Voyager 2 Uranus Plasma Wave Spectrometer (PWS) Edited, Uncalibrated Spectrum Analyzer, Version 1.0, 4 s Reduced Data Record (RDR) Data

* Data Set Overview\n* =================\n\nThis Data Set consists of 4 s edited, Wave Electric Field Intensities from the Voyager 2 Plasma Wave Receiver Spectrum Analyzer obtained in the Vicinity of the Uranian Magnetosphere. For each 4 s Interval, a Field Strength is determined for each of the sixteen Spectrum Analyzer Channels whose Center Frequencies range from 10 Hz to 56.2 kHz and which are logarithmically spaced in Frequency, four Channels per Decade. The Time associated with each Set of Intensities (sixteen Channels) is the Time of the Beginning of the Scan. During Data Gaps where complete 4 s Spectra are missing, no Entries exist in the File, that is, the Gaps are not Zero-filled or Tagged in any other way. When one or more Channels are missing within a Scan, the missing Measurements are Zero-filled. Data are edited but not calibrated. The Data Numbers in this Data Set can be plotted in raw Form for Event Searches and simple Trend Analysis since they are roughly proportional to the Log of the Electric Field Strength. Calibration Procedures and Tables are provided for use with this Data Set; the use of these is described below.\n\n* Use of Voyager PWS Calibration Tables\n* =====================================\n\nThe Voyager PWS Calibration Tables are given in two plain ASCII Text Files named VG1PWSCL.TAB and VG2PWSCL.TAB (for Voyager 1 and Voyager 2, respectively). These provide Information to convert the uncalibrated 'Data Number' Output of the PWS sixteen-channel Spectrum Analyzer to calibrated Antenna Voltages for each Frequency Channel. Following is a brief Description of these Files and a Tutorial in their Application.\n\nThe first Column lists an uncalibrated Data Number followed by the corresponding Value in calibrated Volts for each of the sixteen Frequency Channels of the PWS Spectrum Analyzer. Each Line contains Calibrations for successive Data Number Values ranging from 0 through 255. (Data Number 0 actually represents the Lack of Data since the Baseline Noise Values for each Channel are all above that.)\n\nA Data Analysis Program may load the appropriate Table into a Data Structure and thus provide a simple Look-up Scheme to obtain the appropriate Voltage for a given Data Number and Frequency Channel. For example, the following VAX FORTRAN Code may be used to load a Calibration Array for Voyager 2 PWS:\n\n* real*4 cal(16,0:255)\n* open(unit=10,file='vg2pwscl.tab'status='old'\n*\n* do i=0,38\n* read(10,*) ! Skip 38 Lines of Label Info\n* end do\n*\n* do i=0,255\n* read(10,*) idn,(cal(ichan,i),ichan=1,16)\n* end do\n*\n* close(10)\n\nThen, given an uncalibrated Data Value idn for the Frequency Channel ichan, the corresponding calibrated Antenna Voltage would be given by the following Array Reference:\n\n* volts=cal(ichan,idn)\n\nThis may be converted to a Wave Electric Field Amplitude by dividing by the effective Antenna Length in meters, 7.07 m. That is:\n\n* efield=cal(ichan,idn)/7.07\n\nSpectral Density Units may be obtained by dividing the Square of the Electric Field Value by the nominal Frequency Bandwidth of the corresponding Spectrum Analyzer Channel.\n\n* specdens=(cal(ichan,idn)/7.07)^2/bandwidth(ichan)\n\nFinally, Power Flux may be obtained by dividing the Spectral Density by the Impedance of Free Space in Ohms:\n\n* pwrflux=((cal(ichan,idn)/7.07)^2/bandwidth(ichan))/376.73\n\nOf course, for a particular Application, it may be more efficient to apply the above Conversions to the Calibration Table directly.\n\nThe Center Frequencies and Bandwidths of each PWS Spectrum Analyzer Channel for the Voyager 2 PWS are given below:\n\n+----------------------------------------+\n| Channel | Center Frequency | Bandwidth |\n------------------------------------------\n| 1       | 10.0 Hz          | 2.16 Hz   |\n| 2       | 17.8 Hz          | 3.58 Hz   |\n| 3       | 31.1 Hz          | 4.50 Hz   |\n| 4       | 56.2 Hz          | 10.7 Hz   |\n| 5       | 100 Hz           | 13.8 Hz   |\n| 6       | 178 Hz           | 28.8 Hz   |\n| 7       | 311 Hz           | 39.8 Hz   |\n| 8       | 562 Hz           | 75.9 Hz   |\n| 9       | 1.00 kHz         | 75.9 Hz   |\n| 10      | 1.78 kHz         | 151 Hz    |\n| 11      | 3.11 kHz         | 324 Hz    |\n| 12      | 5.62 kHz         | 513 Hz    |\n| 13      | 10.0 kHz         | 832 Hz    |\n| 14      | 17.8 kHz         | 1260 Hz   |\n| 15      | 31.1 kHz         | 2400 Hz   |\n| 16      | 56.2 kHz         | 3800 Hz   |\n+----------------------------------------+\n\nA Failure in the Voyager 2 Flight Data System which occurred about three Months after Launch has adversely affected the Calibration of PWS Channels 9 through 16. An Algorithm has been devised to partially correct for this Failure, and has proven useful for Voyager 2 Jupiter, Saturn, and Uranus Encounters, but is not valid for Earth-Jupiter Cruise and may be modified in the Future. The following Implementation of this Correction Algorithm in VAX FORTRAN assumes that uncalibrated Data Numbers are stored in a sixteen-element Integer Array, idn, with the Array Index equal to the PWS Channel Number:\n\n* real*4 tonl(9:16) ! The Old Noise Level for v2\n* Data tonl/2.0,1.0,-1.0,-2.0,-3.0,1.0,2.0,1.0/\n*\n* do ichan=9,16\n* if(idn(ichan).gt.0) then\n* if(idn(ichan).lt.64) idn(ichan)=64\n* if(idn(ichan).le.72) then\n* idn(ichan)=int(tonl(ichan)-530.4+8.6*real(idn(ichan)))\n* else\n* idn(ichan)=int(tonl(ichan)+20.113+0.99*real(idn(ichan)))\n* end if\n* end if\n* end do\n\nThis Correction should not be applied permanently to the Voyager 2 Calibration Table since it is valid for a limited Time Span and may be modified in the Future.\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., 1986) and a complete Instrument Description can be found in (Scarf and Gurnett, 1977).\n\n+-------------------------------------------------------+\n| Parameter Characteristics      | Value                |\n---------------------------------------------------------\n| Sampling Parameter Name        | TIME                 |\n| Sampling Parameter Resolution  | 4.000000             |\n| Minimum Sampling Parameter     | 197708201553.000000  |\n| Maximum Sampling Parameter     | N/A                  |\n| Sampling Parameter Interval    | 4.000000             |\n| Minimum Available Sampling Int | 4.000000             |\n| Sampling Parameter Unit        | SECOND               |\n| Data Set Parameter Name        | PLASMA WAVE SPECTRUM |\n| Noise Level                    | 0.000005             |\n| Data Set Parameter Unit        | VOLT/METER           |\n+-------------------------------------------------------+

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