Data Set Information
|
DATA_SET_NAME |
VG1 J/S/SS PLASMA WAVE SPECTROMETER RAW WAVEFORM 60MS V1.0
|
DATA_SET_ID |
VG1-J/S/SS-PWS-1-EDR-WFRM-60MS-V1.0
|
NSSDC_DATA_SET_ID |
|
DATA_SET_TERSE_DESCRIPTION |
The Voyager 1 Plasma Wave Spectrometer
(PWS) raw full resolution data set includes all electric field waveform
data for the entire Voyager 1 mission.
|
DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set consists of electric field waveform samples from
the Voyager 1 Plasma Wave Subsystem waveform receiver obtained
during the entire mission. Data after 2017-12-30 will be added to the
archive on subsequent volumes. The data set encompasses all
waveform 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
=============
The waveform is sampled at 4-bit resolution through a bandpass
filter with a passband of 40 Hz to 12 kHz. 1600 samples are
collected in 55.56 msec (at a rate of 28,800 samples per second)
followed by a 4.44-msec gap. Each 60-msec interval constitutes
a line of waveform samples. The data set includes frames of
waveform samples consisting of up to 800 lines, or 48 seconds,
each. The telemetry format for the waveform data is identical
to that for images, hence the use of line and frame as
constructs in describing the form of the data.
Data Processing
===============
Because there is no direct method for calibrating these data and
because the raw format of packed, 4-bit samples is
space-efficient, these data are not processed for archiving.
The data may be plotted in raw form to show the actual waveform;
this is useful for studying events such as dust impacts on the
spacecraft. But the normal method of analyzing the waveform
data is by Fourier transforming the samples from each line to
arrive at an amplitude versus frequency spectrum. By stacking
the spectra side-by-side in time order, a frequency-time
spectrogram can be produced.
Data
====
The waveforms are collections of samples of the electric field
measured by the dipole electric antenna at a rate of 28,800
samples per second. The 4-bit samples provide sixteen digital
values of the electric field with a linear amplitude scale, but
the amplitude scale is arbitrary because of the automatic gain
control used in the waveform receiver. The instantaneous
dynamic range afforded by the 4 bit samples is about 23 dB, but
the automatic gain control allows the dominant signal in the
passband to be set at the optimum level to fit within the
instantaneous dynamic range. With the gain control, the overall
dynamic range of the waveform receiver is about 100 dB. The
automatic gain control gain setting is not returned to the
ground, hence, there is no absolute calibration for the data.
However, by comparing the waveform spectrum derived by Fourier
transforming the waveform to the spectrum provided by the
spectrum analyzer data, an absolute calibration may be obtained
in most cases.
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
remains in a 3-axis stabilized orientation almost continuously,
and these data are not obtained during the infrequent
calibration turns. Furthermore, the automatic gain control
feature would tend to counteract any orientation-dependent
amplitude variations.
|
DATA_SET_RELEASE_DATE |
2018-09-07T00:00:00.000Z
|
START_TIME |
1978-08-21T05:41:36.300Z
|
STOP_TIME |
2017-12-30T12:43:06.186Z
|
MISSION_NAME |
VOYAGER
|
MISSION_START_DATE |
1972-07-01T12:00:00.000Z
|
MISSION_STOP_DATE |
N/A (ongoing)
|
TARGET_NAME |
SOLAR SYSTEM
SATURN
JUPITER
|
TARGET_TYPE |
PLANETARY SYSTEM
PLANET
PLANET
|
INSTRUMENT_HOST_ID |
VG1
|
INSTRUMENT_NAME |
PLASMA WAVE RECEIVER
|
INSTRUMENT_ID |
PWS
|
INSTRUMENT_TYPE |
PLASMA WAVE SPECTROMETER
|
NODE_NAME |
Planetary Plasma Interactions
|
ARCHIVE_STATUS |
ARCHIVED - ACCUMULATING
|
CONFIDENCE_LEVEL_NOTE |
Overview
========
The Spacecraft Event Time (SCET) originally included in
Cxxxxxxx.DAT files is very often incorrect or missing (zero),
especially through the Jupiter encounter. It is important to
use the SCET which is provided in the Cxxxxxxx.LBL file for the
.DAT file your are using. The SCET from the .LBL file is the
best known time for the data, based on the use of the
appropriate SPICE kernel. The originally-provided data file
includes no consistently present spacecraft identification. The
SPACECRAFT_ID in the .LBL file is the most reliable indicator of
the host spacecraft. Because the .LBL files are detached from
the .DAT files, it is possible to lose the SCET and
SPACECRAFT_ID information. Therefore, an ASCII entry has been
added to spare words in the .DAT file header at byte 249
including SPACECRAFT_ID, spacecraft clock partition (rollover
indicator), and SCET. In both the PDS .LBL file and this ASCII
SCET entry in the .DAT file header, the SCET refers to the time
of the first sample of the 48-second frame, assuming all data
are present. For example, if the first 10 seconds of data is
missing, the SCET provided in these two locations would be 10
seconds earlier than that of the first data present in the
frame. Given this time, the line and sample number of a
measurement provides an accurate time for the sample with the
understanding that the time between the beginning of two
adjacent lines is 60 milliseconds and the time between samples
is 34.72 microseconds.
This data set includes all available waveform receiver data
obtained from launch through at least the end of 2011. Data are
added at regular intervals after 2011.
Note that for data acquired during the Voyager 1 Jupiter
Encounter mission phase, it is usually the case that the first
16 samples (8 bytes) of waveform data per data line are invalid.
Hence, it is strongly recommended that these bytes be skipped by
any analysis software.
Beginning on 1992-11-03, the telecom performance would no longer
support playing data off the tape recorder at its lowest
playback rate. As a work-around, four data lines of every five
are discarded during playback beginning with this date. For
various reasons, the one data line out of five which is returned
to the ground are repeated 5 times in the *.DAT files. The
DATA_LINES parameter in the *.LBL file, therefore, counts only
UNIQUE valid data lines; the maximum DATA_LINES after this date,
then is 160.
There has been no attempt to clean various interference signals
from the data. Most of these can normally be easily seen in
frequency-time spectrograms as narrowband, fixed-frequency
tones. The most common include narrow-band tones at 2.4 and 4.8
kHz which are power supply harmonics. There is sometimes a tone
near 1.7 kHz which is associated with the operation of the
spacecraft gyros. The spacecraft tape recorder results in a
rather intense band in the frequency range of a few hundred
Hertz. There are few times when the data in this frequency
range can be used. However, there are times when the real
signals in this frequency range can exceed the intensity of the
interference sufficiently so that the frequency range near a few
hundred Hz can be used. Use of the spectrum analyzer data can
be of use to determine when these time periods occur. The
stepper motor of the LECP instrument also interferes in the
frequency range of a few hundred Hz, but for periods of a few
seconds. The LECP interference is very intense and captures the
automatic gain control so that real signals, even where there is
no interference, will appear to decrease in amplitude until the
LECP interference fades in amplitude. The PLS instrument
periodically interferes at 400 Hz and odd harmonics because of a
400-Hz square wave used to modulate a grid in the detector. The
PLS interference lasts for several seconds and ends abruptly.
Telemetry errors result in a fairly graceful degradation of the
waveform data. Assuming the telemetry errors are randomly
occurring bursts, they typically appear as an enhanced
background level in the spectrum. Since the bursts are short,
their Fourier transform is a broadband spectrum. When looking
for relatively narrowband features or features with distinct
frequency-time characteristics, the result of the bursts simply
reduce the signal-to-noise in the spectrum. One way of reducing
the effect of burst telemetry errors is to pass the waveform
data through a low-pass filter to despike it, prior to running
the Fourier transform. The waveform data is not subject to the
negative effects of the failure in the Voyager 2 Flight Data
System which reduces the sensitivity of the spectrum analyzer
and affects the calibration above 1 kHz. In fact, use of the
1-12 kHz waveform data is an effective way of avoiding the
problems with the spectrum analyzer data in this frequency
range.
File Edits
==========
Minor edits have been applied to the original EDR files in order
to provide reliable spacecraft and time identification and to
adjust for missing file header records. Detailed format
information is provided elsewhere, but briefly, an ASCII text
string has been inserted starting at byte 249 of the first
record of each file. This string provides the most reliable
spacecraft and time identification and is in the format:
VOYAGER-n PWS n/nnnnn.nn yyyy-mm-ddThh:mm:ss.sssZ\0\0
In cases where the EDR file header record was missing, a pseudo
header was created by duplicating the first available record of
the file, inserting the ASCII text string starting at byte 249,
and zero-filling the remaining bytes of the record. Since these
files are a possible source of confusion for anyone attempting
to extract detailed engineering information from EDR headers,
they are listed below. The first element of the directory path
is actually the volume name.
VGPW_1001/DATA/WFRM/P2/V10101/C1050125.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1050126.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1050900.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1050901.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1051003.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1051004.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1152525.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1152526.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1153300.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1153301.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1153403.DAT
VGPW_1001/DATA/WFRM/P2/V10101/C1153404.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200713.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200715.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200717.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200725.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200727.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200729.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200731.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200733.DAT
VGPW_1001/DATA/WFRM/P2/V10102/C1200737.DAT
VGPW_1001/DATA/WFRM/P2/V10108/C1552337.DAT
VGPW_1001/DATA/WFRM/P2/V10116/C1579901.DAT
VGPW_1001/DATA/WFRM/P2/V10117/C1579902.DAT
VGPW_1001/DATA/WFRM/P2/V10129/C1622419.DAT
VGPW_1001/DATA/WFRM/P2/V10129/C1622422.DAT
VGPW_1001/DATA/WFRM/P2/V10129/C1622423.DAT
VGPW_1001/DATA/WFRM/P2/V10135/C1622948.DAT
VGPW_1004/DATA/WFRM/P2/V10409/C1627624.DAT
VGPW_1004/DATA/WFRM/P2/V10435/C1629025.DAT
VGPW_1005/DATA/WFRM/P2/V10534/C1631259.DAT
VGPW_1006/DATA/WFRM/P2/V10601/C1631356.DAT
VGPW_1006/DATA/WFRM/P2/V10624/C1633702.DAT
VGPW_1006/DATA/WFRM/P2/V10635/C1634718.DAT
VGPW_1007/DATA/WFRM/P2/V10701/C1634818.DAT
VGPW_1007/DATA/WFRM/P2/V10721/C1636302.DAT
VGPW_1007/DATA/WFRM/P2/V10723/C1636707.DAT
VGPW_1007/DATA/WFRM/P2/V10723/C1636744.DAT
VGPW_1007/DATA/WFRM/P2/V10731/C1637719.DAT
VGPW_1007/DATA/WFRM/P2/V10735/C1638242.DAT
VGPW_1008/DATA/WFRM/P2/V10814/C1640636.DAT
VGPW_1008/DATA/WFRM/P2/V10823/C1641232.DAT
VGPW_1008/DATA/WFRM/P2/V10829/C1641543.DAT
VGPW_1010/DATA/WFRM/P2/V11017/C1647452.DAT
VGPW_1010/DATA/WFRM/P2/V11018/C1647617.DAT
VGPW_1010/DATA/WFRM/P2/V11024/C1648814.DAT
VGPW_1010/DATA/WFRM/P2/V11035/C1683643.DAT
VGPW_1011/DATA/WFRM/P2/V11103/C1750333.DAT
VGPW_1011/DATA/WFRM/P2/V11107/C3074538.DAT
VGPW_1011/DATA/WFRM/P2/V11116/C5530536.DAT
Review
======
This archival data set was examined by a peer review panel prior
to its acceptance by the Planetary Data System (PDS). The peer
review was conducted in accordance with PDS procedures.
Prior to creation of the final version of the archival data set,
key elements of the archive were distributed for preliminary
review. These included electronic versions of example PDS
labels, CATALOG files, and Software Interface Specifications.
These materials were distributed to PDS personnel, the
experiment investigator, and others, as appropriate.
|
CITATION_DESCRIPTION |
Kurth, W.S., and L.J. Granroth,
VG1-J/S/SS-PWS-1-EDR-WFRM-60MS-V1.0, VG1 J/S/SS PLASMA
WAVE SPECTROMETER RAW WAVEFORM 60MS V1.0,
NASA Planetary Data System, 2018.
|
ABSTRACT_TEXT |
The Voyager 1 Plasma Wave Spectrometer
(PWS) raw full resolution data set consists of electric field waveform
samples from the Voyager 1 Plasma Wave Subsystem waveform receiver
obtained during the entire mission. Data will continue to be added to
the archive on subsequent volumes. The data set encompasses all waveform
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. Data for this data set are acquired
from the PWS waveform receiver. Data are presented as time series of
4-bit voltage measurements acquired at the rate of 28,800 samples per
second through a 40 Hz to 12 kHz bandpass filter. An automatic gain
control is used to keep the signal within the usable range of the 4-bit
digitization, however, the gain information is not returned to the
ground, hence, there is no direct, absolute calibration. However, a
power spectrum analysis returns a spectrum that has accurate relative
amplitudes between spectral elements. This data set provides the highest
temporal resolution data from the Voyager mission. A browse data set is
included with these data which provides for a graphical search of the
data using a series of thumbnail and full-sized spectrograms which lead
the user to the particular data file(s) of interest.
|
PRODUCER_FULL_NAME |
DR WILLIAM S. KURTH
|
SEARCH/ACCESS DATA |
Planetary Plasma Interactions Website
Planetary Plasma Interactions Website
|
|