HR: 10:20h
AN: AE42A-01    [Abstracts]
TI: VHF Broadband Digital Interferometer on Panel Extension Satellite
AU: * Kawasaki, Z
EM: zen@comm.eng.osaka-u.ac.jp
AF: Osaka University, 2-1 Yamada-oka, Suita, 5650871 Japan
AU: Morimoto, T
EM: morimoto@comf5.comm.eng.osaka-u.ac.jp
AF: Osaka University, 2-1 Yamada-oka, Suita, 5650871 Japan
AU: Ushio, T
EM: ushio@aero.osakafu-u.ac.jp
AF: Osaka Prefecture University, 1-1 Gakuencho, Sakai, 5997531 Japan
AU: Nakasuka, S
EM: nakasuka@space.t.u-tokyo.jp
AF: University of Tokyo, 7-3-1 Hongo, Bunkyo, 1138656 Japan
AU: Aoki, T
EM: aoki.cop@sage.ocn.ne.jp
AF: SOHOLA, 50-5 Aramoto-kita, Higashi-oska, 577011 Japan
AB: {\br INTRODUCTION} The usefulness of thunderstorm observations from space has been shown by Tropical Rainfall Measuring Mission (TRMM) satellite. As one of the principal organizations of Lightning Imaging Sensor (LIS) on TRMM, {\it Lightning Research Group of Osaka University} (LRG-OU) demonstrates the universal power-five law between lightning activity and thunderstorm snow depth. _eSnow depth_f means the height of cloud top from the freezing level, and it is unveiled to be a key index of the thunderstorm activity. LRG-OU also demonstrates less lightning activity over East asia during El Ni\~{n}o period than the ordinary period. Los Alamos Science Team is concerned with VHF observations by Fast On-orbit Recording of Transient Events (FORTE) satellite. LRG-OU concludes that the combination of optical observations and VHF ones is complementary each other, and join the {\br {\it SOHLA Satellite Project}} . This is a preliminary report how our team plans the VHF observations from space. {\br VHF BROADBAND DIGITAL INTERFEROMETRY} LRG-OU has been developing a VHF Broadband Digital Interferometer (DITF) to image precise lightning channels and monitor lightning activity widely. The feature of broadband DITF is its bandwidth (from 25MHz to 100MHz). The principle of the DITF is direction-of-arrival (DOA) estimation for electromagnetic (EM) wave caused by lightning discharges from the phase differences between EM signals captured by antenna array. This procedure is applied to all Fourier components of VHF broadband EM pulses. In other words, a few tens Fourier components are contribute to obtain one VHF source location, and this _e{\br implicit redundancy}_f is the noticeable superiority to any other source location techniques. It is well known that one lightning flash emits a few thousands of VHF impulses, and imaging VHF source train could give us the development of lightning discharges. According to the previous observations and numerical calculations the accuracy of 0.01 radians may be feasible. It is noticed that a few meters base line may present the sufficient accuracy for source locations. The time resolution is also enough to discriminate the branching of the lightning channel. Because of the advantage of the DITF it may be cleaver to equip on a satellite. {\br PETSAT AND VHF BROADBAD DITF} Panel Extension Satellite (PETSAT) may consist of ten and a few of independent panels. Each panel will be designed to own individual function and the configuration of PETSAT is adjustable depending on the objectives. Since it is shown that the short baseline of DITF could accomplish the high time and space resolutions for VHF source locations, we can reach an idea of VHF broadband DITF operation on PETSAT. PETSAT is planed to be a low altitude satellite about several hundred kilometers from the ground, and the locations accuracy of 0.01 radians may provide us the sufficient and unique opportunity to discriminate between the active thunderclouds from non active ones by satellite observations. We are expecting to launch PETSAT by 2007.
DE: 1694 Instruments and techniques
DE: 1640 Remote sensing
DE: 0604 Antenna arrays
DE: 0694 Instrumentation and techniques
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting