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CDAWeb Served Heliophysics Datasets Beginning with 'V'

VG1_PWS_LR: Lowrate Plasma Waves Instrument - Bill Kurth (University of Iowa)
VG2_PWS_LR: Lowrate Plasma Waves Instrument - Bill Kurth (University of Iowa)
VOYAGER1_10S_MAG: 9.6 Second Averaged Interplanetary Magnetic Field - Norman F. Ness (Bartol Research Institute)
VOYAGER1_2S_MAG: 1.92 Second Averaged Interplanetary Magnetic Field - Norman F. Ness (Bartol Research Institute)
VOYAGER1_48S_MAG: 48 Second Averaged Interplanetary Magnetic Field - Norman F. Ness (Bartol Research Institute)
VOYAGER1_48S_MAG-VIM: Voyager1 Magnetic field VIM - Len Burlaga (NASA/GSFC)
VOYAGER1_COHO1HR_MERGED_MAG_PLASMA: Merged hourly magnetic field, plasma, proton fluxes, and ephemeris data - Norman F. Ness (Bartol Research Institute)
VOYAGER1_PLS_COMPOSITION: Voyager1, VIPER-Fit Plasma Ion Composition near Jupiter - Dr. John D. Richardson (MIT Kavli Institute)
VOYAGER1_PLS_HIRES_PLASMA_DATA: HiRes plasma data - John D. Richardson (Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology.)
VOYAGER2_10S_MAG: 9.6 Second Averaged Interplanetary Magnetic Field - Norman F. Ness (Bartol Research Institute)
VOYAGER2_2S_MAG: 1.92 Second Averaged Interplanetary Magnetic Field - Norman F. Ness (Bartol Research Institute)
VOYAGER2_48S_MAG: 48 Second Averaged Interplanetary Magnetic Field - Norman F. Ness (Bartol Research Institute)
VOYAGER2_48S_MAG-VIM: Voyager2 Magnetic field VIM - Len Burlaga (NASA/GSFC)
VOYAGER2_COHO1HR_MERGED_MAG_PLASMA: Voyager-2 merged hourly magnetic field, plasma, proton fluxes, and ephemeris data - N. Ness (MAG) and J. Richardson (PLS) (Bartol, MIT)
VOYAGER2_PLS_COMPOSITION: Voyager2, VIPER-Fit Plasma Ion Composition near Jupiter - Dr. John D. Richardson (MIT Kavli Institute)
VOYAGER2_PLS_HIRES_PLASMA_DATA: HiRes plasma data - John D. Richardson (Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology.)

VG1_PWS_LR
Description
  Data Set Overview
  =================
    This data set consists of electric field spectrum analyzer data
    from the Voyager 1 Plasma Wave Subsystem obtained during the
    entire mission.  Data after 2014-12-31 will be added to the archive
    on subsequent volumes.  The data set encompasses all spectrum
    analyzer observations obtained in the cruise mission phases
    before, between, and after the Jupiter and Saturn encounter phases
    as well as those obtained during the two encounter phases.
    The Voyager 1 spacecraft travels from Earth to beyond 100 AU over
    the course of this data set.  To provide some guidance on when
    some key events occurred during the mission, the following table
    is provided.
    Date         Event
    1977-09-05   Launch
    1979-02-28   First inbound bow shock crossing at Jupiter
    1979-03-22   Last outbound bow shock crossing at Jupiter
    1980-11-11   First inbound bow shock crossing at Saturn
    1980-11-16   Last outbound bow shock crossing at Saturn
    1981-02-20   10 AU
    1983-08-30   Onset of first major LF heliospheric radio event
    1984-06-19   20 AU
    1987-04-08   30 AU
    1990-01-09   40 AU
    1992-07-06   Onset of second major LF heliospheric radio event
    1992-10-10   50 AU
    1995-07-14   60 AU
    1998-04-18   70 AU
    2001-01-25   80 AU
    2002-11-01   Onset of third major LF heliospheric radio event
    2003-11-05   90 AU
    2004-12-16   Termination shock crossing
    2006-08-16   100 AU
    2009-05-31   110 AU
    2012-03-16   120 AU
    2015-01-01   130 AU
  Data Sampling
  =============
    This data set consists of full resolution edited, wave electric
    field intensities from the Voyager 1 Plasma Wave Receiver spectrum
    analyzer obtained during the entire mission.  For each time
    interval, a field strength is determined for each of the 16
    spectrum analyzer channels whose center frequencies range from 10
    Hertz to 56.2 kiloHertz and which are logarithmically spaced in
    frequency, four channels per decade.  The time associated with
    each set of intensities (16 channels) is the time of the beginning
    of the scan.  The time between spectra in this data set vary by
    telemetry mode and range from 4 seconds to 96 seconds.  During
    data gaps where complete 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.
    For the cruise data sets, the timing of samples is dependent upon
    the spacecraft telemetry mode.  In principle, one can determine
    the temporal resolution between spectra simply by noting the
    difference in time between two records in the files.  In some
    studies, more precise timing information is necessary.  Here, we
    describe the timing of the samples for the PWS low rate data as a
    function of telemetry mode.
    The PWS instrument uses two logarithmic compressors as detectors
    for the 16-channel spectrum analyzer, one for the bottom (lower
    frequency) 8 channels, and one for the upper (higher frequency) 8
    channels.  For each bank of 8 channels, the compressor
    sequentially steps from the lowest frequency of the 8 to the
    highest in a regular time step to obtain a complete spectrum.  At
    each time step, the higher frequency channel is sampled 1/8 s
    prior to the lower frequency channel so that the channels are
    sampled in the following order with channel 1 being the lowest
    frequency channel (10 Hz) and 16 being the highest (56.2 kHz): 9,
    1, 10, 2, 11, 3, ...  15, 7, 16, 8.  The primary difference
    between the various data modes is the stepping rate from one
    channel to the next (ranging from 0.5 to 12 s, corresponding to
    temporal resolutions between complete spectra of 4 s to 96 s).
    In the following table, we present the hexadecimal id for the
    various telemetry modes, the mode mnemonic ID, the time between
    frequency steps, and the time between complete spectra.  We also
    provide the offset from the beginning of the instrument cycle (one
    complete spectrum) identified as the time of each record's time
    tag to the time of the sampling for the first high-frequency
    channel (channel 9) and for the first low-frequency channel
    (channel 1).
                                    Time
                        Frequency   Between      High Freq.  Low Freq.
  MODE (Hex)  MODE ID   Step (s)    Spectra (s)  offset (s)  offset (s)
     01         CR-2    0.5              4.0         0.425     0.4325
     02         CR-3    1.2              9.6         1.125     1.1325
     03         CR-4    4.8             38.4         0.425     0.4325
     04         CR-5    9.6             76.8         0.425     0.4325
     05         CR-6    12.             96.0         0.9275    0.935
     06         CR-7    NOT IMPLEMENTED
     07         CR-1    0.5              4.0         0.225     0.2325
     08         GS-10A  SAME AS GS-3
     0A         GS-3    0.5              4.0         0.425     0.4325
     0C         GS-7    SAME AS GS-3
     0E         GS-6    SAME AS GS-3
     16         OC-2    SAME AS GS-3
     17         OC-1    SAME AS GS-3
     18       **CR-5A   0.5              4.0         0.425     0.4325
     19         GS-10   SAME AS GS-3
     1A         GS-8    SAME AS GS-3
     1D       **UV-5A   SAME AS CR-5A
    **In CR-5A and UV-5A, the PWS is cycled at its 0.5 sec/frequency
    step or 4 sec/spectrum rate, but 4 measurements are summed on
    board in 10-bit accumulators and these 10-bit sums are downlinked.
    On the ground, the sums are divided by 4, hence providing, in a
    sense, 16-second averages.  One of every 12 sets of sums is
    dropped on board in order to avoid LECP stepper motor
    interference.
  Data Processing
  ===============
    The spectrum analyzer data are a continuous (where data are
    available) low resolution data set which provides wave intensity as
    a function of frequency (16 log-spaced channels) and time (one
    spectrum per time intervals ranging from 4 seconds to 96 seconds,
    depending on telemetry mode).  The data are typically plotted as
    amplitude vs. time for one or more of the channels in a strip-chart
    like display, or can be displayed as a frequency-time spectrogram
    using a gray- or color-bar to indicate amplitude.  With only sixteen
    channels, it is usually best to stretch the frequency axis by
    interpolating from one frequency channel to the next either linearly
    or with a spline fit.  One must be aware if the frequency axis is
    stretched that more resolution may be implied than is really
    present.  The Voyager PWS calibration table is given in an ASCII
    text file named VG1PWSCL.TAB (for Voyager-1).  This provides
    information to convert the uncalibrated 'data number' output of the
    PWS 16-channel spectrum analyzer to calibrated antenna voltages for
    each frequency channel.  Following is a brief description of this
    file and a tutorial in its application.
    Descriptive headers have been removed from this file.  The columns
    included are IDN, ICHAN01, ICHAN02, ICHAN03, ICHAN04, ICHAN05,
    ICHAN06, ... ICHAN16.
    The first column lists an uncalibrated data number followed by the
    corresponding value in calibrated volts for each of the 16
    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.)
    A 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 1 PWS:
      real*4 cal (16,0:255)
      open ( unit = 10, file = 'VG1PWSCL.TAB', status = 'old' )
      do i = 0, 255
        read (10, *) idn, (cal(ichan,i), ichan = 1, 16)
      end do
      close (10)
    Then, given an uncalibrated data value idn for the frequency
    channel ichan, the corresponding calibrated antenna voltage would
    be given by the following array reference:
      volts = cal (ichan, idn)
    This may be converted to a wave electric field amplitude by
    dividing by the effective antenna length in meters, 7.07 m.  That
    is:
      efield = cal(ichan, idn) / 7.07
    Spectral 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.
      specdens = (cal(ichan,idn) / 7.07) ** 2 / bandwidth(ichan)
    Finally, power flux may be obtained by dividing the spectral
    density by the impedance of free space in ohms:
      pwrflux = (cal(ichan,idn) / 7.07) ** 2 / bandwidth(ichan) / 376.73
    Of course, for a particular application, it may be more efficient
    to apply the above conversions to the calibration table directly.
    The center frequencies and bandwidths of each PWS spectrum
    analyzer channel for the Voyager 1 spacecraft are given below:
      VOYAGER 1 PWS SPECTRUM ANALYZER
      Voyager-1
      Channel    Center Frequency      Bandwidth
          1          10.0  Hz           2.99 Hz
          2          17.8  Hz           3.77 Hz
          3          31.1  Hz           7.50 Hz
          4          56.2  Hz          10.06 Hz
          5         100.   Hz          13.3  Hz
          6         178.   Hz          29.8  Hz
          7         311.   Hz          59.5  Hz
          8         562.   Hz         106.   Hz
          9           1.00 kHz        133.   Hz
         10           1.78 kHz        211.   Hz
         11           3.11 kHz        298.   Hz
         12           5.62 kHz        421.   Hz
         13          10.0  kHz        943.   Hz
         14          17.8  kHz       2110    Hz
         15          31.1  kHz       4210    Hz
         16          56.2  kHz       5950    Hz
    Additional information about this data set and the instrument
    which produced it can be found elsewhere in this catalog.  A
    complete instrument description can be found in
    [SCARF&GURNETT1977].
  Data
  ====
    The spectrum analyzer data are a continuous (where data are
    available) low resolution data set which provides wave intensity as
    a function of frequency (16 log-spaced channels) and time (one
    spectrum per time intervals ranging from 4 seconds to 96 seconds,
    depending on telemetry mode).  Each sample is nominally an 8-bit
    value which is roughly proportional to the log of the signal
    strength.  In telemetry modes CR-5A and UV-5A the values are 10-bit
    sums of 4 original 8-bit instrument samples.  Zero values indicate
    missing samples and negative values indicate samples flagged as
    contaminated by interference (see below).
  Ancillary Data
  ==============
    None
  Coordinates
  ===========
    The electric dipole antenna detects electric fields in a dipole
    pattern with peak sensitivity parallel to the spacecraft x-axis.
    However, no attempt has been made to correlate the measured field
    to any particular direction such as the local magnetic field or
    direction to a planet.  This is because the spacecraft usually
    remains in a 3-axis stabilized orientation almost continuously.
    The only exception to this are a small number of occasions during
    calibration turns when the modulation of the low-frequency
    heliospheric radio emission could be used to do direction-finding
    on the source of these emissions [GURNETTETAL1998].
F. L. Scarf and D. A. Gurnett, A Plasma Wave Investigation  for the Voyager
Mission,  Space Sci. Rev., 21, 289,  1977. 
http://www-pw.physics.uiowa.edu/voyager/ 
 
Dataset in CDAWeb
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VG2_PWS_LR
Description
  Data Set Overview
  =================
    This data set consists of electric field spectrum analyzer data
    from the Voyager 1 Plasma Wave Subsystem obtained during the
    entire mission.  Data after 2014-12-31 will be added to the archive
    on subsequent volumes.  The data set encompasses all spectrum
    analyzer observations obtained in the cruise mission phases
    before, between, and after the Jupiter and Saturn encounter phases
    as well as those obtained during the two encounter phases.
    The Voyager 1 spacecraft travels from Earth to beyond 100 AU over
    the course of this data set.  To provide some guidance on when
    some key events occurred during the mission, the following table
    is provided.
    Date         Event
    1977-09-05   Launch
    1979-02-28   First inbound bow shock crossing at Jupiter
    1979-03-22   Last outbound bow shock crossing at Jupiter
    1980-11-11   First inbound bow shock crossing at Saturn
    1980-11-16   Last outbound bow shock crossing at Saturn
    1981-02-20   10 AU
    1983-08-30   Onset of first major LF heliospheric radio event
    1984-06-19   20 AU
    1987-04-08   30 AU
    1990-01-09   40 AU
    1992-07-06   Onset of second major LF heliospheric radio event
    1992-10-10   50 AU
    1995-07-14   60 AU
    1998-04-18   70 AU
    2001-01-25   80 AU
    2002-11-01   Onset of third major LF heliospheric radio event
    2003-11-05   90 AU
    2004-12-16   Termination shock crossing
    2006-08-16   100 AU
    2009-05-31   110 AU
    2012-03-16   120 AU
    2015-01-01   130 AU
  Data Sampling
  =============
    This data set consists of full resolution edited, wave electric
    field intensities from the Voyager 1 Plasma Wave Receiver spectrum
    analyzer obtained during the entire mission.  For each time
    interval, a field strength is determined for each of the 16
    spectrum analyzer channels whose center frequencies range from 10
    Hertz to 56.2 kiloHertz and which are logarithmically spaced in
    frequency, four channels per decade.  The time associated with
    each set of intensities (16 channels) is the time of the beginning
    of the scan.  The time between spectra in this data set vary by
    telemetry mode and range from 4 seconds to 96 seconds.  During
    data gaps where complete 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.
    For the cruise data sets, the timing of samples is dependent upon
    the spacecraft telemetry mode.  In principle, one can determine
    the temporal resolution between spectra simply by noting the
    difference in time between two records in the files.  In some
    studies, more precise timing information is necessary.  Here, we
    describe the timing of the samples for the PWS low rate data as a
    function of telemetry mode.
    The PWS instrument uses two logarithmic compressors as detectors
    for the 16-channel spectrum analyzer, one for the bottom (lower
    frequency) 8 channels, and one for the upper (higher frequency) 8
    channels.  For each bank of 8 channels, the compressor
    sequentially steps from the lowest frequency of the 8 to the
    highest in a regular time step to obtain a complete spectrum.  At
    each time step, the higher frequency channel is sampled 1/8 s
    prior to the lower frequency channel so that the channels are
    sampled in the following order with channel 1 being the lowest
    frequency channel (10 Hz) and 16 being the highest (56.2 kHz): 9,
    1, 10, 2, 11, 3, ...  15, 7, 16, 8.  The primary difference
    between the various data modes is the stepping rate from one
    channel to the next (ranging from 0.5 to 12 s, corresponding to
    temporal resolutions between complete spectra of 4 s to 96 s).
    In the following table, we present the hexadecimal id for the
    various telemetry modes, the mode mnemonic ID, the time between
    frequency steps, and the time between complete spectra.  We also
    provide the offset from the beginning of the instrument cycle (one
    complete spectrum) identified as the time of each record's time
    tag to the time of the sampling for the first high-frequency
    channel (channel 9) and for the first low-frequency channel
    (channel 1).
                                    Time
                        Frequency   Between      High Freq.  Low Freq.
  MODE (Hex)  MODE ID   Step (s)    Spectra (s)  offset (s)  offset (s)
     01         CR-2    0.5              4.0         0.425     0.4325
     02         CR-3    1.2              9.6         1.125     1.1325
     03         CR-4    4.8             38.4         0.425     0.4325
     04         CR-5    9.6             76.8         0.425     0.4325
     05         CR-6    12.             96.0         0.9275    0.935
     06         CR-7    NOT IMPLEMENTED
     07         CR-1    0.5              4.0         0.225     0.2325
     08         GS-10A  SAME AS GS-3
     0A         GS-3    0.5              4.0         0.425     0.4325
     0C         GS-7    SAME AS GS-3
     0E         GS-6    SAME AS GS-3
     16         OC-2    SAME AS GS-3
     17         OC-1    SAME AS GS-3
     18       **CR-5A   0.5              4.0         0.425     0.4325
     19         GS-10   SAME AS GS-3
     1A         GS-8    SAME AS GS-3
     1D       **UV-5A   SAME AS CR-5A
    **In CR-5A and UV-5A, the PWS is cycled at its 0.5 sec/frequency
    step or 4 sec/spectrum rate, but 4 measurements are summed on
    board in 10-bit accumulators and these 10-bit sums are downlinked.
    On the ground, the sums are divided by 4, hence providing, in a
    sense, 16-second averages.  One of every 12 sets of sums is
    dropped on board in order to avoid LECP stepper motor
    interference.
  Data Processing
  ===============
    The spectrum analyzer data are a continuous (where data are
    available) low resolution data set which provides wave intensity as
    a function of frequency (16 log-spaced channels) and time (one
    spectrum per time intervals ranging from 4 seconds to 96 seconds,
    depending on telemetry mode).  The data are typically plotted as
    amplitude vs. time for one or more of the channels in a strip-chart
    like display, or can be displayed as a frequency-time spectrogram
    using a gray- or color-bar to indicate amplitude.  With only sixteen
    channels, it is usually best to stretch the frequency axis by
    interpolating from one frequency channel to the next either linearly
    or with a spline fit.  One must be aware if the frequency axis is
    stretched that more resolution may be implied than is really
    present.  The Voyager PWS calibration table is given in an ASCII
    text file named VG1PWSCL.TAB (for Voyager-1).  This provides
    information to convert the uncalibrated 'data number' output of the
    PWS 16-channel spectrum analyzer to calibrated antenna voltages for
    each frequency channel.  Following is a brief description of this
    file and a tutorial in its application.
    Descriptive headers have been removed from this file.  The columns
    included are IDN, ICHAN01, ICHAN02, ICHAN03, ICHAN04, ICHAN05,
    ICHAN06, ... ICHAN16.
    The first column lists an uncalibrated data number followed by the
    corresponding value in calibrated volts for each of the 16
    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.)
    A 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 1 PWS:
      real*4 cal (16,0:255)
      open ( unit = 10, file = 'VG1PWSCL.TAB', status = 'old' )
      do i = 0, 255
        read (10, *) idn, (cal(ichan,i), ichan = 1, 16)
      end do
      close (10)
    Then, given an uncalibrated data value idn for the frequency
    channel ichan, the corresponding calibrated antenna voltage would
    be given by the following array reference:
      volts = cal (ichan, idn)
    This may be converted to a wave electric field amplitude by
    dividing by the effective antenna length in meters, 7.07 m.  That
    is:
      efield = cal(ichan, idn) / 7.07
    Spectral 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.
      specdens = (cal(ichan,idn) / 7.07) ** 2 / bandwidth(ichan)
    Finally, power flux may be obtained by dividing the spectral
    density by the impedance of free space in ohms:
      pwrflux = (cal(ichan,idn) / 7.07) ** 2 / bandwidth(ichan) / 376.73
    Of course, for a particular application, it may be more efficient
    to apply the above conversions to the calibration table directly.
    The center frequencies and bandwidths of each PWS spectrum
    analyzer channel for the Voyager 1 spacecraft are given below:
      VOYAGER 1 PWS SPECTRUM ANALYZER
      Voyager-1
      Channel    Center Frequency      Bandwidth
          1          10.0  Hz           2.99 Hz
          2          17.8  Hz           3.77 Hz
          3          31.1  Hz           7.50 Hz
          4          56.2  Hz          10.06 Hz
          5         100.   Hz          13.3  Hz
          6         178.   Hz          29.8  Hz
          7         311.   Hz          59.5  Hz
          8         562.   Hz         106.   Hz
          9           1.00 kHz        133.   Hz
         10           1.78 kHz        211.   Hz
         11           3.11 kHz        298.   Hz
         12           5.62 kHz        421.   Hz
         13          10.0  kHz        943.   Hz
         14          17.8  kHz       2110    Hz
         15          31.1  kHz       4210    Hz
         16          56.2  kHz       5950    Hz
    Additional information about this data set and the instrument
    which produced it can be found elsewhere in this catalog.  A
    complete instrument description can be found in
    [SCARF&GURNETT1977].
  Data
  ====
    The spectrum analyzer data are a continuous (where data are
    available) low resolution data set which provides wave intensity as
    a function of frequency (16 log-spaced channels) and time (one
    spectrum per time intervals ranging from 4 seconds to 96 seconds,
    depending on telemetry mode).  Each sample is nominally an 8-bit
    value which is roughly proportional to the log of the signal
    strength.  In telemetry modes CR-5A and UV-5A the values are 10-bit
    sums of 4 original 8-bit instrument samples.  Zero values indicate
    missing samples and negative values indicate samples flagged as
    contaminated by interference (see below).
  Ancillary Data
  ==============
    None
  Coordinates
  ===========
    The electric dipole antenna detects electric fields in a dipole
    pattern with peak sensitivity parallel to the spacecraft x-axis.
    However, no attempt has been made to correlate the measured field
    to any particular direction such as the local magnetic field or
    direction to a planet.  This is because the spacecraft usually
    remains in a 3-axis stabilized orientation almost continuously.
    The only exception to this are a small number of occasions during
    calibration turns when the modulation of the low-frequency
    heliospheric radio emission could be used to do direction-finding
    on the source of these emissions [GURNETTETAL1998].
F. L. Scarf and D. A. Gurnett, A Plasma Wave Investigation  for the Voyager
Mission,  Space Sci. Rev., 21, 289,  1977. 
http://www-pw.physics.uiowa.edu/voyager/ 
 
Dataset in CDAWeb
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VOYAGER1_10S_MAG
Description
This data set includes the Voyager spacecraft number (1 or 2), the date-time in
decimal year (90.00000 is day 1 of 1990), the magnetic field strength F1
computed from high-resolution magnitudes, the elevation and azimuth angles
(degrees) in heliographic (RTN) coordinates, and the magnetic field strength F2
computed from hour averages of the components. The vector components of B can be
computed from F2 and the two angles. Elevation angle is the latitude angle above
or below the solar equatorial plane, and azimuth angle is in the direction
orbital motion around the Sun from the projection of the Sun-to-spacecraft axis
into the solar equatorial plane. The Voyager MAG experiment and coordinates are
further described in the following publication:  Behannon, K.W., M.H. Acuna,
L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field
Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257,
1977...At the time of experiment proposal, it was expected that the required
accuracy of the measurements would be 0.1 nT, determined by the combined noise
of the sensors and the spacecraft field. The spacecraft magnetic field at the
outboard magnetic field sensor, referred to as the primary unit, was expected to
be 0.2 nT and highly variable, consistent with current estimates. Hence, the
dual magnetometer design (Ness et al., 1971, 1973; Behannon et al. 1977). ..At
distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
..References: ..Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F.
Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2,
Space Science Reviews, 21 (3), 235-257, 1977. ..Burlaga, L.F., Merged
interaction regions and large-scale magnetic field fluctuations during 1991 -
Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994.
..Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. ..Ness, N., K.W.
Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971.
..Ness et al., 1973
At distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting  about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
COORDINATE SYSTEMS:  Interplanetary magnetic field studies make use of two
important coordinate systems, the Inertial Heliographic (IHG) coordinate system
and the Heliographic (HG) coordinate system.
The IHG coordinate system is use to define the spacecraft's position.  The IHG
system is defined with its origin at the Sun.  There are three orthogonal axes,
X(IHG), Y(IHG), and Z(IHG).  The Z(IHG) axis points northward along the Sun's 
spin axis.  The X(IHG) - Y(IHG) plane lays in the solar equatorial plane.  The
intersection of the solar equatorial plane with the ecliptic plane defines a
line, the longitude of the ascending node, which is taken to be the X(IHG) axis.
The X(IHG) axis drifts slowly with time, approximately one degree per 72 years.
Magnetic field orientation is defined in relation to the spacecraft.  Drawing a
line from the Sun's center (IHG origin) to the spacecraft defines the X axis of
the HG coordinate system.  The HG coordinate system is defined with its origin
centered at the spacecraft.  Three orthogonal axes are defined, X(HG), Y(HG),
and Z(HG).  The X(HG) axis points radially away from the Sun and the Y(HG) axis
is parallel to the solar equatorial plane and therefore parallel to the
X(IHG)-Y(IHG) plane too.  The Z(HG) axis is chosen to complete the orthonormal
triad. 
An excellent reference guide with diagrams explaining the IHG and HG systems may
be found in Space and Science Reviews, Volume 39 (1984), pages 255-316, MHD
Processes in the Outer Heliosphere,  L. F. Burlaga.
 
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VOYAGER1_2S_MAG
Description
This data set includes the Voyager spacecraft number (1 or 2), the date-time in
decimal year (90.00000 is day 1 of 1990), the magnetic field strength F1
computed from high-resolution magnitudes, the elevation and azimuth angles
(degrees) in heliographic (RTN) coordinates, and the magnetic field strength F2
computed from hour averages of the components. The vector components of B can be
computed from F2 and the two angles. Elevation angle is the latitude angle above
or below the solar equatorial plane, and azimuth angle is in the direction
orbital motion around the Sun from the projection of the Sun-to-spacecraft axis
into the solar equatorial plane. The Voyager MAG experiment and coordinates are
further described in the following publication:  Behannon, K.W., M.H. Acuna,
L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field
Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257,
1977...At the time of experiment proposal, it was expected that the required
accuracy of the measurements would be 0.1 nT, determined by the combined noise
of the sensors and the spacecraft field. The spacecraft magnetic field at the
outboard magnetic field sensor, referred to as the primary unit, was expected to
be 0.2 nT and highly variable, consistent with current estimates. Hence, the
dual magnetometer design (Ness et al., 1971, 1973; Behannon et al. 1977). ..At
distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
..References: ..Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F.
Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2,
Space Science Reviews, 21 (3), 235-257, 1977. ..Burlaga, L.F., Merged
interaction regions and large-scale magnetic field fluctuations during 1991 -
Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994.
..Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. ..Ness, N., K.W.
Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971.
..Ness et al., 1973
At distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting  about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
COORDINATE SYSTEMS:  Interplanetary magnetic field studies make use of two
important coordinate systems, the Inertial Heliographic (IHG) coordinate system
and the Heliographic (HG) coordinate system.
The IHG coordinate system is use to define the spacecraft's position.  The IHG
system is defined with its origin at the Sun.  There are three orthogonal axes,
X(IHG), Y(IHG), and Z(IHG).  The Z(IHG) axis points northward along the Sun's 
spin axis.  The X(IHG) - Y(IHG) plane lays in the solar equatorial plane.  The
intersection of the solar equatorial plane with the ecliptic plane defines a
line, the longitude of the ascending node, which is taken to be the X(IHG) axis.
The X(IHG) axis drifts slowly with time, approximately one degree per 72 years.
Magnetic field orientation is defined in relation to the spacecraft.  Drawing a
line from the Sun's center (IHG origin) to the spacecraft defines the X axis of
the HG coordinate system.  The HG coordinate system is defined with its origin
centered at the spacecraft.  Three orthogonal axes are defined, X(HG), Y(HG),
and Z(HG).  The X(HG) axis points radially away from the Sun and the Y(HG) axis
is parallel to the solar equatorial plane and therefore parallel to the
X(IHG)-Y(IHG) plane too.  The Z(HG) axis is chosen to complete the orthonormal
triad. 
An excellent reference guide with diagrams explaining the IHG and HG systems may
be found in Space and Science Reviews, Volume 39 (1984), pages 255-316, MHD
Processes in the Outer Heliosphere,  L. F. Burlaga.
 
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VOYAGER1_48S_MAG
Description
This data set includes the Voyager spacecraft number (1 or 2), the date-time in
decimal year (90.00000 is day 1 of 1990), the magnetic field strength F1
computed from high-resolution magnitudes, the elevation and azimuth angles
(degrees) in heliographic (RTN) coordinates, and the magnetic field strength F2
computed from hour averages of the components. The vector components of B can be
computed from F2 and the two angles. Elevation angle is the latitude angle above
or below the solar equatorial plane, and azimuth angle is in the direction
orbital motion around the Sun from the projection of the Sun-to-spacecraft axis
into the solar equatorial plane. The Voyager MAG experiment and coordinates are
further described in the following publication:  Behannon, K.W., M.H. Acuna,
L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field
Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257,
1977...At the time of experiment proposal, it was expected that the required
accuracy of the measurements would be 0.1 nT, determined by the combined noise
of the sensors and the spacecraft field. The spacecraft magnetic field at the
outboard magnetic field sensor, referred to as the primary unit, was expected to
be 0.2 nT and highly variable, consistent with current estimates. Hence, the
dual magnetometer design (Ness et al., 1971, 1973; Behannon et al. 1977). ..At
distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
..References: ..Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F.
Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2,
Space Science Reviews, 21 (3), 235-257, 1977. ..Burlaga, L.F., Merged
interaction regions and large-scale magnetic field fluctuations during 1991 -
Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994.
..Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. ..Ness, N., K.W.
Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971.
..Ness et al., 1973
At distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting  about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
COORDINATE SYSTEMS:  Interplanetary magnetic field studies make use of two
important coordinate systems, the Inertial Heliographic (IHG) coordinate system
and the Heliographic (HG) coordinate system.
The IHG coordinate system is use to define the spacecraft's position.  The IHG
system is defined with its origin at the Sun.  There are three orthogonal axes,
X(IHG), Y(IHG), and Z(IHG).  The Z(IHG) axis points northward along the Sun's 
spin axis.  The X(IHG) - Y(IHG) plane lays in the solar equatorial plane.  The
intersection of the solar equatorial plane with the ecliptic plane defines a
line, the longitude of the ascending node, which is taken to be the X(IHG) axis.
The X(IHG) axis drifts slowly with time, approximately one degree per 72 years.
Magnetic field orientation is defined in relation to the spacecraft.  Drawing a
line from the Sun's center (IHG origin) to the spacecraft defines the X axis of
the HG coordinate system.  The HG coordinate system is defined with its origin
centered at the spacecraft.  Three orthogonal axes are defined, X(HG), Y(HG),
and Z(HG).  The X(HG) axis points radially away from the Sun and the Y(HG) axis
is parallel to the solar equatorial plane and therefore parallel to the
X(IHG)-Y(IHG) plane too.  The Z(HG) axis is chosen to complete the orthonormal
triad. 
An excellent reference guide with diagrams explaining the IHG and HG systems may
be found in Space and Science Reviews, Volume 39 (1984), pages 255-316, MHD
Processes in the Outer Heliosphere,  L. F. Burlaga.
Support data calib_flag_on, calib_flag_MF and calib_flag_offset are added to
file version 2. Variable calib_flag_on consists of points where bit 4 or 5 in
variable magStatus equal 1. Variable calib_flag_MF represents observations where
magnetometer was in cailbration mode. Variable calib_flag_offset represent delay
between data points where magnetometer was in calibration mode and data points
where magStatus variable indicated calibration periods.Due to specific shape of
magnetometer data profile variable calibration_flag_MF may cover larger
intervals than calibration_flag_on.
 
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VOYAGER1_48S_MAG-VIM
Description
The  main science objectives for the VOYAGER interplanetary mission are as  
follows: 
- investigate the structure of the solar wind magnetic fields and plasma in the
inner and outer heliosphere; 
- conduct long term study of heliospheric evolution during different phases of
the twenty-two year solar magnetic cycle and the eleven-year solar activity
cycle;
- study the long term solar modulation and determine the elemental and isotopic
abundances of galactic cosmic ray particles in the heliosphere;
- measure  radial gradients, spectra, and nuclear abundances of the anomalous
component of cosmic rays  from  acceleration at the solar wind termination
shock; 
- investigate local particle acceleration in the interplanetary medium from
solar flare shocks and corotating interaction regions; 
- study propagation of solar energetic particles in the heliosphere.
The average magnetic field strength produced by the spacecraft at the location
of the outboard magnetometer of the dual magnetometers system on V1 and V2 is
about 0.1 - 0.2 nT, comparable to the most probable magnetic field strength in
the inner heliosheath and significantly larger than the most probable magnetic
field strength in the distant supersonic solar wind. The spacecraft magnetic
field is a complex, time-dependent signal that must be removed from the measured
magnetic field signal in order to derive the ambient magnetic fields of the
solar wind and heliosheath. Corrections must also be made for spurious magnetic
signals and noise associated with the telemetry system, ground tracking systems,
and other factors. Extracting the signal describing the solar wind and
heliosheath from the many sources of uncertainty is a complex and partly
subjective process that requires understanding of the instrument and judgment
based on experience in dealing with the ever-changing extraneous signals. We
estimate that for the V1 MAG data the 1-sigma the uncertainty the 48 sec
averages for each of the components of the magnetic field  BR, BT, and BN is
typically +/- 0.02 nT; the uncertainty in magnitude F1 is typically +/- 0.03 nT.
F1, BR, BT, and BN can differ from one another and they may vary with time, but
there is no practical way to determine these uncertainties more precisely at
present.
References
Daniel B. Berdichevsky, Voyager Mission, Detailed processing of weak magnetic
fields; I - Constraints to the uncertainties of the calibrated magnetic field
signal in the Voyager missions , 2009;
https://vgrmag.gsfc.nasa.gov/Berdichevsky-VOY_sensor_opu090518.pdf
Behannon, K.W., M.H. Acu..a, L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M.
Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2, Space Science
Reviews, 21 (3), 235-257, 1977. Burlaga, L.F., Merged interaction regions and
large-scale magnetic field fluctuations during 1991 - Voyager-2 observations, J.
Geophys. Res., 99 (A10), 19341-19350, 1994.
Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002.
Ness, N., K.W. Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., , 76,
3564, 1971.
 
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VOYAGER1_COHO1HR_MERGED_MAG_PLASMA (spase://VHO/NumericalData/Voyager1/MAGandPLS/PT1H)
Description
The  main science objectives for the VOYAGER interplanetary mission are as  
follows: 
- investigate the structure of the solar wind magnetic fields and plasma in the
inner and outer heliosphere; 
- conduct long term study of heliospheric evolution during different phases of
the twenty-two year solar magnetic cycle and the eleven-year solar activity
cycle;
- study the long term solar modulation and determine the elemental and isotopic
abundances of galactic cosmic ray particles in the heliosphere;
- measure  radial gradients, spectra, and nuclear abundances of the anomalous
component of cosmic rays  from  acceleration at the solar wind termination
shock; 
- investigate local particle acceleration in the interplanetary medium from
solar flare shocks and corotating interaction regions; 
- study propagation of solar energetic particles in the heliosphere.
This directory contains hourly averages of parameters for the interplanetary
magnetic field, solar wind plasma and spacecraft trajectory coordinates
VOYAGER-1 data have been reprocessed to ensure a uniformity of content and
coordinate systems relative to data from other deep-space missions:
 - All spacecraft trajectory data were transformed to a Heliographic Inertial
(HGI) coordinate system.
- calculation of the RTN Cartesian components of interplanetary magnetic field
from the RTN spherical components: 
         BR=|B|*cos(THETA)*cos(PHI) 
         BT=|B|*cos(THETA)*sin(PHI) 
         BN=|B|*sin(THETA)          
where THETA - spherical RTN latitude, PHI- spherical RTN longtitude 
- calculation of RTN Spherical components of the solar wind velocity from RTN
cartesian components:
         V = (Vr^2 + Vt^2 + Vn^2)^0.5
         THETA=asin(Vn/V)
         PHI=atan(Vt/Vr)
where THETA - spherical RTN latitude, PHI- spherical RTN longtitude
- calculation of given thermal speed Vth into temperature T (Kelvin):
         T=60.5*Vth^2 (Vth in km/s)
- merging of trajectory coordinates, magnetic field data, and plasma data files
into a single annual file VY1_YR.DAT, where YR is the year
- Data gaps were filled with dummy numbers for the missing hours or entire days
to make all files of equal length.  The character \Ə\' is used to fill all
fields for missing data according to their format, e.g. \' 9999.9\' for a field
with the FORTRAN format F7.1. Note that format F7.1 below really means
(1X,F6.1),etc.a
Notes on Voyager 1 and 2 Magnetometer Data After 1989.
  At the time of experiment proposal, it was expected that the required accuracy
of the measurements would be 0.1 nT, determined by the combined noise of the
sensors and the spacecraft field.  The spacecraft magnetic field at the outboard
magnetic field sensor, referred to as the primary unit, was expected to be 0.2
nT and highly variable, consistent with current estimates. Hence, the dual
magnetometer design (Ness et al., 1971; Behannon et al. 1977).  At distances 
40 AU, the heliospheric magnetic fields are generally much weaker than 0.4 nT;
the average magnetic field strength near 40 AU and 85 AU is ..0.15 nT and ..0.05
nT, respectively. The use of roll calibrations lasting ..6 hours permits
determination of the effective zero levels for the two independent magnetic axes
that are perpendicular to the roll axis (which is nearly parallel to the radius
vector to the Sun) at intervals of ..3 months. There is no roll calibration for
the third magnetic axis. Comparison of the two derived magnetic vectors from the
two magnetometers permits validation of the primary magnetometer data with an
accuracy of 0.02 nT - 0.05 nT. further informaion look at
https://omniweb.gsfc.nasa.gov/coho/html/cw_data.html
The Heliographic Inertial (HGI) coordinates are Sun-centered and inertially
fixed with respect to an X-axis directed along the intersection line of the
ecliptic and solar equatorial planes.  The solar equator plane is inclined at
7.25 degrees from the ecliptic.  This direction was towards ecliptic longitude
of 74.36 degrees on 1 January 1900 at 1200 UT; because of precession of the
celestial equator, this longitude increases by 1.4 degrees/century. The Z axis
is directed perpendicular and northward from the solar equator, and the  Y-axis
completes the right-handed set. This system differs from the usual  heliographic
 coordinates  (e.g. Carrington longitudes) which are fixed in the frame of the
rotating Sun. 
The RTN system is fixed at a spacecraft (or the planet). The R axis is  directed
radially away from the Sun, the T axis is the cross product of the solar
rotation axis and the R axis, and the N axis is the cross product of R and T. 
At zero Heliographic Latitude when the spacecraft is in the solar equatorial
plane the N and solar rotation axes are parallel.
Hour averages of the interplanetary solar wind data from, and hourly
heliocentric coordinates of, Voyager1/2 and other interplanetary spacecraft may
be also be accessed and plotted on-line through the COHOWeb service 
http://cohoweb.gsfc.nasa.gov/
Acknowledgement: Use of these data in publications should be accompanied at
minimum by acknowledgements of the National Space Science Data Center and the
responsible Principal Investigator defined in the experiment documentation
provided here.  Citation of NSSDC's Coordinated Heliospheric Observations (COHO)
data base would also be appreciated, so that other potential users will be made
aware of this service. 
For questions about this data set, please contact: Dr. N. Papitashvili,
natalia.e.papitashvili@nasa.gov, GSFC-Code 672 
 
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VOYAGER1_PLS_COMPOSITION (spase://VSPO/NumericalData/Voyager1/PLS/JupiterViperComposition/P96S)
Description
These data are from a re-analysis of the Voyager Plasma Spectrometer (PLS) data
at Jupiter by the PLS group at the Laboratory for Atmospheric and Space Physics
(LASP) at the University of Colorado. Density, temperature, and flow velocity
fits for total and individual ions were done using the Voyager Ion PLS
Experiment Response (VIPER) code and error analysis as described at
http://lasp.colorado.edu/home.mop/missions/voyager/viper/. Fits are determined
from processing of the ion currents from the A, B, C, and D cups of the
instrument.. As per the Fit Case variable, one of five different constraints
were used in the VIPER fits for each 96-sec time interval: (1) free variation of
all parameters (mainly for the cold ion torus); (2) constraint of the ion
abundances for the five major species (O+, O++, S+, S++, S+++) to standard
composition as determined from Delamere et al. (2005); (3) fixed ion composition
and flow speed; (4) cold blobs in the plasma sheet where resolved peaks can be
fit with allowance for some variance in composition; (5) interpolation between
composition of cold torus and standard abundances at 6 RJ from Delamere et al.
(2005). 
Reference: Delamere, P. A., Bagenal, F., and Steffl, A. (2005), Radial
Variations in the Io Plasma Torus During the Cassini Era, Journal of Geophysical
Research Space Physics, 110(A12), A12223, doi: 10.1029/2005JA011251. 
 
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VOYAGER1_PLS_HIRES_PLASMA_DATA
Description
The files in this directory contain the Voyager fine resolution plasma data. The
plasma parameters are obtained by finding the best fit of a convected isotropic
Maxwellian distribution to the data. One sigma errors are typically less than
0.5% in the speed and VR, less than 5% for the density and thermal speed, and
vary greatly for VT and VN. Sampling times range from 12 to 192 sec., with
sampling generally more frequent early in the mission.
The velocity components are given in the RTN coordinate system, where R is
radially outward, T is in a plane parallel to the solar equatorial plane and
positive in the direction of solar rotation, and N completes a right-handed
system.
(WARNING: V_t, and V_n parameters are often NOT reliable after 1989)
Please consult with us, or at least send preprints, when you use this data to
prevent grievous errors or misconceptions. (John Richardson, jdr@space.mit.edu)
 
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VOYAGER2_10S_MAG
Description
This data set includes the Voyager spacecraft number (1 or 2), the date-time in
decimal year (90.00000 is day 1 of 1990), the magnetic field strength F1
computed from high-resolution magnitudes, the elevation and azimuth angles
(degrees) in heliographic (RTN) coordinates, and the magnetic field strength F2
computed from hour averages of the components. The vector components of B can be
computed from F2 and the two angles. Elevation angle is the latitude angle above
or below the solar equatorial plane, and azimuth angle is in the direction
orbital motion around the Sun from the projection of the Sun-to-spacecraft axis
into the solar equatorial plane. The Voyager MAG experiment and coordinates are
further described in the following publication:  Behannon, K.W., M.H. Acuna,
L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field
Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257,
1977...At the time of experiment proposal, it was expected that the required
accuracy of the measurements would be 0.1 nT, determined by the combined noise
of the sensors and the spacecraft field. The spacecraft magnetic field at the
outboard magnetic field sensor, referred to as the primary unit, was expected to
be 0.2 nT and highly variable, consistent with current estimates. Hence, the
dual magnetometer design (Ness et al., 1971, 1973; Behannon et al. 1977). ..At
distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
..References: ..Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F.
Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2,
Space Science Reviews, 21 (3), 235-257, 1977. ..Burlaga, L.F., Merged
interaction regions and large-scale magnetic field fluctuations during 1991 -
Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994.
..Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. ..Ness, N., K.W.
Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971.
..Ness et al., 1973
At distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting  about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
COORDINATE SYSTEMS:  Interplanetary magnetic field studies make use of two
important coordinate systems, the Inertial Heliographic (IHG) coordinate system
and the Heliographic (HG) coordinate system.
The IHG coordinate system is use to define the spacecraft's position.  The IHG
system is defined with its origin at the Sun.  There are three orthogonal axes,
X(IHG), Y(IHG), and Z(IHG).  The Z(IHG) axis points northward along the Sun's 
spin axis.  The X(IHG) - Y(IHG) plane lays in the solar equatorial plane.  The
intersection of the solar equatorial plane with the ecliptic plane defines a
line, the longitude of the ascending node, which is taken to be the X(IHG) axis.
The X(IHG) axis drifts slowly with time, approximately one degree per 72 years.
Magnetic field orientation is defined in relation to the spacecraft.  Drawing a
line from the Sun's center (IHG origin) to the spacecraft defines the X axis of
the HG coordinate system.  The HG coordinate system is defined with its origin
centered at the spacecraft.  Three orthogonal axes are defined, X(HG), Y(HG),
and Z(HG).  The X(HG) axis points radially away from the Sun and the Y(HG) axis
is parallel to the solar equatorial plane and therefore parallel to the
X(IHG)-Y(IHG) plane too.  The Z(HG) axis is chosen to complete the orthonormal
triad. 
An excellent reference guide with diagrams explaining the IHG and HG systems may
be found in Space and Science Reviews, Volume 39 (1984), pages 255-316, MHD
Processes in the Outer Heliosphere,  L. F. Burlaga.
 
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VOYAGER2_2S_MAG
Description
This data set includes the Voyager spacecraft number (1 or 2), the date-time in
decimal year (90.00000 is day 1 of 1990), the magnetic field strength F1
computed from high-resolution magnitudes, the elevation and azimuth angles
(degrees) in heliographic (RTN) coordinates, and the magnetic field strength F2
computed from hour averages of the components. The vector components of B can be
computed from F2 and the two angles. Elevation angle is the latitude angle above
or below the solar equatorial plane, and azimuth angle is in the direction
orbital motion around the Sun from the projection of the Sun-to-spacecraft axis
into the solar equatorial plane. The Voyager MAG experiment and coordinates are
further described in the following publication:  Behannon, K.W., M.H. Acuna,
L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field
Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257,
1977...At the time of experiment proposal, it was expected that the required
accuracy of the measurements would be 0.1 nT, determined by the combined noise
of the sensors and the spacecraft field. The spacecraft magnetic field at the
outboard magnetic field sensor, referred to as the primary unit, was expected to
be 0.2 nT and highly variable, consistent with current estimates. Hence, the
dual magnetometer design (Ness et al., 1971, 1973; Behannon et al. 1977). ..At
distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
..References: ..Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F.
Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2,
Space Science Reviews, 21 (3), 235-257, 1977. ..Burlaga, L.F., Merged
interaction regions and large-scale magnetic field fluctuations during 1991 -
Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994.
..Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. ..Ness, N., K.W.
Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971.
..Ness et al., 1973
At distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting  about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
COORDINATE SYSTEMS:  Interplanetary magnetic field studies make use of two
important coordinate systems, the Inertial Heliographic (IHG) coordinate system
and the Heliographic (HG) coordinate system.
The IHG coordinate system is use to define the spacecraft's position.  The IHG
system is defined with its origin at the Sun.  There are three orthogonal axes,
X(IHG), Y(IHG), and Z(IHG).  The Z(IHG) axis points northward along the Sun's 
spin axis.  The X(IHG) - Y(IHG) plane lays in the solar equatorial plane.  The
intersection of the solar equatorial plane with the ecliptic plane defines a
line, the longitude of the ascending node, which is taken to be the X(IHG) axis.
The X(IHG) axis drifts slowly with time, approximately one degree per 72 years.
Magnetic field orientation is defined in relation to the spacecraft.  Drawing a
line from the Sun's center (IHG origin) to the spacecraft defines the X axis of
the HG coordinate system.  The HG coordinate system is defined with its origin
centered at the spacecraft.  Three orthogonal axes are defined, X(HG), Y(HG),
and Z(HG).  The X(HG) axis points radially away from the Sun and the Y(HG) axis
is parallel to the solar equatorial plane and therefore parallel to the
X(IHG)-Y(IHG) plane too.  The Z(HG) axis is chosen to complete the orthonormal
triad. 
An excellent reference guide with diagrams explaining the IHG and HG systems may
be found in Space and Science Reviews, Volume 39 (1984), pages 255-316, MHD
Processes in the Outer Heliosphere,  L. F. Burlaga.
 
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VOYAGER2_48S_MAG
Description
This data set includes the Voyager spacecraft number (1 or 2), the date-time in
decimal year (90.00000 is day 1 of 1990), the magnetic field strength F1
computed from high-resolution magnitudes, the elevation and azimuth angles
(degrees) in heliographic (RTN) coordinates, and the magnetic field strength F2
computed from hour averages of the components. The vector components of B can be
computed from F2 and the two angles. Elevation angle is the latitude angle above
or below the solar equatorial plane, and azimuth angle is in the direction
orbital motion around the Sun from the projection of the Sun-to-spacecraft axis
into the solar equatorial plane. The Voyager MAG experiment and coordinates are
further described in the following publication:  Behannon, K.W., M.H. Acuna,
L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field
Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257,
1977...At the time of experiment proposal, it was expected that the required
accuracy of the measurements would be 0.1 nT, determined by the combined noise
of the sensors and the spacecraft field. The spacecraft magnetic field at the
outboard magnetic field sensor, referred to as the primary unit, was expected to
be 0.2 nT and highly variable, consistent with current estimates. Hence, the
dual magnetometer design (Ness et al., 1971, 1973; Behannon et al. 1977). ..At
distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
..References: ..Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F.
Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2,
Space Science Reviews, 21 (3), 235-257, 1977. ..Burlaga, L.F., Merged
interaction regions and large-scale magnetic field fluctuations during 1991 -
Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994.
..Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. ..Ness, N., K.W.
Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971.
..Ness et al., 1973
At distances > 40 AU, the heliospheric magnetic fields are generally much weaker
than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about
0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting  about 6
hours permits determination of the effective zero levels for the two independent
magnetic axes that are perpendicular to the roll axis (which is nearly parallel
to the radius vector to the Sun) at intervals of about 3 months. There is no
roll calibration for the third magnetic axis. Comparison of the two derived
magnetic vectors from the two magnetometers permits validation of the primary
magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the
uncertainties that must be considered when using these data is given in the
Appendix of Burlaga et al. [1994] and in Appendix A of Burlaga et al. [2002].
COORDINATE SYSTEMS:  Interplanetary magnetic field studies make use of two
important coordinate systems, the Inertial Heliographic (IHG) coordinate system
and the Heliographic (HG) coordinate system.
The IHG coordinate system is use to define the spacecraft's position.  The IHG
system is defined with its origin at the Sun.  There are three orthogonal axes,
X(IHG), Y(IHG), and Z(IHG).  The Z(IHG) axis points northward along the Sun's 
spin axis.  The X(IHG) - Y(IHG) plane lays in the solar equatorial plane.  The
intersection of the solar equatorial plane with the ecliptic plane defines a
line, the longitude of the ascending node, which is taken to be the X(IHG) axis.
The X(IHG) axis drifts slowly with time, approximately one degree per 72 years.
Magnetic field orientation is defined in relation to the spacecraft.  Drawing a
line from the Sun's center (IHG origin) to the spacecraft defines the X axis of
the HG coordinate system.  The HG coordinate system is defined with its origin
centered at the spacecraft.  Three orthogonal axes are defined, X(HG), Y(HG),
and Z(HG).  The X(HG) axis points radially away from the Sun and the Y(HG) axis
is parallel to the solar equatorial plane and therefore parallel to the
X(IHG)-Y(IHG) plane too.  The Z(HG) axis is chosen to complete the orthonormal
triad. 
An excellent reference guide with diagrams explaining the IHG and HG systems may
be found in Space and Science Reviews, Volume 39 (1984), pages 255-316, MHD
Processes in the Outer Heliosphere,  L. F. Burlaga.
Support data calib_flag_on, calib_flag_MF and calib_flag_offset are added to
file version 2. Variable calib_flag_on consists of points where bit 4 or 5 in
variable magStatus equal 1. Variable calib_flag_MF represents observations where
magnetometer was in cailbration mode. Variable calib_flag_offset represent delay
between data points where magnetometer was in calibration mode and data points
where magStatus variable indicated calibration periods.Due to specific shape of
magnetometer data profile variable calibration_flag_MF may cover larger
intervals than calibration_flag_on.
 
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VOYAGER2_48S_MAG-VIM
Description
The  main science objectives for the VOYAGER interplanetary mission are as  
follows: 
- investigate the structure of the solar wind magnetic fields and plasma in the
inner and outer heliosphere; 
- conduct long term study of heliospheric evolution during different phases of
the twenty-two year solar magnetic cycle and the eleven-year solar activity
cycle;
- study the long term solar modulation and determine the elemental and isotopic
abundances of galactic cosmic ray particles in the heliosphere;
- measure  radial gradients, spectra, and nuclear abundances of the anomalous
component of cosmic rays  from  acceleration at the solar wind termination
shock; 
- investigate local particle acceleration in the interplanetary medium from
solar flare shocks and corotating interaction regions; 
- study propagation of solar energetic particles in the heliosphere.
The average magnetic field strength produced by the spacecraft at the location
of the outboard magnetometer of the dual magnetometers system on V1 and V2 is
about 0.1 - 0.2 nT, comparable to the most probable magnetic field strength in
the inner heliosheath and significantly larger than the most probable magnetic
field strength in the distant supersonic solar wind. The spacecraft magnetic
field is a complex, time-dependent signal that must be removed from the measured
magnetic field signal in order to derive the ambient magnetic fields of the
solar wind and heliosheath. Corrections must also be made for spurious magnetic
signals and noise associated with the telemetry system, ground tracking systems,
and other factors. Extracting the signal describing the solar wind and
heliosheath from the many sources of uncertainty is a complex and partly
subjective process that requires understanding of the instrument and judgment
based on experience in dealing with the ever-changing extraneous signals. We
estimate that for the V1 MAG data the 1-sigma the uncertainty the 48 sec
averages for each of the components of the magnetic field  BR, BT, and BN is
typically +/- 0.02 nT; the uncertainty in magnitude F1 is typically +/- 0.03 nT.
F1, BR, BT, and BN can differ from one another and they may vary with time, but
there is no practical way to determine these uncertainties more precisely at
present.
References
Daniel B. Berdichevsky, Voyager Mission, Detailed processing of weak magnetic
fields; I - Constraints to the uncertainties of the calibrated magnetic field
signal in the Voyager missions , 2009;
https://vgrmag.gsfc.nasa.gov/Berdichevsky-VOY_sensor_opu090518.pdf
Behannon, K.W., M.H. Acu..a, L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M.
Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2, Space Science
Reviews, 21 (3), 235-257, 1977. Burlaga, L.F., Merged interaction regions and
large-scale magnetic field fluctuations during 1991 - Voyager-2 observations, J.
Geophys. Res., 99 (A10), 19341-19350, 1994.
Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley Jr., Heliospheric
magnetic field strength and polarity from 1 to 81 AU during the ascending phase
of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002.
Ness, N., K.W. Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., , 76,
3564, 1971.
 
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VOYAGER2_COHO1HR_MERGED_MAG_PLASMA (spase://VHO/NumericalData/Voyager2/MAGandPLS/PT1H)
Description
The  main science objectives for the VOYAGER interplanetary mission are as  
follows: 
- investigate the structure of the solar wind magnetic fields and plasma in the
inner and outer heliosphere; 
- conduct long term study of heliospheric evolution during different phases of
the twenty-two year solar magnetic cycle and the eleven-year solar activity
cycle;
- study the long term solar modulation and determine the elemental and isotopic
abundances of galactic cosmic ray particles in the heliosphere;
- measure  radial gradients, spectra, and nuclear abundances of the anomalous
component of cosmic rays  from  acceleration at the solar wind termination
shock; 
- investigate local particle acceleration in the interplanetary medium from
solar flare shocks and corotating interaction regions; 
- study propagation of solar energetic particles in the heliosphere.
This directory contains hourly averages of parameters for the interplanetary
magnetic field, solar wind plasma and spacecraft trajectory coordinates
VOYAGER-1 data have been reprocessed to ensure a uniformity of content and
coordinate systems relative to data from other deep-space missions:
 - All spacecraft trajectory data were transformed to a Heliographic Inertial
(HGI) coordinate system.
- calculation of the RTN Cartesian components of interplanetary magnetic field
from the RTN spherical components: 
         BR=|B|*cos(THETA)*cos(PHI) 
         BT=|B|*cos(THETA)*sin(PHI) 
         BN=|B|*sin(THETA)          
where THETA - spherical RTN latitude, PHI- spherical RTN longtitude 
- calculation of RTN Spherical components of the solar wind velocity from RTN
cartesian components:
         V = (Vr^2 + Vt^2 + Vn^2)^0.5
         THETA=asin(Vn/V)
         PHI=atan(Vt/Vr)
where THETA - spherical RTN latitude, PHI- spherical RTN longtitude
- calculation of given thermal speed Vth into temperature T (Kelvin):
         T=60.5*Vth^2 (Vth in km/s)
- merging of trajectory coordinates, magnetic field data, and plasma data files
into a single annual file VY1_YR.DAT, where YR is the year
- Data gaps were filled with dummy numbers for the missing hours or entire days
to make all files of equal length.  The character \Ə\' is used to fill all
fields for missing data according to their format, e.g. \' 9999.9\' for a field
with the FORTRAN format F7.1. Note that format F7.1 below really means
(1X,F6.1),etc.a
Notes on Voyager 1 and 2 Magnetometer Data After 1989.
  At the time of experiment proposal, it was expected that the required accuracy
of the measurements would be 0.1 nT, determined by the combined noise of the
sensors and the spacecraft field.  The spacecraft magnetic field at the outboard
magnetic field sensor, referred to as the primary unit, was expected to be 0.2
nT and highly variable, consistent with current estimates. Hence, the dual
magnetometer design (Ness et al., 1971; Behannon et al. 1977).  At distances 
40 AU, the heliospheric magnetic fields are generally much weaker than 0.4 nT;
the average magnetic field strength near 40 AU and 85 AU is ..0.15 nT and ..0.05
nT, respectively. The use of roll calibrations lasting ..6 hours permits
determination of the effective zero levels for the two independent magnetic axes
that are perpendicular to the roll axis (which is nearly parallel to the radius
vector to the Sun) at intervals of ..3 months. There is no roll calibration for
the third magnetic axis. Comparison of the two derived magnetic vectors from the
two magnetometers permits validation of the primary magnetometer data with an
accuracy of 0.02 nT - 0.05 nT. further informaion look at
https://omniweb.gsfc.nasa.gov/coho/html/cw_data.html
The Heliographic Inertial (HGI) coordinates are Sun-centered and inertially
fixed with respect to an X-axis directed along the intersection line of the
ecliptic and solar equatorial planes.  The solar equator plane is inclined at
7.25 degrees from the ecliptic.  This direction was towards ecliptic longitude
of 74.36 degrees on 1 January 1900 at 1200 UT; because of precession of the
celestial equator, this longitude increases by 1.4 degrees/century. The Z axis
is directed perpendicular and northward from the solar equator, and the  Y-axis
completes the right-handed set. This system differs from the usual  heliographic
 coordinates  (e.g. Carrington longitudes) which are fixed in the frame of the
rotating Sun. 
The RTN system is fixed at a spacecraft (or the planet). The R axis is  directed
radially away from the Sun, the T axis is the cross product of the solar
rotation axis and the R axis, and the N axis is the cross product of R and T. 
At zero Heliographic Latitude when the spacecraft is in the solar equatorial
plane the N and solar rotation axes are parallel.
Hour averages of the interplanetary solar wind data from, and hourly
heliocentric coordinates of, Voyager1/2 and other interplanetary spacecraft may
be also be accessed and plotted on-line through the COHOWeb service 
http://cohoweb.gsfc.nasa.gov/
Acknowledgement: Use of these data in publications should be accompanied at
minimum by acknowledgements of the National Space Science Data Center and the
responsible Principal Investigator defined in the experiment documentation
provided here.  Citation of NSSDC's Coordinated Heliospheric Observations (COHO)
data base would also be appreciated, so that other potential users will be made
aware of this service. 
For questions about this data set, please contact: Dr. N. Papitashvili,
natalia.e.papitashvili@nasa.gov, GSFC-Code 672 
 
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VOYAGER2_PLS_COMPOSITION (spase://VSPO/NumericalData/Voyager2/PLS/JupiterViperComposition/P96S)
Description
These data are from a re-analysis of the Voyager Plasma Spectrometer (PLS) data
at Jupiter by the PLS group at the Laboratory for Atmospheric and Space Physics
(LASP) at the University of Colorado. Density, temperature, and flow velocity
fits for total and individual ions were done using the Voyager Ion PLS
Experiment Response (VIPER) code and error analysis as described at
http://lasp.colorado.edu/home.mop/missions/voyager/viper/. Fits are determined
from processing of the ion currents from the A, B, C, and D cups of the
instrument.. As per the Fit Case variable, one of five different constraints
were used in the VIPER fits for each 96-sec time interval: (1) free variation of
all parameters (mainly for the cold ion torus); (2) constraint of the ion
abundances for the five major species (O+, O++, S+, S++, S+++) to standard
composition as determined from Delamere et al. (2005); (3) fixed ion composition
and flow speed; (4) cold blobs in the plasma sheet where resolved peaks can be
fit with allowance for some variance in composition; (5) interpolation between
composition of cold torus and standard abundances at 6 RJ from Delamere et al.
(2005). 
Reference: Delamere, P. A., Bagenal, F., and Steffl, A. (2005), Radial
Variations in the Io Plasma Torus During the Cassini Era, Journal of Geophysical
Research Space Physics, 110(A12), A12223, doi: 10.1029/2005JA011251. 
 
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VOYAGER2_PLS_HIRES_PLASMA_DATA
Description
The files in this directory contain the Voyager fine resolution plasma data. The
plasma parameters are obtained by finding the best fit of a convected isotropic
Maxwellian distribution to the data. One sigma errors are typically less than
0.5% in the speed and VR, less than 5% for the density and thermal speed, and
vary greatly for VT and VN. Sampling times range from 12 to 192 sec., with
sampling generally more frequent early in the mission.
The velocity components are given in the RTN coordinate system, where R is
radially outward, T is in a plane parallel to the solar equatorial plane and
positive in the direction of solar rotation, and N completes a right-handed
system.
(WARNING: V_t, and V_n parameters are often NOT reliable after 1989)
Please consult with us, or at least send preprints, when you use this data to
prevent grievous errors or misconceptions. (John Richardson, jdr@space.mit.edu)
 
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