that it was to the ship's discredit that someone with criminal tendencies should have been permitted aboard. What did Captain Branson think of those colonists who killed each other on the Weblor I ?
 He will be observing an inside job meant to protect the crew
 He knows there are secrets  too gruesome for public consumption  He is going to ask Ellason to sign a Non-Disclosure Agreement  He does not think they will make it back to Earth alive  He will be observing an inside job meant to protect the crew