Plenoptic imaging of meteorite shape change during plasma wind tunnel experiments

Experimental meteors are produced by exposing samples of meteoritic material to an air plasma flow in an arcjet driven plasma wind tunnel facility, simulating the aerothermal conditions of an entry into the Earth's atmosphere. A plenoptic camera is used to record sequences of light field images during the tests, allowing for the first time to derive the transient evolution of the ablating and melting surface in three dimensions. Results are presented for samples of various meteorites, which show the potential of this technique for the volumetric analysis of the complex interaction between an extraterrestrial body and the upper atmosphere. Data allow to derive recession rates, heats of ablation and a shape factor, which has been redefined to meet the recorded information. Recession is found to be non-linear, with different rates for different meteorite types, with mean rates between 0.28 and 0.7 mm/s. Heats of ablation are not constant, but decrease during the experiment, with mean values between 1.7 and 10.1 MJ/kg. A fairly linear correlation is found between the materials' iron content and both the recession rate and the heat of ablation. Shape factors decrease with time and reach a plateau after about 3 s.