Systems Check

Milton Garces and Claus HetzerInfrasound Laboratory, University of Hawaii, Manoa

PMCC analyses of signals from the North American and Pacific Infrasound Network

2003 Infrasound Technology Workshop, San Diego, California

Outline• Apply Progressive Multiple Channel Correlation (PMCC)

detector to various events and array geometries

• Bolides, microbaroms, aircraft, surf, volcanoes, and Columbia reentry for small aperture and large aperture arrays

PMCC: Consistency

• Define consistency threshold

• Can also define correlation filter

• Select different frequency bands

• Provides detailed frequency information

• Can add F-stat for further screening

Consistency is based on closure relationship for plane waves arriving on elements i,j,k:

tij+tjk+tki = 0

April 23, 2001

Automatic processing at IS59: OperationsPMCC Parameter HF Microbarom High-Speed VLF

Window Length 30 sec 90 sec 30 sec 300 sec

Window Overlap 5 sec 20 sec 5 sec 50 sec

Max Consistency 0.2 sec 0.5 sec 0.2 sec 5 sec

Passband 0.5-4.0 Hz 0.1-0.5 Hz 0.5-4.0 Hz 0.033-0.1 Hz

Trace Velocity 0.3-0.45 km/s 0.3-0.45 km/s 0.5-0.8 km/s 0.25-0.45 sec

Min # of Sensors 3 3 3 3

Max Interpixel Time Variation

2 x Window Overlap

2 x Window Overlap

2 x Window Overlap

2 x Window Overlap

Max Interpixel Frequency Variation

0.8 Hz 0.1 Hz 0.8 Hz 0.02

Max Interpixel Azimuth Variation

10 10 10 10

Max Interpixel Velocity Variation

10% 10% 10% 10%

ISLA Parameter

Correlation 0.6 0.7 N/A N/A

Family Size 14 N/A N/A N/A

Automatic processing at IS59Microbaroms

• 14415 arrivals, Jan 1-Oct 24

• Max consistency for im (0.1-0.5 Hz): 0.5 s

Microbaroms: blocking by topography

Portable Stations• Airport and coastline (19.7421 N, 156.05221 W)

Portable Station: Keahole Point• Airport and coastline

Surf• High Surf: Arrivals

Surf• High Surf: Arrivals

Surf• High Surf: Acoustic amplitude

Surf

Volcano infrasound

Sound timbre is determined by gas and/or lava composition, temperature, and speed, as well as by structure of conduit

Cookie Monster, Hawaii

Kuju, Japan

Volcano infrasound

Volcano infrasound

• Kilauea volcano: discovered continuous infrasonic vibration

Detector response to different array sites and configurations

• Columbia reentry STS-107

• Looked at 30s and 5s windows

STS-107 at NVIAR

• N-wave and later arrivals corresponding to approach

STS-107 at TXIAR

• No N-wave, multiple pulses from multipathing

STS-107 at SGAR

• Backazimuth points south of trajectory: February 1, 2003

Shuttle reentries with orbital declination of 39o

STS-78 at SGAR• N-wave, approach, and departure

• July 7, 1996 – Summer!

Concluding Remarks• PMCC detector can be optimized to find particular signal features

• Detector handles well different array geometries

• Yearly microbarom detections highlight shadow zones from topography and possible phase inconsistencies between Chaparral sensors

• Portable stations permit better source location and characterization

• STS-107 Columbia reentry over Western US detected by most of the N American Infrasound Network

• Tuned detector to search for relatively brief coherent bursts corresponding to the approach trajectory

• Infrasound from STS-107 does not appear to be much different from other Shuttle reentries with a similar orbital inclination

• Infrasonic studies are consistent with NASA’s interpretation