This science-fiction writer's designated task is to make intelligible to the layman the activities surrounding one major project in our space program. He succeeds admirably, because of his skills as a science-fact man, and his judicious inclusion of narrative, dialogue and the pace that has served him well in his novels. Popularizing usually connotes vulgarizing, but not so here. Great scientific and engineering feats become clear as Bester translates the jargon of harried performers into common language. He pays careful attention to Hogarth and Lindsay, the scientist-engineer team who direct the space probe OSO-I, from its conception through the trials of funding, construction, testing and launching. Their perseverance, endurance and sacrifice is part of the real story of our trek into space and the new exploration of the unknown.