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.
NASA has developed a sensor suite to inspect the Space Shuttle Thermal Protection System while the Shuttle is flying in orbit. When the Space Shuttle returns to flight, it will carry a 3D Imaging Laser Radar as part of the sensor suite to observe the Thermal Protection System and indicate any damages that may need to be repaired before return to earth. The 3D laser sensor provides accurate images that include precise measurement of the depth of any flaws that may be present. This paper describes the 3D laser sensor for the next shuttle flight and indicates the remaining challenge to industry to provide a sensor that can be even more capable for future flights.
The Gemini, Apollo, and Space Shuttle astronauts have accomplished rendezvous and docking using navigation sensor technologies that were state-of-the-art in their days. However, new applications require more advanced technologies and a more capable, autonomous relative navigation sensor will be important for future space operations. Potential benefits include reduced crew training, reduced reliance on ground systems, and more operational flexibility. Additionally, new sensor technologies enable uncrewed automated operations in low earth orbit and beyond. New sensors can reduce or eliminate the need to augment target spacecraft with cooperative devices and thus provide for greater flexibility and enhanced mission success. This paper identifies a set of specific sensor capabilities for future space operations and describes a 3-D imaging ladar sensor conceptual design to provide those capabilities.