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Robert C. Byrd Green Bank Telescope Inspection

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At 9:43 p.m. on Tuesday, November 15, 1988, the 300-ft radio telescope collapsed. The cause was a sudden failure of a key structural element – a large gusset plate in the box girder assembly that formed the main support for the antenna. The telescope’s loss was attributed to a lack of inspection and maintenance. Between 1991 and 2002, a replacement telescope was designed and constructed. It was no ordinary instrument. It was, in fact, the world’s largest fully steerable radio telescope. To help it avoid the same fate as its predecessor, the National Radio Astronomy Observatory sought the expertise of a structural engineering firm to develop an inspection plan and procedure for their new landmark telescope. The specs of the new telescope were awe-inspiring: a surface of 100 by 110 meters; a weight exceeding 16,000,000 pounds; and over 13,000 structural steel members and joints. Developing an inspection plan and executing an inspection appeared to be a daunting task.

Modjeski and Masters (M&M) was prepared for the challenge. We drew upon decades of steel bridge inspection experience and, with close collaboration with our client, developed an inspection plan and procedure. It ensures that all members of the structure are inspected. We also created a custom record-keeping database to use as the primary administrative tool for managing the inspection process, recording the inspection findings, and programming maintenance. That the National Radio Astronomy Observatory was satisfied with the results is evident. After completion of the inspection plan and program, they hired M&M to conduct multi-year inspections of the telescope.

Structure Geometry
Telescope Surface 100m x 110m
Weight 16,000,000 pounds
Viewing Area the entire sky above 5 degrees elevation

…We are pleased to have had the Modjeski and Masters crew inspect our telescope structure. In all cases they work with a level of professionalism, thoroughness, reliability and competence rarely seen these days. We cannot inspect the entire structure ourselves but we can rest assured that the telescope is sound because of the trustworthiness of the fine folks of M&M - Thanks for the peace of mind…

-Harry Morton, Technical Support Supervisor, National Radio Astronomy Observatory