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The loss of Space Shuttle Columbia and her crew led to the creation of the Columbia Accident Investigation Board (CAIB), which concluded that a piece of external fuel tank insulating foam impacted the Shuttle’s wing leading edge. The foam created a hole in the reinforced carbon/carbon (RCC) insulating material which gravely compromised the Shuttle’s thermal protection system (TPS). In response to the CAIB recommendation, the upcoming Return to Flight Shuttle Mission (STS-114) NASA will include a Shuttle deployed sensor suite which, among other sensors, will include two laser sensing systems, Sandia National Lab’s Laser Dynamic Range Imager (LDRI) and Neptec’s Laser Camera System (LCS) to collect 3-D imagery of the Shuttle’s exterior. Herein is described a ground-based statistical testing procedure that will be used by NASA as part of a damage detection performance assessment studying the performance of each of the two laser radar systems in detecting and identifying impact damage to the Shuttle. A statistical framework based on binomial and Bayesian statistics is used to describe the probability of detection and associated statistical confidence. A mock-up of a section of Shuttle wing RCC with interchangeable panels includes a random pattern of 1/4” and 1” diameter holes on the simulated RCC panels and is cataloged prior to double-blind testing. A team of ladar sensor operators will acquire laser radar imagery of the wing mock-up using a robotic platform in a laboratory at Johnson Space Center to execute linear image scans of the wing mock-up. The test matrix will vary robotic platform motion to simulate boom wobble and alter lighting and background conditions at the 6.5 foot and 10 foot sensor-wing stand-off distances to be used on orbit. A separate team of image analysts will process and review the data and characterize and record the damage that is found. A suite of software programs has been developed to support hole location definition, damage disposition recording, statistical data analysis and results presentation. The result of the statistical analysis will provide a quantitative indication of the laboratory performance of the ladar systems in the role of through hole damage detection.
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