GRAB

Though only two of the five satellites made it into orbit, they returned a wealth of information on Soviet air defense radar capabilities as well as useful astronomical observations of the Sun. In 1957, the Soviet Union began deploying the S-75 Dvina surface-to-air missile, controlled by Fan Song fire control radars. The United States Air Force began a program of cataloging the rough location and individual operating frequencies of these radars, using electronic reconnaissance aircraft flying off the borders of the Soviet Union. This program provided information on radars on the periphery of the Soviet Union, but information on the sites in the interior of the country was lacking. Lorenzen promoted the idea within the Department of Defense , and six months later the concept was approved under the name "Tattletale".:?364?President Eisenhower approved full development of the program on 24 August 1959.:?4? When news of the project leaked in The New York Times, Eisenhower canceled the project. The project was restarted under the name "Walnut" after heightened security had been implemented, including greater oversight and restriction of access to "need-to-know" personnel.:?2? American space launches were not classified at the time, and a cover mission that would share the satellite bus with DYNO was desired to conceal DYNO's electronic surveillance mission from its intended targets.:?300? The study of the Sun's electromagnetic spectrum provided an ideal cover opportunity. The Navy had wanted to determine the role of solar flares in radio communications disruptions:?300? and the level of hazard to satellites and astronauts posed by ultraviolet and X-ray radiation.:?76? Such a study had not previously been possible, as the Earth's atmosphere blocks much of the Sun's X-ray and ultraviolet output from ground observation. A satellite was required for long-term, continuous study of the complete solar spectrum.:?5–6,?63–65? The NRL already had a purpose-built solar observatory in the form of Vanguard 3, which had been launched in 1959. Vanguard 3 had carried X-ray and ultraviolet detectors, though they had been completely saturated by the background radiation of the Van Allen radiation belt.:?63? Development of the DYNO satellite from the Vanguard design was managed by NRL engineer Martin Votaw, leading a team of Project Vanguard engineers and scientists who had not migrated to NASA. The SOLRAD experiment remained operational for ten months and it returned the first real-time X-ray and ultraviolet observations of the Sun. During the second launch attempt, the Thor booster shut down 12 seconds early, and the flight was subsequently terminated by range safety, raining fragments over Cuba. To ensure this did not happen again, subsequent launches from Cape Canaveral flew a dogleg trajectory to reach 70° inclination, avoiding the island nation. The other successful GRAB mission, GRAB 2, was launched 29 June 1961, atop the same Thor-Ablestar launch vehicle as Injun, a geophysical science satellite from the University of Iowa, and Transit 4A.