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 = "INCA IMAGE ALGORITHM DESCRIPTION"
DESCRIPTION = "(Title page information follows.)
----------------------------------------------------------------------
Cassini Mission
Magnetospheric Imaging Instrument
INCA Image 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/INCA Images
AUTHOR: Jerry W. Manweiler, Ph.D., Fundamental Technologies, LLC
DATE: 03/01/2005
INTRODUCTION:
Unlike the calibration algorithms for other Cassini/MIMI PDS data products,
this calibration algorithm does not convert the measured counts to fluxes.
Instead this calibration algorithm produces rates that represent the actual
number of counts divided by the pixels exposure time and adjusted for
sensitivity variations between pixels.
The maximum resolution of INCA images is 64X64 pixels, however the sensor also
produces images in other, smaller sizes. When this is the case multiple actual
pixels must be combined to form a virtual pixel. For example, one virtual
pixel of a 32X32 image would be made of four actual subpixels, one virtual
pixel of a 16X16 image would be made of 16 actual subpixels and so on.
ALGORITHM:
exposure_sensitivity_adjusted_rate[ row ][ column ]
= actual_count[ row ][ column ] /( Duration * flux_factor[ row ][ column ])
RESULT VARIABLES:
exposure_sensitivity_adjust_rate: the count rate in the "pixel" adjusted for
efficiencies, exposure, etc.
INPUT VARIABLES FROM A DATA PRODUCT:
actual_count: dp:IIMG:"sci":[column]: actual_count is the measured count rate
by the "pixel"
Duration: Endtime - Starttime, Duration is a calculated value from two data
product columns
Endtime: dp:IIMG:"sci":["End_Ephemeris_s"], the ending time of the measurement
in seconds
Starttime: dp:IIMG:"sci":["Start_Ephemeris_s"], the starting time of the
measurement in seconds
INPUT VARIABLES FROM A CALIBRATION FILE:
INCA Images calibration files are stored within the INCA_IMAGES subdirectory
The subdirectory contains additional subdirectories that are based upon
specific segments of the mission Each mission segment subdirectory then
contains two subdirectories based upon whether the spacecraft is in spin mode
or staring mode. these subdirectories contain the set of exposure factor
matrices organized by size of the image and time of flight the exposure_factor
matrix is then multiplied by the count matrix for the entire image (including
all pixels)
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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