---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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: ::::...: :[] where: = dp or cdp where dp = data product and cdp = calibration data product = CACC, CPHA, CSCI, IACC, IIMG, IPHA, IACC, LFRT. The cdp does not include a identifier. = 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 "( )". = 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".