PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2014-08-08, Jan-Erik Wahlund (IRF UPPSALA), initial; 2014-08-19, Larry Granroth (UIowa), edits;" RECORD_TYPE = STREAM OBJECT = DATA_SET DATA_SET_ID = "CO-SS/S-RPWS-3-LPUI-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = " CASSINI SS/S RPWS CALIBRATED LP POTENTIAL CURRENT V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = TABLE ARCHIVE_STATUS = "PRE PEER REVIEW - ACCUMULATING" START_TIME = 1997-298T00:00:00.000Z STOP_TIME = NULL DATA_SET_RELEASE_DATE = 2014-08-19 PRODUCER_FULL_NAME = "DR. JAN-ERIK WAHLUND" DETAILED_CATALOG_FLAG = "N" DATA_SET_TERSE_DESC = " The RPWS Langmuir Probe Sweep voltage-current data set comprises calibrated Voltage-Current (U-I) characteristics acquired almost continuously during the entire Cassini mission." ABSTRACT_DESC = " The Cassini Radio and Plasma Wave Science (RPWS) Langmuir Probe Sweep voltage-current data set comprises calibrated Voltage-Current (U-I) characteristics acquired almost continuously from most mission phases during the entire Cassini mission. The full data set of Voltage-Current characteristics is intended to become the most comprehensive and complete data set from which thermal plasma parameters can be derived in the Cassini RPWS archive. Data are presented in text tables and are organised so as to have fixed-length records for ease in data handling. These can be used to derive higher level data products like thermal plasma parameters, e.g., electron density and temperature." CITATION_DESC = "Wahlund, J.-E, Kurth, W.S., and L.J. Granroth, CASSINI SS/S RPWS CALIBRATED LP POTENTIAL CURRENT V1.0, CO-SS/S-RPWS-3-LPUI-V1.0, NASA Planetary Data System, 2014." DATA_SET_DESC = " Data Set Overview ================= The Cassini Radio and Plasma Wave Science (RPWS) Langmuir Probe Sweep voltage-current data set comprises calibrated Voltage-Current (U-I) characteristics acquired almost continuously from most mission phases during the entire Cassini mission. This particular data set includes spacecraft event time, bias voltage, and measured current for each sampled data point. Data are presented in tables organised so as to have fixed-length records for ease in data handling. These can be used to derive higher level data products like thermal plasma parameters, e.g., electron density and temperature. Parameters ========== This data set comprises spacecraft event time, bias voltage, and measured current for each sampled data point that was acquired by the RPWS. Processing ========== Data in this data set were processed by the use of a number of software programs which assemble segmented mini-packets in the raw telemetry packets into complete sets then de-compress the data that were compressed by one of a number of compression algorithms by the RPWS flight software onboard. The conversion from telemetry data to physical measured electric current units is made through lookup tables created by two 3rd order polynomial fits to the ground tests calibration data. The ground test calibration data are presented in Chapter 9 of the RPWSCAL document in the DOCUMENT directory. These data are calibrated using the best calibration tables and algorithms available at the time the data were archived. The sweep data themselves consist of 0.5s long current-voltage characteristics consisting of 512 or 1024 samples each. The sweeps are usually made every 24s during targeted moon flybys or during inner magnetosphere crossings, or every 600s during survey mode. The bias voltage sweep range is most often between +/-32V, except for Titan flybys below 1200km altitude where the voltage range is +/-4V. The voltage sweeps are usually swept from both negative and positive voltage bias (i.e., two sweeps occur per 0.5s) to check for hysteresis artefacts. Some of the sweep data show data spikes of external interference origin. These have not been corrected for, but can easily be filtered away by the user. There are several literature references regarding how to do analyse Langmuir probe sweeps, and the following references, specific for the RPWS Langmuir probe analysis, are probably useful: Titan ionosphere: Wahlund et al., 2005; Shebanits et al., 2013 Enceladus plume: Morooka et al., 2011 Inner plasma disk: Gustafsson & Wahlund, 2010; Holmberg et al., 2012 Outer magnetosphere proxy density data: Morooka et al., 2009. The Langmuir probe spherical sensor is 5 cm in diameter, and coated with TiN. Data ==== The RPWS Langmuir Probe sweep voltage-current data set is given as daily ASCII tables of three columns. The first column is spacecraft event time (SCET), the second column is the set bias potential in volts, and the third column is the measured current in amps. Ancillary Data ============== Ancillary data archived separately with volume set id USA_NASA_PDS_CORPWS_0XXX include a series of files that describe the modes of the RPWS as a function of time and provide a time-ordered listing of Instrument Expanded Block (IEB) trigger commands (the mode by which the RPWS is reconfigured). Also a detailed description of each of the modes (or IEBs) is provided. Other data which are ancillary to this data set and which are archived separately from this collection are the Navigation and Ancillary Information Facility's SPICE kernels describing the position and attitude of Cassini and various solar system bodies as a function of time. Coordinate System ================= The data in this data set are calibrated Voltage-Current characteristics measured by the RPWS Langmuir probe. These data are presented as detected by the sensor and are not rotated into any other coordinate system. If desired, the SPICE kernels can be used with the SPICE toolkit to convert from the spacecraft frame to virtually any frame which may be of use in analysing these data. However, for most purposes, the data may be considered point measurements at Cassini (a Langmuir probe Voltage sweep is at most 0.5s long) and may be entirely adequate with no coordinate transformations at all. However, for analysis purposes using this data set, the photo-electron cloud around the spacecraft, the photo-electron emission from the Langmuir probe itself, as well as possible ram plasma wake effects will indeed depend on the orientation of the spacecraft versus the solar and plasma ram flow directions. Media/Format ============ These data are supplied to the Planetary Data System as an online collection of files in a PDS volume directory structure or as a standard compressed archive, such as ZIP or TAR.GZ, of this collection." CONFIDENCE_LEVEL_NOTE = " Confidence Level Overview ========================= This data set contains calibrated Voltage-Current characteristics acquired by the Cassini RPWS Langmuir probe for the interval described below. Every effort has been made to ensure that all data returned to JPL from the spacecraft is included and that the calibration is accurate. The noise level of the Langmuir probe is estimated to be close to 100 pA derived from the sampled current data for negative bias voltage in thin plasma regions (<0.1 cm**-3). Calibration and other systematic errors are smaller than the noise level. In micro-meter sized dust regions the individual dust hits can be seen as spikes in the voltage sweep data. These have not been corrected for since it contains potential science results. Furthermore, some of the sweep data show artificial data spikes of external interference origin. These have not been corrected either, but can easily be filtered away by the user. Wake effects may also affect the quality of the data if the probe is in the wake of the spacecraft. The voltage-current characteristics data set has otherwise a very good confidence level. Review ====== The RPWS Langmuir probe sweep calibrated data will be reviewed internally by the Cassini RPWS team prior to release to the PDS. The data set will also be peer reviewed by the PDS. Data Coverage and Quality ========================= All data in the stated interval are included, to the best of our knowledge and attempts to determine completeness. In general, the RPWS/LP instrument started to operate just after launch in 1997, thereafter with intermittent operation periods near Earth and Jupiter flybys until three months before Saturn Orbit Insertion (SOI). The RPWS/LP was thereafter operated more or less continuously from SOI and forward, and gave higher resolution data during each moon flyby. Data gaps are due to spacecraft anomaly resolution or simply to downlink gaps, some of which were imposed by limitations on DSN station availability. Limitations =========== Occasional RPWS Langmuir probe voltage sweeps has an interference in individual sweep samples. The RPWS HFR receiver give these interference signals in the LPR in certain negative bias voltage ranges. These samples can been easily filtered away before analysis and should not pose a problem for the user analysis that deliver output parameters. The user will find out that thermal electron output data will usually not be available, due to spacecraft photoelectron current contamination, for number densities below 1 cm**-3 and/or for temperatures above 10eV. The thermal ion ram current is usually not detectable below 5-10 cm**-3. Derived electron temperatures below 0.03eV should be regarded as uncertain, as the rms electric field surface variability of the spherical TiN coated probes is 0.015eV, and the number of sweep samples used for the temperature estimation becomes small (4-5 samples out of 1024 samples over +/-4V). " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = SATURN END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = SOLAR_SYSTEM END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = TITAN END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = ENCELADUS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = MIMAS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = DIONE END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = TETHYS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = PHOEBE END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = IAPETUS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = HYPERION END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_TARGET TARGET_NAME = RHEA END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = CO INSTRUMENT_ID = RPWS END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_MISSION MISSION_NAME = "CASSINI-HUYGENS" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "GURNETTETAL2004" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END