INSTRUMENT DESCRIPTION

The Plasma Wave Instrument (PWI) on Dynamics Explorer 1 measured plasma wave phenomena and quasi-static electric fields using paired combinations of five PWI sensors: a 200m long wire electric antenna deployed in the spacecraft spin plane, an 8m tubular electric antenna deployed along the spacecraft spin axis, a short 0.6m electric antenna, mounted on the boom and oriented perpendicular to the long wire antenna, a magnetic loop antenna mounted on the boom and oriented to measure the component of the magnetic field perpendicular to the spin axis, and a magnetic search coil antenna, also mounted on the boom and oriented to measure the magnetic field parallel to the spacecraft spin axis.

The PWI consisted of a Step Frequency Correlator (SFC), a Low Frequency Correlator (LFC), a Wideband Analog Receiver (WBR) and a Linear Wave Receiver (LWR). The SFC consisted of two Step Frequency Receivers (SFR) which provided amplitude measurements of the electric and magnetic fields from 100 Hz to 400 kHz and in-phase and quadrature-phase correlations of signals from any selected pair of antennas. The LFC consisted of two spectrum analyzers, each with eight filters at 1.8, 3.1, 5.6, 10, 18, 31, 56, and 100 Hz. The LFC provided measurements comparable to the SFR, in the low frequency part of the spectrum. The WBR detected wideband analog waveform signals in 10 kHz or 40 kHz bandwidths with selectable lower band edges at .65, 31.25, 62.5, 125, 250, 500, 1000 or 2000 kHz. High resolution frequency-time analysis was performed on the wideband analog data at the University of Iowa. The LWR was designed to deliver continuous waveforms in the 1.5 - 16 kHz frequency range for high-resolution spectrum processing. For a detailed description of the Plasma Wave Instrument, the reader is referred to [S. D. Shawhan, D. A. Gurnett, D. L. Odem, R. A. Helliwell, and C. G. Park, The plasma wave and quasi-static electric field instrument (PWI) for Dynamics Explorer-A, Space Sci. Intrumen., 5, 535, 1981.]