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VG2 J/S/U/N/SS PWS RESAMP SPECTRUM ANALYZER HOUR AVG V1.0 (PDS)

NSSDCA ID: PSFP-00642

Availability: Archived at NSSDC, accessible from elsewhere

Time span: 1977-08-20 to 

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview

This data set consists of electric field spectrum analyzer data from the Voyager 2 Plasma Wave Subsystem obtained during the entire mission. Data after 2007-08-31 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 2 spacecraft travels from Earth to beyond 75 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 1977-08-20 Launch 1979-07-02 First inbound bow shock crossing at Jupiter 1979-08-03 Last outbound bow shock crossing at Jupiter 1981-08-24 First inbound bow shock crossing at Saturn 1981-08-31 Last outbound bow shock crossing at Saturn 1982-04-26 10 AU 1983-08-30 Onset of first major LF heliospheric radio event 1986-01-24 First inbound bow shock crossing at Uranus 1986-01-29 Last outbound bow shock crossing at Uranus 1986-05-26 20 AU 1989-08-07 30 AU 1989-08-24 First inbound bow shock crossing at Neptune 1989-08-28 Last outbound bow shock crossing at Neptune 1992-07-06 Onset of second major LF heliospheric radio event 1993-05-08 40 AU 1996-10-10 50 AU 2000-01-27 60 AU 2002-11-01 Onset of third major LF heliospheric radio event 2003-04-21 70 AU 2006-07-01 80 AU 2009-09-03 90 AU 2012-11-04 100 AU Data Sampling ============= This data set consists of average and peak wave electric field intensities accumulated over 1-hour intervals from the Voyager 2 Plasma Wave Receiver spectrum analyzer obtained during the entire mission. For each 1-hour time interval squares of the calibrated electric field measurements obtained during each hour-long interval in each of the 16 spectrum analyzer channels are summed and then divided by the number of measurements. The square root of the resulting value is obtained and stored as the average electric field strength for the respective channel. During the same hour-long interval, the maximum electric field strength acquired in each of the 16 channels is also recorded and stored as the peak electric field strength for the respective channel. Hence, for each hour, an average and peak electric field spectrum from 10 Hz to 56.2 kHz is obtained. The 16 spectrum analyzer channels have center frequencies that range from 10 Hertz to 56.2 kiloHertz and are logarithmically spaced in frequency, four channels per decade. The time associated with each peak and average spectrum is the time of the beginning of the averaging interval. Given variations in the sweep rate of the instrument (from a minimum of 4 seconds/sweep to a maximum of 96 seconds/sweep) the maximum number of samples in an hour-long interval can range from 900 to 38. Data gaps within the interval can further reduce the number of samples. 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. 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 in the full-resolution data set, depending on telemetry mode.) This data set includes one-hour average and peak values for each channel. 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 measurements provided in the average and peak electric field spectra included in this data set are in units of electric field (volts/meter). 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 = (efield(ichan))**2 / bandwidth(ichan) Finally, power flux may be obtained by dividing the spectral density by the impedance of free space in ohms: pwrflux = (efield(ichan))**2 / bandwidth(ichan) / 376.73 The center frequencies and bandwidths of each PWS spectrum analyzer channel for each Voyager spacecraft are given below: VOYAGER 2 PWS SPECTRUM ANALYZER Voyager-2 Channel Center Frequency Bandwidth 1 10.0 Hz 2.16 Hz 2 17.8 Hz 3.58 Hz 3 31.1 Hz 4.50 Hz 4 56.2 Hz 10.7 Hz 5 100. Hz 13.8 Hz 6 178. Hz 28.8 Hz 7 311. Hz 39.8 Hz 8 562. Hz 75.9 Hz 9 1.00 kHz 75.9 Hz 10 1.78 kHz 151. Hz 11 3.11 kHz 324. Hz 12 5.62 kHz 513. Hz 13 10.0 kHz 832. Hz 14 17.8 kHz 1260 Hz 15 31.1 kHz 2400 Hz 16 56.2 kHz 3800 Hz A failure in the Voyager 2 Flight Data System which occurred about 3 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, Uranus, and Neptune encounters, but is not valid for Earth-Jupiter cruise and may be modified in the future. The following implementation of this correction algorithm in FORTRAN assumes that uncalibrated data numbers are stored in a 16-element integer array, idn, with the array index equal to the PWS channel number: c 'the old noise level' for vg2 pws real tonl(9:16) /2.0, 1.0, -1.0, -2.0, -3.0, 1.0, 2.0, 1.0/ do ichan = 9, 16 if (idn(ichan) .gt. 0) then if (idn(ichan) .lt. 64) idn(ichan) = 64 if (idn(ichan) .le. 72) then idn(ichan) = int (tonl(ichan) - 530.4 + & 8.6 * float (idn(ichan))) else idn(ichan) = int (tonl(ichan) + 20.113 + & 0.99 * float (idn(ichan))) end if end if end do This correction has been applied to the appropriate data in this data set. 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 average and peak 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 hour). Each sample is a floating point electric field strength in units of volts/meter. 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. Furthermore, even during the rare times when the spacecraft is turned, the hour-long averages in this data set would almost completely mask any modulation caused by the rotating dipole antenna pattern.

These data are available on-line from the Planetary Data System (PDS) at:

https://pds-ppi.igpp.ucla.edu/data/VG2-J-S-U-N-SS-PWS-4-SUMM-SA1HOUR-V1.0/

Alternate Names

  • VG2-J/S/U/N/SS-PWS-4-SUMM-SA1HOUR-V1.0

Discipline

  • Planetary Science: Fields and Particles

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II

 

Personnel

NameRoleOriginal AffiliationE-mail
Prof. Donald A. GurnettData ProviderUniversity of Iowa
Dr. William S. KurthGeneral ContactUniversity of Iowawsk@space.physics.uiowa.edu
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