The effect of Doppler rate on small aperture bearing estimation

2016 ◽  
Vol 139 (4) ◽  
pp. 2020-2020 ◽  
Author(s):  
David C. Swanson ◽  
Robert L. Culver
Keyword(s):  
Small Aperture ◽  
Bearing Estimation

Detection and source parameterization of small-energy fireball events in Western Alps with ground-based infrasonic arrays

2021 ◽  
Author(s):  
Giacomo Belli ◽  
Emanuele Pace ◽  
Emanuele Marchetti
Keyword(s):  
Western Alps ◽  
Apparent Velocity ◽  
Array Analysis ◽  
Small Energy ◽  
Small Aperture ◽  
Energy Estimation ◽  
Trajectory Reconstruction ◽  
Tnt Equivalent ◽  
Back Azimuth ◽  
Aperture Arrays

Summary We present infrasound signals generated by four fireball events occurred in Western Alps between 2016 and 2019 and that were recorded by small aperture arrays at source-to receiver distances < 300 km. Signals consist in a series of short-lived infrasonic arrivals that are closely spaced in time. Each arrival is identified as a cluster of detections with constant wave parameters (back-azimuth and apparent velocity), that change however from cluster to cluster. These arrivals are likely generated by multiple infrasonic sources (fragmentations or hypersonic flow) along the entry trajectory. We developed a method, based on 2D ray-tracing and on the independent optically determined time of the event, to locate the source position of the multiple arrivals from a single infrasonic array data and to reconstruct the 3D trajectory of a meteoroid in the Earth's atmosphere. The trajectories derived from infrasound array analysis are in excellent agreement with trajectories reconstructed from eyewitnesses reports for the four fireballs. Results suggest that the trajectory reconstruction is possible for meteoroid entries located up to ∼300 km from the array, with an accuracy that depends on the source-to-receiver distance and on the signal-to-noise level. We also estimate the energy of the four fireballs using three different empirical laws, based both on period and amplitude of recorded infrasonic signals, and discuss their applicability for the energy estimation of small energy fireball events ($\le 1{\rm{kt\,\,TNT\,\,equivalent}}$).

scholarly journals Ultraprecision grinding of small-aperture concave aspheric mould insert with tilt axis method

Procedia CIRP ◽  
2018 ◽  
Vol 71 ◽  
pp. 505-510 ◽  
Author(s):  
Guangpeng Yan ◽  
Kaiyuan You ◽  
Fengzhou Fang
Keyword(s):  
Mould Insert ◽  
Small Aperture ◽  
Tilt Axis

A New Method of Field Measurements for Small-Aperture Magnets

1991 ◽  
Vol 30 (Part 1, No. 9A) ◽  
pp. 2082-2084
Author(s):  
Mitsuo Kikuchi ◽  
Hisayoshi Nakayama
Keyword(s):  
Field Measurements ◽  
New Method ◽  
Small Aperture
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