DATA SET OVERVIEW : Version 1.1 ----------- This version 1.1 data set replaces the version 1.0 data set (DATA_SET_ID : VG1-J-LECP-4-15MIN) previously archived with the PDS. Data records from the version 1.0 data set provided data for each of 8 sectors, plus the average for all sectors in a separate record for each channel. This resulted in 9 repeated times per channel. Data records for the version 1.1 data set provide all data for a given channel and time period (8 sectors, plus the average for all sectors) in a single record. Other changes to this version include upgrading of the associated labels and templates to PDS version 3.2 compliance, modification of the time formats and flag values. Data Set Description -------------------- This data set consists of resampled data from the Low Energy Charged Particle (LECP) experiment on Voyager 1 while the spacecraft was in the vicinity of Jupiter. 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 instrument has a rotating head for obtaining angular anisotropy measurements of the medium energy charged particles that it measures. The cycle time for the rotation is variable, but during encounters it is always faster than 15 minutes. Thus, the full angular anisotropy information is preserved with this data. 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 and passes for other 'Z' values are not all known, but some are given in the literature (e.g. [KRIMIGISETAL1979A]). The final product of these instructions will be the particle intensity with the units: counts/(cm^2 str sec keV).This figure represents the structure of a single data record. Note that the'SECTOR_STRUCTURE' (SECTOR1, SECTOR2, etc.) are not columns, but rather agrouping of the DATA_VALUE and STANDARD_DEVIATION columns. SECTOR1 SECTOR2 AVERAGE __________________ __________________ __________________ ____ | _____ _________ || _____ _________ | | _____ _________ || |||DATA ||STANDARD ||||DATA ||STANDARD || ||DATA ||STANDARD |||TIME|||VALUE||DEVIATION||||VALUE||DEVIATION|| ... ||VALUE||DEVIATION|||____|||_____||_________||||_____||_________|| ||_____||_________|| |__________________||__________________| |__________________| Parameters : Electron Rate ------------- Sampling Parameter Name : TIME Data Set Parameter Name : ELECTRON RATE Sampling Parameter Resolution : 15.000000 Sampling Parameter Interval : 15.000000 Data Set Parameter Unit : COUNTS/SECOND Noise Level : 0.000000 Sampling Parameter Unit : MINUTE A measured parameter equaling the number of electrons hitting a particle detector per specified accumulation interval. The counted electrons may or may not be discriminated as to their energies (e.g. greater than E1, or between E1 and E2). Ion Rate -------- Sampling Parameter Name : TIME Data Set Parameter Name : ION RATE Sampling Parameter Resolution : 15.000000 Sampling Parameter Interval : 15.000000 Data Set Parameter Unit : COUNTS/SECOND Noise Level : 0.000000 Sampling Parameter Unit : MINUTE A measured parameter equaling the number of ions striking a particle detector per specified accumulation interval. The counted ions may or may not be discriminated as to their energies (e.g. energy/nucleon or energy/charge between E1 and E2 or greater than E1) and/or as to their ion composition (atomic number Z or mass number greater than Z1 or M1, or between Z1 and z2 or M1 and M2). Source Instrument Parameters : Instrument Host ID : VG1 Data Set Parameter Name : ION RATE Instrument Parameter Name : ION RATE Important Instrument Parameters : 1 Instrument Host ID : VG1 Data Set Parameter Name : ELECTRON RATE Instrument Parameter Name : ELECTRON RATE Important Instrument Parameters : 1 Processing : Processing Level Id : 4 Software Flag : Y Processing Start Time : 1988-08-01 Processing History ------------------ Source Data Set ID : VG1-J-LECP-2- Software : PFAT:VGER Product Data Set ID : VG1-J-LECP-4-15MIN Software 'PFAT:VGER' -------------------- Software Name : PFAT:VGER Software Type : PIN Software Release Date : N/A Node ID : N/A Cognizant Engineer : N/A Software Access Description : N/A Data Coverage : Filename Records Start Stop ------------------------------------------------------------------- T790228 2112 1979-02-28T00:00:11.000Z 1979-02-28T23:44:35.000Z T790301 2112 1979-03-01T00:00:11.000Z 1979-03-01T23:59:47.000Z T790302 1936 1979-03-02T00:15:47.000Z 1979-03-02T23:59:47.000Z T790303 1760 1979-03-03T00:15:23.000Z 1979-03-03T23:59:47.000Z T790304 1892 1979-03-04T00:19:23.000Z 1979-03-04T22:59:48.000Z T790305 2112 1979-03-05T00:01:00.000Z 1979-03-05T23:59:47.000Z T790306 2068 1979-03-06T00:14:59.000Z 1979-03-07T00:14:44.000Z T790307 2068 1979-03-07T00:29:56.000Z 1979-03-07T23:59:56.000Z T790308 1848 1979-03-08T00:14:44.000Z 1979-03-08T23:59:08.000Z T790309 2112 1979-03-09T00:15:08.000Z 1979-03-10T00:14:44.000Z T790310 1980 1979-03-10T00:29:56.000Z 1979-03-10T23:59:56.000Z T790311 2112 1979-03-11T00:14:44.000Z 1979-03-12T00:14:44.000Z T790312 2068 1979-03-12T00:29:56.000Z 1979-03-12T23:59:32.000Z T790313 1980 1979-03-13T00:14:44.000Z 1979-03-13T23:29:56.000Z T790314 2024 1979-03-14T00:02:20.000Z 1979-03-14T23:59:32.000Z T790315 2112 1979-03-15T00:15:08.000Z 1979-03-16T00:14:44.000Z T790316 2068 1979-03-16T00:29:56.000Z 1979-03-16T23:44:44.000Z T790317 2112 1979-03-17T00:00:20.000Z 1979-03-17T23:55:08.000Z T790318 1936 1979-03-18T00:15:08.000Z 1979-03-18T23:44:44.000Z T790319 2156 1979-03-19T00:00:44.000Z 1979-03-20T00:14:20.000Z T790320 2112 1979-03-20T00:29:56.000Z 1979-03-21T00:14:20.000Z T790321 1980 1979-03-21T00:29:56.000Z 1979-03-21T23:59:32.000Z T790322 2024 1979-03-22T00:15:08.000Z 1979-03-22T23:44:44.000Z

Confidence Level Overview : At all times during this planetary encounter there exist data in this data set that can be rated with the highest confidence level. However, some of the channels of data are contaminated by various kinds and various levels of contaminations. It is therefore imperative, in using this data set, that the contamination tables within the catalog be examined. Also, not all kinds of contamination have been fully documented. When in doubt the data supplier must be contacted. 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. Also included with this data are one standard deviation statistical uncertainties for the directional data (sectors 1 through 8 and an average) expressed as a percent. Unknown values are generally coded as such, however in some instances the value will read 'zero' when its status is unknown. An ancillary data file (SUMMARY.TAB) describes data confidence for the period covered in the data files. This file provides the following information: parameter name description ---------------------------------------------------------- time time in the format yyyy-mm-ddThh:mm:ss.sssZ coverage percent coverage during hour sector_confidence_structure this structure consists of two columns (contamination_id and data_quality_id) repeated 8 times (once each for sectors 1-8) contamination_id contamination ID during hour for sector data_quality_id data quality ID during hour for sector Also included with this data are one standard deviation statistical uncertainties for the directional data (sectors 1 through 8) expressed as a percent. Unknown values are generally coded as such, however in some instances the value will read 'zero' when its status is unknown. Contamination Desc ------------------ -1: affected data is unrated with regard to contamination type 0: affected data is uncontaminated by contamination type 1: affected data is marginally contaminated by contamination type 2: affected data is seriously contaminated by a contamination type, but the measurement is probably retrievable 3: affected data is seriously contaminated by contamination type, and the retrievability of the measurement is questionable 4: affected data is so contaminated by contamination type that the measurement cannot be retrieved Data Quality Desc ----------------- 1: Ion channels penetrating background. All ion channels are subject to background due to high energy particles that penetrate detector shielding. Channels that are the result of 'particle multiple parameters' measurements are less subject to such contamination (channels 'CH__'). A crude quality parameter has been derived from the ratio of the shielded and unshielded 53 to 85 keV 'pl01' ion channel. All other channels must be judged independently from context and from a corresponding ratio. No corrections have been applied. 2: Solar UV. When the lowest energy ion and electron detectors (electron detector less affected) face the sun (sector 1) substantial background counts can occur in the lowest (pl01) and (somewhat) next to lowest (pl02) ion channels. A very crude quality parameter is derived from the ratio of the sun-facing and adjacent sector for the pl01 channel. This parameter should not be accepted as the last word but should be only used for guidance, and it can be misleading. Electrons must be judged separately. No corrections have been applied. 3: Ion channel electron contamination. The lowest energy ion channels (pl01 through pl05) are subject to contamination from > 400 keV electrons which penetrate the magnetic shielding. This condition is well diagnosed on Voyager 2 but not on Voyager 1. Context, corresponding Voyager 2 measurements, and the correlation between moderate energy electron channels and these ion channels must be use to diagnose this condition for Voyager 1. A correction has been applied only to the Voyager 2 Uranus data. 4: Ion detector overdrive. If the fluxes striking a detector is too high, the output of that detector becomes anomalous due to pulse pileup (linear effects) and baseline restoration (non-linear effects) problems. All detectors are subject to possible problems. A crude quality parameter has been derived based on the total rate striking the detector that measures the lowest energy ions (pl01-pl08). Pl01-5 are the channels most strongly affected, with the greatest effects occurring for the lowest energy channels. A dead-time correction procedure has been applied to the data to help alleviate the less severe problems. 5: Detector noise. The detector/electronics noise for the lowest energy detectors (ions in particular) is not too far below the lowest energy discrimination levels. That noise can appear as background counts in the lowest energy channels if the detector noise increases as a result of the detector being overdriven, etc. The lowest discrimination can be adjusted by ground command to help alleviate this problem. A crude quality parameter has been derived based on reasonable/unreasonable ratios of the ion channels pl01 and pl02. This parameter should be used only as a rough guide and can be misleading. No correction has been applied. 6: Electron channels penetrating background. All electron channels are subject to background due to high energy particles that penetrate detector shielding. A crude quality parameter has been derived based on the ratio of the shielded and unshielded 37 to 70 keV 'eb02' electron channel. All other channels must be judged independently from context and from a corresponding ratio. No correction has been applied. 7: Electron detector overdrive. If the fluxes striking a detector is too high, the output of that detector becomes anomalous due to pulse pileup (linear effects) and baseline restoration (non-linear effects) problems. All detectors are subject to possible problems. A crude quality parameter has been derived based on the total rate striking the detector that measures the lowest energy electrons (eb01-eb05). The greatest effects occur for the lowest energy channels. A dead-time correction procedure has been applied to the data to help alleviate less severe problems. 8: Miscellaneous bad data spikes. There are 'spikes' in the data processed for this instrument due to telemetry problems and other processing problems. Their are routines to eliminate these spikes, however, sometimes real events (fast changing) are also eliminated. We have chosen to leave the spikes in and to eliminate them when needed from context.