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 = "
LEMMS ACCUMULATION RATES ALGORITHM DESCRIPTION"
DESCRIPTION = "(Title page information follows.)
----------------------------------------------------------------------
Cassini Mission
Magnetospheric Imaging Instrument
LEMMS Accumulation Rates Algorithm Description
Version 2.0
rev. February 28, 2005
J. W. Manweiler
Fundamental Technologies, LLC
Lawrence, KS 66046
---------------------------------------------------------------------- "
PUBLICATION_DATE = 2005-03-01
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/LEMMS Accumulation rates
AUTHOR: Jerry W. Manweiler, Ph.D., Fundamental Technologies, LLC
DATE: 03/01/2005
INTRODUCTION:
This file contains a text and pseudo code algorithm to covert the counts
contained in the Cassini/MIMI/LEMMS Level 1A accumulator rates PDS data
products into particle fluxes.
FLUX EQUATION:
See below for general information on Cassini/MIMI Level 1A calibration. If you
have not read this information, it is highly recommended that you do do now.
flux = (count-background)/(duration*factor*geom_fact*(ehi-elo))
RESULT VARIABLES:
flux: the result of the calibration in nucleon/(mm^2*sec*sr*MeV)
INPUT VARIABLES FROM A DATA PRODUCT:
count: dp:LACC:"sci":[detector_channel], a count from a LACC data product
duration = dp:LACC:"sci":["End_Ephemeris_s"]-["Start_Ephemeris_s"],
the calculation of the Duration from a LACC data product in seconds
INPUT VARIABLES FROM A CALIBRATION FILE:
ehi: cdf:"ENERGY":"ACC":"LEMMS":(detector_channel):(detector_channel_no):
["Hi"], the pass band high energy in KeV/nucleon
ehi: cdf:"ENERGY":"ACC":"LEMMS":(detector_channel):(detector_channel_no):
["Low"], the pass band low energy in KeV/nucleon
geom_fact: cdf:"GEOM_FACTOR":"ACC":"LEMMS":(detector_channel):
(detector_channel_no):["Midpoint_Value"] the geometrical factor in cm^2*sr
VARIABLES TO BE PROVIDED BY DATA USERS:
factor: a catch all scaling factor used to account for detector efficiencies
and other phenomenon that cause count rates to be lower than they
should be based on geometrical factors and pass bands. A generalized
formula cannot be easily described to allow for the specification of a
"cookie cutter" algorithm due to the complexity of evaluation of all
factors that might exist to reduce the effectiveness of the sensor. In
general, Using a factor of 1.0 will produces fluxes not corrected for
the phenomena expected to reduce the overall ability to count
particles.
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".
|