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-SOLAR-WIND-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "SMART1 PLASMA SPEDE 4 REFDR SOLAR-WIND V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = TABLE START_TIME = 2004-02-02T22:46:14 STOP_TIME = 2004-02-25T19:31:38 DATA_SET_RELEASE_DATE = 2006-06-20 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 205-227. The main objectives during this time were instrument and probe characterization measurements in natural plasma environment with EP off." 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 most of February 2004, during which the electric propulsion (EP) was off, in order to secure an undisturbed environment for instrument commissioning activities. SPEDE also performed commissioning activities, consisting of instrument and probe characterisation measurements. These activities and the results have been reported in S1-SPE-RP-3008 'SMART-1 SPEDE Commissioning Report'. The probe on the +X face of the spaceraft has behaved non-nominally since 20 October 2003. An anomaly report has been generated (S1-SPE-RP-3009 'SMART-1 SPEDE Anomaly Report: Probe +X Malfunction'). For SPEDE instrument description see SPEDEPAPER in DOCUMENT directory. The operation of the instrument was controlled by specific Instrument Operations Timeline (ITL) and Direct Operations Request (DOR) sequences, developed for the commissioning activities. During periods between the measurements off 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. The two specific measurements for the commissioning period were 1) cleaning of SPEDE probes and 2) characterisation of the photoelectron flux of the probes. The measurements are described in the document 'Payload Second Commissioning Scenario Parameter List' (S1-RSSD-LI-004 Issue 5 21 Feb 2004). During the probe cleaning operation, both probes SPEDE were biased to their maximum positive value (-X: 13,9 V, +X: 14,05 V), in order to the probes to repel as much positive ions as possible. Data were collected once per second in Langmuir mode with both probes. The range of angles that could be covered (Y-axis w.r.t. the Sun) was limited by an operational constraint that the angle between the sun direction and the Solar Panels should not exceed 45 degrees. The photoelectron current characterisation was performed by rotating the spacecraft around the Y axis, with XZ-plane in the ecliptic plane. SPEDE was continuously measuring in Langmuir sweep mode, collecting data from both probes on a wide range of bias voltage values. From the current values at negative bias voltages, one can obtain the variation of the photoelectron contribution to the measured current by comparing values at different angles between the probe and the sun direction. Theoretically, the photoelectron contribution to the probe current is directly proportional to the area illuminated by solar UV radiation. Comparing values at different bias voltages, one can obtain information on the variation of plasma parameters during the measurement, as in nominal Langmuir sweep measurements. Data were successfully collected for probe angles between -90 degrees (-X to the sun) and +90 degrees (+X to the sun). The level 2 data consist of measurements processed from SPEDE level 1b data using current calibration algorithms and coefficients 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 a 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'. Review ====== The data were manually checked for clearly visible anomalies. Data Coverage and Quality ========================= The data cover the commissioning period from 2 to 25 February 2004 (orbits 205-227). Probe clean-up and characterisation measurements were performed on 10 February 2004 from 05:59 to 08:51 UT and 20 Feb 2004 at 17:30 UT, respectively. 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. The first measurement of each telemetry packet is flagged (see Data flags 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 will be corrected in future releases of Level 2 datasets. The data are flagged accordingly. 3. Data from probe '2' (or +X) shows non-nominal behavior since 13:01 UT on 20 October 2003. These data are not processed to Level 2 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