WBFORMAT.TXT describes the format of the Cluster WBD LEVEL1 data files. The current form of this document may be found online at: http://www-pw.physics.uiowa.edu/custer/dvd/WBFORMAT.TXT ---------------------------- Overview of format ----------------------------- SFDU record as received from DSN with bytes 0-2, 94, and 96-103 modified. Byte 0 |-------------------------------|Bytes 0-2 used to | SFDU LABEL |store record type and | |file version info |-------------------------------| | HEADER AGGREGATION | | CHDP LABEL | | | |-------------------------------| | PRIMARY HEADER | | | | | |-------------------------------| | SECONDARY HEADER | | | | | Byte 96 |-------------------------------| Bytes 96-103 are used | Uncorrected ERT at CTIB | for storage of ERT at |-------------------------------| the CTIB reset flag Byte 104 | First 1119 bytes of 1279- | | byte transfer frame for | See byte 104 for | WBD instrument sent from S/C | overview of transfer | to DSN stations (160 bytes | frame | of Reed Solomon code block | | not included) | |-------------------------------| This is the end of the SFDU record with above noted modifications in Bytes 0-2, 94, and 96-103. The next blocks are generated by the LEVEL1 processing software. Byte 1224 |-------------------------------| | UT_OBT and UT_GRT values: | | Time of measurement for the | | data, using two different | | calculation methods | |-------------------------------| Byte 1248 | Various reference values used | | in calculating UT | |-------------------------------| Byte 1262 | Instrument Status | |-------------------------------| Byte 1275 | Fraction of milliseconds | | component for UT_OBT | |-------------------------------| Real time telemetry data (TDA-8 Mode) contain either VC5 or VC7 transfer frames. The VC5 records contain the WBD data while the VC7 hold fill data, but will contain the On-Board time fields and usually also the CTIB flag, all of which are used when computing UT. Burst mode (TDA-5.2 or BM2) records may contain either duty cycled data or filtered data from the solid state recorder. Duty cycled data are received when the spacecraft sends one out of every three normal data records. This type of data is not continuous. The time between these records will be 3*39.718628 = 119.155884 milliseconds when duty cycling is 100%. Times between records will vary when duty cycling is less than 100%. When not duty cycling, the data are filtered (by WEC-DWP, not by WBD) so that they contain only 1/3 the bandwidth but still maintain continuity. Within the LEVEL1 files, three filtered data records have been combined into one, so that each data set contains 1090 values. (Prior to decommutation by TED, the ESA records contain only 1090/3 ~ 394 values each.) In the WBD LEVEL1 file, the start time of each filtered data set will be the start time of the first snapshot used to make the record, so that the time between records will also be 119.155884 milliseconds. The data record contains Universal Times derived from two sources. One source is from the Earth Received Time (ERT) placed in the record by DSN. This time, called UT_GRT, has been corrected for delays in the system and propagation delays between the spacecraft and the ground antenna. Burst mode data records do not contain this time. The other time is derived from the On-Board Time counter and the calibration data supplied by ESA. This time should be the one closest to the values used by the other instruments. This time is called UT_OBT. The difference between the UT_GRT and the UT_OBT, when both are available, is supposed to be at most 2 milliseconds, but occasionally can be up to 4 milliseconds. ----------------------------------------------------------------------------- The SFDU header information is described below in the LEVEL1 WBD Format section, for use in the interferometry studies, and in case data quality becomes an issue. The following JPL documents were used to determine SFDU formats: For data acquired prior to Dec. 27, 2002: TLM-3-24 DSMS Document 820-13 Module TLM-3-24 Deep Space Mission System External Interface Specification-Telemetry SFDU Interface for ISTP/Cluster For data acquired after Oct. 13, 2003: TLM-3-29 DSMS Document 820-13 Module TLM-3-29 Deep Space Mission System External Interface Specification-Telemetry SFDU Interface for ISTP/Cluster For data acquired in the transition period Dec. 27, 2002 to Oct. 13, 2003, both TLM-3-24 and TLM-3-29 were used depending on which antenna was in operation. In all cases, refer to Byte 5, Class Identifier, to determine which format was used for any given raw data file (see explanation of Byte 5 below). Note that the TLM-3-29 format is 4 bytes shorter than that of TLM-3-24. To compensate, files using the TLM-3-29 format have had their SFDU contents shifted slightly from their original positions during LEVEL1 processing. This allows the same LEVEL1 format (as specified below) to be used for all files. When differences between formats TLM-3-24 and TLM-3-29 exist, the specific bytes pertaining to the differences will be noted below, and will be labelled with "(3-24)" or "(3-29)". ----------------------------------------------------------------------------- ------------------------------- LEVEL1 WBD Format --------------------------- Bytes Description 0-1 ASCII "55" (hexadecimal 3535) for DSN VC5 records. ASCII "77" (hexadecimal 3737) for DSN VC7 records. ASCII "5" in byte 0 and a zero in byte 1 (hexadecimal 3500) for Burst mode. 2-95 Bytes 2-95 of the JPL Telemetry SFDU, unmodified except byte 94, for DSN mode. In burst mode bytes 2-65 contain the burst mode header information. (See Burst Mode section below.) The SFDU header in DSN mode contains the following pertinent information: Telemetry SFDU Label (bytes 2-19): 2 LEVEL1 File Version or ASCII "P" for "NJPL" (NASA/JPL) NOTE: If byte 2 is not the ASCII character "P" (equivalent integer value of 80), then the integer value of this byte impacts how bytes 94, 1266, and 1274 are used. See bytes 94, 1266, and 1274. 3 ASCII "L" for "NJPL" (NASA/JPL) 4 Version Identifier: ASCII "2" (equivalent integer value of 50) -> Length Attribute in bytes 12-19 is formatted as a binary unsigned integer 5 Class Identifier: (3-24) ASCII "Z" (equivalent integer value of 90) (3-29) ASCII "I" (equivalent integer value of 73) -> Indicates that this SFDU is an application data object 6-7 ASCII "00" 8-11 Data Description Identifier: (3-24) ASCII "0001" (3-29) Integer value of 9999 12-19 Length Attribute: Integer that is the sum of the total lengths (number of bytes) of the aggregation CHDO and the telemetry data CHDO. Aggregation CHDO Label (bytes 20-23): 20-21 Type Attribute: Integer value of 1 22-23 Length Attribute: (3-24) Integer value of 76. (3-29) Integer that is the length (number of bytes) of the aggregation CHDO which is the sum of the lengths of the primary CHDO and secondary CHDO which is 72. Primary CHDO (bytes 24-31): 24-25 Type Attribute: Integer value of 2 indicating that this CHDO is a primary CHDO. 26-27 Length Attribute: Integer value of 4 indicating remaining length of primary CHDO. 28 Major Data Class: Integer value of 1 indicating that this SFDU contains spacecraft telemetry. 29 Minor Data Class (0-2): See following tables. ------------------------------- 3-24 Format --------------------------------- CLASS DESCRIPTION 0 Raw Data Bits are blocked arbitrarily 1 Frame Alignment. An attempt is made to begin each block on a telemetry frame boundary. 2 Decoding. An attempt is made to decode the outer code (RS) in each telemetry frame. ----------------------------------------------------------------------------- ------------------------------- 3-29 Format --------------------------------- CLASS FRAME SYNCHRONIZER CONFIGURATION REED-SOLOMON DECODER CONFIGURATION 0 Disabled Disabled 1 Enabled Disabled 2 Enabled Enabled ----------------------------------------------------------------------------- 30 Mission Identifier (0-255): (3-24) Integer value of 0 for ISTP Cluster. (3-29) Used only for missions supported by AMMOS. Missions not supported by AMMOS, the value of this field is 254. 31 Format Code: Integer value of 0 indicates this is a DSS-formatted SFDU Secondary CHDO (bytes 32-95): 32-33 Type Attribute: (3-24) Integer value of 70 indicates this CHDO is a telemetry secondary CHDO. (3-29) Integer value of 71 indicates this CHDO is a telemetry secondary CHDO. 34-35 Length Attribute: (3-24) Integer value of 64 indicates remaining length of secondary CHDO. (3-29) Integer value of 60 indicates remaining length of secondary CHDO. 36 Originator Identifier: Integer value of 48 indicates the SFDU originated within DSN. 37 Last Modifier Identifier: Integer value of 48 indicates this SFDU was last modified by DSN. 38 Spacecraft Identifier 39 Data Source (DSN Antenna/Facility Identifier): For example, an integer value of 15 would indicate the data were received by DSS-15 at Goldstone. The Goldstone complex consists of antennas 14, 15, 24, 26, and 27; the Canberra complex of 34, 43, 45, 46; and the Madrid complex of 54, 63, 65, 66. 40-41 Flags: See following tables. ---------------------------------- 3-24 Format ------------------------------ Byte Bit Description 40 7 0 if ERT is valid or 1 if ERT is known to be invalid 6-0 Reserved 41 7-0 Reserved ----------------------------------------------------------------------------- ---------------------------------- 3-29 Format ------------------------------ Byte Bit Description 40 7 0 if ERT is valid or 1 if ERT is known to be invalid 6 Reserved 5 0 if ERT should be ignored or 1 if ERT is valid 4 0 if ERT refers to trailing edge of last received telemetry bit in SFDU or 1 if ERT refers to leading edge of first telemetry bit in SFDU 3-0 Reserved 41 7 0 if diagnostic mode is disabled or 1 if diagnostic mode is enabled 6 0 if SNR (bytes 76-79) is estimated in the symbol domain or 1 if SNR is estimated in the bit domain 5-0 Reserved ----------------------------------------------------------------------------- 42-49 Earth Received Time (ERT) Format: Bytes 42-43 Days since Jan. 1, 1958 Bytes 44-47 Milliseconds of day Bytes 48-49 Microseconds of MS 50-53 Record Sequence number (should be 1 to 2**32 - 1). Caveat: These numbers will probably not be sequential in places where data from one DSN file has been joined with data from another, or across LEVEL1 file boundaries. There can be discontinuous jumps in value, either forward or backward, in these places. 54 Acquisition BET (bit error tolerance): Integer value of 0-15 indicating number of allowed bit errors in the attached sync marker during search and verify modes. 55 Maintenance BET: Integer value of 0-15 indicating number of allowed bit errors in the attached sync marker during lock and flywheel modes. 56 Verify Count (0-15): Number of within-tolerance telemetry frames required, during verify mode, to transition to lock mode. 57 Flywheel Count (0-15): Number of out-of-tolerance telemetry frames required, during flywheel mode, to transition to search mode. 58-59 Number of Received Telemetry Bits: Indicates number of received telemetry bits contained in telemetry data CHDO. If number is less than length of telemetry data CHDO, then unused bits appear at the end of the field and should be ignored. 60 Frame sync mode flags: See following table. ----------------------------------------------------------------------------- Bit Description if bit = 1 7 Frame synchronizer is in bypass mode 6 Frame synchronizer is in search mode 5 Frame synchronizer is in verify mode 4 Frame synchronizer is in lock mode 3 Frame synchronizer is in flywheel mode 2 Automatic polarity correction (APC) is enabled 1 Reserved 0 Operator forced resynchronization ----------------------------------------------------------------------------- 61 Sync Status (bits 0-4): See following table. ----------------------------------------------------------------------------- Bit Description 4-1 Reserved 0 Data Polarity flag. 0 indicates the true sync marker is detected. 1 indicates complemented sync marker is detected, and if APC is enabled (see byte 60), the frame synchronizer inverts all bits in the frame. Ignore this bit if frame synchronizer is in bypass or search mode. ----------------------------------------------------------------------------- 61 Bit slip status code (bits 5-7): A non zero code indicates telemetry data CHDO contains a telemetry frame that is longer or shorter than the nominal length. See following tables. ---------------------------------- 3-24 Format ------------------------------ Code Description 010 Frame is two bits shorter than nominal frame 001 Frame is one bit shorter than nominal frame 000 Frame equals a nominal frame in length 101 Frame is one bit longer than nominal frame 110 Frame is two bits longer than nominal frame ----------------------------------------------------------------------------- ---------------------------------- 3-29 Format ------------------------------ TCA* Code TLP* Code Description 011 101 Frame is three bits shorter than nominal frame 010 110 Frame is two bits shorter than nominal frame 011 111 Frame is one bit shorter than nominal frame 000 000 Frame equals a nominal frame in length 111 001 Frame is one bit longer than nominal frame 110 010 Frame is two bits longer than nominal frame 101 011 Frame is three bits longer than nominal frame ----------------------------------------------------------------------------- * TCA/TLP is provided in bytes 88 and 89 (Bit slip status code should be ignored if frame synchronizer is in bypass or search mode). 62 Reed-Solomon status: 0 No Reed Solomon checking was done 1 Reed Solomon was done no errors 2 Reed Solomon was done and errors were corrected 3 Reed Solomon was done and errors were not fixed * Ingore if frame synchronizer is in bypass or search mode. 63 Reed-Solomon symbol error count (0-80): Number of corrected Reed-Solomon symbol errors in this frame. This field is valid if byte 62 is 1 or 2 and if the frame synchronizer is in bypass or search mode this byte should be ignored. 64 Sync bit errors: Number of bit errors in attached sync marker detected by the frame synchronizer. This byte should be ignored if the frame synchronizer is in bypass or search mode. This value cannot exceed the acquisition bit tolerance (byte 54). 65 Frequency band of the receiver: ASCII "S", "X", or "K" indicate S-band, X-band, or Ka-band. 66-69 Measured bit rate of received telemetry data (bits/sec): Accuracy of 0.1 bits/second; 32-bit floating point format described below: ----------------------------------------------------------------------------- IEEE Standard for Binary Floating-Point Arithmetic (ANSI/IEEE Std 754-1985) q.v. Single precision 32-bit floating point format BIT +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |31|30|29|28|27|26|25|24|23|22|21|20|19|18|17|16| +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | S| EXPONENT e | FRACTION f +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |15|14|13|12|11|10| 9| 8| 7| 6| 5| 4| 3| 2| 1| 0| +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ FRACTION (continued) | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ S - 1-bit Sign Field: 0 positive, 1 negative EXPONENT - 8-bit Exponent Field biased 127 (2^8 - 1) FRACTION - 23-bit Fraction of the significand For normalized numbers, the most common, the value of a number is: v = s * 2^(e-127) * m where s = +1 when the sign bit S is 0 or -1 when the sign bit is 1 e = an unsigned integer in the range 1 through 126 m = 1.f in binary or ( 1 + f / (2^23) ) Note that there are a large number of special cases with numbers very close to zero, positive and negative zeroes, positive and negative infinities, and special NaN (not a number) values. Consult the cited reference for details. Most platforms use IEEE floats, so no conversion is needed on high-byte-first (big endian) platforms, like most RISC UNIX systems, and you can simply reverse the order of the bytes for low-byte-first (little endian) platforms, like most Intel processor systems. ----------------------------------------------------------------------------- 70-71 Reed-Solomon Symbol Error Count: (3-24) Number of Reed-Solomon symbol errors by frame (integer) (3-29) Reserved 72-75 System Noise Temperature (Kelvins): Accuracy of 0.1 Kelvin; 32-bit floating point format (see bytes 66-69). 76-79 Estimated signal-to-noise ratio (dB) in symbol domain (prior to convolution decoding) or bit domain (post convolution decoding). 32-bit floating point format (see bytes 66-69). 80-83 Receiver Signal Level (dBm): 32-bit floating point format (see bytes 66-69). 84 (3-24) Antennas in Use: See following table. ----------------------------------------------------------------------------- Bit Description if bit = 1 7 Reserved 6 DSS 27 used. 5 DSS 24, 25, 26, 34, or 54 used. 4 DSS 14, 43, or 63 used. 3 Reserved 2 DSS 15, 45, or 65 used. 1 DSS 12, 42, or 61 used. 0 DSS 16, 46, or 66 used. ----------------------------------------------------------------------------- (3-29) Virtual Stream ID 85 Reserved 86-87 (3-24) Master Antenna & Master Receiver Numbers: Byte 86 is the same as byte 84 except that one and only one bit (corresponding to the Master Antenna) will be set. Byte 87 shows the Master Receiver used. See following table. ----------------------------------------------------------------------------- Bit Description if bit = 1 7 Receiver #8 used. 6 Receiver #7 used. 5 Receiver #6 used. 4 Receiver #5 used. 3 Receiver #4 used. 2 Receiver #3 used. 1 Receiver #2 used. 0 Receiver #1 used. ----------------------------------------------------------------------------- (3-29) Receiver ID (unsigned integer) 88 (3-24) DTM Group Number (unsigned integer) 89 TLM Channel Number (unsigned integer) (3-24) 88-89 (3-29) Telemetry Processor ID 90-91 Telemetry Lock Status: See following table. ----------------------------------------------------------------------------- Byte Bit Description Possible Values 90 7-6 Symbol synchronization 0 = not in use or lock 5-4 Subcarrier demodulation status unknown 3-2 Array 1 = invalid value 1-0 Carrier demodulation 2 = in lock 91 7-6 Reserved 3 = out of lock 5-4 Reed-Solomon decoding 3-2 Frame synchronization 1-0 Convolution decoding ----------------------------------------------------------------------------- 92-93 Telemetry Software ID: Identifies telemetry software version in use. (ASCII) 94 Least significant digit of UT_OBT Microsecond (as derived from On-Board time counter). The number of microseconds in the UT_OBT Second is given by: UT_OBT Microseconds = (integer in bytes 1246-1247) * 1000 + (integer value in byte 1275) * 10 + integer value in byte 94 NOTE: Byte 94 is used only if byte 2 has an integer value of 2 or greater. If otherwise, then use the above formula as if byte 94 had a value of zero. 95 Reserved Telemetry Data CHDO: (bytes 96-1223) 96-103 ERT (Earth Received Time) corresponding to current CTIB Flag. See bytes 1224-1231 for format. -------------------------------- Burst Mode --------------------------------- For burst mode data, most of the SFDU header byte locations will be used for burst mode processing information. Below is the format for this information, as provided by the WEC-DWP team: 2 Software Version (Ted Decommutation software) 3 Software Revision (Ted) 4 Software Patch (Ted) 5 Software User Patch (Ted) 6-7 Spacecraft ID 8-9 Ground Station ID 10-11 Source Instrument 12-13 Diagnostics Word 14-15 Length of Science Data 16-17 SCE_year - 1900 18-19 SCE_month 20-21 SCE_day_of_month 22-23 SCE_hour 24-25 SCE_minute 26-27 SCE_second 28-29 SCE_millisecond 30-31 SCE_usec 36 Gain Index (multipy by 5 to obtain gain) 37 EW4PRCTL (0 if duty cycling, 1 if filtering) 38 EW4VMON0 (WBD Voltage Monitor) 39 EW4VTMON (WBD Temperature Monitor) 40 EW4WBDHK if 1, WBD data is via DWP and is in burst mode; if 0 then the HK bytes assigned to gain contain Whisper information 41 EW4STSCN (WBD status count) 42-57 8 sets of Gain indicators from WEC Housekeeping, 2 bytes each 58-59 WBD STAT1 (STAT1 & 0030) >> 4 indicates conversion frequency: 0 0 kHz 1 125 kHz 2 250 kHz 3 500 kHz 60-61 WBD STAT0 62-63 WBD STAT2 (STAT2 & 0003) indicates antenna: 0 Ey 1 Bx 2 By 3 Ez (STAT2 & 001C) >> 2 indicates Frequency Mode 0-7 64-65 EW5SSOFF The remaining bytes (64-103) are filled with zeroes. ----------------------------------------------------------------------------- Cluster Telemetry Transfer Frame (bytes 104-1222): ------------------------- Overview of Transfer Frame ------------------------ Byte 0 |-------------------------------| | ESA SYNC MARKER | | | |-------------------------------| Byte 4 | PRIMARY HEADER | | | |-------------------------------| Byte 10 | SECONDARY HEADER | | | |-------------------------------| Byte 14 | DATA FIELD | | (6 WBD sync/status bytes + | | 1090 data bytes) | |-------------------------------| Byte 1110 | ON BOARD TIME COUNTER | | | |-------------------------------| Byte 1117 | RFB | | | |-------------------------------| Byte 1118 | CAB | | | |-------------------------------| Byte 1119 | REED-SOLOMON CODE BLOCK | | | |-------------------------------| Bytes 104 to 1222 in the LEVEL1 files are bytes 0 to 1118 of the transfer frame as illustrated above and sent by the spacecraft; i.e., the transfer frame minus the Reed-Solomon code block. With the removal of the Reed-Solomon code block a time quality flag has been added and is byte 1223 of the LEVEL1 file. ----------------------------------------------------------------------------- Transfer Frame header (bytes 104-117): 104-107 ESA Sync Marker (Hex: 1A CF FC 1D) Primary Header (bytes 108-113): 108-109 Frame Identification NOTE: In DSN data, the record type may be found from the low order 3 bits of (byte 109)/2 (i.e. bits 1-3 of byte, 109), which will give the Virtual Channel (VC) ID (should only have a value of 5 or 7). 110 Master Channel Frame Counter NOTE: This counter keeps a running count of the total virtual channel frames (VC5 and VC7 combined). 111 Virtual Channel Frame Counter (32 bytes) NOTE: The highest order byte for this counter is in byte 117, followed by bytes 116, 115, and 111. If the current frame has a VC ID of 5, then this counter supplies the count of this VC5 frame. If the current frame has a VC ID of 7, then this counter supplies the count of this VC7 frame. 112-113 Frame Data/Field Status Secondary Header (bytes 114-117): 114 Secondary Header ID 115-117 Virtual Channel Frame Counter (32 bytes) NOTE: See byte 111. WBD Data block (bytes 118-1213): 118-123 For DSN data these bytes will contain sync and instrument status; for burst mode data these bytes will be all zeros. ---------- Byte number -------------- 118 119 120 121 122 123 Frame 00 FA F3 34 frame# count2 count1 Frame 01 FA F3 34 frame# count0 stat3 Frame 10 FA F3 34 frame# stat2 stat1 Frame 11 FA F3 34 frame# stat0 stat3 Four frames (numbered 0-3) comprise a major frame. It takes 1 major frame to get all of the status informa- tion. The time between Major Frames is 158.8745116 msec. The time between minor frames depends upon the percent of the duty cycle. See DUTY CYCLE MODE below. The Frame value (0-3) is contained in the low order two bits of byte 121. See Status Word Formats below for details of status word encoding. We have placed the decoded status information in bytes 1262-1274. 124-1213 Data Field: 1090 data bytes. Trailer block of transfer frame (bytes 1214-1223): On Board Time (OBT) Counter (7 bytes): 1214-1217 OBT counter Seconds for this record. 1218-1220 OBT counter Sub-Seconds as a 20 bit integer left justified for this record. 1221 RFB (low order bit = 1 => time is good ) 1222 CAB Contains the CTIB flag in low order bit. NOTE: Byte 1223 of the DSN record contained the Reed- Solomon status and was a part of the trailer block. We have modified it as shown below. 1223 Time quality flag: See following table. ----------------------------------------------------------------------------- Bit Description if bit = 1 7 Raw clock value (bytes 1256-1259) was adjusted 6 Frequency mode value (byte 1272) was adjusted 5 Frequency offset value (byte 1269) was adjusted 4 Antenna value (byte 1268) was adjusted 3 Second gain value (byte 1274) was adjusted 2 First gain value (byte 1266) was adjusted 1 Uncorrected ERT value (bytes 96-103) was not expected 0 Uncorrected OBT value (bytes 1248-1255) was not expected ----------------------------------------------------------------------------- An adjusted value does not mean that the value was bad but that the value computed in the normal manner appeared to be incorrect. END OF TRANSFER FRAME ----------------------------------------------------------------------------- The following UT_GRT is the UT time of measurement for the data, as calculated using the Earth Received Time as its basis. It has been corrected for all delays between when the data were acquired at the WBD instrument and the time when the data arrived at the ground: 1224-1231 UT_GRT Format: Bytes 1224-1225 Days from start of year 2000 Bytes 1226-1229 Milliseconds of day Bytes 1230-1231 Microseconds of MS The following UT_OBT is the UT time of measurement for the data, as calculated using the On-Board time counter and the calibration data supplied by ESA. 1232-1233 UT_OBT Year (2xxx) 1234-1235 UT_OBT Month of year 1236-1337 UT_OBT Day of month 1238-1239 UT_OBT Day of year 1240-1241 UT_OBT Hour 1242-1243 UT_OBT Minute 1244-1245 UT_OBT Second 1246-1247 UT_OBT Milliseconds (0 - 999) The number of microseconds in the UT Second is given by: UT_OBT Microseconds = (integer in bytes 1246-1247) * 1000 + (integer value in byte 1275) * 10 + integer value in byte 94 NOTE: Byte 94 is used only if byte 2 has an integer value of 2 or greater. If otherwise, then use the above formula as if byte 94 had a value of zero. 1248-1255 OBT Counter value corresponding to current CTIB flag (format is the same as for bytes 1214-1220). NOTE: This is used as the reference time when calculating UT_OBT. The CTIB flag will be set every 5.152221 seconds, when the instrument clock/counter is reset. Thus, this counter value will change every 5.152221 seconds. For UT_GRT, the equivalent reference time is contained in bytes 96-103. 1256-1259 The WBD instrument counter value (WBDClock) for the current major frame. The CTIB flag indicates a reset of this counter. Sybolically, both the UT_OBT and UT_GRT times are calculated as follows: T = reference_time + WBDClock / 1003631.274 (seconds) + minor_frame_number * 39.718628 (milliseconds) Note however, that the actual time calculations are more complex than this (see the TIMETAGS.TXT file for further information). 1260-1261 In DSN mode these bytes contain the number of bits by which the LEVEL1 software has shifted the WBD Data block (bytes 118-1213) within the transfer frame. In the raw transfer frames, the WBD data block is not aligned such that a single block is wholly contained within a single transfer frame. With this shift, the LEVEL1 software corrects this. In burst mode these bytes contain the processing control, a 2-byte integer: 0 => filtered data, 1 => duty cycled data. INSTRUMENT STATUS for both DSN and Burst Mode data (bytes 1262-1274): In DSN data, these are determined from bytes 122 and 123. In Burst mode this information is obtained from the housekeeping data and placed in the record header by the Ted decommutation software. 1262 1 = VCXO not locked 0 = VCXO locked 1263 0 = OBDH interface primary 1 = OBDH interface redundant 1264 0 = no cmds 1 = cmds 1265 0 = a/d power off 1 = a/d power on 1266 Gain/Select (Gain in dB = (byte 1266) * 5) NOTE: If LEVEL1 File Version (byte 2) is 2 or greater, then this gain is that for the current minor frame. For earlier versions, the usage depends on the duty cycle mode (see byte 1272): 100% duty cycle -> gain is for frames 1 and 2 of the current major frame not 100% duty cycle -> gain is for frames 2 and 3 of the current major frame 1267 0 = gain auto 1 = gain manual 1268 Antenna select: 0 = Ez 1 = Bx 2 = By 3 = Ey 1269 Frequency offset: 0 = 0 Hz 1 = 125.454 kHz 2 = 250.908 kHz 3 = 501.816 kHz 1270 AGC upper threshold 1271 Instrument ID value Inst. Spacecraft 4 F6 2 5 F7 3 6 F8 4 7 F9 1 1272 Frequency Mode (0-7): See table of modes & duty cyling below. 1273 AGC lower threshold 1274 Gain/Select (Gain in dB = (byte 1266) * 5) NOTE: If LEVEL1 File Version (byte 2) is 2 or greater, then this gain is that for the current minor frame. For earlier versions, the usage depends on the duty cycle mode (see byte 1272): 100% duty cycle -> gain is for frame 3 of the current major frame and frame 0 of the *next* major frame not 100% duty cycle -> gain is for frames 0 and 1 of the *next* major frame 1275 Most significant two digits of fractional UT_OBT milliseconds (0-99, hundredths of ms) The number of microseconds in the UT_OBT Second is given by: UT_OBT Microseconds = (integer in bytes 1246-1247) * 1000 + (integer value in byte 1275) * 10 + integer value in byte 94 NOTE: Byte 94 is used only if byte 2 has an integer value of 2 or greater. If otherwise, then use the above formula as if byte 94 had a value of zero. ----------------------------- End of LEVEL1 WBD Format ---------------------- NOTE: Unless otherwise noted, all byte values are unsigned integers. --------------------------------- Instrument Modes -------------------------- There are eight modes that the WBD instrument can be set to use (although only the first seven are distinct from a user's point of view). The modes are differentiated by: Bandwidth - the frequency span of the input bandpass filter. Sample Rate - the sampling rate of the instrument. Bits/Sample - the number of bits with which each sample is encoded. Duty Cycle - the fraction of time that the instrument is sampling. Sample Time - the time spanned by one complete minor frame. The mode for a data frame is given in byte 1272. The different modes are: Mode Bandwidth Sample Rate Bits/Sample Duty Cycle Sample Time (msec) 0 100Hz-9.5kHz 27.4kHz 8 100% 39.7186279 1 100Hz-9.5kHz 27.4kHz 8 100% 39.7186279 2 100Hz-19kHz 54.9kHz 4 100% 39.7186279 3 100Hz-19kHz 54.9kHz 8 50% 19.85931395 4 700Hz-77kHz 219.5kHz 8 12.5% 4.96482848 5 700Hz-77kHz 219.5kHz 1 100% 39.7186279 6 700Hz-77kHz 219.5kHz 4 25% 9.92965697 7 700Hz-77kHz 219.5kHz 8 12.5% 4.96482848 Note that these parameters are not all independent. Some of the parameters, and their interdependencies, are expanded upon further below. Duty Cycle Modes: For some combinations of sample rate and bits/sample, the resulting data stream, if sampled continuously, would be produced at a rate greater than the available downlink rate. In these cases, the instrument instead samples the incident waveform in a duty cycle mode. In such modes, high-rate data is acquired (and saved in an internal WBD buffer) for a fixed sample period, and simultaneously read out to the downlink module at a lower rate over a longer interval. The read-out interval is always two minor frames (2180 data bytes) in length, so the sample period always begins at the start of every second minor frame (specifically, at the start of minor frames 0 and 2). The case of 50% duty cycling is illustrated below: SAMPLE SAMPLE SAMPLE SAMPLE PERIOD PERIOD PERIOD PERIOD ________ ________ ________ ________ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ | \ | \ | \ | \ |-------|-------|-------|-------|-------|-------|-------|-------| Frame 0 1 2 3 0 1 2 3 READ_OUT_PERIOD READ_OUT_PERIOD READ_OUT_PERIOD READ_OUT_PERIOD The length of the sample period is always such that 2048 samples are acquired. The timestamps on each minor frame of duty cycled data will clearly not be regularly spaced. Frames 0 and 2 will always begin 2*39.718628 milliseconds apart, but frames 1 and 3 will follow their preceeding frames by the interval given in the Sample Time column in the instrument mode table above. Reduced Bits/Sample Modes: An alternative way to acquire high-rate data, within the constraints of the available downlink rate, is to reduce the number of bits used to encode each sample. In these cases, the samples (either four bits or one bit in length) are packed into bytes as follows: 4-bit mode: In each byte, the low order nibble (bits 0-3) contains the oldest sample, so the byte should be unpacked from low nibble to high. 1-bit mode: In each byte, the low order bit (bit 0) contains the oldest sample, so the byte should be unpacked from the low bit towards the high. Burst Mode: For burst mode data, the data streams described above are further attenuated (by WEC-DWP, not by the WBD instrument), in one of two ways: Burst Mode/Duty Cycled - Only every third minor frame is stored on (and later transmitted by) the spacecraft. This means that when the duty cycle is 100%, only 1 out of every 3 minor frames is recovered, at 50%, only 1 out of every 6, at 25% only 1 out of 12, and at 12.5% only 1 out of 24 minor frames is recovered. (See Instrument Modes table above.) Burst Mode/Filtered - All frames will be transmitted, but are low pass filtered to one third of the frequency bandwidth. Since each snapshot in this data is 1/3 the usual length of 1090 bytes, data from 3 consecutive frames will be concatenated into one frame by the Ted software. The 1090 sample frames are always constructed with a fixed relation to the repeating sequence of 6 input packets (sizes of 360, then 5 sets of 364 bytes). That is 360+364+364+2 for the first frame, then 362+364+364 for the second. ------------------------------- Status Word Formats ------------------------- The following shows how to decode status bits from bytes 122-123 (of minor frames 2-3). The decoded status values are found in bytes 1262 through 1274. Byte Bit Description stat3 7 VCX0 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 3-0 Gain Level/Select stat2 7-6 11 5 Gain Mode (1=Manual; 0=Auto) 4-1 Gain Level/Select 0 OBDH Interface (0=Primary; 1=Redundant) stat1 7-6 01 5-4 Antenna Select (see byte 1268 above) 3-2 Frequency Select (see byte 1269 above) 1-0 Upper AGC Threshold stat0 7-5 Instrument ID (see byte 1271 above) 4-2 Output Mode (see byte 1272 above) 1-0 Lower AGC Threshold ----------------------------------------------------------------------------- Glossary: Burst Mode Data Data stored on the solid state recorder and telemetered non-real-time to the ESA ground station. CHDO Compressed Header Data Object. CTIB Coincident Transmission Indication Bit: This is a bit in the Transfer Frame, which is set whenever the transmission of that frame is coincident with the resetting of the WBD instrument counter (WBDClock). DSN Deep Space Network: The NASA ground station network at which most of the WBD data are received. ERT Earth Received Time: This time is put in the SFDU header at the time the data were received by the DSN ground station. ESA European Space Agency. OBT Spacecraft On Board Time counter, driven by an ultra-stable oscillator. Time calibration (tcal) files provided by ESA allow for the conversion of counter values into UT times. SFDU Standard Formatted Data Unit. UT_GRT UT timestamp on data, based on Earth (Ground) Received Time: GRT adjusted time for delays in the system, and all signal propagation effects, so that it is the time when the data were acquired at the WBD instrument, i.e. the time of measurement. UT_OBT Timestamp on data, based on the On Board Time: The time calculated using the OBT and the ESA time calibration files. WEC-DWP The Ditigal Wave Processor instrument that is part of the Wave Experiment Consortium (WEC) on Cluster. ----------------------------------------------------------------------------- For C programmers, most of this format information is incorporated in an include file SOFTWARE/EXAMPLES/WBDL1.H which contains macro and table definitions to make extracting the fields described above (and some derived items) much easier. Care was taken to construct macros that should work on most common platforms. ----------------------------------------------------------------------------- -----------------------------------------------------------------------------