Data Set Information
DATA_SET_NAME CASSINI SS/S RPWS LP DENSITY FROM FLOATING POTENTIAL V1.0
DATA_SET_ID CO-SS/S-RPWS-5-NEPROXY-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview ================= The Cassini Radio and Plasma Wave Science (RPWS) Langmuir Probe proxy electron density data set contains electron densities derived using an empirical relation between the floating potential and electron densities from the Cassini Plasma Spectrometer during the entire Cassini mission. This dataset also includes the spacecraft potential which can be derived from the floating potential. This particular data set includes spacecraft event time, floating potential, spacecraft potential, and electron number density. Data are presented in ASCII text tables of fixed-length records for ease in data handling. Parameters ========== This data set comprises spacecraft event time, floating potential, spacecraft potential, and electron number density that were derived from RPWS measurements. 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, de-compress the data that were compressed by one of a number of compression algorithms by the RPWS flight software onboard, apply conversion lookup tables or algorithms to convert telemetry data numbers into physical units, and make any corrections required. See chapters 5-11 of the RPWSCAL document in the DOCUMENT directory for details on how the data included in this data set were calibrated. These data are calibrated using the best calibration tables and algorithms available at the time the data were archived. Should a significant improvement in calibration become available, an erratum will be noted in the erratum section. Later versions of the products may contain better calibrations. The floating potential (Ufloat) is directly measured by the Langmuir Probe. The spacecraft potential Usc is derived from the floating potential Ufloat using the formula: Usc = Ufloat / (1-(5/6)*exp(ds/D)) where ds is LP distance from spacecraft, 150cm, D is the Debye length in centimeters calculated from D = 6.9 * sqrt(Te*11600/Ne), Ne is proxy electron density in cm**-3, and we assume Te, magnetospheric electron temperature to be 100eV. The proxy electron density is determined by an empirical relation found between Ufloat and the electron density measured by the CAPS electron spectrometer as described in MOROOKAETAL2009. Data ==== The archived data are the results of applying the above derivation of the spacecraft potential and of the proxy electron density based on the RPWS LP measurement of the floating potential, presented as ASCII tables as a function of spacecraft event time. Ancillary Data ============== 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 are archived separately. Coordinate System ================= The data in this data set are floating and spacecraft potentials and a proxy for the electron density measured by the RPWS Langmuir probe. The floating potential is corrected with spacecraft attitudes so that it represents the value in the LP sunlit condition. 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 analyzing these data. However, for most purposes, the parameters may be considered point measurements at Cassini (they are at most 0.5s long) and may be entirely adequate with no coordinate transformations at all. 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.
DATA_SET_RELEASE_DATE 2018-07-10T00:00:00.000Z
START_TIME 1997-10-25T12:00:00.000Z
STOP_TIME 2017-09-16T12:00:00.000Z
MISSION_NAME CASSINI-HUYGENS
MISSION_START_DATE 1997-10-15T12:00:00.000Z
MISSION_STOP_DATE 2017-09-15T12:00:00.000Z
TARGET_NAME DIONE
SOLAR SYSTEM
RHEA
TETHYS
SATURN
ENCELADUS
HYPERION
MIMAS
IAPETUS
TITAN
PHOEBE
TARGET_TYPE SATELLITE
PLANETARY SYSTEM
PLANET
INSTRUMENT_HOST_ID CO
INSTRUMENT_NAME RADIO AND PLASMA WAVE SCIENCE
INSTRUMENT_ID RPWS
INSTRUMENT_TYPE PLASMA WAVE SPECTROMETER
NODE_NAME planetary plasma interactions
ARCHIVE_STATUS LOCALLY ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview ========================= This data set contains floating and spacecraft potentials and a proxy for the electron density acquired by the Cassini RPWS instrument for the interval described below. Every effort has been made to ensure that all data returned to JPL from the spacecraft are included and that the calibration is accurate. Electron densities will not be available for number densities above 5 cm**-3. The accuracy of the electron densities depends on the scatter in the Ufloat-to-density relation and in the accuracy of the CAPS electron densities, themselves. The absolute accuracy of the electron density is likely 50% (factor of 2) but the relative density from time-to-time is likely reliable. See MOROOKAETAL2009 for a discussion of the electron density accuracy. Review ====== The RPWS Langmuir proxy electron density 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/LPR instrument was operated continuously most of the time 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. The floating potential measurements are made with variable cadence through the entire mission at Saturn. This data set presently includes data through day 234 of 2010. Later measurements will be added at a later date. Limitations =========== Occasional RPWS Langmuir probe voltage sweeps have interference in individual sweep samples. These samples have been filtered away before analysis and should not pose a problem for the delivered output parameters. The Ufloat proxy method for this data set is applicable only for densities below 5 cm**-3. To avoid uncertainty of the transition region, data are limited to radial distance beyond 7 Rs from Saturn and absolute magnetic latitude above 15 degrees. Also the data inside 10 Rt from Titan are not included for the same reason. The proxy method uses the photoelectron condition directly measured by the instrument and therefore not available when LP is totally in shadow.
CITATION_DESCRIPTION Wahlund, J.-E., W.S. Kurth, and L.J. Granroth, CASSINI SS/S RPWS DERIVED DENSITY FROM FLOATING POTENTIAL V1.0, CO-SS/S-RPWS-5-NEPROXY-V1.0, NASA Planetary Data System, 2014.
ABSTRACT_TEXT The Cassini Radio and Plasma Wave Science (RPWS) Langmuir Probe proxy electron density data set contains electron densities derived using an empirical relation between the floating potential and electron densities from the Cassini Plasma Spectrometer during the entire Cassini mission. This data set also includes the spacecraft potential which can be derived from the floating potential. The submitted data set includes spacecraft potential, floating potential, and electron density, and is intended to become the most comprehensive and complete data set of electron densities and spacecraft potential in Saturn's low-density, outer magnetosphere derived from the Langmuir Probe floating potential measurement in the Cassini RPWS archive. Data are presented in tables with fixed-length records for ease in data handling.
PRODUCER_FULL_NAME DR. JAN-ERIK WAHLUND
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