NSSDCA ID: PSFP-00751
Availability: Data Identified but not Received
This description was generated automatically using input from the Planetary Data System.
Data Set Overview ================= The Cassini Radio and Plasma Wave Science (RPWS) Langmuir Probe continuous current data set comprises calibrated probe current measurements acquired at up to 20 Hz rate at fixed bias voltage 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 organized so as to have fixed-length records for ease in data handling. These can be used to infer high temporal resolution density fluctuations between standard Langmuir Probe sweeps. If related to densities determined during a sweep prior to or following the 20 Hz data, or using other electron density estimates, the relative currents can be assigned absolute densities. 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 continuous current data themselves consist either of 21.5s long time series of currents at the indicated bias voltage consisting of 432 samples each (20Hz), or of 624s long time series of currents consisting of 38 samples (survey, 61mHz). The time series are usually made every 24s (20Hz) each during targeted moon flybys or during inner magnetosphere crossings. In the outer magnetosphere the rate is lower with time series starting each 680s (survey). Prior to and during SOI the bias voltage was set based on the most recent sweep to use an optimum setting. Afterwards the bias was set to +11.5V, except during deep (<1200km from C/A) Titan flybys where a fixed bias of +4V was used. Some of the time series 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 utilize the continuous current data specific for the RPWS Langmuir probe analysis. The Langmuir probe spherical sensor is 5 cm in diameter, and coated with (baked) TiN. Data ==== The RPWS Langmuir Probe continuous 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 ================= This data set consists of calibrated current time series 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 analyzing these data. For some applications, the data may be considered point measurements at Cassini 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.
These data are available on-line from the Planetary Data System (PDS) at:
https://pds-ppi.igpp.ucla.edu/data/CO-SS_S-RPWS-3-LPCNTCUR-V1.0/
Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II
Name | Role | Original Affiliation | |
---|---|---|---|
Prof. Donald A. Gurnett | Data Provider | University of Iowa | |
Dr. Jan-Erik Wahlund | General Contact | jwe@irfu.se |