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