Evaluation of atmospheric characterizations by modeling observed events using ground truth
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Evaluation of Atmospheric Characterizations by Modeling Observed Events Using Ground Truth. Robert Gibson and David Norris BBN Technologies Arlington, Virginia USA Infrasound Technology Workshop Kailua-Kona, Hawaii 12-15 November 2001 Sponsored by the U.S. Defense Threat Reduction Agency

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Evaluation of Atmospheric Characterizations by Modeling Observed Events Using Ground Truth

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Evaluation of atmospheric characterizations by modeling observed events using ground truth

Evaluation of Atmospheric Characterizations by Modeling Observed Events Using Ground Truth

Robert Gibson and David Norris

BBN Technologies

Arlington, Virginia USA

Infrasound Technology Workshop

Kailua-Kona, Hawaii

12-15 November 2001

Sponsored by the U.S. Defense Threat Reduction Agency

Contract No. DTRA01-01-C-0084


Inframap objectives

InfraMAP Objectives

  • Integrate the software tools needed to perform infrasound propagation modeling

  • Define the state of the atmosphere (temperature, wind) as required for input to propagation models

  • Predict phases (travel times, bearings, amplitudes) from atmospheric explosions as measured by infrasound sensors

  • Apply tools to support nuclear explosion monitoring R&D and resolve operational issues

    • environmental variability and propagation sensitivity

    • prediction of localization area of uncertainty and detection performance

    • performance model of an infrasound network


Inframap

InfraMAP


Environmental analysis

Environmental Analysis


Propagation analysis

Propagation Analysis


Inframap software schematic

InfraMAP Software Schematic

Azimuth Deviation

Travel Time

Elevation Angle

Attenuation

Synthetic Waveform

from modes

Variability Statistics

Propagation

Environment

GUI

GUI

Date

Time

Latitude

Longitude

Altitude

Environmental

Characterization

  • MSIS-90

  • HWM-93

  • User-defined profile

  • Environmental Variability

Propagation

Modeling

Near-Real-Time Updates

  • NRL-MSIS-00

  • NRL-HWM-02

  • Next Generation Model

Model

Parameters

Source Localization

Area of Uncertainty

Network Performance

Synthetic Phases

from rays

  • Ray Tracing

  • Normal Mode

  • Parabolic Equation

  • Model-based assimilation

  • In-situ measurements

  • Solar/Magnetic parameters

Network Performance

Modeling

GUI

GUI


Development and applications

Development and Applications

  • Incorporate updated atmospheric characterizations

    • Determine required spatial and temporal resolutions

    • Evaluate best available sources

    • Conduct sensitivity studies

  • Model observed infrasound events

    • Obtain ground truth source location

    • Compare model results with observations

    • Assess quality of atmospheric characterization

  • Examples:

    • 23-Apr-01 Pacific Bolide

    • Space Shuttle launches from Kennedy Space Center


Radiosondes and climatology

Radiosondes and Climatology

  • Example: Temperature profiles from seven radiosondes in SW USA


Synoptic model and climatology

Synoptic Model and Climatology

NOGAPS Meridional

NOGAPS Zonal

  • Example: Wind profiles over 7 by 6 degree grid in SW USA


Daily solar flux f10 7 for 1998

Daily Solar Flux, F10.7 (for 1998)

  • Solar flux and geomagnetic disturbance can affect infrasound propagation in the thermosphere

    • F10.7 is the daily solar radio flux at 10.7 cm wavelength, adjusted to 1 AU


Pacific bolide 23 apr 01

Pacific Bolide: 23-Apr-01

IS10

SGAR

DLIAR

IS57

IS59

  • Impulsive infrasound event detected at multiple stations

  • Nominal event location shown

  • Five stations used in localization analysis

  • Propagation through modeled atmosphere

    • Empirical characterizations

    • Spline through radiosondes


Spectrograms at two stations

Spectrograms at Two Stations

  • Pacific event, 23-Apr-2001; One hour of data shown


Localization procedure

Localization Procedure

Shoot rays back from each array:

Launch rays at mean observed azimuth.

Fan of rays in elevation.

“Reverse Propagation”

Initial location estimate from ray intersections:

Estimate range, travel times, signal velocities.

See rays in figure below.

Predict event time using each array:

(Arrival time – travel time).

Range of travel times determined by ray trace.

Identify Eigenrays from estimated location to each array

Revise location estimate

Perturb location to improve consistency in event time

Result of two iterations shown


Estimated source location

Estimated Source Location

From

IS10

From

SGAR

IR / Visible

(Satellites, 22 May)

27.90 N, 133.89 W

From

DLIAR

Estimated Event Location

(BBN, 18 May)

28.6 N, 134.1 W

From

IS57

From

IS59

  • Pacific event, 23-Apr-2001; Initial bundles of rays are shown

    • Predicted location and reported ground truth are shown


Radiosonde locations 23 apr 01

Radiosonde Locations: 23-Apr-01

Latitude (deg)

Longitude (deg)

Blue diamonds indicate radiosonde locations

Data from circled radiosondes are shown

Green Triangles are infrasound stations

Source

Location


Radiosondes and climatology 23 apr 01

Radiosondes and Climatology: 23-Apr-01

IS10 Path: Temperature

DLIAR Path: Temperature

IS59 Path: Temperature


Radiosondes and climatology 23 apr 011

Radiosondes and Climatology: 23-Apr-01

IS10 Path: Zonal

IS59 Path: Zonal

DLIAR Path: Zonal

IS10 Path: Meridional

DLIAR Path: Meridional

IS59 Path: Meridional


Source location using in situ data

Source Location Using In Situ Data

From

IS10

From

SGAR

IR / Visible

(Satellites, 22 May)

27.90 N, 133.89 W

From

IS57

Estimated Event Location

(BBN, w/ radiosondes)

28.7 N, 134.6 W

From

DLIAR

From

IS59

  • Pacific event, 23-Apr-2001; Initial bundles of rays are shown

    • Ray projections shown use shooting method, not eigenrays

  • Localization shifted toward west


Space shuttle importance of trajectory

Space Shuttle - Importance of Trajectory

  • Infrasound from Saturn V and other rockets was observed and studied in the 60’s and 70’s

    • Lamont-Doherty, Palisades, NY

    • US Army, Ft Monmouth, NJ

  • Energy arrived in two bundles with different azimuths

  • Two source regions were identified

    • Rocket ascent

    • First stage descent

  • Trajectory must be understood in order to model source

Typical Space Shuttle Ascent trajectory (alt. vs. time)

for orbiter and solid rocket boosters


Space shuttle trajectories

Space Shuttle Trajectories

& -88

  • Space shuttle trajectory depends on desired orbit

  • Two typical mission trajectories are shown

  • Example presented follows more northern trajectory

    • STS-96

    • STS-88

  • Shuttle reaches supersonic velocity approximately 1 minute after launch

  • Main engine cutoff occurs at 8.5 minutes after launch

Trajectories determined using

commercially available modeling software


Shuttle modeling approach

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 launch trajectory to infrasound array

    • Orbiter

    • Solid rocket boosters (SRB)

  • Determine arrival time and azimuth for each eigenray

Example of eigenrays from one point on trajectory to array location


Shuttle comparison at los alamos

Shuttle – Comparison at Los Alamos


Conclusions

Conclusions

  • Software models have been successfully used to predict travel time and bearing biases for atmospheric infrasound.

  • Empirical atmospheric models are adequate for many scenarios, but not all.

    • In situ measurements demonstrate high variability of winds

  • Software development underway to incorporate updated atmospheric characterizations in InfraMAP.

  • Bolides and rocket launches are examples of model calibration sources, since ground truth may be available.

  • Pacific bolide example indicates complexity of modeling issues.

  • Space shuttle launches are a promising source of ongoing calibration data to validate environmental characterizations.


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