An essential part of the experiment complement on GEOTAIL is the Plasma Wave Instrument (PWI) for which Professor Hiroshi Matsumoto of Kyoto University is Principal Investigator. The three major components of the GEOTAIL PWI are the Multi-Channel Analyzer (MCA), the Sweep Frequency Analyzer (SFA) and the Waveform Capture (WFC) system. The MCA includes a 20-channel Electric Spectrum Analyzer covering the frequency range from 5.6 Hz to 311 kHz with broadband filters spaced logarithmically (four filters per decade in frequency) and a 14-channel Magnetic Spectrum Analyzer covering the frequency range from 5.6 Hz to 10 kHz with identical filters. The SFA has five electric bands (Band 1: 25 Hz to 200 Hz, Band 2: 200 Hz to 1.6 kHz, Band 3: 1.6 kHz to 12.5 kHz, Band 4: 12.5 kHz to 100 kHz and Band 5: 100 kHz to 800 kHz). The SFA has three magnetic bands identical to the electric bands 1, 2, and 3. Each band has 128 steps spaced linearly in frequency. The sweep rate is 128 steps in 64 seconds for bands 1 and 2 and 8 seconds for bands 3, 4, and 5. The WFC system measures the waveform from the three magnetic search coil sensors and the two electric antennae at a rate of 12000 samples per second for each component. The WFC provides spectra from 10 Hz to 4 kHz. A detailed description of the entire PWI experiment and the initial results are contained in Matsumoto et al., [1994]*. The United States National Aeronautics and Space Administration (NASA) provided the Multi-Channel Analyzer (MCA) portion of PWI under contract to The University of Iowa for which Dr. Roger R. Anderson is Principal Investigator and U. S. Lead Investigator for the U. S. GEOTAIL MCA Investigation. Dr. Anderson is a Co-Investigator on the GEOTAIL PWI. Dr. Anderson has two Co-Investigators on the U. S. GEOTAIL MCA Investigation: Professor Donald A. Gurnett of The University of Iowa and Dr. William W. L. Taylor of Hughes STX Corporation.
*Matsumoto, H., I. Nagano, R. R. Anderson, H. Kojima, K. Hashimoto, M. Tsutsui, T. Okada, I. Kimura, Y. Omura, and M. Okada, Plasma wave observations with GEOTAIL spacecraft, J. Geomag. Geoelectr., 46, 59-95, 1994.
All parts of the GEOTAIL Plasma Wave Instrument including the MCA, the Sweep Frequency Analyzer (SFA) and the Waveform Capture (WFC) system have operated perfectly since the GEOTAIL launch on July 24, 1992. The WANT (Wire ANTenna) and PANT (Probe ANTenna) electric antennas were each successfully deployed on August 27, 1992, to their 100 meter tip-to-tip lengths. The MAST antennas for the Flux-gate and Search Coil magnetometers were deployed to their full lengths on September 16, 1992. Nearly continuous low-bit-rate Editor-B tape-recorded data (complete 20-channel Electric and 14-Channel Magnetic spectra every 1/2 second from the MCA and 5-Band Electric and 3-Band Magnetic spectra every 8 to 64 seconds from the SFA) have been acquired from the GEOTAIL PWI since early September, 1992. Approximately eight hours per day of high-bit-rate Editor-A Real Time data (complete Electric and Magnetic spectra every 1/4 second from the MCA, 5-Band Electric and 3-Band Magnetic spectra every 8 to 64 seconds from the SFA, and 8.7 seconds of 5-Component WFC data every 275 seconds) have also been accumulated since early September, 1992. Many new interesting phenomena have been detected during these orbits using the PWI MCA, SFA, and WFC measurements. It is important to note that the three PWI systems are quite complementary to each other. The MCA provides continuous high-time resolution with broad frequency resolution while the PWI SFA provides high-frequency resolution but coarse time resolution. Another advantage of the MCA is that it measures down to 5 Hz while the SFA begins at 24 Hz. The low frequency range of the MCA has provided an abundant amount of interesting electromagnetic data in the 5 Hz to 20 Hz range not reachable by the SFA. Data from both the MCA and SFA can be used to identify periods from which the PWI WaveForm Capture (WFC) data analysis efforts should be concentrated. The WFC provides both high-time resolution and high-frequency resolution but only for very limited periods.
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