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Availability: Archived at NSSDC, accessible from elsewhere

Time span: 1989-08-24 to 1989-08-27


This description was generated automatically using input from the Planetary Data System.

Description of the PDS LECP Neptune Scan data. This data consists of resampled data from the Low Energy Charged Particle (LECP) Experiment on the Voyager 2 Spacecraft for the period when Voyager 2 was in the vicinity of the planet Neptune. The period covered is 1989-08-24T00:00:00.000 SCET to 1989-08-27T00:00:00.000 SCET. This data approximates a time series of charged particle fluxes from a selection of channels available from the instrument. The word approximates is used because the angle scanning modes of the instrument complicates the nature of the data. At times the instrument mechanically scans, and at times it is fixed to look at a specific direction. With the type of data given here, the fluxes are angle averaged for those time periods when the instrument is scanning, and are time averaged over an arbitrary period (12 or 24 sec, see below) for the periods when the detectors are stationary. The angle averaged records represent periods of time equal to 48 or 96 sec (see below). This kind of data presentation has been called the LECP Scan data. Another form that is also available is the LECP Step data that gives the angle distributions sampled during the scanning periods. Three scanning situations occurred during the time of this data. They are: 1) continuous 48 sec stepping (48 seconds for each of 8 look directions for a total of 6.4 minutes per scan; note that sector 8 is shielded with 2 mm Al), 2) a special Neptune scan cyclic with the following sequence: 7, scan, 1, scan, 7, scan, scan, repeat; where the 7 and the 1 represent 5.2 minute periods when the instrument is fixed in sectors 7 or 1, respectively, and where the word scan represents a period of scanning (6 sec stepping for a total scan time of 48 sec); and 3) periods when the detectors are fixed for more extended periods in sector 7 (periods bracketing the ring plane crossings). For this Neptune Scan data, the 6.4 minute scan records during stepping mode (1) have been time averaged to 12.8 minute records. Also, during stepping mode (2), the double scans that have no fixed periods between them have been averaged together into a single (96 sec) record. The single scans represent 48 sec records. The schedule for the three stepping modes is as follows: prior to day 236/1600 SCET: Mode (1) 236/1600 to 237/0239: Mode (2) 237/0239 to 237/0319: Mode (3) 237/0319 to 237/0503: Mode (2) 237/0503 to 237/0554: Mode (3) 237/0554 to 238/0400: Mode (2) after 237/0400: Mode (1) Obviously these stepping mode changes, and the angle sample switching that occurs during stepping mode (2), gives the data a disjointed appearance. Two channel sample modes also occurred during the Neptune encounter. These two modes affect this data set only by changing the primary record time length for the LECP Experiment Data Records (EDR's). These time lengths have, in turn, been utilized for the averaging times of this data set for non-stepping periods. The schedule is: prior to day 237/0200 SCET: Far Encounter (24 sec records) 237/0200 to 237/0551: Near Encounter (12 sec records) after 237/0551: Far Encounter (24 sec records) The LECP channels utilized with this data set are: EB01: electrons, 22 to 35 keV EB02: electrons, 35 to 61 keV EB03: electrons, 61 to 112 keV EB04: electrons, 112 to 183 keV EG06-EG07: electrons, 252 to 480 keV EG07-EG08: electrons, 480 to 853 keV EG08-EG09: electrons, 853 to 1200 keV PL01: ions, 28 to 43 keV PL02: ions, 43 to 80 keV PL03: ions, 80 to 137 keV PL04: ions, 137 to 215 keV PL05: ions, 215 to 540 keV PL06: ions, 540 to 990 keV PL07: ions, 990 to 2140 keV PL08: ions, 2140 to 3500 keV Please note that 3 of the electron channels are derived from 4 of the instrumental channels by taking differences between adjacent (in energy) channels. The channel data is given in units of intensity: counts/(cm^2.sec.str.keV). For the ions, it has been assumed that they consist only of protons. Intensity is derived from the raw count rates via the relation: I = CR/(eG.(E2-E1), where eG is geometric factor times detector efficiency, and (E2-E1) is the band pass of the channel in energy. The proton values of these parameters were used in deriving the intensities for this data set. To obtain the Intensities under the assumption that some other mass species dominates, one must convert back to count rate (CR) utilizing the proton parameters, and then convert to intensity using the parameters corresponding to the mass species in question. The parameters can be found in Table 1 of Krimigis et al. (Journal of Geophysical Research, V. 86, page 8227, 1981) The corresponding parameters for electrons can be found in Mauk et al. (Journal of Geophysical Research, V. 92, page 15283, 1987). Prior to the conversion to intensity, the count rates have been corrected for: (1) Background, (2) electron contamination of the lower energy ion channels, and (3) solar UV contamination of the lowest energy ion channel. The uncertainty parameters given with the data associated with each channel (expressed as a percent) is the largest of the two quantities: (i) one standard deviation Poisson statistical error, and (ii) a percentage assigned by the data supplier based on the amount of contamination correction that has been performed on each data channel. Also supplied with each record of this data set is the fraction of the data accumulations that correspond to each of the 8 angle sectors. For example, during a sector 7 stow period, this number will be 1.0 for sector 7 and 0.0 for all of the other sectors. A sector 9 has also been defined corresponding to those accumulations with no known sector assignment. Additionally supplied for each data channel a one bit code that tells whether that channel had any accumulations at all associated with it (1 = yes; 0 = no). This code must be used to distinguish between accumulations that yielded no counts and situations where the channel simply had no accumulations (results in Intensity = 0.0). SAMPLING_PARAMETER_NAME = TIME SAMPLING_PARAMETER_RESOLUTION = 24.0 MINIMUM_SAMPLING_PARAMETER = N/A MAXIMUM_SAMPLING_PARAMETER = N/A SAMPLING_PARAMETER_INTERVAL = 24.0 MINIMUM_AVAILABLE_SAMPLING_INT = 6.0 SAMPLING_PARAMETER_UNIT = SECOND DATA_SET_PARAMETER_NAME = PARTICLE FLUX INTENSITY NOISE_LEVEL = N/A DATA_SET_PARAMETER_UNIT = COUNTS/(CM**2*SECOND*STERRADIAN*KEV)

These data are available on-line from the Planetary Data System (PDS) at:

Alternate Names



  • Planetary Science: Fields and Particles

Additional Information



Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II



NameRoleOriginal AffiliationE-mail
Dr. Stamatios M. KrimigisData ProviderApplied Physics
Dr. Barry H. MaukGeneral ContactApplied Physics Laboratory
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