Non-Intrusive Optical Diagnostics for Ground Test Facilities and Flight/Space Applications

Non-intrusive measurement techniques are a vital tool for researchers aiming to understand the underlying flow physics of aircraft and spacecraft during both ground wind tunnel testing and in situ flight testing. This seminar will discuss several of these diagnostics currently in use at NASA Langley Research Center. First, the development of several variants of Focused Laser Differential Interferometry (FLDI) are discussed, with an emphasis on high frequency flow fluctuation measurements for boundary layer transition at hypersonic wind tunnels such as the 20-Inch Mach 6 and 31-Inch Mach 10 tunnels. Second, the addition of an absorption spectroscopy system into the FLDI system will be introduced, allowing for simultaneous mean flow property (pressure, temperature, species concentration) and flow fluctuation measurements. Third, the invention of the self-aligned focusing schlieren (SAFS) system will be detailed, along with an overview of its applications at many ground test facilities including NASA Langley’s 20-Inch Mach 6, 31-Inch Mach 10, 0.3-M Transonic Cryogenic Tunnel (0.3-M TCT), National Transonic Facility (NTF), Transonic Dynamics Tunnel (TDT), NASA Ames’ National Full-Scale Aerodynamics Complex (NFAC), and the University of Virginia Supersonic Combustion Facility (UVASCF). Several exciting versions of the SAFS system and the current state-of-the-art will also be outlined, including digital SAFS, Scheimpflug configurations, spectral-spatial SAFS, plenoptic SAFS, event-based SAFS, and aminiaturized system developed for flight on an F-15 aircraft. Finally, a brief overview will be given of the recent landing (March 2025) of the Firefly Blue Ghost lander on the Moon, specifically about the Stereo Cameras for Lunar Plume-Surface Studies (SCALPSS) payload and the science results that are anticipated from the images acquired during and after landing. I will also discuss my path from undergraduate, through graduate school, and to my current position, along with information for those interested in internship opportunities.

Dr. Joshua Weisberger is a research engineer at NASA Langley Research Center in the Advanced Measurements and Data Systems Branch. He earned his BS in Mechanical and Aerospace Engineering in 2012, followed by his MS (2015) and PhD (2020) in Aerospace Engineering, all at the University at Buffalo. He has been working at NASA Langley since 2018, first as a Pathways Intern (2018-2020) and currently as a Civil Servant. His research interests include the development of non-intrusive optical and laser diagnostics, and their application at various wind tunnels and ground test facilities, and for flight vehicles and spacecraft. He has received two NASA Group Achievement Awards, a NASA Space Flight Awareness Team Award, recognition for the HJE Reid Award for best research publication at NASA Langley (3rd place in 2021, 2nd place in 2023), and 1st place in 2022 and 2025 for the AIAA Hampton Roads Section Laurence J. Bement Young Professional Paper Competition. He was awarded NASA Langley CIF/IRAD funding in both 2021 and 2026 for development of advanced optical methods for lunar lander terrain mapping. Along with co-worker Dr. Brett Bathel, he holds five patents. One of these patents, the Self-Aligned Focusing Schlieren (SAFS) system, was highlighted by Optica in the July 2021 Spotlight on Optics and was an honorable mention for the 2024 NASA Associate Administrator Award. The SAFS system was recently awarded both the 2025 NASA Invention of the Year and the 2025 R&D 100 Award.