| Data Set Abstract |
THIS BROWSE DATA CONSISTS OF RESAMPLED DATA FROM THE LOW ENERGY
CHARGED PARTICLE (LECP) EXPERIMENT ON VOYAGER 2 WHILE THE
SPACECRAFT WAS IN THE VICINITY OF SATURN. THIS INSTRUMENT
MEASURES THE INTENSITIES OF IN-SITU CHARGED PARTICLES (>26 KEV
ELECTRONS AND >30 KEV IONS) WITH VARIOUS LEVELS OF
DISCRIMINATION BASED ON ENERGY, MASS SPECIES, AND ANGULAR ARRIVAL
DIRECTION. A SUBSET OF ALMOST 100 LECP CHANNELS ARE INCLUDED WITH
THIS DATA SET. THE LECP DATA ARE GLOBALLY CALIBRATED TO THE
EXTENT POSSIBLE (SEE BELOW) AND THEY ARE TIME AVERAGED TO ABOUT
15 MINUTE TIME INTERVALS WITH THE EXACT BEGINNING AND ENDING
TIMES FOR THOSE INTERVALS MATCHING THE LECP INSTRUMENTAL CYCLE
PERIODS (THE ANGULAR SCANNING PERIODS). THE LECP INSTUMENT HAS A
ROTATING HEAD FOR OBTAINING ANGULAR ANISOTROPY MEASUREMENTS OF
THE MEDIUM ENERGY CHARGED PARTICLES THAT IT MEASURES. THE CYCLE
TIME FOR THE ROTATION IF VARIABLE, BUT DURING ENCOUNTERS IT IS
ALWAYS FASTER THAN 15 MINUTES. FOR THIS BROWSE DATA SET ONLY SCAN
AVERAGE DATA IS GIVEN (NO ANGULAR INFORMATION). THE DATA IS IN
THE FORM OF 'RATE' DATA WHICH HAS NOT BEEN CONVERTED TO
THE USUAL PHYSICAL UNITS. THE REASON IS THAT SUCH A CONVERSION
WOULD DEPEND ON UNCERTAIN DETERMINATIONS SUCH AS THE MASS SPECIES
OF THE PARTICLES AND THE LEVEL OF BACKGROUND. BOTH MASS SPECIES
AND BACKGROUND ARE GENERALLY DETERMINED FROM CONTEXT DURING THE
STUDY OF PARTICULAR REGIONS. TO CONVERT 'RATE' TO
'INTENSITY' FOR A PARTICULAR CHANNEL ONE PERFORMS THE
FOLLOWING TASKS: 1) DECIDE ON THE LEVEL OF BACKGROUND
CONTAMINATION AND SUBTRACT THAT OFF THE GIVEN RATE LEVEL.
BACKGROUND IS TO BE DETERMINED FROM CONTEXT AND FROM MAKING USE
OF SECTOR 8 RATES (SECTOR 8 HAS A 2 mm AL SHIELD COVERING IT). 2)
DIVIDE THE BACKGROUND CORRECTED RATE BY THE CHANNEL GEOMETRIC
FACTOR AND BY THE ENERGY BANDPASS OF THE CHANNEL. THE GEOMETRIC
FACTOR IS FOUND IN ENTRY 'channel_geometric_ factor' AS
ASSOCIATED WITH EACH CHANNEL 'channel_id'. TO DETERMINE
THE ENERGY BANDPASS, ONE MUST JUDGE THE MASS SPECIES OF THE OF
THE DETECTED PARTICLES (FOR IONS BUT NOT FOR ELECTRONS). THE
ENERGY BAND PASSES ARE GIVEN IN ENTRIES
'minimum_instrument_parameter' and
'maximum_instrument_ parameter' IN TABLE
'FPLECPENERGY', AND ARE GIVEN IN THE FORM
'ENERGY/NUCLEON'. FOR CHANNELS THAT BEGIN THEIR NAMES
WITH THE DESIGNATIONS 'CH' THESE BANDPASSES CAN BE USED
ON MASS SPECIES THAT ARE ACCEPTED INTO THAT CHANNEL (SEE ENTRIES
'minimum_instrument_parameter' and
'maximum_instrument_ parameter' IN TABLE
'FPLECPCHANZ', WHICH GIVE THE MINIMUM AND MAXIMUM
'Z' VALUE ACCEPTED -- THESE ENTRIES ARE BLANK FOR
ELECTRON CHANNELS). FOR OTHER CHANNELS THE GIVEN BANDPASS REFERS
ONLY TO THE LOWEST 'Z' VALUE ACCEPTED. THE BANDPASSES
FOR OTHER 'Z' VALUES ARE NOT ALL KNOWN, BUT SOME ARE
GIVEN IN THE LITERATURE (E.G. KRIMIGIS ET AL., 1979). THE FINAL
PRODUCT OF THESE INSTRUCTIONS WILL BE THE PARTICLE INTENSITY WITH
THE UNITS: COUNTS/(CM**2.STR.SEC.KEV). SOME CHANNELS ARE SUBJECT
TO SERIOUS CONTAMINATIONS, AND MANY OF THESE CONTAMINATIONS
CANNOT BE REMOVED EXCEPT WITH A REGION-BY-REGION ANALYSIS, WHICH
HAS NOT BEEN DONE FOR THIS DATA. THUS, TO USE THIS DATA IT IS
ABSOLUTELY VITAL THAT THE CONTAMINATION TYPES
('contamination_id' , 'contamination_desc')
AND THE LEVELS OF CONTAMINATION ('data_quality_id'
CORRESPONDING TO THE DEFINITIONS 'data_quality_desc')
BE CAREFULLY EXAMINED FOR ALL REGIONS OF STUDY. A DEAD TIME
CORRECTION PROCEDURE HAS BEEN APPLIED IN AN ATTEMPT TO CORRECT
THE LINEAR EFFECTS OF DETECTOR OVERDRIVE (PULSE-PILEUP). THIS
PROCEDURE DOES NOT FIX SEVERELY OVERDRIVEN DETECTORS. A PROCEDURE
IS AVAILABLE FOR CORRECTING VOYAGER 2 LECP ELECTRON CONTAMINATION
OF LOW ENERGY ION CHANNELS, BUT ITS EFFECTIVENESS HAS BEEN
EVALUATED ONLY FOR THE URANUS DATA SET. THUS, CORRECTIONS HAVE
BEEN APPLIED ONLY TO THE URANUS DATA SET. |
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