An infrasound source analysis of the OSIRIS-REx sample return capsule hypersonic re-entry

TL;DR

This study leverages six ground-based infrasonic measurements from the OSIRIS-REx sample return capsule re-entry to test analytic and reduced-order sonic boom models. By coupling atmospheric ensembles with Mach-cone ray tracing and Burgers’ equation propagation, the work assesses Whitham, Carlson, and Tiegerman drag-dominated source models. The results show Carlson and especially the drag-dominated model yield predictions closest to observed overpressures, with propagation physics accounting for remaining discrepancies, highlighting the value of simplified models for high-altitude infrasonic sources. The findings inform future SRC observation campaigns and advance understanding of high-altitude sonic-boom source mechanisms.

Abstract

The OSIRIS-REx sample return capsule hypersonic re-entry into the atmosphere is a rare opportunity to test a variety of sonic boom source models since the projectile dimensions are well characterized. While the as-flown flight path is unknown, the predicted flight path enables a rough approximation of the source Mach number and location. Six infrasound microphones deployed in the boom carpet along the predicted flight path recorded impulsive signals from the OSIRIS-REx re-entry. Using a suite of atmosphere profiles and the geometric acoustics approximation, we estimate locations with uncertainty estimates along the flight path from which the signals were emitted. Acoustic overpressure and signal duration predictions from Whitham's far field theory, Carlson's simplified sonic boom prediction method, and a drag-dominated hypersonic model are analyzed with uncertainty estimates from the location estimate. While the Carlson simplified sonic boom prediction method could be accurate, our preference is for the drag-dominated source model. Using this source model with an inviscid Burgers' equation solver for propagation, we obtained an excellent match to the recorded data. These results will help better inform future sample return capsule re-entry observation campaigns as well as contribute to a better understanding of high altitude infrasonic sources.

Figures (9)

• Figure 1: (A) Location of Eureka, NV with deployed microphone locations (black triangles), the post-flight simulated trajectory (thick black line; Francis2024), and the ensonified region predicted from InfraGABlom2024_MachCone. The arrows along the trajectory denote the direction of motion. Ray piercing points are shaded by the predicted propagation time, and the thin black lines denote isochrones. The elliptical isochronic regions indicate that the source is descending through the atmosphere. Ray paths with turning heights above 120.0 km, which would form additional boom carpets, are not shown. This simulation used the Naval Research Laboratory Ground-to-Space atmosphere profile at Eureka, NV on 09/24/2023 at 15:00:00 UTC. The adiabatic sound speed and wind speeds (meridional and zonal) are shown in (B) and (C), respectively.
• Figure 2: Microphone locations (black triangles) with recorded waveforms. (A) The Eureka Airport microphone geometry south of the simulated, post-flight trajectory (black line; Francis2024). (B) The Newark Valley infrasound microphones south of the predicted SRC trajectory. (C) The unfiltered, recorded waveforms at OREXA - OREXF. Note that the y-axis scale bar is different between the two locations.
• Figure 3: Array processing results from stations OREXA, OREXB, and OREXC (Figure \ref{['fig:stns']}A). (A) The unfiltered waveform from OREXA, which is replicated here from Figure \ref{['fig:stns']}C. (B) Estimated trace velocity v$_{tr}$ and (C) back azimuth $\theta$. Warmer colors denote a higher median of the cross correlation maxima (MdCCM) with cooler colors denoting a lower median cross correlation maxima value. The dotted region denotes the shock wave and the dash-dotted region denotes the turbulent wake signal. We note that there is a 0.25 second lag (half the window length) in the trace velocity and back azimuth times due to the use of overlapping, discrete time windows in the array processing.
• Figure 4: Ensembles of atmosphere sound speed and wind speed profiles for Eureka, Nevada. Panels (A) - (C) depict 100 realizations of (A) the adiabatic sound speed, (B) the zonal wind speed, and (C) the meridional wind speed. The dark, dashed lines in (A) - (C) show the profiles in Figures \ref{['fig:trajectory']}B and \ref{['fig:trajectory']}C for reference, and the horizontal dashed line denotes the altitude (approximately 30 km) when the modeled SRC speed drops below Mach 1.
• Figure 5: Estimates of N-wave source location for each station. (A) Latitude and (B) longitude probability density estimates $\pi_d$ with dashed gray lines denoting one standard deviation around the mean values for OREXA and OREXD. (C) Map view of the trajectory with station locations (markers) and example eigenrays to OREXA and OREXD. One standard deviation latitude and longitude locations in (A) and (B) are denoted with gray boxes. (D) Vertical transect projected along longitude of the eigenrays in (C). The bottom axis in blue shows the OREXA longitudes, and the top axis in red denotes the OREXD longitudes with the trajectory in this region shown as a dashed line. (E) Altitude probability density estimates $\pi_d$ with the Mach numbers predicted by the post-flight trajectory with one deviation around the OREXA and OREXD mean values. The colors for each sensor are the same across (A) through (E), and the arrows along the trajectories denote the direction of motion.