The following are a few figures from the OSIRIS-REx re-entry rocket infrasound stations.

The purpose of this presentation is to compare the arrivals and reflections at 3 stations floating at 22.6, 21.2 and 26.9 km above sealevel. The OSIRIS rocket is traveling at 10 km/s, so it’s associated shock wavecan be considered to be a line source, i.e. a simple cylindrical wave propagation.

We would like to model the acoustic arrivals at these three stations given the topographic relief extracted from the ASTER data base.

The dark red numbers are the altitudes of the stations, the violet numbers are the altitudes of OSIRIS closest to the associated station. The stars indicate possible bounce-points for each balloon station, given height of OSIRIS and height of station.

knitr::include_graphics("./ProjectedBREX1topoIMG.png")

knitr::include_graphics("ProjectedBREX1topoCont.png")

The three acoustic traces are represented here following a 1Hz high-pass filter. The critical issue is the lack of a strong, high frequency arrival at Station BREX1 as compared to BREX2 and BREX3. I note that stations BREX3 had different microphone and digitizer configuration.

knitr::include_graphics("/Users/lees/Site/OSIRIS/JML/FIGS/ThreeBalloons.png")

The question is:

What happened to the reflected wave on BREX1?

I see that the source and the station are both located above steep mountain ranges. The hypothesis is that the reflected wave has been scattered by topographic variations, as opposed to stations BREX2 and BREX3, where the reflected signal arrives clearly.

We note that while BREX2 and BREX3 each have clear, impulsive, reflected wave arrivals at appropriate times, a low amplitude coda appears to follow. Possibly these are also topographic effects due to mountain ranges on either side of their respective locations relative to the OSIRIS line source.

I have a detailed interpolated topography of the area presented in the topo maps above. The data was extracted from ASTER and interpolated onto a (1000 by 1000) grid, about (35 by 46km). The topography varies from 1.78-3.13 km elevation.

Relavent parameters:

KMinfo = readRDS(file='KMinfo.RDS')

knitr::kable(KMinfo  )
sta stax stay staz srcx srcy srcz
BREX1 10.166 9.6159 22.6 5.0772 31.120 51.7
BREX2 16.719 26.1200 21.2 16.2820 34.965 50.7
BREX3 17.255 11.5700 26.9 11.7210 33.399 51.1