PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2005-05-16, Anssi Malkki,v1.0" RELEASE_ID = 0001 REVISION_ID = 0000 RECORD_TYPE = STREAM OBJECT = DATA_SET DATA_SET_ID = "S1-X-SPEDE-4-REFDR-EP-MONITORING-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "SMART1 PLASMA SPEDE 4 REFDR EP-MONITORING V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = TABLE START_TIME = 2003-10-04T21:48:03 STOP_TIME = 2004-02-01T22:46:14 DATA_SET_RELEASE_DATE = 2005-10-18 PRODUCER_FULL_NAME = "Dr. Anssi Malkki" DETAILED_CATALOG_FLAG = "N" DATA_SET_TERSE_DESC = "SPEDE EP monitoring data set of Level 2 contains calibrated SPEDE data from SMART-1 orbits 15-205. The main objective during this time was monitoring the plasma environment during operation of the EP thruster." CITATION_DESC = "N/A" ARCHIVE_STATUS = "N/A" ABSTRACT_DESC = "N/A" DATA_SET_DESC = " Data Set Overview ================= This data set contains level 2 processed data for the SPEDE instrument on SMART-1. The set covers the time period from start of SPEDE nominal operations on orbit 15 (4 October 2003) to the start of commissioning activities on orbit 204 (1 February 2004). Activities during this period will be covered in more detail in later documents and reports of science analysis. For SPEDE instrument description see SPEDEPAPER in /DOCUMENT directory. The main activity performed during the period was monitoring the plasma environment of SMART-1 during operation of the EP thruster. EP was operated most of the time in order to raise the SMART-1 orbit outside of the radiation belts. Thus very little data other than EP monitoring was collected. Especially during christmas period, EP was on almost two weeks continuously. On October 20, 2004, the +X probe of SPEDE started showing anomalous behavior, resulting in non-nominal data. The event has been analysed and reported in S1-SPE-RP-3009 'SMART-1 SPEDE Anomaly Report: Probe +X Malfunction'. For this delivery, data from +X probe have not been processed to Level 2 for orbits that occur after that event. For the remainder of the orbit corresponding to the event of anomaly, data are flagged (for flags see below). The Probe +X data has not been processed for the remainder of the data set because the calibration of the probe after the malfunction is not known to an accuracy that would allow for normalising the measurements with sufficient confidence on the results. The end of October and beginning of November was a period of extremely high Solar activity. Interesting results can be expected from later analysis of SPEDE data taken during that period. The operation of the instrument was controlled by nominal Instrument Operations Timeline (ITL) sequences, developed for EP monitoring. The activities in the ITL were coordinated with the EPDP instrument. During EP off SPEDE was either in housekeeping mode (mode 1, which is a mode with 1 sample / minute) or in some of specific natural plasma modes. 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. The level 2 data consist of measurements processed from SPEDE level 1b data using current calibration algorithms and coefficients are documented in /CALIB directory. For the first delivery, no extensive quality control has been performed, and all data are flagged appropriately (confidence flag 9 'unchecked'). Parameters ========== The measured parameters in the level 2 data are either probe voltages as a function of time (when the instrument is in Voltage mode, see SPEDEPAPER), or probe currents either in constant bias voltage mode ('Langmuir mode') or with varying bias voltage ('Langmuir sweep'). The data format for the different modes are different, as described in SPEDESIS document. For the Langmuir sweep data, the data are stored in arrays, with each row representing data from one SPEDE telemetry packet. The length of the row depends on the number of points in the Langmuir sweep. Data from -X and +X probes and different measurement types are stored in separate files. In Langmuir mode, for each measurement value (given in Amperes) the corresponding bias value (voltage in Volts) is given. Instrument housekeeping data are included in HK data product (see SPEDESIS for details). No Probe Voltage data is included in this data set. Processing ========== The data are processed from the PDS level 1b products of type PC (Probe Current), with ancillary data. These data are accessible from the ESTEC PDS server. The algorithms and calibration used for Level 2 processing factors are archived separately from the same server. 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. No corrections are applied to the SPEDE data in the processing in this delivery. For future releases, flags have been defined for correcting known features in the data. Data ==== Electron/ion flux measurement ----------------------------- Electron/ion flux measurement data row starts with the time of the measurement, in UTC and MJD2000, shadow status, angular separation of the spacecraft and sun, angular separation of the spacecraft +Z-axis and solar array, spacecraft position in GSE and LSE coordinates and followed by the bias value (in Volts), the probe current (in Amperes), and the status flag. The probe current is defined such that positive current corresponds to electrons being collected by the probe. Thus a probe biased positively with respect to the plasma would result in a positive current. Electron/ion flux data is originated from Level 1b Probe Current data with fixed bias. Plasma data measurement ----------------------- Each plasma data measurement row starts with the time of the measurement, in UTC and MJD2000, shadow status, angular separation of the spacecraft and sun, angular separation of the spacecraft +Z-axis and solar array, spacecraft position in GSE and LSE coordinates and followed by the time increment (delta time between two measurement points), the bias vector containing bias values for all measurement points in Volts, the measurement vector containing all measurement results in Amperes, and the status flag vector. DATA FLAGS: Each data point is associated with a status and quality flag of 16 fields. The current assignment of the flags is as follows. o 16th (LS) flag: 0 = the result is checked and found correct 1 = the result is checked and possibly corrected, warnings concerning quality 2 = the result is checked, and found unreliable (no corrections) 9 = the result is unchecked o 15th flag: F = frequency measurement, p = original pulse measurement, P = corrected pulse measurement o 14th flag: 1 = the first measurement in an measurement vector, _ = following measurements o 13th flag: R = the reference voltage was fluctuating during this measurement, _ = the reference voltage was OK (the reference voltage value is obtained from housekeeping data) Housekeeping data ----------------- Each housekeeping data row starts with the time of the measurement, in UTC and MJD2000, followed by reference voltages for +X and -X (Volts, nominal values around 2.5 V), temperature of +X electronics in Celcius degrees, ground reference voltage (in Volts), and status flag defining whether a reference voltage was fluctuating during the measurement. Ancillary Data ============== Ancillary data needed to calibrate and interpret the measurements are Electric Propulsion on and off times, and spacecraft attitude, position, and velocity. In the SPEDE dataset we have included spacecraft position in Geocentric Solar Ecliptic (for cruise phase) and Moon-centric Solar Ecliptic (for lunar phase) coordinates. In addition, two derived quantities are included, namely the angle between the SPEDE +X probe and the Sun, and shadow indicator. From the sun-probe angle one can calculate the photoelectron current, which is directly proportional to the sunlit area of the cylindrical probe. Due to strongly negative charging of the SMART-1 spacecraft and thus negative potential of the probe with respect to the plasma, photoelectrons are always repelled from the SPEDE probeS. The saturation photoelectron current for SPEDE probes is 140 nA, so the contribution of this term is significant in low-density plasmas. The purpose of the shadow (or eclipse) indicator is the same as above. When the probe enters spacecraft (or Earth or Moon) shadow, photoelectrons are no longer emitted, which can be seen as an abrupt change in the Langmuir probe signal. Thus the Level 2 data set includes an indicator of when this happens, and those events can be identified. The shadow indicator (as well as the probe vs. sun angle) are only calculated for the -X probe, since this is the probe that is still fully functional. EP propulsion information is provided in dataset S1-L-ESOC-6-AUXILIARY-DATA-V1.0, product S1_EP_THRUST_LOG.TAB. 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. 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. For this first delivery of Level 2 data, all data are flagged with quality status 9 'unchecked'. Exception to this are the data from Probe 2 after failure, that are flagged with quality flag 2 (see above for quality flag description) to the extent they have been processed (see below). Known features are discussed in the Data Quality section below. Review ====== The data were manually checked for clearly visible anomalies. Data from probe +X was discarded after 20 October 2003 due to detected anomalous behavior as described in S1-SPE-RP-3009. Data Coverage and Quality ========================= The data cover the pre-commissioning period from orbit 15 (4 Ocotber 2003) to orbit 204 (1 February 2004). 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 data flag description above). 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. This will be done in a future release. Data are flagged accordingly to the reprocessing status (see data flag description above). 3. Data from probe '2' (or +X) shows non-nominal behavior since 13:30 UT on 20 October 2003. These data were not be processed to Level 2 for this release. Processing of those data will wait until a full understanding of instrument calibration in the new situation has been achieved. Analysis of the anomaly has been reported in S1-SPE-RP-3009 'SMART-1 SPEDE Anomaly Report: Probe +X Malfunction'. Limitations =========== Due to the early status of calibration at the time of the first release, the data shall be used in close consultation with the SPEDE PI only. No publication of presentation shall be made without the explicit written approval of the SPEDE PI. " 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