The reentry of spacecraft into the atmospheres of earth, Mars and other planetary bodies is characterized by hypersonic flows with real gas effects and tremendous heat loading. These conditions are simulated on the ground by arc jet facilities, such as the NASA Ames Interaction Heating Facility (IHF) arc jet. However, the flow produced in such ground test facilities is substantially different than at high altitudes, as a consequence of the arc plasma heating and non-equilibrium expansion process. We are developing a non-intrusive, laser-based diagnostic technique to determine temperature, velocity and Mach number in the free-stream flow. The technique is based on thermal acoustic wave (TAW) generation by laser heating deposition. An example of the acoustic wave generation process is exhibited in the figure at right, which shows the gas density profile around a region of heating generated by a focused femtosecond laser. Our research effort is focused on understanding the plasma-, fluid- and thermo- dynamics of this process and overcoming practical barriers to application. The successful completion of this project will result in an improved understanding of the non-equilibrium flow field, heat transfer and model uncertainties, ultimately improving the testing and design of advanced thermal protection systems developed by NASA and private industry.