PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2005-05-26, 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-MONITORING2-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "SMART1 PLASMA SPEDE 4 REFDR EP-MONITORING2 V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = TABLE START_TIME = 2004-02-25T19:31:38 STOP_TIME = 2005-03-01T01:11:20 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 2 contains SPEDE data from SMART-1 Earth orbit 228 to Moon orbit 235 (Feb-04 to Mar-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 2 processed data for the SPEDE instrument on SMART-1. The set covers data from last week of February 2004 to start of March 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 n 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 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'). Some measurements contain wave electric field data, which is extracted from raw measurement packets and saved as separate data products. The data format for the different modes are different, as described in SPEDESIS document. For the Langmuir sweep (plasma) 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 constant bias mode (electron/ion flux), 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 E-field data (Probe Voltage measurements) is included in this data set. Wave electric field data is stored in arrays, where each row gives wave power in 10 frequency points. 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. 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. Wave data measurement --------------------- Each wave 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 time increment (delta time between two measurement points), the biases for -X and +X probes in Volts, and the wave power vector giving wave power at steps 5000 Hz, 2500 Hz, 1250 Hz, 625 Hz, 313 Hz, 156 Hz, 78 Hz, 39 Hz, 20 Hz and 10 Hz. 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 _ = not applicable (wave 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 delivery of Level 2 data, all data are flagged with quality status 9 'unchecked'. 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 commissioning period from 25 February 2004 to 1 March 2005 (Earth orbit 228 - Moon orbit 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 the entire period of this 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 =========== 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