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CASSINI E/J/S/SW MIMI CHEMS SENSOR UNCALIBRATED DATA V1.1 (PDS)

NSSDCA ID: PSFP-00810

Availability: Archived at NSSDC, accessible from elsewhere

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview

The Cassini Magnetospheric Imaging Instrument(MIMI) Charge Energy Mass Spectrometer (CHEMS) uncalibrated data set includes all data collected from the MIMI Data Processing Unit during the entire Cassini mission [MANWEILERETAL2005]. The original data has been decommutated and decoded by software at the Applied Physics Laboratory (APL) and has been then further ordered and filtered by software at Fundamental Technologies, LLC. The data is provided in an uncalibrated form in conjunction with a PDS MIMI calibration volume COMIMI_0000 which provides specific algorithms for the derivation of calibrated data. This data set includes uncalibrated values for each energy channel for the CHEMS sensor for all times during the mission including the Earth flyby, the Jupiter flyby, interplanetary cruise, and the entire Saturn tour. Data are presented in a set of tables which are of variable length and use a comma to separate various fields. This data set is intended to be the most comprehensive and complete data set included in the Cassini MIMI CHEMS archive. A browse data set is included with Key Parameter data that is calibrated using the algorithms provided in the Calibration volume. In addition, a series of images are provided with the KP browse data that displays the KP data which can lead the user to the particular times of interest. This data set should be among the first used by a user of any of the MIMI CHEMS archive as it will lead one to information required to search for more detailed or highly specialized features in the original data.

Parameters

This data set comprises count rates associated with mass, energy, and charge state spectrometer measurements for each telescope of the CHEMS detector in accumulation and science modes. In addition this data set includes CHEMS PULSE HEIGHT ANALYSIS measurement data for a statistically select sample of the particle measurements. The standard product ID's are: CHEMS Accumulation Rate Data - telescope count rate measurements CHEMS Science Rate Data - mass per charge, mass and charge count rate measurements. CHEMS Pulse Height Analysis Data - Statistically sampled set of discrete particle measurements. The data is organized in time by the spin of the spacecraft. When the spacecraft is in staring mode then the MIMI DPU automatically creates a virtual spin that divides the time collection periods into 16 sectors, 16 subsectors, and 16 microsectors and maintains a simple organizational structure for characterizing the collection of the time into time segments. When the spacecraft is spinning at a minimally defined spin rate (adopted by the MIMI DPU) then the MIMI data is automatically segregated into 16 sectors, 16 subsectors, and 16 microsectors. When the spacecraft is spinning and the LEMMS instrument is rotating the LEMMS rotation period is synchronized to the spacecraft spin period so that there are 16 sectors in a spin, 16 subsectors in a sector and 16 microsectors in a subsector. The CHEMS and INCA instrument collection times are then also keyed to these values.

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 MIMI flight software onboard and organize the channel data into appropriate time segments. Data ==== The MIMI CHEMS uncalibrated data set includes three ASCII CSV tables (each associated with a Standard Product ID of CHEMS Rate data as a function of time collected from the MIMI CHEMS Detectors and collated into data sets. Each table contains variable length records for which the fields are comma delimited. CHEMS Accumulation Rate Data ---------------------------Fields include: a purpose identifier where science data records are identified with purpose = sci starting and ending ephemeris times Spin, sector, subsector (and for CHEMS Fine Rate (FRT) data microsector) SCLOCK and spin period that are used to derive the starting ephemeris time Notes regarding the SCLOCK value: 1. Only the SCLOCK major segment value is provided - MIMI currently does not have access to the fine SCLOCK value hence SCLOCK resolution is limited to +- 1/2 SCLOCK count 2. The SCLOCK is only available from telemetry at the beginning of each spin. All other published SCLOCKS are derived from the spin starting SCLOCK, the spin numbers (for the current and next available spins), and the spin period. 3. SCLOCK values are assumed to drive the value of the ephemeris times and not vice-versa. All effort is made to validate the published ephemeris times but since updates to the Cassini SCLOCK kernel in SPICE can occur the values of ephemeris time are only as accurate as the currently published Cassini SCLOCK SPICE kernel. Spacecraft staring mode where staring = 0 when spinning and 1 otherwise CHEMS Accumulation rate data organized as: DPPS Step - the controlling parameter that identifies the current Spectrometer energy level Start, Stop, and Sum of the number of triggering events for each telescope Energy count of the number of triggering events for each telescope and a summation Double coincidence counts for each telescope and a summation triple coincidence counts for each telescope and a summation UFSR counts (Universal Front SEDA Rate - Secondary Electron Detector Assembly) URSR counts (Universal Rear SEDA Rates) CHEMS Science Rate Data ----------------------Fields include: a purpose identifier where science data records are identified with purpose = sci starting and ending ephemeris times Spin, sector, subsector SCLOCK and spin period that are used to derive the starting ephemeris time Notes regarding the SCLOCK value: 1. Only the SCLOCK major segment value is provided - MIMI currently does not have access to the fine SCLOCK value hence SCLOCK resolution is limited to +- 1/2 SCLOCK count 2. The SCLOCK is only available from telemetry at the beginning of each spin. All other published SCLOCKS are derived from the spin starting SCLOCK, the spin numbers (for the current and next available spins), and the spin period. 3. SCLOCK values are assumed to drive the value of the ephemeris times and not vice-versa. All effort is made to validate the published ephemeris times but since updates to the Cassini SCLOCK kernel in SPICE can occur the values of ephemeris time are only as accurate as the currently published Cassini SCLOCK SPICE kernel. Spacecraft staring mode where staring = 0 when spinning and 1 otherwise CHEMS Science rate data organized as: DPPS Step - the controlling parameter that identifies the current Spectrometer energy level Counts associated with Ranges 0-6 for each telescope plus the sum over telescopes He+, He++ doubles and triples count rates O+ doubles and triples count rate per telescope plus the sum over telescopes CNO (mass 4 and higher) triples count rate Counts of energy, tof, and mass (mass/q) under and overflow conditions CHEMS Pulse Height Analysis Data -------------------------------Fields include: a purpose identifier where science data records are identified with purpose = sci starting and ending ephemeris times Spin, sector, subsector SCLOCK and spin period that are used to derive the starting ephemeris time Notes regarding the SCLOCK value: 1. Only the SCLOCK major segment value is provided - MIMI currently does not have access to the fine SCLOCK value hence SCLOCK resolution is limited to +- 1/2 SCLOCK count 2. The SCLOCK is only available from telemetry at the beginning of each spin. All other published SCLOCKS are derived from the spin starting SCLOCK, the spin numbers (for the current and next available spins), and the spin period. 3. SCLOCK values are assumed to drive the value of the ephemeris times and not vice-versa. All effort is made to validate the published ephemeris times but since updates to the Cassini SCLOCK kernel in SPICE can occur the values of ephemeris time are only as accurate as the currently published Cassini SCLOCK SPICE kernel. Spacecraft staring mode where staring = 0 when spinning and 1 otherwise Index in sector number - auto generated number to guarantee uniqueness within a sector CHEMS Pulse Height Analysis data organized as: DPPS Step - the controlling parameter that identifies the current Spectrometer energy/charge level Energy - calibrated measure of the energy deposited into the SSD TOF - calibrated measure of the time of flight for the particle SSD - identifies which solid state detector was triggered Start microchannel plate - identifies which microchannel plate was used in particle identification Range - identifies which PHA range was identified by the CHEMS DPU for this particle.

Ancillary Data

Included with the CHEMS data set volumes are ancillary data files representing the MIMI Key Parameter (KP) data. The MIMI KP data is a calibrated subset of the important channels for each of the MIMI detectors. The subset of channels have been identified to most reasonably show characteristic energetic particle events during the mission. The KP data is calculated at an arbitrarily defined 60 second cadence which is different than the approximate collection times for the instruments as identified below for standard operations: (It must be realized that the collection times vary based upon the telemetry rate but nothing more than a factor of 2, 4, or 8.) Instrument Product Type Approx Collection Time (s) -----------------------------------------------------------LEMMS Accumulation 5 (each subsector) LEMMS Fine Rate 0.6 (each microsector) LEMMS PHA 5 (each subsector) CHEMS Accumulation 4 CHEMS Science 5 (each subsector) CHEMS PHA 80 (each sector) INCA Accumulation 7.5 INCA IMAGES 180 (2 sectors) INCA PHA 22 Data points for each record of the KP data are first Median Quartile Filtered then averaged (except in the case where the median is zero) for each sector. The sectored data is then interpolated into the 60 second data cadence of the KP data file. The KP data is then converted into a flux in units of 1/(cm^2*sr*sec*KeV) or for the case of CHEMS 1/(cm^2*sr*sec*keV/e) Browse plots for each of the KP data files are produced. There are 7 different browse plots available. Inst Wild Card File Name Plotted KP data --------------------------------------------------------------------LEMMS LEMMS_KP_ELEC_(yyyydoy)_(ver#).JPG KP LEMMS Electron flux LEMMS LEMMS_KP_ION_(yyyydoy)_(ver#).JPG KP LEMMS Ion flux CHEMS CHEMS_KP_HEP_(yyyydoy)_(ver#).JPG KP CHEMS Helium Plus flux per charge CHEMS CHEMS_KP_HEPP_(yyyydoy)_(ver#).JPG KP CHEMS Helium Plus Plus flux per charge CHEMS CHEMS_KP_HP_(yyyydoy)_(ver#).JPG KP CHEMS Hydrogen Plus flux per charge CHEMS CHEMS_KP_OP_(yyyydoy)_(ver#).JPG KP CHEMS Oxygen Plus per charge INCA INCA_KP_(yyyydoy)_(ver#).JPG Hydrogen TOF flux Usage Note ---------The KP browse data and associated browse plots are to be used as an initial characterization of the particle environment and are NOT to be used for publications. The data is not at publication quality and is provided as is.

Coordinate System

The data in this data set are measurements of count rates based upon the orientation of the CHEMS instrument (CHEMS Center look direction). Particle flux effects are then determined by transforming from a spacecraft centered coordinate system, properly rotated to account for the appropriate CHEMS telescope direction, into whatever external coordinate (reference system) is most appropriate.

Software

There is no sample software provided as of the writing of this catalog file although the calibration volume does provide algorithms for conversion of count rates into flux. In general the CHEMS Science data can be converted into a measurement of flux per species with these algorithms and the CHEMS PHA and Accumulation Rates data are used for determining the health and wellness of the CHEMS detectors.

Media/Format

These data are supplied to the Planetary Data System via electronic means and are then broken into segments based upon the media currently prescribed by PDS.

These data are available on-line from the Planetary Data System (PDS) at:

https://pds-ppi.igpp.ucla.edu/data/CO-E_J_S_SW-MIMI-2-CHEMS-UNCALIB-V1.1/

Alternate Names

  • CO-E/J/S/SW-MIMI-2-CHEMS-UNCALIB-V1.1

Discipline

  • Planetary Science: Fields and Particles

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Stamatios M. KrimigisData ProviderApplied Physics Laboratorytom.krimigis@jhuapl.edu
Dr. Jerry W. ManweilerGeneral ContactFundamental Technologies, LLCmanweiler@ftecs.com
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