Foreword: An Exploration-Driven Renaissance in Lunar Science

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In the 31⁄2 years between the first human lunar landing and the final launch, the Apollo engineering team enormously expanded the range and performance of surface systems and added orbital mapping capabilities. High-resolution cameras and a laser altimeter in the Service Module Bay photographed and profiled the lunar surface, including areas that might be future Apollo landing sites. A gamma ray spectrometer and an X-ray spectrometer provided data for construction of maps indicating the concentration of certain elements. In today’s mode of doing business, a similar systems evolution would take a decade or more. While the gains in surface mobility, astronaut EVA time, and precision landing were impressive and productive, the first geochemical (elemental) maps from the orbital spectrometers startled many planetary scientists. Those maps could be interpreted in terms of the rock types identified in the returned samples. In principle, scientists could begin to infer the geological evolution of a planet had the mapping been global. To that end, leaders in the lunar science community approached NASA about the addition of a small, unmanned polar orbiter mission. When the Administrator suggested that Apollo 17 could be an orbit-only mission, the conversation ceased. In 1973, the Manned Spacecraft Center (now the Johnson Space Center) submitted an unsolicited proposal to NASA Headquarters for an inexpensive lunar polar orbiter with only geochemical instruments, i.e., no cameras. The Office of Space Science was taken by surprise and eventually decided to compete the mission. Of the three NASA Centers that proposed, MSC had the most robust lunar science capability; but the evaluation board doubted that a human spaceflight center would be capable of cost containment on a small spacecraft project. The mission was first assigned to the Goddard Space Flight Center and, after a year of little progress, was transferred to the Jet Propulsion Laboratory. There, the mission acquired the designation Terrestrial Bodies Orbiter—Lunar (TBOL) to be consistent with the recently issued report of the Terrestrial Bodies Science Working Group. That advisory com-