/************** Neptune PWS Edited 4 second Data Set ************************/ /* MODIFICATIONS /* 920806 -- JPLPDS::RMONARREZ /* received by mail /* 92-08 -- EFRIED /* 920911 -- EFRIED /* 920918 -- EFRIED /* updated Data Set templates according to new std. /* Data Set Template -> Spacecraft Data Set Template /* event_start_time, event_stop_time -> start_time, stop_time /* 920922 -- EFRIED /* Revised DATA_SET_ID and DATA_SET_NAME /* last changes made. /* */ /* Template: Spacecraft Data Set Template - Rev: 19890121*/ /* Note: The following templates form part of a standard set */ /* for the submission of a single dataset to the PDS. */ /* */ /* Hierarchy: SCDATASET */ /* DATASETINFO */ /* DATASETTARG */ /* DSPARMINFO */ /* SCDSHOST */ /* DSREFINFO */ /* REFERENCE */ /* REFAUTHORS */ OBJECT = SCDATASET DATA_SET_ID = "VG2-N-PWS-2-RDR-SA-4SEC-V1.0" OBJECT = DATASETINFO DATA_SET_NAME = "VG2 NEP PWS EDITED RDR UNCALIB SPECTRUM ANALYZER 4SEC V1.0" DATA_SET_COLLECTION_MEMBER_FLG = N START_TIME = 1989-08-21 STOP_TIME = 1989-08-31 NATIVE_START_TIME = "N/A" NATIVE_STOP_TIME = "N/A" DATA_OBJECT_TYPE = "TIME SERIES" DATA_SET_RELEASE_DATE = 1991-02-19 PROCESSING_LEVEL_ID = 2 PRODUCER_FULL_NAME = "DR. WILLIAM S. KURTH" PRODUCER_INSTITUTION_NAME = "UNIVERSITY OF IOWA" SOFTWARE_FLAG = Y DETAILED_CATALOG_FLAG = Y PROCESSING_START_TIME = 1990-02-19 PROCESSING_STOP_TIME = "N/A" DATA_SET_DESC = " This data set consists of 4-second edited, wave electric field intensities from the Voyager 2 Plasma Wave Receiver (PWS) spectrum analyzer obtained in the vicinity of the Neptunian magnetosphere. For each 4-second interval, a field strength is determined for each of the 16 spectrum analyzer channels whose center frequencies range from 10 Hertz to 56.2 kiloHertz and which are logarithmically spaced in frequency, four channels per decade. The time associated with each set of intensities (16 channels) is the time of the beginning of the scan. During data gaps where complete 4-second spectra are missing, no entries exist in the file, that is, the gaps are not zero-filled or tagged in any other way. When one or more channels are missing within a scan, the missing measurements are zero-filled. Data are edited but not calibrated. The data numbers in this data set can be plotted in raw form for event searches and simple trend analysis since they are roughly proportional to the log of the electric field strength. Calibration procedures and tables are provided for use with this data set; the use of these is described below. Use of Voyager PWS Calibration Tables The Voyager PWS calibration tables are given in two plain ASCII text files named VG1PWSCL.TAB and VG2PWSCL.TAB (for Voyagers-1 and -2, respectively). These provide information to convert the uncalibrated `data number' output of the PWS 16-channel spectrum analyzer to calibrated antenna voltages for each frequency channel. These calibration files are always provided with the dataset when the data are extracted from PDS by a user. Following is a brief description of these files and a tutorial in their application. The first column lists an uncalibrated data number followed by the corresponding value in calibrated volts for each of the 16 frequency channels of the PWS spectrum analyzer. Each line contains calibrations for successive data number values ranging from 0 through 255. (Data number 0 actually represents the lack of data since the baseline noise values for each channel are all above that.) A data analysis program may load the appropriate table into a data structure and thus provide a simple look-up scheme to obtain the appropriate voltage for a given data number and frequency channel. For example, the following VAX FORTRAN code may be used to load a calibration array for Voyager 2 PWS: ' real*4 cal (16,0:255) ' ' open ( unit=10, file='vg2pwscl.tab', status='old' )' ' do i=0,38 ' ' read (10,*) ! skip 38 lines of label info ' ' end do ' ' do i=0,255 ' ' read (10,*) idn, (cal(ichan,i),ichan=1,16) ' ' end do ' ' close (10) ' Then, given an uncalibrated data value idn for the frequency channel ichan, the corresponding calibrated antenna voltage would be given by the following array reference: 'volts = cal (ichan, idn)' This may be converted to a wave electric field amplitude by dividing by the effective antenna length in meters, 7.07m. That is: 'efield = cal(ichan, idn) / 7.07' Spectral density units may be obtained by dividing the square of the electric field value by the nominal frequency bandwidth of the corresponding spectrum analyzer channel. 'specdens = (cal(ichan,idn)/7.07)**2 / bandwidth(ichan)' Finally, power flux may be obtained by dividing the spectral density by the impedance of free space in ohms: 'pwrflux = ((cal(ichan,idn)/7.07)**2/bandwidth(ichan))' ' / (120. * pi)' Of course, for a particular application, it may be more efficient to apply the above conversions to the calibration table directly. The center frequencies and bandwidths of each PWS spectrum analyzer channel for the Voyager 2 PWS are given below: ' VOYAGER 2 PWS SPECTRUM ANALYZER ' ' ' ' Voyager-2 ' ' Channel Center Frequency Bandwidth ' ' ' ' 1 10.0 Hz 2.16 Hz ' ' 2 17.8 Hz 3.58 Hz ' ' 3 31.1 Hz 4.50 Hz ' ' 4 56.2 Hz 10.7 Hz ' ' 5 100. Hz 13.8 Hz ' ' 6 178. Hz 28.8 Hz ' ' 7 311. Hz 39.8 Hz ' ' 8 562. Hz 75.9 Hz ' ' 9 1.00 kHz 75.9 Hz ' ' 10 1.78 kHz 151. Hz ' ' 11 3.11 kHz 324. Hz ' ' 12 5.62 kHz 513. Hz ' ' 13 10.0 kHz 832. Hz ' ' 14 17.8 kHz 1260. Hz ' ' 15 31.1 kHz 2400. Hz ' ' 16 56.2 kHz 3800. Hz ' A failure in the Voyager 2 Flight Data System which occurred about 3 months after launch has adversely affected the calibration of PWS channels 9 through 16. An algorithm has been devised to partially correct for this failure, and has proven useful for Voyager 2 Jupiter, Saturn, Uranus, and Neptune encounters, but is not valid for Earth-Jupiter cruise and may be modified in the future. The following implementation of this correction algorithm in VAX FORTRAN assumes that uncalibrated data numbers are stored in a 16-element integer array, idn, with the array index equal to the PWS channel number: 'real*4 tonl(9:16) ! the old noise level for v2 ' 'data tonl/2.0,1.0,-1.0,-2.0,-3.0,1.0,2.0,1.0/ ' ' ' 'do ichan=9,16 ' ' if (idn(ichan).gt.0) then ' ' if(idn(ichan).lt.64) idn(ichan)=64 ' ' if (idn(ichan).le.72) then ' ' idn(ichan)=int(tonl(ichan)-530.4+8.6 ' ' *real(idn(ichan))) ' ' else ' ' idn(ichan)=int(tonl(ichan)+20.113+0.99 ' ' *real(idn(ichan))) ' ' end if ' ' end if ' 'end do ' { ---------------------------- -------------------------------- This PASCAL function roughly corrects the upper 8 channels of the Voyager 2 PWS spectrum analyzer instrument after the Flight Data System failure which occurred during Earth-Jupiter cruise. Input is a raw integer data number and the PWS channel number in which it occurred. Output is the corrected integer data number. ---------------------------- -------------------------------- } { Define a table of constants to be indexed by Voyager 2 PWS channel numbers in the range 9 through 16, inclusive. (These are the only channels affected by this correction algorithm.) } CONST oldNoiseLevel : ARRAY [9..16] OF REAL = (2.0, 1.0, -1.0, -2.0, -3.0, 1.0, 2.0, 1.0); BEGIN { function correctV2PwsUpper8Channels } { Correct only Voyager 2 PWS upper 8 channels. } IF (channel >= 9) AND (channel <= 16) THEN BEGIN { Non-positive data numbers represent missing or invalid data. } IF dataNumber > 0 THEN BEGIN { Set positive data numbers less than 64 to 64. } IF dataNumber < 64 THEN dataNumber := 64; { If the data number is less than or equal to 74 then set the data number to the integer truncation of the result of the sum of the table value indexed by the channel number, minus 530.4, plus 8.6 times the dataNumber. } IF dataNumber <= 72 THEN dataNumber := TRUNC ( oldNoiseLevel[channel] - 530.4 + 8.6 * dataNumber ) { Otherwise, if the data number is greater than 74 then set the data number to the integer truncation of the result of the sum of the table value indexed by the channel number, plus 20.113, plus 0.99 times the dataNumber. } ELSE dataNumber := TRUNC ( oldNoiseLevel[channel] + 20.113 + 0.99 * dataNumber ); END END; correctV2PwsUpper8Channels := dataNumber; END; { function correctV2PwsUpper8Channels } BEGIN END. This correction should not be applied permanently to the Voyager 2 calibration table since it is valid for a limited time span and may be modified in the future. Additional information about this dataset and the instrument which produced it can be found elsewhere in this catalog. An overview of the data in this data set can be found in Gurnett et al. [1989] and a complete instrument description can be found in Scarf and Gurnett [1977]." CONFIDENCE_LEVEL_NOTE = " This data set includes all available spectrum analyzer data within the interval of time covered. The data set has been cleaned as well as possible for periodic noise spikes due to a stepper motor operating on the LECP and a modulated grid within the PLS. The 'bad' points remain in the data set as negative numbers with the same absolute value as the original data point so that the point can be skipped in normal data processing by testing for negative values or recovered for special inspection by converting the sign back to a positive one. Other possible sources of noise which have not been eliminated include random intense spikes of noise below 1 kiloHertz due to the operation of attitude control thrusters. Other randomly occurring spikes or time periods of intense spikes over the entire frequency range are indicative of telemetry errors. No attempt has been made to remove spikes since some could be valid data, i.e. real bursts of wave activity. The 17.8-Hz channel is sometimes contaminated by interference from the PRA instrument, depending on that instrument's mode. This interference is at a relatively constant level. A failure in the Voyager 2 flight data system a few months after launch has decreased the sensitivity and the calibration accuracy of the upper 8 spectrum analyzer channels (i.e. 1 kiloHertz and higher). During the closest approach to Neptune, an enhancement of the periodic PLS noise was observed and has remained unchanged through the end of the Neptune encounter. This interference occurs in the 100 Hz channel." END_OBJECT = DATASETINFO OBJECT = DATASETTARG TARGET_NAME = NEPTUNE END_OBJECT = DATASETTARG OBJECT = DSPARMINFO SAMPLING_PARAMETER_NAME = TIME SAMPLING_PARAMETER_RESOLUTION = 4.0 MINIMUM_SAMPLING_PARAMETER = "N/A" MAXIMUM_SAMPLING_PARAMETER = "N/A" SAMPLING_PARAMETER_INTERVAL = 4.0 MINIMUM_AVAILABLE_SAMPLING_INT = 4.0 SAMPLING_PARAMETER_UNIT = SECOND DATA_SET_PARAMETER_NAME = "PLASMA WAVE SPECTRUM" NOISE_LEVEL = 0.000005 DATA_SET_PARAMETER_UNIT = "VOLT/METER" END_OBJECT = DSPARMINFO OBJECT = SCDSHOST INSTRUMENT_HOST_ID = VG2 INSTRUMENT_ID = PWS END_OBJECT = SCDSHOST OBJECT = DSREFINFO REFERENCE_KEY_ID = GURNETTETAL1989 OBJECT = REFERENCE DOCUMENT_TOPIC_TYPE = "VG2 PWS NEPTUNE OVERVIEW" JOURNAL_NAME = SCIENCE PUBLICATION_DATE = 1989-12-15 REFERENCE_DESC = " Gurnett, D. A., W. S. Kurth, R. L. Poynter, L. J. Granroth, I. H. Cairns, W. M. Macek, S. L. Moses, F. V. Coroniti, C. F. Kennel, and D. D. Barbosa, First plasma wave observations at Neptune, Science, 246, 1494, 1989." OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. DONALD A. GURNETT" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. WILLIAM S. KURTH" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. ROBERT L. POYNTER" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "MR. LARRY J. GRANROTH" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. IVER H. CAIRNS" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. WIESLAW M. MACEK" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. STEWART L. MOSES" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. FERDINAND V. CORONITI" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. CHARLES F. KENNEL" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. DAVID D. BARBOSA" END_OBJECT = REFAUTHORS END_OBJECT = REFERENCE END_OBJECT = DSREFINFO END_OBJECT = SCDATASET /****** Neptune PWS Resampled 48 Second Data Set ***************************/ /* MODIFICATIONS /* 920806 -- JPLPDS::RMONARREZ /* received by mail /* 92-08 -- EFRIED /* 920911 -- EFRIED /* 920918 -- EFRIED /* updated Data Set templates according to new std. /* Data Set Template -> Spacecraft Data Set Template /* event_start_time, event_stop_time -> start_time, stop_time /* 920922 -- EFRIED /* Revised DATA_SET_ID and DATA_SET_NAME /* last changes made. /* */ /* Template: Spacecraft Data Set Template - Rev: 19890121*/ /* Note: The following templates form part of a standard set */ /* for the submission of a single dataset to the PDS. */ /* */ /* Hierarchy: SCDATASET */ /* DATASETINFO */ /* DATASETTARG */ /* DSPARMINFO */ /* SCDSHOST */ /* DSREFINFO */ /* REFERENCE */ /* REFAUTHORS */ OBJECT = SCDATASET DATA_SET_ID = "VG2-N-PWS-4-SUMM-SA-48SEC-V1.0" OBJECT = DATASETINFO DATA_SET_NAME = "VG2 NEP PWS RESAMPLED SUMMARY SPECTRUM ANALYZER 48SEC V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" START_TIME = 1989-08-21T00:00:00 STOP_TIME = 1989-08-31T00:00:00 NATIVE_START_TIME = 11265.22 NATIVE_STOP_TIME = 11565.22 DATA_OBJECT_TYPE = "TIME SERIES" DATA_SET_RELEASE_DATE = 1991-04-10 PROCESSING_LEVEL_ID = 4 PRODUCER_FULL_NAME = "DR. WILLIAM S. KURTH" PRODUCER_INSTITUTION_NAME = "UNIVERSITY OF IOWA" SOFTWARE_FLAG = Y DETAILED_CATALOG_FLAG = Y PROCESSING_START_TIME = 1991-04-01 PROCESSING_STOP_TIME = "N/A" DATA_SET_DESC = " This data set consists of 48-second calibrated, averaged wave electric field intensities from the Voyager 2 Plasma Wave Receiver spectrum analyzer obtained in the vicinity of the Neptunian magnetosphere. For each 48-second interval, a geometric average field strength is determined for each of the 16 spectrum analyzer channels whose center frequencies range from 10 Hertz to 56.2 kiloHertz and which are logarithmically spaced in frequency, four channels per decade. The time associated with each set of averages is the beginning of the averaging interval. Averages are stored in units of volt/meter. During data gaps where complete 48-second intervals are missing, no entries exist in the file, that is, the gaps are not zero-filled or tagged in any other way. Additional information about this dataset and the instrument which produced it can be found elsewhere in this catalog. An overview of the data in this data set can be found in Gurnett et al. [1989] and a complete instrument description can be found in Scarf and Gurnett [1977]." CONFIDENCE_LEVEL_NOTE = " This data set includes all available spectrum analyzer data within the interval of time covered. The data set has been cleaned as well as possible for periodic noise spikes due to a stepper motor operating on the LECP and a modulated grid within the PLS. The averages do not include these noise spikes. Other possible sources of noise which have not been eliminated include random intense spikes of noise below 1 kiloHertz due to the operation of attitude control thrusters. Other randomly occurring spikes or time periods of intense spikes over the entire frequency range are indicative of telemetry errors. No attempt has been made to remove spikes since some could be valid data, i.e. real bursts of wave activity. The 17.8-Hz channel is sometimes contaminated by interference from the PRA instrument, depending on that instrument's mode. This interference is at a relatively constant level. A failure in the Voyager 2 flight data system a few months after launch has decreased the sensitivity and the calibration accuracy of the upper 8 spectrum analyzer channels (i.e. 1 kiloHertz and higher). During the closest approach to Neptune, an enhancement of the periodic PLS noise was observed and has remained unchanged through the end of the Neptune encounter. This interference occurs in the 100 Hz channel." END_OBJECT = DATASETINFO OBJECT = DATASETTARG TARGET_NAME = NEPTUNE END_OBJECT = DATASETTARG OBJECT = DSPARMINFO SAMPLING_PARAMETER_NAME = TIME SAMPLING_PARAMETER_RESOLUTION = 48.0 MINIMUM_SAMPLING_PARAMETER = "N/A" /* 1977-08-20T15:53:00Z */ MAXIMUM_SAMPLING_PARAMETER = "N/A" SAMPLING_PARAMETER_INTERVAL = 48.0 MINIMUM_AVAILABLE_SAMPLING_INT = 4.0 SAMPLING_PARAMETER_UNIT = SECOND DATA_SET_PARAMETER_NAME = "PLASMA WAVE SPECTRUM" NOISE_LEVEL = 0.000005 DATA_SET_PARAMETER_UNIT = "VOLT/METER" END_OBJECT = DSPARMINFO OBJECT = SCDSHOST INSTRUMENT_HOST_ID = VG2 INSTRUMENT_ID = PWS END_OBJECT = SCDSHOST OBJECT = DSREFINFO REFERENCE_KEY_ID = GURNETTETAL1989 OBJECT = REFERENCE DOCUMENT_TOPIC_TYPE = "VG2 PWS NEPTUNE OVERVIEW" JOURNAL_NAME = SCIENCE PUBLICATION_DATE = 1989-12-15 REFERENCE_DESC = " Gurnett, D.A., W.S. Kurth, R.L. Poynter, L.J. Granroth, I.H. Cairns, W.M. Macek, S.L. Moses, F.V. Coroniti, C.F. Kennel, D.D. Barbosa, First plasma wave observations at Neptune, Science, 246, 1494, 1989." OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. DONALD A. GURNETT" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. WILLIAM S. KURTH" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. ROBERT L. POYNTER" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "MR. LARRY J. GRANROTH" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. IVER H. CAIRNS" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. WIESLAW M. MACEK" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. STEWART L. MOSES" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. FERDINAND V. CORONITI" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. CHARLES F. KENNEL" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. DAVID D. BARBOSA" END_OBJECT = REFAUTHORS END_OBJECT = REFERENCE END_OBJECT = DSREFINFO END_OBJECT = SCDATASET /********** VG2 Neptune PWS Edited Waveform 60ms Data Set ******************/ /* MODIFICATIONS /* 920806 -- JPLPDS::RMONARREZ /* received by mail /* 92-08 -- EFRIED /* 920911 -- EFRIED /* 920918 -- EFRIED /* updated Data Set templates according to new std. /* Data Set Template -> Spacecraft Data Set Template /* event_start_time, event_stop_time -> start_time, stop_time /* 920922 -- EFRIED /* Revised DATA_SET_ID and DATA_SET_NAME /* 920925 -- RMONARREZ /* Update processing_level_id to match DATA_SET_ID /* last changes made. /* */ /* Template: Spacecraft Data Set Template - Rev: 19890121*/ /* Note: The following templates form part of a standard set */ /* for the submission of a single dataset to the PDS. */ /* */ /* Hierarchy: SCDATASET */ /* DATASETINFO */ /* DATASETTARG */ /* DSPARMINFO */ /* SCDSHOST */ /* DSREFINFO */ /* REFERENCE */ /* REFAUTHORS */ OBJECT = SCDATASET DATA_SET_ID = "VG2-N-PWS-1-EDR-WFRM-60MS-V1.0" OBJECT = DATASETINFO DATA_SET_NAME = "VG2 NEP PWS RAW EXPERIMENT WAVEFORM 60MS V1.0" DATA_SET_COLLECTION_MEMBER_FLG = N START_TIME = 1989-06-06T14:16:56.980 STOP_TIME = 1989-09-27T17:52:43.287 NATIVE_START_TIME = "9003.13" NATIVE_STOP_TIME = "12397.43" DATA_OBJECT_TYPE = "TIME SERIES" DATA_SET_RELEASE_DATE = 1990-09-01 PROCESSING_LEVEL_ID = 1 PRODUCER_FULL_NAME = "DR. WILLIAM S. KURTH" PRODUCER_INSTITUTION_NAME = "UNIVERSITY OF IOWA" SOFTWARE_FLAG = N DETAILED_CATALOG_FLAG = N PROCESSING_START_TIME = 1990-04-07 PROCESSING_STOP_TIME = 1990-07-30 DATA_SET_DESC = " This data set consists of electric field waveform samples from the Voyager 2 Plasma Wave Receiver waveform receiver obtained during the Neptune encounter. The waveforms are collections of 4-bit samples of the electric field measured by the dipole electric antenna at a rate of 28,800 samples per second. 1600 samples are collected in 55.56 msec followed by a 4.44-msec gap. Each 60-msec interval constitutes a line of waveform samples. The data set includes about 271 frames of waveform samples consisting of up to 800 lines, each. The telemetry format for the waveform data is identical to that for images, hence the use of line and frame as constructs in describing the form of the data. The waveform is sampled through a bandpass filter with a passband of 40 Hz to 12 kHz. The 4-bit samples provide sixteen digital values of the electric field with a linear amplitude scale, but the amplitude scale is arbitrary because of the automatic gain control used in the waveform receiver. The instantaneous dynamic range afforded by the 4 bit samples is about 23 db, but the automatic gain control allows the dominant signal in the passband to be set at the optimum level to fit within the instantaneous dynamic range. With the gain control, the overall dynamic range of the waveform receiver is about 100 db. The automatic gain control gain setting is not returned to the ground, hence, there is no absolute calibration for the data. However, by comparing the waveform spectrum derived by Fourier transforming the waveform to the spectrum provided by the spectrum analyzer data, an absolute calibration may be obtained in most cases. The data may be plotted in raw form to show the actual waveform; this is useful for studying events such as dust impacts on the spacecraft. But the normal method of analyzing the waveform data is by Fourier transforming the samples from each line to arrive at an amplitude versus frequency spectrum. By stacking the spectra side-by-side in time order, a frequency- time spectrogram can be produced. Additional information about this dataset and the instrument which produced it can be found elsewhere in this catalog. An overview of the data in this data set can be found in Gurnett et al. [1989] and a complete instrument description can be found in Scarf and Gurnett [1977]." CONFIDENCE_LEVEL_NOTE = " This data set includes all available waveform receiver data obtained during the Neptune encounter. There has been no attempt to clean various interference signals from the data. Most of these can normally be easily seen in frequency-time spectrograms as narrowband, fixed-frequency tones. The most common include narrow- band tones at 2.4 and 4.8 kHz which are power supply harmonics. There is sometimes a tone near 1.7 kHz which is associated with the operation of the spacecraft gyros. The spacecraft tape recorder results in a rather intense band in the frequency range of a few hundred Hz. There are few times when the data in this frequency range can be used. However, there are times when the real signals in this frequency range can exceed the intensity of the interference sufficiently so that the frequency range near a few hundred Hz can be used. Use of the spectrum analyzer data can be of use to determine when these time periods occur. The stepper motor of the LECP instrument also interferes in the frequency range of a few hundred Hz, but for periods of a few seconds. The LECP interference is very intense and captures the automatic gain control so that real signals, even where there is no interference, will appear to decrease in amplitude until the LECP interference fades in amplitude. The PLS instrument periodically interferes at 400 Hz and odd harmonics because of a 400-Hz square wave used to modulate a grid in the detector. The PLS interference lasts for several seconds and ends abruptly. Telemetry errors result in a fairly graceful degradation of the waveform data. Assuming the telemetry errors are randomly occurring bursts, they typically appear as an enhanced background level in the spectrum. Since the bursts are short, their Fourier transform is a broadband spectrum. When looking for relatively narrowband features or features with distinct frequency-time characteristics, the result of the bursts simply reduce the signal-to-noise in the spectrum. One way of reducing the effect of burst telemetry errors is to pass the waveform data through a low-pass filter to despike it, prior to running the Fourier transform. The waveform data is not subject to the negative effects of the failure in the Voyager 2 Flight Data System which reduces the sensitivity of the spectrum analyzer and affects the calibration above 1 kHz. In fact, use of the 1 - 12 kHz waveform data is an effective way of avoiding the problems with the spectrum analyzer data in this frequency range." END_OBJECT = DATASETINFO OBJECT = DATASETTARG TARGET_NAME = NEPTUNE END_OBJECT = DATASETTARG OBJECT = DSPARMINFO SAMPLING_PARAMETER_NAME = TIME SAMPLING_PARAMETER_RESOLUTION = 0.000034722 MINIMUM_SAMPLING_PARAMETER = "N/A" MAXIMUM_SAMPLING_PARAMETER = "N/A" SAMPLING_PARAMETER_INTERVAL = 0.000034722 MINIMUM_AVAILABLE_SAMPLING_INT = 0.000034722 SAMPLING_PARAMETER_UNIT = SECOND DATA_SET_PARAMETER_NAME = "PLASMA WAVE WAVEFORM" NOISE_LEVEL = 0.000005 DATA_SET_PARAMETER_UNIT = "VOLT/METER" /* Data not absolutely */ /* calibrated */ END_OBJECT = DSPARMINFO OBJECT = SCDSHOST INSTRUMENT_HOST_ID = VG2 INSTRUMENT_ID = PWS END_OBJECT = SCDSHOST OBJECT = DSREFINFO REFERENCE_KEY_ID = "GURNETTETAL1989" OBJECT = REFERENCE DOCUMENT_TOPIC_TYPE = "VG2 PWS NEPTUNE OVERVIEW" JOURNAL_NAME = SCIENCE PUBLICATION_DATE = 1989-12-15 REFERENCE_DESC = " Gurnett, D.A., W.S. Kurth, R.L. Poynter, L.J. Granroth, I.H. Cairns, W.M. Macek, S.L. Moses, F.V. Coroniti, C.F. Kennel, D.D. Barbosa, First plasma wave observations at Neptune, Science, 246, 1494, 1989." OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. DONALD A. GURNETT" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. WILLIAM S. KURTH" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. ROBERT L. POYNTER" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "MR. LARRY J. GRANROTH" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. IVER H. CAIRNS" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. WIESLAW M. MACEK" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. STEWART L. MOSES" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. FERDINAND V. CORONITI" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. CHARLES F. KENNEL" END_OBJECT = REFAUTHORS OBJECT = REFAUTHORS AUTHOR_FULL_NAME = "DR. DAVID D. BARBOSA" END_OBJECT = REFAUTHORS END_OBJECT = REFERENCE END_OBJECT = DSREFINFO END_OBJECT = SCDATASET