Voyager 2 Neptune Plasma Wave Spectrometer (PWS) Raw Experiment Waveforms, Version 1.0, 60 ms Data

* Data Set Overview\n* =================\n\nThis Data Set consists of Electric Field Waveform Samples from the Voyager 2 Plasma Wave Receiver Waveform Receiver obtained during the Neptune Encounter. The Waveforms are Collections of 4-bit Samples of the Electric Field measured by the Dipole Electric Antenna at a Rate of 28,800 samples per second. A Set of 1600 Samples are collected in 55.56 ms followed by a 4.44 ms Gap. Each 60 ms Interval constitutes a Line of Waveform Samples. The Data Set includes about 271 Frames of Waveform Samples consisting of up to 800 Lines, each. The Telemetry Format for the Waveform Data is identical to that for Images, hence the use of Line and Frame as constructs in describing the Form of the Data. The Waveform is sampled through a Bandpass Filter with a Passband of 40 Hz to 12 kHz. The 4-bit Samples provide sixteen digital Values of the Electric Field with a linear Amplitude Scale, but the Amplitude Scale is arbitrary because of the Automatic Gain Control used in the Waveform Receiver. The instantaneous Dynamic Range afforded by the 4-bit samples is about 23 db, but the Automatic Gain Control allows the dominant Signal in the Passband to be set at the optimum Level to fit within the instantaneous Dynamic Range. With the Gain Control, the overall Dynamic Range of the Waveform Receiver is about 100 db. The Automatic Gain Control Gain Setting is not returned to the Ground, hence, there is no absolute Calibration for the Data. However, by comparing the Waveform Spectrum derived by Fourier transforming the Waveform to the Spectrum provided by the Spectrum Analyzer Data, an absolute Calibration may be obtained in most Cases. The Data may be plotted in raw Form to show the actual Waveform; this is useful for studying Events such as Dust Impacts on the Spacecraft. But the normal Method of analyzing the Waveform Data is by Fourier transforming the Samples from each Line to arrive at an Amplitude versus Frequency Spectrum. By stacking the Spectra side-by-side in Time Order, a Frequency-Time Spectrogram can be produced.\n\nAdditional Information about this Data Set and the Instrument which produced it can be found elsewhere in this Catalog. An Overview of the Data in this Data Set can be found in (Gurnett et al., 1989) and a complete Instrument Description can be found in (Scarf and Gurnett, 1977).\n\n* Parameters\n* ==========\n\n* Derived Parameters\n* ==================\n\n+-----------------------------------------------------------------------------------+\n| Parameter Characteristics           | Value                                       |\n-------------------------------------------------------------------------------------\n| Sampling Parameter Name             | TIME                                        |\n| Sampling Parameter Resolution       | 0.000034722 SECONDS                         |\n| Minimum Sampling Parameter          | N/A                                         |\n| Maximum Sampling Parameter          | N/A                                         |\n| Sampling Parameter Interval         | 0.000034722 SECONDS                         |\n| Minimum Available Sampling Interval | 0.000034722 SECONDS                         |\n| Data Set Parameter Name             | PLASMA WAVE WAVEFORM                        |\n| Noise Level                         | 0.000005                                    |\n| Data Set Parameter Unit             | VOLT/METER (DATA NOT ABSOLUTELY CALIBRATED) |\n+-----------------------------------------------------------------------------------+\n\nPlasma Wave Waveform: A Plasma Wave Waveform is a Time Series of Measurements of the Electric or Magnetic Field Component of the Wave Spectrum taken through a Broadband Filter. The Temporal Sample Rate is normally such that Samples are made at more than twice the Analysis Filter Bandwidth. A typical Waveform will consist of the order of 1000 contiguous Samples of between 4 and 12 bits each. For a 10 kHz Analysis Bandwidth, the Sample Rate would normally be approximately 25 kHz or 25,000 samples per second. received, the Waveforms are typically Fourier transformed in order to provide an Amplitude versus Frequency Spectrum across the Analysis Bandwidth. The Sample Rate, then, is required to be at least a Factor of two greater than the Filter Bandwidth in order to avoid aliasing in the transformed Spectrum. The Spectra can be stacked side-by-side in Time to build a Frequency-Time Spectrogram (that is, Amplitude as a Function of Time and Frequency) in order to identify the temporal and spectral Variations in the Wave Spectrum. Alternately, the untransformed Time Series can be used to study the Details of the Waveform. This has been useful for measuring small-scale Structures in the Plasma and for identifying the Signature of micron-sized Dust Impacts on the Spacecraft.\n\n* Measured Parameters\n* ===================\n\nElectric Field Component: A measured Parameter equaling the Electric Field Strength (e.g. in mV/m) along a particular Axis Direction.\n\nWave Magnetic Field Intensity: A measured Parameter equaling the Magnetic Field Strength in a specific Frequency Passband (in MKS Unit: V/m) measured in a single Sensor or Antenna.\n\nWave Electric Field Intensity: A measured Parameter equaling the Electric Field Strength in a specific Frequency Passband (in MKS Unit: V/m) measured in a single Sensor or Antenna.\n\n* Processing\n* ==========\n\nThe Data Files in this Data Set were created using the CDREF

Tags: waves-passive
Organization: National Aeronautics and Space Administration