1.0     GENERAL INFORMATION

1.1     Introduction

The Wideband (WBD) Plasma Wave Investigation for CLUSTER provides
wideband waveform measurements of plasma waves in the Earth's
magnetosphere.  A Wideband Receiver system which measures electric
and magnetic fields over the frequency range 100 Hz to 577 kHz is
provided by the WBD investigation as part of the Wave Experiment
Consortium (WEC) instrumentation.  The Wideband Receiver provides
unique measurement capabilities required for the detailed study of
terrestrial plasma waves and radio emissions.

1.2     Design Heritage

The use of wideband instrumentation was first introduced with the
Alouette 1 and Injun 3 satellites, and since that time, wideband
measurements have become a standard technique for the study of
space plasma waves.  Wideband instrumentation has been carried by
many spacecraft, including OGO 1 through 6, IMP 6 and 8, S(3),
GEOS 1 and 2, S3-3, ISEE 1 and 2, Prognoz 8, Voyager 1 and 2, DE 1,
Galileo, Cassini, and Polar.  The University of Iowa has constructed
wideband instrumentation for many of the above spacecraft, including
most recently the Galileo, Cassini and Polar missions.  The CLUSTER
Wideband Receiver is similar in design to instruments flown on
ISEE 1, DE 1, and Polar.

1.3     Description of the Wideband Technique

The wideband technique involves transmitting band-limited waveform
data to a ground station using a high-rate data link.  The primary
advantage of this approach is that complete, continuous waveforms
are available for detailed high resolution frequency-time analysis,
which may be performed to a level limited only by the uncertainty
principle, delta omega x delta t ~ 1.  Since the frequency resolu-
tion (delta omega) and time resolution (delta t) may be selected
and modified during data processing on the ground, the wideband
technique is an extremely effective and flexible method for re-
solving features of interest in the plasma wave data.  The high
resolution nature of the wideband technique is of particular impor-
tance for the proper identification and study of plasma emissions
which have very complex frequency-time characteristics.  The dis-
tinctive fine structures of chorus and auroral kilometric radiation,
for example, were first identified using wideband measurements.

1.4     References

Additional sources of information on the Cluster Wideband instrument
and investigation are as follows:

1. Home page of the Cluster Wideband Investigation on World Wide Web:

        http://www-pw.physics.uiowa.edu/cluster/

2. "The Wideband Plasma Wave Investigation", D. A. Gurnett, R. L. Huff,
        and D. L. Kirchner, Space Science Reviews, Vol. 79, pp. 192-208,
        1997.

3.  "First results from the Cluster Wideband Plasma Wave Investigation",
        D. A. Gurnett, R. L. Huff, J. S. Pickett, A. M. Persoon, R. L.
        Mutel, I. W. Christopher, C. A. Kletzing, U. S. Inan, W. M.
        Martin, J. Bougeret, H. St. C. Alleyne, and K. H. Yearby, Ann.
        Geophysicae, 19, 1259, 2001.

4.  "An investigation into instrumental nonlinear effects",  S. N. Walker,
        M. A. Balikhin, I. Bates, and R. L. Huff, Adv. Space Res., 30,
        2815, 2002.

5.  "Modeling of Cluster's electric antennas in space: Application to
        plasma diagnostics", C. Beghin, P. M. E. Decreau, J. Pickett,
        D. Sundkvist, and B. Lefebvre, Radio Science, 40, RS6008,
        doi:10.1029/2005RS003264, 2005.

6.  "The Digital Wave Processing Experiment on Cluster", L. J. C.
        Woolliscroft, H. Alleyne, C. M. Dunford, A. Sumner, J. A. Thompson,
        S. N. Walker, K. H. Yearby, A. Buckley, S. Chapman, and M. P.
        Gough, Space Sci. Rev., 79, 209, 1997.

7.  "The wave experiment consortium (WEC)", A. Pedersen,
        N. Cornilleau-Wehrlin, B. De la Porte, A. Roux, A. Bouabdellah,
        P. M. E. Decreau, F. Lefeuvre, F. X. Sene, D. Gurnett, R. Huff,
        G. Gustafsson, G. Holmgren, L. Woolliscroft, H. S. Alleyne,
        J. A. Thompson, P. H. N. Davies, Space Sci. Rev., 79, 93-105, 1997.


2.0     INSTRUMENT DESIGN DESCRIPTION

2.1     General Information

The Wideband (WBD) Receiver is one experiment in a consortium of five
wave and electric field experiments known as the Wave Experiment
Consortium (WEC) flown on CLUSTER.  In addition to WBD, the WEC
experiment includes an electric field instrument (EFW), a wave magnetic
field instrument (STAFF), a relaxation sounder and wave analyzer
(WHISPER), a data processing unit (DWP), and a power supply (PWR).  The
DWP collects data from the WEC instruments and performs instrument con-
trol and data management functions.  The WEC power supply provides
either bus or regulated power to the WEC instruments.

The Wideband Receiver is divided into three main subsystems:  the Analog
Electronics, the Format Generator, and the Power Supply.

The Wideband Receiver processes signals from one of four sensors which
can be chosen via an antenna selection switch located at the receiver
input.  The four selectable inputs consist of two electric field signals,
and two magnetic field signals.  These inputs are provided by the elec-
tric and magnetic field experiments.

Input bandpass filters limit the incoming signal to one of four possible
frequency bands ranging from baseband to 501.816 kHz. The band-limited sig-
nal then goes to a single-sideband frequency conversion stage which de-
termines the range of frequencies to be received.  Under this scheme,
the filtered input signal is mixed with conversion frequencies f and
f < 90 degrees.  The input signals are thereby converted to baseband with
upper and lower sidebands superposed and with a phase difference of 180
degrees.  A quadrature phase shift network shifts one converted signal by
an additional 90 degrees so that when the converted signals are summed,
the upper sideband components add and lower sideband components cancel.
The output of the conversion stage then goes to one of a set of three
bandpass filters which determines the bandwidth of the output waveform.

Because of the large dynamic range of the input signal, and in order to
maintain a high signal-to-noise ratio for the processed signal, an in-
cremental automatic gain control (AGC) amplifies the signal to the
proper level in steps of 5 dB over a range of 0 dB to 75 dB.  The output
from the gain select then goes to an analog-to-digital converter which
provides 1-bit, 4-bit, or 8-bit resolution for a selection of sample
rates.

Finally, a Format Generator organizes the digitized waveform data into
a data frame suitable for the spacecraft telemetry system.  The
digitized wideband data is then transferred to the spacecraft data
system in either a ~220 kbits/sec real-time data mode (TDA-8), which
requires direct acquisition by a NASA DSN ground station, or a ~73
kbits/sec burst-data mode (TDA-5.2 or BM2), which provides data to the
spacecraft tape recorder via the Wave Experiment Consortium data
processing unit (DWP).  This latter mode provides the capability for
acquiring data when the spacecraft cannot be tracked by a DSN station,
and also provides a means for collecting data from more than one
spacecraft at a time.  The disadvantage of the burst-data mode is that
the WHISPER instrument receives no data when WBD is configured in this
mode.  Thus, the WBD burst mode has been employed only once during the
first four yeas of the Cluster mission operations phase, that being on
March 7, 2001.  On this date digital filtering was used (reduced
bandwidth by two-thirds) to obtain continuous waveforms on spacecraft
2, 3 and 4 (spacecraft 1 data would have been obtained but the DWP
which processes WBD data in this mode was not functioning).

The WBD instrument contains an integral power supply which obtains 27 V
primary power from the WEC power supply unit.  The WEC power supply, in
turn, obtains power from a redundant 28 V source supplied by the
spacecraft.

Commanding and power switching of the WBD instrument is managed by the
DWP.

A summary of WBD instrument parameters, physical dimensions, and mass
and power requirements, is given in Table 2.1-1.  Design details of
the various WBD subsystems are discussed in the following sections.

        Table 2.1-1.  Wideband Instrument Parameters

Sensors                 Two electronic dipole antennas; two search
                        coil magnetometers

Conversion Frequencies  0 (Baseband), 125.454 kHz, 250.908 kHz,
                        501.816 kHz

Bandpass Filter Ranges  1 kHz to 77 kHz
                        50 Hz to 19 kHz
                        50 Hz to 9.5 kHz

Sampling Frequency      27.4 to 219.5 kHz (depending on mode)

Frequency Resolution    Determined by FFT

Time Resolution         10-20 ms (per FFT spectrum)

Gain Select             5 dB steps, 16 levels, dynamic range 75 dB,
                        automatic ranging or set by command

A/D Converter           1-, 4-, or 8-bit resolution for a selection
                        of sample rates


Dimensions              19.0 x 15.8 x 14.3 cm
Mass                    Approx. 1800 grams
Power (primary)         Approx. 1.6 W

Please note that in Table 2.1-1, the lower frequency limits are 100 Hz
and 700 Hz, not 50 Hz and 1 kHz as described in the WBD instrument paper
(Gurnett et al., 1997).  These adjustments in the lower frequency limits
are due to changes in the implementation of the electric field boom buffer.
Please also note that in Table 2.1-1, the conversion frequencies are 0 kHz,
125.454 kHz, 250.908 kHz, and 502.816 kHz.  The nominal conversion
frequencies of the WBD receiver were intended to be 0 kHz, 125 kHz, 250 kHz,
and 500 kHz, as described in the WBD instrument paper (Gurnett et al.,1997).
However, conversion frequencies of 125 kHz, 250 kHz, and 500 kHz were not
realizable due to the way in which the clocks were implemented in the onboard
data handling system.  Joint operations between the Cluster WBD receiver and
the RPI transmitter on board the IMAGE spacecraft verified that the actual
Cluster WBD receiver conversion frequencies are the values given in
Table 2.1-1.

2.2     Sensors and Sensor Interfaces

On CLUSTER, the plasma wave sensors consist of two orthogonal spherical-
probe electric antennas located in the spin plane of the spacecraft, and
a triaxial search coil magnetometer oriented with two measurement axes
in the spin plane and the third measurement axis oriented parallel to
the spacecraft spin axis.

The electric antennas, which are provided by the Electric Fields (EFW)
investigation, have sphere-to-sphere separations of about 90 m.  The
spheres each contain a high-impedance preamplifier which provides sig-
nals to the EFW main electronics, and to the WBD instrument and the
other wave instruments via buffer amplifiers.  The EFW/WBD buffer am-
plifier is a low-noise, low power design which meets WBD frequency/
amplitude response requirements, particularly the need to maintain a
nearly flat response up to about 600 kHz.

The three orthogonal search coils are part of the STAFF instrumentation,
and provide magnetic field signals up to 4 kHz.

The WBD instrument has the capability of processing signals from one
of four sensors which may be selected by spacecraft command.  Under the
control of the DWP, the WBD may be switched to either of the electric
sensors, to a spin-plane search coil, or to the spin-axis search coil.
Four dedicated differential amplifiers are provided as part of the
Wideband Receiver electronics, two amplifiers for the electric sensor
interface, and two for the magnetic sensor interface.

The WBD antenna select combinations are summarized in Table 2.2-1.
The Ez electric antenna was chosen as the default because the WHISPER
sounder always uses the electric Ey antenna as its active sounding
antenna.  However, as of January 10, 2002 and August 6, 2002, WBD has
been required to use the Ey antenna on spacecraft 1 and 3, respectively,
due to hardware failures of boom 1 on the Ez antenna on each of these
spacecraft. If any WBD survey plots or data are found from the Ez
antenna on spacecraft 1 after January 10, 2002 and from spacecraft 3
after August 6, 2002, please contact the WBD principal investigator,
Jolene Pickett, as the calibration of these data is not possible.

        Table 2.2-1.  WBD Antenna Select

Mode    Cmd/Status      Antenna                         Comments

0       00              Ez (electric)/spheres 1 and 2   Default Mode

1       01              Bx (search coil)

2       10              By (search coil)

3       11              Ey (electric)/spheres 3 and 4



2.3     Frequency Bands

The input frequency range of the WBD instrument can be shifted by the
frequency converter to any one of four frequency ranges, where the con-
version frequency f determines the lower edge of the frequency range to
be received.  The conversion frequency is obtained by dividing down a
reference oscillator with a frequency of 14.0508 MHz.  To maintain phase
stability in the entire system, the 14.0508 MHz oscillator is syn-
chronized to a spacecraft high frequency clock signal of 220.752 kHz,
which is the frequency of the spacecraft's Ultra Stable Oscillator (USO)
divided by 38.

A spacecraft command to select a particular frequency band causes the
DWP to switch the WBD instrument to the appropriate input bandpass fil-
ter and to select the appropriate conversion frequency.  If baseband
(f = 0) is selected, the mixing stage is bypassed so that the signal is
routed directly to the output bandpass stage with no frequency conversion.
The WBD frequency bands are summarized in Table 2.3-1.


        Table 2.3-1. WBD Frequency Band Select

Mode    Cmd/Status      Conversion Frequency            Comments

0       00              0 kHz/Baseband (no conversion)  Default Mode

1       01              125.454 kHz

2       10              250.908 kHz

3       11              501.816 kHz



The bandwidth of the WBD output waveform is determined by one of three
bandpass filters selected in combination with a given WBD output mode.
Output modes are discussed further in Section 2.5.

2.4     Gain Control

The gain select stage of the wideband receiver employs multi-gain ampli-
fiers which may be programmed to provide gain control in increments of
5 dB.  This programmable amplifier stage consists of amplifiers having
gains of 0/5 dB, 0/10/20/30 dB, and 0/40 dB gain.  The gain combinations
used are listed in Table 2.4-1.  In manual gain select mode, the total
receiver gain can be set to one of the sixteen levels by the appropriate
spacecraft command processed through the DWP.

Additionally, the Wideband Receiver has the capability of auto-ranging
through the gain steps.  The auto-ranging mode is enabled by command and
allows WBD to automatically manage large changes in signal intensity.
In this operational mode, the output from the programmable amplifier is
compared to a pair of reference amplitudes.  If the criteria for changing
the gain are met, the gain state is either increased by one step (5 dB)
or decreased by one step, accordingly.  In order to avoid excessive
toggling between gain steps, and to provide proper gain control for both
4- and 8-bit sample modes, a commandable threshold must be exceeded in
either direction.  The upper and lower AGC thresholds are selected
independently of each other.  The available threshold levels for the two
AGC functions are given in Tables 2.4-2 and 2.4-3.  The gain is updated
(if required) at the rate of the gain update clock, which is a DWP
function selected by spacecraft command.  The period of the clock is
programmable from 0.1 seconds to 10 seconds in increments of 0.1 second.
The actual gain change occurs at the beginning of the next major frame.


        Table 2.4-1.  WBD Gain Select

Gain Step       Cmd/Status      Amplifier Combination   Total Gain (dB)

0               0000            0 + 0 + 0               0

1               0001            0 + 0 + 5               5

2               0010            0 + 10 + 0              10

3               0011            0 + 10 + 5              15

4               0100            0 + 20 + 0              20

5               0101            0 + 20 + 5              25

6               0110            0 + 30 + 0              30

7               0111            0 + 30 + 5              35

8               1000            40 + 0 + 0              40 *

9               1001            40 + 0 + 5              45 *

10              1010            40 + 10 + 0             50 *

11              1011            40 + 10 + 5             55

12              1100            40 + 20 + 0             60

13              1101            40 + 20 + 5             65

14              1110            40 + 30 + 0             70

15              1111            40 + 30 + 5             75

* The 35 dB to 40 dB, 50 dB to 45 dB, and 45 dB to 50 dB gain transitions
  produce ringing.  See the “WBD Interpretation Issues” document for
  details.


        Table 2.4-2.  WBD Upper AGC Threshold


        Mode    Cmd/Status      Comments

        0       00              Default Mode

        1       01

        2       10

        3       11



        Table 2.4-3.  WBD Lower AGC Threshold


        Mode    Cmd/Status      Comments

        0       00              Default Mode

        1       01

        2       10

        3       11


2.5     A/D Converter and Format Generator

The output analog waveform is sampled by an analog-to-digital converter
which provides sampling resolution and data output rates which are listed
in Table 2.5-1.


        Table 2.5-1.  WBD Output Modes


Mode  Cmd/Status  Bandwidth     Sample          Bits/   Duty    Comments
                                Rate            Sample  Cycle

0       000     50 Hz-9.5 kHz   27.4 kHz        8       100%    Default Mode

1       001     50 Hz-9.5 kHz   27.4 kHz        8       100%

2       010     50 Hz-19 kHz    54.9 kHz        4       100%

3       011     50 Hz-19 kHz    54.9 kHz        8       50%     *Note a

4       100     1 kHz-77 kHz    219.5 kHz       8       12.5%   *Note b

5       101     1 kHz-77 kHz    219.5 kHz       1       100%

6       110     1 kHz-77 kHz    219.5 kHz       4       25%     *Note c

7       111     1 kHz-77 kHz    219.5 kHz       8       12.5%   *Note b, d

* Notes:
(a) 2180 samples (contained in two adjacent 1090 bit minor frames) equal
    to 39.719 msec of data followed by 39.719 msec of data gap.
(b) 2180 samples (contained in two adjacent 1090 bit minor frames) equal
    to 9.9297 msec of data followed by 69.508 msec of data gap.
(c) 2180 samples (contained in two adjacent 1090 bit minor frames) equal
    to 19.859 msec of data followed by 59.578 msec of data gap.
(d) This mode is a repeat of output Mode 4, but also toggles the primary
    and redundant OBDH (On Board Data Handling System) interfaces.


For sample rates where the bit rate exceeds the allowable WBD telemetry
rate (220 kbits/sec), the digitized wideband data is buffered by the
Format Generator and read out at a reduced average bit rate of 220
kbits/sec.  The Format Generator organizes the digitized waveform data
into an output frame, along with appropriate timing and status infor-
mation, and makes the frame available to the spacecraft OBDH (On Board
Data Handling) system.  Alternatively, the WBD data stream is read out
through the DWP to the OBDH solid state recorder.

2.6     WBD Data Interfaces

The Wideband Receiver has two different output modes for providing digi-
tized data to the spacecraft data handling system.  These modes consist of
a realtime data mode (TDA-8) which provides data at about 220 kbits/sec
and a burst-data mode (TDA-5.2 or BM2) which provides data at about 73
kbits/sec.  These two output modes require separate data interfaces as
discussed in the following sections.

2.6.1  OBDH Interface

The WBD/OBDH serial data interface is a direct connection between the WEC
(originating at WBD) and the spacecraft's OBDH system.  The interface sup-
plies the primary path for data from the Wideband instrument, allowing real-
time acquisition of WBD data at a DSN ground receiving station.  The WBD
data goes directly to the Central Terminal Unit (CTU) of the OBDH bypassing
the Remote Terminal Unit (RTU).  The data appears on virtual channel VC5 as
described in the Cluster EID Part A, embedded in the 1096 byte Data Field
of the standard 1279-byte transfer frame.

The OBDH supplies the sampling clock, a synchronizing pulse, and access to
a high-rate data port.

The WBD/OBDH interface functions are described below.

        WBD Clock - A special clock is provided continuously by the
        spacecraft at a rate of 220.753 kHz.  The clock is used to
        shift telemetry out of WBD, and is also used to phase-lock
        the WBD VCXO (Voltage Controlled Crystal Oscillator).  The
        clock signal is obtained by dividing the frequency of the
        Ultra Stable Oscillator by 38.

        WBD Data Out - Serial data are transferred from WBD to the
        OBDH via the WBD Data Out line most significant bit first
        at a rate determined by the WBD Clock described above.  Data
        will be present on this line whenever WBD is powered.

        VCO Reset Pulse - This pulse is correlated with the first
        bit of the housekeeping transfer frame (Virtual Channel 0)
        and is used to gate the contents of the 7-byte onboard time
        counter into the Onboard Time Field of the housekeeping
        frame.  The pulse is also distributed continuously to WBD to
        determine the timing of the WBD data frame.

It is assumed that the VCO Reset interval is 5.15222168 seconds, and that
this interval corresponds to a fixed number of cycles of a counter operating
at an integer fraction of the USO frequency.  It is also assumed that the
Reset Pulse has an associated time jitter of less than a microsecond.  WBD
will achieve microsecond sample timing by maintaining an internal counter,
the contents of which will be gated out for each WBD minor frame and stored
within a special field of the minor frame as a time offset.  The counter
will be zeroed by the VCO Reset Pulse.

2.6.2  WBD Data Frame Format

The high-rate WBD data is transmitted in a Minor-Frame/ Major-Frame format.
A WBD major frame consists of four minor frames, with overall format as
shown in Table 2.6.2-1.  Each minor frame contains 1096 bytes of data, of
which the first six bytes supply frame and byte synchronization, status
information, and time information.

        Table 2.6.2-1.  WBD Frame Format

Frame #  Byte 0  Byte 1  Byte 2  Byte 3  Byte 4  Byte 5  Bytes 6-1095

0=00B    FA      F3      34      Frame   COUNT2  COUNT1  Data

1=01B    FA      F3      34      Frame   COUNT0  STAT3   Data

2=10B    FA      F3      34      Frame   STAT2   STAT1   Data

3=11B    FA      F3      34      Frame   STAT0   STAT3   Data


The four fields in a minor frame are listed below:

        1.      Frame Sync - (bytes 0-2)
                Should always have values FA, F3, 34 Hex.
        2.      Frame Count - (byte 3)
                Sequential count of each minor frame.  Allows the data
                system to assemble the received frames in order, and
                allows the data system to determine if any frames have
                been lost.  The two least significant bits of the frame
                count byte give the minor frame number.
        3.      Status/Clock - (bytes 4-5)
                These two bytes provide different functions in each minor
                frame of the major frame.  The use of these two bytes, as a
                function of the two least significant frame count bits, are
                as follows:

        Minor Frame #   Function

                00      Two most significant bytes of the three byte VCO
                        time offset counter.

                01      Least significant byte of VCO time offset counter
                        and status byte 3.

                10      Status bytes 1 and 2.

                11      Status byte 0 and a repeat of status byte 3.

        The format of the four status bytes is given in Table 2.6.2-2.

        4.      Data - (bytes 6-1095)
        Data are presented most-significant-bit first.  When either a
        4-bit or 1-bit mode (see Table 2.5-1) is enabled, the samples
        are packed into each byte in reverse time order.


        Table 2.6.2-2.  WBD/OBDH Status Word Format


Byte    Bit             Description

STAT3   7               VCXO Lock (0=Not Working; 1=Lock)
        6               OBDH Interface (0=Primary; 1=Redundant)
        5               Command Status (0=No cmds; 1=Cmds received)
        4               A/D Converter Power
        3,2,1,0         Gain Level/Select


STAT2   7,6             11
        5               Gain Mode (Manual=1; Auto=0)
        4,3,2,1         Gain Level/Select
        0               OBDH Interface (0=Primary; 1=Redundant)


STAT1   7,6             01
        5,4             Antenna Select
        3,2             Frequency Select
        1,0             Upper AGC Threshold

STAT0   7,6,5           WBD Model (000=EM; 100=PFM; 101=F2; 110=F3; 111=F4)
        4,3,2           Output Mode
        1,0             Lower AGC Threshold



2.6.3  DWP Interface

The DWP/WBD interface provides three main functions:  a second path for
WBD data (to the solid state recorder), a means for controlling WBD via
serial command, and a means for acquiring housekeeping and status informa-
tion from WBD.  These functions are discussed in the following sections.

2.6.4  Burst Data Mode

The burst mode (TDA-5.2 or BM2) provides high-rate data to the spacecraft
solid state recorder via the DWP.  This data mode uses a high-rate serial
interface between WBD and the DWP.  Data is transferred to the DWP through
this serial interface at 220 kbits/sec, and the DWP, in turn, reduces the
wideband data by a factor of three (73 kbits/sec) via either digital fil-
tering or duty cycling (which is command selectable) and transfers the
wideband data to the spacecraft data system for recording and subsequent
playback.

2.6.5  Serial Command

The DWP controls the Wideband Receiver through a 16-bit command word.
The bit assignments for the command word are given in Table 2.6.5-1:


        Table 2.6.5-1.  WBD/DWP Command Word Format


        Bit             Description

        15, 14, 13, 12  Gain Select

        11, 10          Upper AGC Threshold

        9, 8            Lower AGC Threshold

        7               Gain Mode, manual(=1)/auto(=0)

        6, 5            Frequency Select

        4, 3, 2         Output Mode

        1, 0            Antenna Select

The list below shows all states (actions) for each of the seven command-
able WBD functions, maps each state to a unique bit combination for a
given functions' bit field, and assigns a command mnemonic with argument
if appropriate, to each state.

Mnemonic        MSB             LSB             Action

WB_GN_SEL 0     0000xxxx        xxxxxxxx        set gain = 0 dB
WB_GN_SEL 5     0001xxxx        xxxxxxxx        set gain = 5 dB
WB_GN_SEL 10    0010xxxx        xxxxxxxx        set gain = 10 dB
WB_GN_SEL 15    0011xxxx        xxxxxxxx        set gain = 15 dB
WB_GN_SEL 20    0100xxxx        xxxxxxxx        set gain = 20 dB
WB_GN_SEL 25    0101xxxx        xxxxxxxx        set gain = 25 dB
WB_GN_SEL 30    0110xxxx        xxxxxxxx        set gain = 30 dB
WB_GN_SEL 35    0111xxxx        xxxxxxxx        set gain = 35 dB
WB_GN_SEL 40    1000xxxx        xxxxxxxx        set gain = 40 dB
WB_GN_SEL 45    1001xxxx        xxxxxxxx        set gain = 45 dB
WB_GN_SEL 50    1010xxxx        xxxxxxxx        set gain = 50 dB
WB_GN_SEL 55    1011xxxx        xxxxxxxx        set gain = 55 dB
WB_GN_SEL 60    1100xxxx        xxxxxxxx        set gain = 60 dB
WB_GN_SEL 65    1101xxxx        xxxxxxxx        set gain = 65 dB
WB_GN_SEL 70    1110xxxx        xxxxxxxx        set gain = 70 dB
WB_GN_SEL 75    1111xxxx        xxxxxxxx        set gain = 75 dB

WB_AGC_UP 0     xxxx00xx        xxxxxxxx        upper agc = UV0
WB_AGC_UP 1     xxxx01xx        xxxxxxxx        upper agc = UV1
WB_AGC_UP 2     xxxx10xx        xxxxxxxx        upper agc = UV2
WB_AGC_UP 3     xxxx11xx        xxxxxxxx        upper agc = UV3

WB_AGC_LO 0     xxxxxx00        xxxxxxxx        lower agc = LV0
WB_AGC_LO 1     xxxxxx01        xxxxxxxx        lower agc = LV1
WB_AGC_LO 2     xxxxxx10        xxxxxxxx        lower agc = LV2
WB_AGC_LO 3     xxxxxx11        xxxxxxxx        lower agc = LV3

WB_GN_AUT       xxxxxxxx        0xxxxxxx        auto gain select
WB_GN_MAN       xxxxxxxx        1xxxxxxx        manual gain select

WB_FREQ 0       xxxxxxxx        x00xxxxx        conv. freq. = 0 Hz
WB_FREQ 125     xxxxxxxx        x01xxxxx        conv. freq. = 125.454 kHz
WB_FREQ 250     xxxxxxxx        x10xxxxx        conv. freq. = 250.908 kHz
WB_FREQ 500     xxxxxxxx        x11xxxxx        conv. freq. = 501.816 kHz

WB_OUT 0        xxxxxxxx        xxx000xx        BW = 9.5 kHz; 8-bits
WB_OUT 1        xxxxxxxx        xxx001xx        BW = 9.5 kHz; 8-bits
WB_OUT 2        xxxxxxxx        xxx010xx        BW = 19 kHz; 4-bits
WB_OUT 3        xxxxxxxx        xxx011xx        BW = 19 kHz; 8-bits
WB_OUT 4        xxxxxxxx        xxx100xx        BW = 77 kHz; 8-bits
WB_OUT 5        xxxxxxxx        xxx101xx        BW = 77 kHz; 1-bit
WB_OUT 6        xxxxxxxx        xxx110xx        BW = 77 kHz; 4-bits
WB_OUT 7        xxxxxxxx        xxx111xx        BW = 77 kHz; 8-bits,
                                                    (redundant OBDH interface)
WB_SEN Ez       xxxxxxxx        xxxxxx00        select Ez antenna
WB_SEN Bx       xxxxxxxx        xxxxxx01        select Bx search coil
WB_SEN By       xxxxxxxx        xxxxxx10        select By search coil
WB_SEN Ey       xxxxxxxx        xxxxxx11        select Ey antenna


2.6.6  Instrument Status and Housekeeping Data

The WBD gain status, along with all other status information (auto/fixed
gain, gain select, frequency select, output bandwidth select, and antenna
select) are sampled by the DWP via a 3-byte status polling sequence and
provided as housekeeping parameters.  The format of these three bytes is
shown in Table 2.6.6-1.

        Table 2.6.6-1.  WBD/DWP Status Word Format


        Byte    Bit             Description

        0       7, 6            11

        0       5               Gain Mode, manual (=1) / auto (=0)

        0       4, 3, 2, 1      Gain Select

        0       0               1 = Redundant Interface

        1       7, 6            01

        1       5, 4            Frequency Select

        1       3, 2            Lower AGC Threshold

        1       1, 0            Upper AGC Threshold

        2       7, 6            00

        2       5               VCXO Lock (1=not working, 0=Lock)

        2       4, 3, 2         Output Mode

        2       1, 0            Antenna Select

The unique status bit combinations for all instrument states are given
in the list below.

Byte 1 (MSB)    Byte 2          Byte 3 (LSB)    Instrument State

110xxxxx        01xxxxxx        00xxxxxx        auto gain select
111xxxxx        01xxxxxx        00xxxxxx        manual gain select
11x0000x        01xxxxxx        00xxxxxx        gain set to 0 dB
11x0001x        01xxxxxx        00xxxxxx        gain set to 5 dB
11x0010x        01xxxxxx        00xxxxxx        gain set to 10 dB
11x0011x        01xxxxxx        00xxxxxx        gain set to 15 dB
11x0100x        01xxxxxx        00xxxxxx        gain set to 20 dB
11x0101x        01xxxxxx        00xxxxxx        gain set to 25 dB
11x0110x        01xxxxxx        00xxxxxx        gain set to 30 dB
11x0111x        01xxxxxx        00xxxxxx        gain set to 35 dB
11x1000x        01xxxxxx        00xxxxxx        gain set to 40 dB
11x1001x        01xxxxxx        00xxxxxx        gain set to 45 dB
11x1010x        01xxxxxx        00xxxxxx        gain set to 50 dB
11x1011x        01xxxxxx        00xxxxxx        gain set to 55 dB
11x1100x        01xxxxxx        00xxxxxx        gain set to 60 dB
11x1101x        01xxxxxx        00xxxxxx        gain set to 65 dB
11x1110x        01xxxxxx        00xxxxxx        gain set to 70 dB
11x1111x        01xxxxxx        00xxxxxx        gain set to 75 dB
11xxxxx0        01xxxxxx        00xxxxxx        primary OBDH interface
11xxxxx1        01xxxxxx        00xxxxxx        redundant OBDH interface

11xxxxxx        0100xxxx        00xxxxxx        conv. freq. = 0 Hz
11xxxxxx        0101xxxx        00xxxxxx        conv. freq. = 125.454 kHz
11xxxxxx        0110xxxx        00xxxxxx        conv. freq. = 250.908 kHz
11xxxxxx        0111xxxx        00xxxxxx        conv. freq. = 501.816 kHz
11xxxxxx        01xx00xx        00xxxxxx        lower agc = LV0
11xxxxxx        01xx01xx        00xxxxxx        lower agc = LV2
11xxxxxx        01xx10xx        00xxxxxx        lower agc = LV1
11xxxxxx        01xx11xx        00xxxxxx        lower agc = LV3
11xxxxxx        01xxxx00        00xxxxxx        upper agc = UV0
11xxxxxx        01xxxx01        00xxxxxx        upper agc = UV2
11xxxxxx        01xxxx10        00xxxxxx        upper agc = UV1
11xxxxxx        01xxxx11        00xxxxxx        upper agc = UV3

11xxxxxx        01xxxxxx        000xxxxx        VCXO locked
11xxxxxx        01xxxxxx        001xxxxx        VCXO not locked
11xxxxxx        01xxxxxx        00x000xx        BW = 9.5 kHz; 8-bits
11xxxxxx        01xxxxxx        00x001xx        BW = 9.5 kHz; 8-bits
11xxxxxx        01xxxxxx        00x010xx        BW = 19 kHz; 4-bits
11xxxxxx        01xxxxxx        00x011xx        BW = 19 kHz; 8-bits
11xxxxxx        01xxxxxx        00x100xx        BW = 77 kHz; 8-bits
11xxxxxx        01xxxxxx        00x101xx        BW = 77 kHz; 1-bit
11xxxxxx        01xxxxxx        00x110xx        BW = 77 kHz; 4-bits
11xxxxxx        01xxxxxx        00x111xx        BW = 77 kHz; 8-bits
11xxxxxx        01xxxxxx        00xxxx00        antenna = Ez
11xxxxxx        01xxxxxx        00xxxx01        antenna = By
11xxxxxx        01xxxxxx        00xxxx10        antenna = Bx
11xxxxxx        01xxxxxx        00xxxx11        antenna = Ey


2.7  Instrument Power Supply

The WBD Power Supply is a simple PWM system which supplies plus/minus 12,
plus/minus 6, and a +5 regulated voltages for the various WBD subsystems.
The WBD Power Supply receives a 27V bus supply and a convertor synchron-
ization signal through the WEC Power Supply.  Power to WBD is managed by
the WEC DWP, which controls a latching relay in the WEC Power Supply.

The WBD unit on Cluster 3 developed an overheating problem at about
22:05 UT on December 13, 2003, tentatively attributed to a degraded
capacitor on the power supply board.  The degraded component has been deemed
to be non-critical, with the WBD unit on Cluster 3 still providing good
science data as long as it is powered ON for no more than 10 minutes
approximately once every 60-70 minutes.  Consequently, after January 13,
2004, all Cluster 3 operations were limited to high priority science
campaigns with 10-minute data periods.

2.8  Mechanical Design

The WBD consists of a single physical unit, about the size of a toaster.
The electronics housing is milled from a single block of AZ31B magnesium
with walls approximately .040 inches thick, and is supported by six feet
attached to the experiment platform.  Total weight is approximately 1800
grams.

Inside the housing, the box is divided into two compartments, one for
analog electronics, and one for digital/power supply.  The circuit boards
are .0625 polyamide and are stacked together via aluminum standoffs, and
fastened to the housing via stainless steel screws.  Electrical parts are
placed on the boards by a combination of vapor phase reflow and hand
soldering by a NASA certified assembly technician.  Some of the digital
electronics are constructed on multilayer boards.

