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: ::::...: :[] 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".