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CASSINI S MIMI CHEMS SENSOR CALIBRATED DATA V1.0 (PDS)

NSSDCA ID: PSFP-00678

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) contains a deflection system and an overall field of view of 159 x 4 deg. that is comprised of three distinct energetic particle telescopes each having a field of view of 53 deg. x 4 deg. All telescopes share the same deflection mechanism, but each has its own start and stop microchannel plate (MCP) and its own solid-state detector (SSD). Much of the data returned by CHEMS is separated by telescope. The deflection plate power supply (DPPS) has 32 different voltages that can be applied across the deflection plates. For any single DPPS step, the electrostatic analyzer only transmits incoming ions within a narrow range of energy per charge (a 3% pass band). The CHEMS calibrated data set includes the Pulse Height Analysis (PHA) data collected during the Saturn tour. CHEMS PHA provides a list of individually detected particles, with specific detection parameters for each event, including TOF, energy deposited in the SSD, and telescope number. Telemetry data volume constraints do not allow all particle events detected by CHEMS to be sent in the MIMI data stream, so the PHA data need to be carefully normalized, and the procedures for doing this are described in the section on CHEMS in the MIMI User Guide [VANDEGRIFFETAL2012]. The energy per charge data for six ion species (H+, He+, H2+, He++, O++, W+) are presented in two forms. One form is a set of tables which are of variable length and use a comma to separate various fields, and the other is a PDF file containing the energy per charge spectrograms and are based on CHEMS PHA data. (The W+ water ion group includes O+, OH+, H20+ and H30+) The original data has been decommutated and decoded by software at the Applied Physics Laboratory (APL) and further processed by software at the University of Maryland. The data is provided in an calibrated form in conjunction with a PDS MIMI calibration volume COMIMI_0000 which provides specific algorithms for the derivation of calibrated data. 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 energy per charge intensities for six ion species (H+, He+, H2+, He++, O++, W+) for each telescope and the sum of all the telescopes of the CHEMS detector. (The W+ water ion group includes O+, OH+, H20+ and H30+). The data consists of 60 minute averages and cover 20 days per file. Each file includes the intensities for each of the 32 energy per charge steps. The product ID's consist of a prefix followed by a date range. The prfixes are: CPHAFLX0_T1_HP The energy per charge data for H+ for telescope 1 CPHAFLX0_T2_HP The energy per charge data for H+ for telescope 2 CPHAFLX0_T3_HP The energy per charge data for H+ for telescope 3 CPHAFLX0_TA_HP The energy per charge data for H+ for all telescopes CPHAFLX0_T1_H2P The energy per charge data for H2+ for telescope 1 CPHAFLX0_T2_H2P The energy per charge data for H2+ for telescope 2 CPHAFLX0_T3_H2P The energy per charge data for H2+ for telescope 3 CPHAFLX0_TA_H2P The energy per charge data for H2+ for all telescopes CPHAFLX0_T1_HEPP The energy per charge data for He++ for telescope 1 CPHAFLX0_T2_HEPP The energy per charge data for He++ for telescope 2 CPHAFLX0_T3_HEPP The energy per charge data for He++ for telescope 3 CPHAFLX0_TA_HEPP The energy per charge data for He++ for all telescopes CPHAFLX0_T1_HEP The energy per charge data for He+ for telescope 1 CPHAFLX0_T2_HEP The energy per charge data for He+ for telescope 2 CPHAFLX0_T3_HEP The energy per charge data for He+ for telescope 3 CPHAFLX0_TA_HEP The energy per charge data for He+ for all telescopes CPHAFLX0_T1_OPP The energy per charge data for O++ for telescope 1 CPHAFLX0_T2_OPP The energy per charge data for O++ for telescope 2 CPHAFLX0_T3_OPP The energy per charge data for O++ for telescope 3 CPHAFLX0_TA_OPP The energy per charge data for O++ for all telescopes CPHAFLX0_T1_WP The energy per charge data for W+ for telescope 1 CPHAFLX0_T2_WP The energy per charge data for W+ for telescope 2 CPHAFLX0_T3_WP The energy per charge data for W+ for telescope 3 CPHAFLX0_TA_WP The energy per charge data for W+ for all telescopes The standard data product ID's are gropuped by species and are: CHEMS_PHAFLUXAV_HP CHEMS_PHAFLUXAV_H2P CHEMS_PHAFLUXAV_HEPP CHEMS_PHAFLUXAV_HEP CHEMS_PHAFLUXAV_OPP CHEMS_PHAFLUXAV_WP Each of these logically incorporates four types of products -- one for each of the three telescopes and one for all telescopes. In addition, this data set includes energy per charge spectrograms for the same six species. Each PDF includes the spectrograms for each of the three telescopes and their sum. The standard data product ID's are: MIMI_CHEMS_SPGM_HP The energy per charge spectrograms for H+ MIMI_CHEMS_SPGM_H2P The energy per charge spectrograms for H2+ MIMI_CHEMS_SPGM_HEPP The energy per charge spectrograms for He++ MIMI_CHEMS_SPGM_HEP The energy per charge spectrograms for He+ MIMI_CHEMS_SPGM_OPP The energy per charge spectrograms for O++ MIMI_CHEMS_SPGM_WP The energy per charge spectrograms for W+. Processing ========== Data in this data set were processed by the use of a number of software programs which calibrate, perform the 1 hour averages on the data, and create the spectrograms. In the original CHEMS data, accumulation interval for basic and species rate counters is one DPPS step, which lasts for one subsector, where 16 subsectors make a sector, and 16 sectors make one spin. 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. Note that for CHEMS, there is a 150 millisecond dead time per DPPS step, and this must be subtracted from the subsector duration. Converting a species count rate in units of counts/sec into a differential intensity in units of counts/(sec*ster*cm2*keV) requires knowledge of the geometry factor of the instrument, the energy width of the channel, the detection efficiency for ions of that species, and the energy width of the channel expressed as an energy per charge. The procedures for calibrating CHEMS data are described in the section on CHEMS in the MIMI User Guide [VANDEGRIFFETAL2012]. Data ==== The MIMI CHEMS calibrated data set includes the 24 ASCII CSV tables (each associated with a Standard Product ID of CHEMS energy per charge 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 Energy Per Charge ASCII data ---------------------------------Fields include: Start and Stop minutes of hour long average Year, and midpoint of the hour-long average interval expressed as a fractional day of year. Radial_distance which is the position of Cassini at midpoint of the interval in Saturn radii Latitude of Cassini at midpoint of measurement in Saturn equatorial frame Local_time of Cassini at the midpoint of the measurement given in hours and in the Saturn equitorial frame. Particle intensity and the uncertainty in particle intensity for each of the 32 energy bands. Units are counts/sec/ster/cm^2/keV. This data set comprises energy per charge intensities in separate files for six ion species (H+, He+, H2+, He++, O++, W+) and for each telescope and the sum of all the telescopes of the CHEMS detector. The data consists of 60 minute averages and cover 20 days per file. Each file includes the intensities for each of the 32 energy per charge steps. CHEMS Energy Per Charge Spectrograms -----------------------------------This data set comprises six ion species plots in PDF files. There are 4 horizontal panels in the plot. The top panel contains the average intensity from all three CHEMS telescopes combined (full 4 degrees x 159 degrees FOV). Each panel below is for an individual telescope (4 degrees x 53 degrees FOV) (1, 2, and 3 respectively). Pixels are 15 percent in energy per charge by 60 minutes and are based on CHEMS PHA data. The bottom axis is time covering a 20 day interval. The y-axis is energy per charge (keV/e). The color represents the differential intensity for this species, and the units are particles per (cm^2 sec sr keV/e). No background has been subtracted. Ancillary Data ============== Coordinate System ================= The data in this data set are measurements of counts/sec/ster/cm^2/keV 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 access on the MIMI web site, to an analysis package currently being used by the MIMI team to browse, plot and analyze MIMI data that reads data directly from the PDS and makes available to anyone the same analysis and visualization capabilities currently used by the MIMI team. The main benifit of the tools is that they provide an intuitive way to browse and analyze the data without having to worry about calibration details or file access and file reading details. 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-S-MIMI-4-CHEMS-CALIB-V1.0/

Alternate Names

  • CO-S-MIMI-4-CHEMS-CALIB-V1.0

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. Jon VandegriffGeneral ContactApplied Physics Laboratoryjon.vandegriff@jhuapl.edu
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