| DATA_SET_DESCRIPTION |
Data Set Overview
=================
The Cassini Magnetospheric Imaging Instrument(MIMI) Imaging Neutral
Camera (INCA) 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 of counts in the form of
rates and of rate images for the INCA 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 INCA 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 INCA 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 counts per readout of charged and neutral
particle imaging measurements for the single telescope of the INCA
sensor accumulators and images. In addition this data set includes
INCA PULSE HEIGHT ANALYSIS measurement data for a statistically select
sample of the particle measurements. The standard product ID's are:
INCA Accumulation Rate Data - individual microchannel plate detector
count rate measurements
INCA Image Data - count rates binned into a maximum of a 64x64
geometrical grid as an image, for various particle
velocities.
INCA 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. Images are preprocessing into appropriate
arrays on board the spacecraft. This preprocessing software
also includes algorithms to handle the various spacecraft rotation
modes.
Data
====
The MIMI INCA uncalibrated data set includes three ASCII CSV tables
(each associated with a Standard Product ID) of INCA Rate data as a
function of time collected from the MIMI INCA sensor and collated
into data sets. Each table contains variable length records for which
the fields are comma delimited.
INCA 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 INCA 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
INCA Accumulation rate data organized as:
Start fast, pulse, and Start-coincidence counts
Stop fast, pulse, and Stop-coincidence counts
Full, Coincidence, and time counts
Events received and processed counts
(MIMI INCA has 3 microchannel plates, the Start, the Stop, and the
Coincidence plates. Start fast is the Start timing signal count;
Start pulse is the Start pulse-height count; Start-coincidence is the
count of the coincidences within the alotted time window of signals
from the Start fast and the Coincidence microchannel plates; Full is
the count of events with a Start fast, Stop fast, and Coincidence
signal; time is the count of events with both a Start fast and a Stop
fast; Events received is the number of valid events sent to the DPU,
and processed counts are the number the DPU sends inot image bins.
These latter two may be different because of additional valid event
criteria imposed by the DPU, and/or inability of the DPU to process
all of the events it receives.)
INCA Images
-----------
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
INCA Images are organized as:
Type ID: a 4 byte word characterized as:
Byte 0 - Type: 0 = High Spatial, 1 = High Time,
2 = High m-TOF
Byte 1 - Charge: 0 = Neutral, 1 = Ion
Byte 2 - Species: 0 = H, 1 = He, 2 = CNO, 3 = Heavy,
4 = Other, 5 = All
Byte 3 - TOF: 0 = Low, 1-6 = Medium, 7 = High
Row ID: the row of the image which can vary from 8 to 64 based
upon the image type
Num Rows: the number of rows for this image
Num Cols: the number of columns for this image which can vary
from 8 to 64 based upon the image type
Compression bits, Compression method, log compressed identifier
Theta and Phi offsets from spacecraft coordinates
Breakout of the type id into Type, Charge, Species, and TOF
Column (0-63) counts representing the number of counts each
pixel of this row x column received
INCA 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
INCA Pulse Height Analysis data organized as:
Coincidence indicator, start and stop indicator
Pulse height data from the front and rear plates
Time of flight of this particle and the azimuth and elevation
for this event
mass range of this particle
Ancillary Data
==============
Included with the INCA 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)
------------------------------------------------------------
INCA Accumulation 7.5
INCA IMAGES 180 (2 sectors)
INCA PHA 22
CHEMS Accumulation 4
CHEMS Science 5 (each subsector)
CHEMS PHA 80 (each sector)
LEMMS Accumulation 5 (each subsector)
LEMMS Fine Rate 0.6 (each microsector)
LEMMS PHA 5 (each subsector)
Data points for each record of the KP data are first 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 INCA instrument (INCA Center look direction).
Particle flux effects are then determined by transforming from a
spacecraft centered coordinate system, properly rotated to account for
the appropriate INCA 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 INCA Images are
the main product and can be converted into a measurement of flux per
species with these algorithms and the INCA PHA and Accumulation Rates
data are used for determining the health and wellness of the INCA
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.
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