PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
INTERCHANGE_FORMAT = ASCII
INSTRUMENT_HOST_NAME = "CASSINI ORBITER"
INSTRUMENT_HOST_ID = "CO"
INSTRUMENT_NAME = "MAGNETOSPHERIC IMAGING INSTRUMENT"
INSTRUMENT_ID = "MIMI"
OBJECT = ASCII_DOCUMENT
DOCUMENT_NAME = "
CHEMS SCIENCE ACCUMULATION ALGORITHM DESCRIPTION"
DESCRIPTION = "(Title page information follows.)
----------------------------------------------------------------------
Cassini Mission
Magnetospheric Imaging Instrument
CHEMS Science Accumulation Algorithm Description
Version 2.1
rev. April 27, 2005
J. W. Manweiler
Fundamental Technologies, LLC
Lawrence, KS 66046
---------------------------------------------------------------------- "
PUBLICATION_DATE = 2005-04-27
DOCUMENT_TOPIC_TYPE = "ALGORITHM SPECIFICATION"
INTERCHANGE_FORMAT = ASCII
DOCUMENT_FORMAT = TEXT
END_OBJECT = ASCII_DOCUMENT
END
FILE CONTENTS: Calibration algorithm for PDS data products containing
Cassini/MIMI/CHEMS Science rates
AUTHOR: Jerry W. Manweiler, Ph.D., Fundamental Technologies, LLC
DATE: 04/27/2005
INTRODUCTION:
This file contains a text and pseudo code algorithm to covert the counts
contained in the Cassini/MIMI/CHEMS Level 1A science rates PDS data products
into differential particle fluxes. The calculation of flux from this data
product is done only as a validation step for the mass and mass per charge
calculations that are already completed by the CHEMS DPU and included as the
main data product for the CHEMS Science rates data.
ALGORITHM:
DIFFERENTIAL FLUX EQUATION:
flux = (count-background)/(duration*efficiency*geom_fact*EPQ)
RESULT VARIABLES:
flux: the mass per charge specific result of the calibration in
particle/(cm^2*sec*sr*keV/e)
INPUT VARIABLES FROM A DATA PRODUCT:
count: dp:CSCI:"sci":[(basic/species rate)], a count from a CSCI data product
or combination thereof
The counts for each species are determined from the following channel
relationships:
H+ : BR0+BR3
He+ : He+_D + He+_T
He++ : He++_D + He++_T
O+ : O+_D + O+_T
duration: Endtime - Starttime, Duration is a calculated value from two data
product columns
Endtime: dp:CSCI:"sci":[End_Ephemeris_s], the ending time of the measurement
in seconds
Starttime: dp:CSCI:"sci":[Start_Ephemeris_s], the starting time of the
measurement in seconds
INPUT VARIABLES FROM A CALIBRATION FILE:
geom_fact: cdf:"GEOM_FACTOR":"SCI":"CHEMS":(telescope_id):"Midpoint_Value",
the geometrical factor in cm^2*sr
EPQ: cdf:"ENERGY/CHARGE":"SCI":"CHEMS":"DPPS":(dpps_step):"Midpoint_Value",
MidPoint is the midpoint energy per charge for the Data processing
step of the CHEMS sensor in KeV/e
efficiency: "EFFICIENCY:"SCI":"CHEMS":"DPPS":(dpps_step):(species):
"Midpoint_value"
The capacity of the instrument to respond to incident particles.
This includes a measurement of the losses due to nuclear effects,
solid state efficiencies, and/or other factors. In general, the
efficiency of the instrument is measured as a function of the
physical characteristics of the instrument as well as other
limiting factors. Efficiencies are evaluated as the instrument
performance is measured over the life of the mission.
VARIABLES TO BE PROVIDED BY DATA USERS:
background: A representation of the expected background radiation counts due
to other sources including but no limited to cosmic rays, gamma
radiation, etc. In general a significant amount of effort is
required to develop an understanding of the background count rates
observed during any particular phase of the mission. There is no
one set of "cookie cutter" algorithms that can be used to derive
the background rates for any particular instrument.
GENERAL Cassini/MIMI CALIBRATION:
Each data product type in the PDS Cassini/MIMI Level 1A data set has two
associated calibration files: a calibration algorithm file that is specific to
each sensor and a calibration data file that is specific to the instrument.
Each calibration algorithm file (this file) contains a text and pseudo code
algorithm that describes how to calibrate the Level 1A data. The calibration
data file is a CSV file that contains data values used in the algorithm
described in the calibration algorithm file.
All records for a data product type in the PDS level 1A files and the
calibration data files have the same format. The first field in each record is
the purpose field. The purpose field indicates the intended use of the record.
For example records containing science data have a purpose field with the
value "sci" and a record containing the geometrical factors of the detectors
in a sensor would have "geom" in the purpose field.
All MIMI calibration algorithm files use a short hand notation to refer to
fields in the data products and calibration data files. This shorthand
notation consists of an instrument/data type, a file type, a purpose field
value, and a column description. This notation is used to specify types of
fields, in types of records, in types of files. This notation allows the
algorithm file to specify the relationship between types of fields in various
files. The syntax and examples of this notation are given below.
SHORTHAND NOTATION:
❮file type❯:❮sensor data type❯:❮row field value 1❯:❮row field value 2❯:...:
❮row field value n❯:[❮column id❯]
where:
❮file type❯ = dp or cdp where dp = data product and cdp = calibration data
product
❮sensor data type❯ = CACC, CPHA, CSCI, IACC, IIMG, IPHA, IACC, LFRT. The cdp
does not include a ❮sensor data type❯ identifier.
❮row field value x❯ = a specification of a particular value of a row in order
of left to right for those rows that apply. It is notec that not all rows
apply for each value. Literal values of identifiers are placed in double
quotation marks. Variable values are in parenthesis "( )".
❮column id❯ = a column identifier (label) to be used to select the final
unique value based upon the combination of row identifiers and the specific
column that has the data value. Literal values are placed in double quotation
marks. Variable values are in parenthesis "( )".
examples:
dp:IACC:"sci":["Start_Ephemeris_s"] =
The starting time of the record with a single row identifier of "sci"
dp:IACC:"sci":("Start_Ephemeris_s"):[(datacolumntype)] =
A field representing a specific column of counts for a record that
includes "sci" and a starting time in the column that uses the literal
for the start time in a column that identifies the source of the
counts.
geom_factor = cdf:"GEOM_FACTOR"":"ACC":"INCA":"DETECTOR":("Particle"):
("Start_Year"):("Start_DDOY"):["midpoint_value"] =
Select the value of the geometrical factor using the literal
"GEOM_FACTOR", "ACC", "INCA", "DETECTOR"
rows and the variable rows for start year and DDOY (decimal day of
year) in the column of "midpoint_value".
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