PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2005-05-26, Anssi Malkki, v1.0 " RECORD_TYPE = STREAM OBJECT = DATA_SET DATA_SET_ID = "S1-X-SPEDE-2-EDR-EP-MONITORING2-V1.0 " OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "SMART1 PLASMA SPEDE 2 EDR EP-MONITORING2 V1.0 " DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = TABLE START_TIME = 2004-02-27T04:42:17 STOP_TIME = 2005-02-28T22:42:40 DATA_SET_RELEASE_DATE = 2005-10-18 PRODUCER_FULL_NAME = "Dr. Anssi Malkki" DETAILED_CATALOG_FLAG = "N" DATA_SET_TERSE_DESC = "This SPEDE data set of Level 1b contains raw SPEDE data from SMART-1 Earth orbit 229 to Moon orbit 235 (Feb-04 to Feb-05). The main objective during this time was monitoring of EP nominal operations." CITATION_DESC = "N/A" ARCHIVE_STATUS = "N/A" ABSTRACT_DESC = "N/A" DATA_SET_DESC = " Data Set Overview ================= This data set contains level 1b processed data for the SPEDE instrument on SMART-1. The set covers data from the end of February 2004 to the end of February 2005. During this period, SPEDE was operated mostly in EP monitoring mode. For SPEDE instrument description see SPEDEPAPER in DOCUMENT directory. The operation of the instrument was controlled by specific Instrument Operations Timelines (ITL). During periods between the measurements SPEDE was either in housekeeping mode (mode 1, which is a mode with 1 sample/minute) or in some of the modes developed for measuring natural plasma. On 18 and 19 March 2004, a special calibration in eclipse was performed (see S1-SPE-PL-3003 for the plan and S1-SPE-RP-3010 for analysis). The photoelectron current calibration reported in S1-SPE-RP-3008 was repeated on 6 April 2005. SPEDE instrument configuration tables were mostly unchanged within this data set. Configuration table dumps as confirmation for successful update were generated. The relevant parameters for each measurement are included in the header of each file. Two instrument flight software updates were performed during this period: on 10 March 2004 to correct an unwanted hysteresis effect in sweep data, and another update on 11 November 2004 to update the wave measurement code. The unwanted feature in sweep data (plasma data in PDS vocabulary) was successfully removed with the first update. After test measurements performed on 24 November 2004 and 8 January 2005, the wave mode has been used only after moon capture in February 2005. The level 1b data consist of measurements decoded from binary to PDS compliant ASCII tables, with instrument readings given in raw telemetry units. All measurements, housekeeping data, and configuration table dumps are included. Parameters ========== The measured parameters in the level 1b data are either frequencies (i.e., number of VFC pulses within a time window of constant length), or number of reference clock pulses for a fixed number of VFC pulses. The former is more generally used, in this data set for measurements in all modes except 4 and 9. When processed to Level 2, these parameters represent probe current, when the instrument is in Langmuir mode, or probe voltage, when the instrument is in voltage mode. The data are stored in arrays, with each row representing data from one SPEDE telemetry packet. The length of the row depends on the mode that is used. Data from -X and +X probes and different measurement types are stored in separate files. In connection with each measurement value, the packet contains the corresponding bias code value. In the beginning of each row the complete timing and configuration information for the following data values are given along with housekeeping parameters measured before the start of the first integration period included in that row. Processing ========== The data are processed from the DDS packages with APIDs 1021 (housekeeping data), 1022 (science data), 1023 (mode configuration table contents) and 1024 (memory dumps of hard-coded timing constants after modification from ground). These data are accessible from the ESOC DDS server. In the processing, the time information of each data set has been converted into UTC and MJD2000, using the originally included spacecraft time (SCET) and tabulated SCET-reset events on the spacecraft, provided by the spacecraft operations team. After correction of the known problems in SCET time, the telemetry packets have been decoded from binary to numerical data or configuration setting values. Data from each probe, measurement type and data vector length are stored in separate files. Each file contains all available data of the same type for one orbit. Inside the files the measurement data are stored in arrays as described above, one row per original telemetry record, with the instrument configuration and housekeeping values relevant for the record stored in the beginning of that row. No corrections are applied to the SPEDE data in the processing. Data ==== The data of each array row have to be interpreted depending on the instrument configuration as specified in the beginning of that row: Langmuir mode ('I') ------------------- In Langmuir mode, the configuration parameters are followed by a vector with bias values (0 to 255), one element for each measurement point, and a vector with data value (integer) of the same length. The bias values correspond to bias voltages applied to the probe with 0 the most negative, 255 the most positive voltage and 128 close to 0 V. The data value is measured as current to or from the probe. Langmuir sweep ('I') -------------------- The data for the Langmuir sweep mode is similar to other Langmuir data, now with a varying bias code. Voltage measurement ('V') ------------------------- For voltage measurement, the data structure is the same as in Langmuir mode. The bias code does not have any meaning, but is included in the data for compatibility reasons. The data value is a measure of the probe voltage with respect to the instrument ground reference voltage. The analog data of both Langmuir and voltage measurements can be digitalized in two different ways: Wave measurement ('W') ---------------------- Raw wave electric field data is extracted from data packets containing probe voltage or probe current measurements. In wave measurements, voltage difference between the two sensors is sampled for one second at 10000 samples/s. The result is 10 logarithmically spaced frequency bins. Frequency measurement ('F') --------------------------- The data value for frequency measurement corresponds to a number of VFC output signal pulses within a given time window. The data value has to be normalised in Level 2 processing to frequency in Hz. The window length used is given as the last parameter before the bias vector. In this data set 4 ms and 998 ms are used. Pulse length measurement ('P') ------------------------------ The data value is the number of pulses of the 16 MHz reference clock during a given number of VFC output signal pulses. The number of pulses used is given as the last parameter before the bias vector. In this data set number of VFC pulses for short pulse length measurements is 20, and for long pulse length measurements 150. Housekeeping data ----------------- The beginning of each data array row contains the following housekeeping parameters: Date and time: DATE Start time of the first measurement point as UTC, ASCII string JULIAN_DATE Start time of the first measurement point as MJD2000, real number representing days and day fractions since 1 Jan 2000 Telemetry packet information: APID Spacecraft application identification for the original telemetry packet SEQ_CNT Packet sequence counter, independent for each APID, reset at SPEDE switch-on SC_TIME Spacecraft time in seconds, uncorrected SPEDE time parameter SC_SUBTIME Spacecraft time, sub-second part in units of 1/256 sec Housekeeping measurements: REF_VOLT_MINUS_X 2.5V -X reference voltage, data value with frequency measurement using 4ms integration REF_VOLT_PLUS_X 2.5V +X reference voltage, data value with frequency measurement using 4ms integration TEMP_PLUS_X Temperature of +X channel electronics, data value with frequency measurement using 20ms integration - 1280, resolution 3C GROUND Ground reference voltage, data value with frequency measurement using 4ms integration Instrument configuration: MODE Number of configuration table defining the measurement for this data set TIME_INC Time difference between start of integration periods of subsequent measurements in units of 1/256 sec PROBE Sensor probe used for the data set: '1'=probe on -X face of spacecraft, '2'=probe on +X face of spacecraft, 'W'=wave measurement using the potential difference between both probes LENGTH Length of measurement bias and data vectors BIAS_TYPE 'I' for Langmuir (current), 'V' for voltage measurement MEASUREMENT_TYPE 'F' for frequency, 'P' for pulse length measurement INTEGRATION_CONSTANT for frequency measurements: integration time in ms, For pulse length measurements: number of VFC pulses used Configuration table dump (ancillary data) ------------------------ The contents of the configuration table define the details of a SPEDE measurement. After any update, a copy of the new table contents is included in the telemetry with APID=1023 and archived. The contents are valid until modified again. The parameters have the following meaning: CONFIGURATION_TABLE table number, range 1-9 MINUS_X_LP_BIAS_START First bias control value for -X probe in Langmuir mode MINUS_X_LP_BIAS_INCREMENT if #0 defines a Langmuir sweep: difference between subsequent measurement points. The related bias voltages are not linearily related to the control values. MINUS_X_STEPS Number of measurement points in one measurement. In Langmuir mode with INCREMENT > 0 this is the mumber of bias voltages used in an upward sweep. If the bias code value would become larger than the largest allowed value 255, the value will be 255 for those measurements. If hysteresis measurements are defined (see CONTROL_MINUS_X/_PLUS_X below) another sequence will be performed with same number of measurements and reversed stepping starting from end value of first measurement. The total measurement vector length will then be twice the given number here. PLUS_X_LP_BIAS_START as for MINUS PLUS_X_LP_BIAS_INCREMENT as for MINUS PLUS_X_STEPS as for MINUS CONTROL_MINUS_X Decimal representation of the control bit pattern for -X probe CONTROL_PLUS_X Decimal representation of the control bit pattern for +X probe The different powers of 2 and groups thereof have the following meaning V*2^0: V=0: Voltage mode, V=1: Langmuir (current) mode F*2^1: F=0: Frequency measurement, F=1: Pulse length measurement H*2^2: H=0: no hysteresis measurement, H=1: Hysteresis measurement I*2^3: I=0: large integration constant, I=1: small integration constant 2^4 - 2^6 are only relevant if H=1 (hysteresis measurement activated) V2*2^4: V2=0 Voltage mode in second measurement phase, V2=1: Langmuir mode F2*2^5: F2=0: Frequency measurement, F2=1: pulse length measurement I2*2^6: I2=0: large integration constant, I2=1: short integration constant W*2^7: W=0: No wave measurement, W=1: wave measurement included STEPPING_INTERVAL Time interval between start of integration times in units of 1/256s REPETITION_INTERVAL Time interval between start of telemetry packets in units of 1/16s REPETITIONS Number of automatic telemetry packet repetitions. 0=infinte (continuous measurement). FREQUENCY_BANDS If wave measurements are activated: number for frequency bins WAVE_BIAS_MINUS_X Bias voltage on -X probe. If =0, probe is set to voltage WAVE_BIAS_PLUS_X Bias voltage on +X probe. If =0, probe is set to voltage SW DUMP (ancillary data) ------------------------ The integration constants are hard-coded in the software area of the non- volatile memory (EEPROM). They are loaded into working memory during the program boot phase. If these values are overwritten by command, the correct command execution is verified by a dump of the corresponding memory area. These software dump telemetry packets are archived in this data set. Their APID is 1024, the archive record structure is: - Header information with times (UTC) - APID - packet sequence number - Instrument time stamp - Integration-constant vector with values for each parameter in EEPROM and RAM Parameters not returned by the related telemetry packet are marked as N/A FREQ_LONG_EEPROM Number of 16-MHz clock pulses defining the long integration time. This value is used after each instrument reboot FREQ_SHORT_EEPROM Number of 16-MHz clock pulses defining the short integration time. This value is used after each instrument reboot PULSE_LONG_MINUS_X_EEPROM Number of pulses from -X sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('long') PULSE_SHORT_MINUS_X_EEPROM Number of pulses from -X sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('short') PULSE_LONG_PLUS_X_EEPROM Number of pulses from +X sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('long') PULSE_SHORT_PLUS_X_EEPROM Number of pulses from -+ sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('short') FREQ_LONG_RAM Number of 16-MHz clock pulses defining the long integration time. This value is used directly, overwritten on reboot FREQ_SHORT_RAM Number of 16-MHz clock pulses defining the short integration time. This value is used directly, overwritten on reboot PULSE_LONG_MINUS_X_RAM Number of pulses from -X sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('long') PULSE_SHORT_MINUS_X_RAM Number of pulses from -X sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('short') PULSE_LONG_PLUS_X_RAM Number of pulses from +X sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('long') PULSE_SHORT_PLUS_X_RAM Number of pulses from -+ sensor VFC used to determine the pulselength by comparison with 16-MHz clock ('short') Other Ancillary Data ==================== Ancillary data needed to calibrate and interpret the measurements are Electric Propulsion on and off times, and spacecraft attitude, position, and velocity. These data are not provided in the data set. EP propulsion information is provided in dataset S1-L-ESOC-6-AUXILIARY-DATA-V1.0, product S1_EP_THRUST_LOG.TAB. Instrument configuration for each measurement is included in the header information of each Level 1b processed telemetry packet. No instrument specific ancillary data, in addition to what is provided in the data set, is needed. Coordinate System ================= The SPEDE probes are at the centre of the -X and +X faces of the spacecraft. Software ======== The data can be ingested to analysis and/or plotting software either by a simple ASCII reading routine, or using PDS tools. There is also software for processing the data to Level 2 (applying calibration factors to the data), which is used by the data producers (FMI). Media/Format ============ The data is delivered as ASCII files, compliant with the PDS standard. " CONFIDENCE_LEVEL_NOTE = " Confidence Level Overview ========================= The data have been automatically processed from raw data, and manually checked for clearly visible anomalies. Since no calibration-related operations are performed, the data is an image of the instrument measurements without correction, and as such fully representative of the raw measurements. Known features are discussed in the Data Quality section below. Review ====== The data were manually checked for clearly visible anomalies. No data was discarded, and no unknown features that could be considered anomalous instrument behaviour at electronics level were found. Physical interpretation and/or review will be performed at Level 2 data. Data Coverage and Quality ========================= The data cover the period from 27 February 2004 to 28 February 2005 (Earth orbit 229 - Moon obrit 235). Probe characterisation measurements were performed on 6 April 2004 (09:11:54 - 10:39:00 UT). At the date of submission of the data set, the following known features affect data quality: 1. The first measurement in each telemetry packet shows an anomalous value, corresponding to a frequency value that deviates clearly from those values obtained for the rest of the measurements in the same packet and the next packet. The origin of this feature is not yet fully understood. A plausible explanation could be capacitive coupling between the probe and the plasma at the beginning of the measurement sequence. The bias voltage is forced to zero volts for 40 ms before each telemetry packet. A fast change of probe bias voltage at the beginning of the measurement sequence could result in a peak in the probe current, visible in the first measurement. In level 2 data, the first measurement of each telemetry packet is flagged (see Level 2 description). 2. In pulse mode, the pulse count jumps between two values for a static input. This is a feature also seen in ground tests, and is due to the pulse counter sometimes missing the last pulse. This is caused by the synchronization between the measurement frequency signal and the internal controller clock. It adds a systematic digital noise of 0.6 percent to the signal. Since the origin and effect are known, this feature can be corrected for in Level 2 processing. In level 2 data, data are flagged accordingly. 3. Data from probe '2' (or +X) shows non-nominal behavior since 13:01 UT on 20 October 2003, that is, over this entire data set. These data are processed to Level 2, even if a full understanding of instrument calibration in this situation has not been achieved. Analysis of the anomaly has been reported in S1-SPE-RP-3009 'SMART-1 SPEDE Anomaly Report: Probe +X Malfunction'. Limitations =========== These data are the basis for calibration processing, and shall be used by the SPEDE team only. " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = "PLASMA" TARGET_TYPE = "PLASMA ENVIRONMENT" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = S1 INSTRUMENT_ID = SPEDE END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = N/A END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END