High-speed broadband radio interferometry for mapping and imaging - - PowerPoint PPT Presentation
High-speed broadband radio interferometry for mapping and imaging lightning Julia Tilles , Ningyu Liu Department of Physics/ Earth, Ocean, and Space Science Center, University of New Hampshire, Durham, NH In collaboration with New Mexico T ech
Julia Tilles, Ningyu Liu
Department of Physics/ Earth, Ocean, and Space Science Center, University of New Hampshire, Durham, NH In collaboration with New Mexico T ech lightning team and Kennedy Space Center
Frame rate: 35 kfps Time/frame: 28.8 µs Playback: 30 fps
High-speed video
1) Three VHF (INTF) antennas: measures dE/dt 20 – 80 MHz (roughly) used as INTF trigger 2) Fast antenna (FA): measures “fast-changing” E decay time constant τ = 100 μsec synchronized with VHF signals 3) DAQ: 16-bit @ 180 MSps (4 channels) pre-/post-trigger of 0.05/0.05 s (VHF trigger) or 1.5/1.5 s (SA trigger) 4) Slow antenna (SA): measures “slow-changing” E. decay time constant τ = 10 sec 24-bit continuously sampled @ 50 kSps used as INTF trigger
100 m
VHF antenna Electric fjeld sensor
Cosine plane
Cosine plane
Cosine plane
Az-El plane
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Frame rate: 130 kfps Time/frame: 7.6 µs Playback: 100 fps
High-speed video
Frame rate: 130 kfps Time/frame: 7.6 µs Playback: 4 fps
High-speed video
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Frame rate: 3.6 Mfps Time/frame: 0.3 µs Playback: 30 fps
High-speed VHFAzimuth angle
High-speed INTF map
Time/dot: 1.4 µs
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v = 105 m/s 50 m 50 µs
High-speed INTF map Narrow Bipolar Event (NBE)/ Fast positive breakdown (FPB)
High-speed INTF map Narrow Bipolar Event (NBE)/ Fast negative breakdown (FNB)
1) Can do meaningful science with three- antenna array. 2) Want better angular resolution sample higher frequencies/ use longer baselines. 3) Can only image/ map one point at a time / can’t resolve multiple sources need larger sample of u-v plane