Modeling of Infrasound from the Space Shuttle Columbia Reentry
Robert Gibson and David Norris
BBN Technologies
Arlington, Virginia, USA
Infrasound Technology Workshop
La Jolla, California
27-30 Oct 2003
Work sponsored by Air Force Research Laboratory, Contract DTRA01-01-C-0084
Introduction
• Space Shuttle Columbia Reentry
– STS-107
• 01-Feb-2003
• Loss of orbiter– 1400 UT
– 0900 EST
– 0600 PST
• Nominal trajectory shown
• Infrasound observed at multiple arrays in North America
Columbia Investigation• Purpose of this presentation
– Explain the infrasound modeling conducted by BBN
– Present example results
• US Infrasound Working Group formed Feb 2003
– Part of the US DoD Columbia Investigation Support Team
– In support of NASA investigation
• Participants:– US Government: Army Research Lab, Los
Alamos National Lab, NOAA Environmental Technology Lab, Naval Research Lab
– Industry: BBN Technologies, Center for Monitoring Research (SAIC)
– Academia: Univ. of California-San Diego (L2A/Scripps), Univ. of Hawaii (ISLA), Univ. of Mississippi (NCPA)
Optical image, showing left wing damage
From AFRL, Kirtland AFB
Background
• Infrasound from supersonic bodies has been observed:
– Bolides– Concorde– Rockets (Apollo, Titan, Ariane, etc.)– Space shuttle launches and reentries
• BBN has used 3-d ray tracing to predict infrasound from Space Shuttle launches
– Favorable model vs. data comparisons– Orbiter ascent – Solid rocket booster reentry
• Ground truth events are of interest for validating or “calibrating” models
– Propagation models– Atmospheric characterizations
Shuttle Modeling Approach
• Source of infrasound is not impulsive, but continuous and moving
• Approximate moving source by modeling a series of discrete events, each with appropriate time delay
• Use 3-D ray tracing to find eigenrays from points on reentry trajectory to infrasound array
• Determine arrival time and azimuth for each eigenray
• Combine all predicted eigenray arrivals at each array
Example of eigenrays from one point on a launch trajectory to an
array location
Sources of Information
• Shuttle reentry trajectory– NASA, based on actual GPS
• Propagation model– InfraMAP tool kit (BBN)
– Implementation of HARPA 3-d ray tracing
• Environmental characterization– Assimilation of climatology with synoptic model output
– NRL-G2S (D. Drob, Naval Research Lab)
• Observations, for comparison– US and Canadian station operators
– Center for Monitoring Research (SAIC)
Columbia Trajectory and Arrays
Alt
itu
de
(km
)
Trajectory in white Arrays in red CPA’s in yellow
Examples of Model Results
• Results are shown for representative arrays– Short range (in sonic boom carpet)
– Medium range (100 – 1000 km)
– Long range (> 1000 km)
• Atmospheric profiles along propagation path– Variability along path
– Presence or absence of stratospheric duct
• Typical ray paths
• Azimuth vs. time– Color coded by source location
• Apparent velocity vs. azimuth (polar plot)– Color coded by signal arrival time
Station List
Time of Closest Approach (h:m:s) UT
Distance of Closest Approach (km)
Array Code
Location
13:54:17 1121 I56US Newport, WA 13:54:33 30 NVIAR Mina, NV 13:55:15 460 I57US Pinon Flat, CA 13:55:39 29 SGAR St. George, UT 13:56:00 683 PDIAR Pinedale, WY 13:57:12 540 NOAA Boulder, CO 13:57:23 65 DLIAR Los Alamos, NM 13:57:44 1857 IS10 Lac du Bonnet, Man. 13:57:43 271 WSMR White Sands, NM 13:58:58 528 TXIAR Lajitas, TX
St. George, UT(CPA range =~ 23 km)
Environmental Variability - SGAR
Atmospheric Characterizations from D. Drob, NRL
Lajitas, TX(CPA range =~ 522 km)
Environmental Variability - TXIAR
Atmospheric Characterizations from D. Drob, NRL
Lac du Bonnet, Manitoba(CPA range =~ 1864 km)
Environmental Variability – IS10
Atmospheric Characterizations from D. Drob, NRL
Typical Ray Path: SGAR
St. George, UT
Typical Ray Paths: TXIAR
Lajitas, TX
Typical Ray Paths: IS10
Lac du Bonnet, Manitoba
Azimuth vs. Time - SGAR
Azimuth vs. Time - TXIAR
Azimuth vs. Time - IS10
Polar Plot – TXIAR(model)
PMCC analysis of observed data from Garces and Hetzer, U. Hawaii (ISLA),“Summary of infrasonic detections and propagation modeling estimates associated with the Columbia reentry of Februrary 1, 2003,” March 2003
Polar Plot – TXIAR(data)
Model vs. Data for Pinon Flat (IS57)
Data analysis by BBN using InfraTool; Passband: 1-8 Hz
Rec
eive
r az
imut
h (d
eg)
gmt (hr:min:sec)
Conclusions
• Model results largely consistent with reentry trajectory– Arrival time
– Azimuth
– Apparent velocity
• Supersonic events with ground truth trajectories represent useful validation sources for infrasound modeling techniques
• “Modeling of the effects of atmospheric propagation was fairly successful … but does not account for all of the signal complexity at the more distant stations”
– From “Report to the Department of Defense on Infrasonic Re-Entry Signals from the Space Shuttle Columbia (STS-107),” ed. by H. Bass, 04-June-2003
