The Deep Space Network (DSN) is a National Aeronautics and Space Administration (NASA) entity managed, technically directed, and operated by the Jet Propulsion Laboratory (JPL) of the California Institute of Technology (Caltech). Designed to maintain communications with spacecraft, the DSN consists of three facilities spaced equidistant from each other—about 120 degrees apart in longitude—around the world. These sites are near Barstow, CA; Madrid, Spain; and Canberra, Australia.
An antenna pedestal recently constructed at the Canberra Deep Space Communications Complex is the subject of this article. The pedestal is a cylindrical structure with a suspended roof slab. After the formwork had been removed, evidence of poor concrete consolidation was visible in the slab soffit. The general contractor contracted with several local testing firms to identify other deficiencies. These firms deployed ground penetrating radar (GPR) and ultrasonic pulse velocity (UPV) test methods, and they removed and tested concrete cores. However, they could find no correlation between the results of the core tests and the observations made using nondestructive test methods. Due to the inconsistency of the results, JPL decided to conduct its own investigation. CTLGroup, Skokie, IL, was contracted to conduct the investigation using alternative nondestructive test methods.
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