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. 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 (1=Not Working; 0=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.