PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
LABEL_REVISION_NOTE = "
2014-04-27, W. Kurth, C. Piker, Revision 1;
2014-04-28, W. Kurth, general edits;
2014-05-02, G. Hospodarsky, calibration updates;
2015-10-l6, C. Piker, Lien Resolution updates;
2018-07-10, J. Mafi, Added instrument paper reference;
"
OBJECT = INSTRUMENT
INSTRUMENT_HOST_ID = JNO
INSTRUMENT_ID = WAV
OBJECT = INSTRUMENT_INFORMATION
INSTRUMENT_NAME = "WAVES"
INSTRUMENT_TYPE = "PLASMA WAVE SPECTROMETER"
INSTRUMENT_DESC = "
Instrument Overview
===================
Instrument Id : WAV
Instrument Host Id : JNO
Principal Investigator : WILLIAM KURTH
PI PDS User Id : WKURTH
Instrument Name : Waves
Instrument Type : PLASMA WAVE SPECTROMETER
Build Date : 2010-10-14
Instrument Manufacturer Name : THE UNIVERSITY OF IOWA
The Waves instrument consists of one electric dipole antenna, one magnetic
search coil, two pre-amplifiers, three receivers, and a digital processing
unit. Taken together these components can detect and digitize wave electric
fields from 50 Hz to 45.25 MHz and wave magnetic fields from 50 Hz to 20
kHz. At the highest duty cycle, Waves can record one sweep per second
across all spectral bands while simultaneously capturing 5 waveforms in
various bands.
Electric fields are detected via an electric dipole antenna deployed from
the aft flight deck in a 'V' configuration with a tip-tip length of about 4
meters. The signal from the electric antenna is conditioned in the electric
preamplifier which has three frequency bands and each band has an attenuator
that can be selected or not, to limit the input to the receivers under
strong signal conditions. When enabled attenuations are 25.3 dB, 25.3 dB,
and 19.0 dB for the 50 Hz - 20 kHz, 10 kHz - 150 kHz and 100 kHz - 45 MHz
bands respectively. Wave magnetic components, are detected via a magnetic
search coil which is also mounted to the aft flight deck. The signals from
the search coil are conditioned by a magnetic preamplifier located close to
the sensor, but within the spacecraft thermal environment.
The instrument includes three receivers to detect signals from the sensors.
The first is a 3-channel low frequency receiver (LFR) that is used to
analyze plasma waves. Two channels measure electric fields in the frequency
ranges of 50 Hz to 20 kHz and 10 to 150 kHz, and one channel measures
magnetic fields in the range of 50 Hz to 20 kHz. The electric channels
include an attenuator that may be toggled either on or off by the automatic
gain control software in the data processing unit. When on signals are
attenuated by 19.8 dB (low-band) and 19.4 dB (high-band) in addition to any
attenuation by the electric preamp. All 3 LFR channels are sampled
simultaneously. This receiver produces a digitized waveform from each
channel which is either sent directly to the ground (after compression) in
burst mode or spectrum analyzed in the Waves digital signal processor to
produce spectra with ~ 10 logarithmically-spaced channels per decade of
frequency.
The LFR also has a noise input from the spacecraft power distribution unit
(PDDU). By subtracting this noise channel from the channel from either
antenna, a noise cancellation process can be carried out. Based on in-flight
experience, there is insufficient spacecraft noise as determined from the
line from the PDDU to merit this additional processing; this will be
re-evaluated at Jupiter.
Waves also contains two nearly identical high frequency receivers, HFR-44
and HFR-45. (The numeric suffix is just a tracking ID and bares no
relationship to frequency.) Each receiver contains three channels. A
baseband channel, which handles measurements in the 0.1 to 3 MHz band, a
down-mixed log response channel for sweep frequency operations in the 3 MHz
to 41 MHz range, and a paired-mixer channel covering the 3 MHz to 45.25 MHz
range for acquiring high frequency resolution spectra near the electron
cyclotron frequency. To provide additional support for handling large
amplitude signals, each HFR has a front-end 32 dB step-attenuator that may
be set to add further attenuation to incoming signals, in 2 dB steps. The
operation of the step-attenuators is handled automatically by the Waves
digital signal processing unit.
The HFR baseband channel operates much as the LFR, though waveforms are
digitized at the much higher rate of 7 Msps. Like the LFR, HFR baseband
samples may be sent out 'as-is' (with compression) in burst mode or sent to
the digital signal processor for conversion to spectra in survey made.
The HFR down-mixed log response channel operates quite differently.
Incoming signals are mixed with a locally generated pure sine wave. The
result is then low-pass filtered below 500 kHz. Due to the low pass filter,
only frequency components within 500 kHz of the of local mixer frequency
contribute to the output signal power. This down-mixed signal is directed
to a log-amplifier which produces an output voltage proportional to the
logarithm of the energy in the band, which is then digitized at 8-bit
resolution. Measurements are taken as in a classic swept frequency
receiver. The mixer signal is set to 3.5 MHz and then incremented in 1 MHz
steps ending at 40.5 MHz, thus producing successive measurements of spectral
density in 1 MHz bands from 3 MHz to 41 MHz. This channel is used
exclusively for generating survey mode data.
The HFR paired-mixer channel shares components with the log response channel
but feeds incoming signals to two frequency mixers instead of just one.
Both mixers are set to the same mixing frequency, but for one mixer, the
local tone is 90 degrees out of phase with the other. As with the log
response channel, the mixer output is low-pass filtered below 500 kHz and
the two resulting down-mixed signals are digitized at 1.3125 MHz and
transmitted to the ground for further processing into high resolution 1 MHz
bandwidth spectra, details of the processing steps are outlined in Appendix
C of VOLSIS.HTM. The purpose for collecting high resolution measurements
far above the baseband is to examine detailed structure near the electron
cyclotron frequency, so instead of merely sweeping the receiver across all
bands in a regular cadence, the mixer tone is either commanded to a
particular frequency or set to automatically track Fce using measurements
provided by the MAG instrument on-board. The mixer frequency can be set
between 3.5 and 44.75 MHz in 0.25 MHz steps, which allows for 1 MHz spectra
covering the range of 3 MHz to 45.25 MHz. In cases where Fce drops below
3 MHz the HFR baseband channel is used for data collection and the mixers
are disabled.
The Waves digital signal processing unit is implemented in a field-
programmable gate array. This unit handles all measurement scheduling,
automatically controls receiver attenuators, provides facilities for
converting digitized waveforms to spectra, provides loss-less Rice
compression, and handles communications with the Juno spacecraft command
and data system.
Platform Mounting Description
-----------------------------
The Waves instrument utilizes two sensors. For the detection of the
electric component of waves, an electric dipole antenna is used. The
antenna is mounted on the aft flight deck, centered under solar panel wing
#1 which has the Magnetometer boom at its end. Each element of the dipole
is 2.8 m long. The two elements are deployed shortly after launch in a
plane that is tilted aft of the aft flight deck by 45 degrees and with a
subtended angle between the two elements of 120 degrees. An electric
preamp is housed at the root of the two dipole elements. The symmetry axis
of the dipole projected into the aft flight deck plane is parallel to the
Magnetometer solar panel. The antenna pattern of the dipole for low
frequencies is approximately a dipole with maximum sensitivity to electric
fields parallel to the Y-axis of the spacecraft, i.e. perpendicular to
both the MAG boom axis and the spin axis.
For the detection of the magnetic component of waves, a magnetic search
coil (MSC) is used. The search coil consists of a rod of mu-metal
(permalloy) material 15 cm long with 10,000 turns of copper wire on a
bobbin surrounding the rod. The coil is attached to the aft flight deck
with its preamplifier mounted close by. The long axis of the MSC is
parallel to the spacecraft Z axis (along the high gain antenna axis),
hence, the antenna pattern is approximately that of a dipole with maximum
sensitivity parallel to the spin axis of the spacecraft. Since Juno's
spin axis is mostly perpendicular to Jupiter's strong magnetic field,
this configuration minimizes the variation of signal at the spin
frequency.
The Waves electronics (other than the preamplifiers mentioned above)
reside in the main electronics box in the Juno radiation vault, which
is located directly behind the high-gain antenna.
Lead Co-Investigator
----------------------
The Lead Co-Investigator for the Waves instrument is William Kurth.
Scientific Objectives
=====================
One of the four overarching science objectives of the Juno mission is to
explore, for the first time, the three-dimensional structure of Jupiter's
polar magnetosphere and auroras. The Waves investigation directly supports
this theme. The Waves science objectives supporting this overarching
objective are to (1) determine the nature of coupling between Jupiter's
internal magnetic field, the ionosphere, and the magnetosphere, (2)
investigate and characterize the three-dimensional structure of Jupiter's
polar magnetosphere, and (3) identify and characterize auroral processes at
Jupiter. These main objectives are further broken down into the following:
* Locate and determine the nature of the auroral acceleration region.
* Identify the major current systems coupling the magnetosphere to the
ionosphere.
* Determine the role wave-particle interactions play in the Jovian aurora.
* Measure radio and plasma wave phenomena (auroral hiss, electron and ion
phase space holes, auroral radio emissions, etc.) emission
characteristics (intensity, electric and magnetic fields) inside source
regions.
* Identify and characterize emission processes.
* Determine the fundamental differences between aurora associated with
+ The breakdown of co-rotation in the middle magnetosphere
+ The solar wind
+ Io (or other Galilean satellite) flux tube
* Determine the beaming properties of Jovian radio emissions at high
latitudes.
* Determine the source locations for Jovian auroral radio emissions.
Additional issues to be addressed by the Waves investigation include (1)
the determination of dust flux in the region above the atmosphere and below
Jupiter's ring system at and near the Jovigraphic equator and (2) to look
for lightning-generated whistlers.
Operational Considerations
==========================
Juno's highly elliptical orbit will carry the Waves instrument through very
different environments at very different velocities. Near perijove full
electric spectra from 50 Hz to 41 MHz and full magnetic spectra from 50 Hz
to 20 kHz will be collected with a temporal resolution of one to two
seconds. For the remainder of the orbit this rate will be stepped down to
one sweep per ~30 seconds. An intermediate cadence of a complete electric
and magnetic spectrum every 10 seconds is available for distant plasmasheet
crossings and/or for regions just outside the periapsis region. For the
auroral regions burst-mode high rate waveform measurements are made. The
burst mode is automatically triggered inside regions of interest based on
the detection of intense waves in various bands.
The majority of the data collected by Waves during each pass occurs during
the ~12 hours near perijove. Most of these are stored for later
transmission through out the remainder of the orbit.
Calibration
===========
The Juno Waves instrument was calibrated in two by applying known amplitude
and frequency signals to the input of the receivers and sensors, and
recording output of instrument. This results in lookup tables of input
signal strength for instrument output data number. Calibrations were
performed on the individual receivers and sensors, and also end-to-end
calibrations were performed on the sensors plus receiver system.
Calibrations and tests were performed at the extremes of the expected
operating range of the instrument (-35C and +75C), and at the expected
typical operating temperature of +22C which is used as the primary
calibration. The individual sensor and receiver calibrations were combined
and compared to the end-to-end calibrations and found to be in good
agreement.
Magnetic Search Coil (MSC) sensor and preamplifier calibrations: The
calibration of the MSC sensor and preamplifier was performed using a
solenoid drive coil to produce a known magnetic field strength over the
amplitude and frequency range of the sensor while the output voltage of the
sensor was recorded, producing a transfer function over frequency of the
output voltage of the preamplifier for a strength of the wave magnetic field
in nT.
Electric Preamplifier Calibrations: The Electric Preamplifier was
calibrated by applying a known voltage to the input of the preamplifier over
the amplitude and frequency range of the instrument and recording the output
voltage of the preamplifier, producing a transfer function over frequency of
the output voltage of the preamplifier for a given input voltage.
Receivers: Each of the Waves receivers were calibrated by applying a known
voltage to the input of the receiver over the amplitude and frequency range
of the receiver and measuring the output data number of the instrument.
End-to-End Calibrations: Calibrations were then performed with the MSC
sensor and preamplifier, and electric preamplifier attached to the Waves
instrument. Input signals of known amplitude and frequency were applied to
the MSC sensor and the electric preamplifier and the data number out of the
instrument were recorded to produce calibration tables showing the measured
electric or magnetic field for each data number out of the instrument.
Operational Modes
=================
Though highly programmable, the Waves Instrument is expected to operate in
four basic modes, in order of increasing data volume:
Apojove Mode, Intermediate Mode, Perijove Mode, Burst Mode
The major mode commands associated with each operational mode are listed
below. This list of operating modes is not exhaustive. For a complete
listing and for more detail on each mode command, consult the Waves User's
Guide on the JNOWAV_1000 volume in the DOCUMENT directory.
Apojove Mode
------------
This will be used for most of the orbit.
* Full electric sweeps from 50 Hz to 41 MHz, once per 30 seconds.
* Full magnetic sweeps from 50 Hz to 20 kHz, once per 30 seconds.
* No waveform data are transmitted outside the instrument.
Major mode commands which place Waves into this state:
APO1, APO2, APO3, APO9, AP0A, APS1, APS2, APS3
Perijove Mode
-------------
This mode is intended for use in the roughly 12 hours centered on
Jupiter closest approach.
* Full electric sweeps from 50 Hz to 41 MHz, once per second.
* Full magnetic sweeps from 50 Hz to 20 kHz, once per second.
* No waveform data are transmitted outside the instrument.
Major mode commands which place Waves into this state:
PER1, PER2, PER3, PER9, PERA, PES1, PES2, PES3
Intermediate Mode
-----------------
This mode is intended for use in selected distant plasmasheet crossings
and possibly before and/or after perijove intervals.
* Full electric sweeps from 50 Hz to 41 MHz, once per 10 seconds.
* Full magnetic sweeps from 50 Hz to 20 kHz, once per 10 seconds.
* No waveform data are transmitted outside the instrument.
Major mode commands which place Waves into this state:
INT1, INT2, INT3, INS1, INS2, INS3
Burst Mode
----------
The Burst Mode is a highly flexible mode and is executed in two distinct
methods. The Binning Mode assigns n buffers (or bins) of fixed length
and, with the assistance of the spacecraft data system and Waves
determination of 'quality factors' based on wave intensities in selectable
bands, the 'best' N buffers are retained for transmission to the ground
based on the quality factors for the data within each buffer. Typically,
the instrument is in a Binning Mode for an interval of time much longer
than the sum of the time that can be stored in the n buffers. The quality
factors allow the instrument to find the 'best' intervals to record. The
primary use of this mode is to record wave phenomena on auroral field
lines. It is expected that auroral field line crossing may take only
seconds, but likely can't be targeted in time any better than 30 to 90
minutes. This mode typically records waveform data from all of the low
frequency receiver bands and one of the high frequency receiver bands
selected on the basis of the onboard determination of the electron
cyclotron frequency.
The Record Mode method of the Burst mode simply records for a specified
interval in time. The primary use for this mode is to collect data
centered on the jovigraphic equator near periapsis to target the region
where dust impacts are expected. Because this location can be accurately
targeted, the selection features of the Binning Mode are not needed.
Also, it is anticipated that only the electric field in the range of 50 Hz
to 20 kHz will be recorded, as this channel is expected to respond best to
dust impacts.
Record Method:
This method was designed with crossings of the Jovian equator near
perijove in mind. Typically data from just the LFR-Lo (E) channel will be
recorded to be used to identify micron-sized dust particle impacts with
the spacecraft as Juno crosses the ring plane.
* Full electric sweeps from 50 Hz to 41 MHz, once per second.
* Full magnetic sweeps from 50 Hz to 20 kHz, once per second.
* Waveform data are collected in a programmed frequency band.
Major mode commands which place Waves into this state:
REC1, REC2, REC3, REC9, RECA, RES1, RES2, RES3
Note this this is a layered mode which may only be triggered on top of an
existing Perijove Mode. It adds in basic waveform data collection
ability.
Binning Method:
When configured to this this state, Waves looks for intense, broadband
signatures of crossings of auroral field lines carrying a host of
intense wave modes. It continuously sends waveform data, to the Juno
Command and Data Handling (C&DH) system which stores them in two or
more buffers sized to hold approximately a minute's worth of waveform
data. Waves also characterizes such broadband bursts with a quality
index, which the C&DH uses to determine whether to keep or over-write a
buffer. At the end of the binning session, the buffers with the highest
quality indices will be formatted by the C&DH for transmission to the
ground.
* Full electric sweeps from 50 Hz to 41 MHz, once per second.
* Full magnetic sweeps from 50 Hz to 20 kHz, once per second.
* Waveform data are collected in bands that automatically track the
electron cyclotron frequency.
* Waveform data bins are ranked in order of most to least activity
Major mode commands which place Waves into this state:
BUR1, BUR2, BUR3, BUR4, BUR9, BURA, BUS1, BUS2, BUS3, BUS4
Note that this is a layered mode which may only be triggered on top of an
existing Perijove Mode. It adds in selective waveform data collection
ability.
Major Mode Names
----------------
It should be noted that the last two characters in the Major Mode names
have more to do with how the instrument is set up than the final data
products from that mode. For example modes xxx1 include noise
cancellation, modes xxx2 include noise cancellation and the un-filtered,
filtered, and noise channel data are all returned for diagnostic purposes.
Modes xxx3 and xxx4 do not utilize noise cancellation. Modes with xxSx do
an instrument reset in the course of setting up the mode.
Also, periapsis modes all execute with 1-second cadence except for xxx2.
Because of the additional overhead required to handle the additional
diagnostics data, the cadence is 2 seconds for this mode.
"
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