Data Set Information
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| DATA_SET_NAME |
VG2 NEP PRA EDITED RDR HIGH RATE 60MS V1.0
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| DATA_SET_ID |
VG2-N-PRA-2-RDR-HIGHRATE-60MS-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
This data set (VG2-N-PRA-2-RDR-HIGHRATE-60MS-V1.0) contains dataacquired by the Voyager-2 Planetary Radio Astronomy (PRA) instrumentduring the Neptune encounter. Since the PRA instrument is able toobserve planetary phenomenon at much larger ranges than other fieldsand particles experiments, thus the PRA data cover a variable andlonger encounter period. PRA lowband data provided here cover theentire Neptune Encounter Phase (1989-05-25 to 1989-09-27).Each file within the dataset represents a single PRA high rate frame,of duration 48 seconds. Each file contains a 28 octet header, followedby 1280000 octets of data.The header format is described as below:--------------------------------------------------------------------Length (bytes) Name Contents--------------------------------------------------------------------2 Year Year A.D.2 Day Day of year (1 Jan == 1)1 Hour Hour of day (midnight == 0)1 Minute Minute of hour (o'clock = 0)1 Second Second of Minute (exact minute == 0)1 Spacecraft 1 == V1, 2 == V22 Integral FDS Integer part of FDS count1 Fractional FDS Fractional part of FDS count4 Freq. 1 Frequency of 1st channel (Hz)4 Freq. 2 Frequency of 2nd channel (Hz)4 Freq. 3 Frequency of 3rd channel (Hz)4 Freq. 4 Frequency of 4th channel (Hz)1 Bandwidth Bandwidth (kHz)--------------------------------------------------------------------where all values are unsigned, and multi-octet values are presentedwith the most significant byte first.The data are 16 bit numbers, most significant byte first, with 0indicating unavailable data. The data are presented as a singlestream of 16 bit numbers. The frame is logically divided into lines(although there is no indication of the lines within the file). Thisterminology comes from the fact that in this high rate mode, the PRAdata are treated exactly as if they were imaging data, and a 48 secondimage comprises 800 horizontal scan lines. Similarly, there are 800logical lines within a PRA frame. Each line comprises 800 values,representing 400 data pairs. In the high rate mode, the PRA measuresthe flux at two frequencies _simultaneously_ and returns these two datasequentially. A sample pair is acquired every (actually every 138.88...microseconds), through an RC filter with a 100 microsecond time constant.A single line comprises 60 milliseconds of data. Lines are NOT contiguousin time. There is a 4444.44... microsecond gap between the ending of oneline and the start of the succeeding line.The PRA samples a frequency pair in this manner for 24 seconds. It thenhas the option of switching to a second pair for the final 24 seconds.These frequencies are designated Freq. 1 through Freq. 4 in the header.The data are presented such that the higher of the relevant frequencypair is presented first.
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| DATA_SET_RELEASE_DATE |
1991-07-22T00:00:00.000Z
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| START_TIME |
1989-05-25T06:58:32.000Z
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| STOP_TIME |
1989-09-27T05:52:43.000Z
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| MISSION_NAME |
VOYAGER
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| MISSION_START_DATE |
1972-07-01T12:00:00.000Z
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| MISSION_STOP_DATE |
N/A (ongoing)
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| TARGET_NAME |
NEPTUNE
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| TARGET_TYPE |
PLANET
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| INSTRUMENT_HOST_ID |
VG2
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| INSTRUMENT_NAME |
PLANETARY RADIO ASTRONOMY RECEIVER
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| INSTRUMENT_ID |
PRA
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| INSTRUMENT_TYPE |
RADIO SPECTROMETER
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| NODE_NAME |
planetary plasma interactions
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| ARCHIVE_STATUS |
ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
Permitted downlink bit error rates are considerably higher for highrate operation than for low rate. Consequently, it is not uncommonfor there to be considerable noise in a high rate frame. The probabilityof any particular datum being incorrect is small, but there are a lot ofdata in a frame. Generally, a datum should not be assumed to be real ifit forms no part of a pattern and is markedly different from its neighbors.Bit error rates are as likely to result in a falsely low reading as afalsely high one.The data presented are calibrated but not otherwise manipulated. Animprovement in data quality can often be obtained by making allowancefor the 2.4 kHz spacecraft switching power supply, whose signal isclearly superimposed on much of the PRA high rate data.The noise background is considerably higher for these data than forlow rate data. This is because of the wide bandwidth usually used(200 kHz instead of the 1 kHz used for low rate), which permits manyharmonics of the spacecraft power supply to appear in the data, as wellas many of the noise products of other spacecraft subsystems. However,most naturally occurring signals last for (at least) several samplesand have an appearance quite unlike the distinctly regular artificialinterferences.
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| CITATION_DESCRIPTION |
Evans, D.R., VG2-N-PRA-2-RDR-HIGHRATE-60MS-V1.0, VG2 NEP PRA EDITED RDR HIGH RATE 60MS V1.0, NASA Planetary Data System, 1991.
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| ABSTRACT_TEXT |
This data set (VG2-N-PRA-2-RDR-HIGHRATE-60MS-V1.0) contains dataacquired by the Voyager-2 Planetary Radio Astronomy (PRA) instrumentduring the Neptune encounter. Since the PRA instrument is able toobserve planetary phenomenon at much larger ranges than other fieldsand particles experiments, thus the PRA data cover a variable andlonger encounter period. PRA lowband data provided here cover theentire Neptune Encounter Phase (1989-05-25 to 1989-09-27).
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| PRODUCER_FULL_NAME |
DR. DAVID R. EVANS
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| SEARCH/ACCESS DATA |
Planetary Plasma Interactions Website
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