Data Set Information
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| DATA_SET_NAME |
PVO VENUS ELECT TMP PROBE RESAMP SOLAR EUV 24 HR AVG VER 1.0
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| DATA_SET_ID |
PVO-V-OETP-5-SOLAREUV-24HRAVG-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 |
The Solar EUV Daily Values File. This file gives the magnitude of thephotoemission current from the radial probe, Ipe, (in units of 10-9 amps).Ipe dominates the ion current measurements outside the Venusianionosphere, making possible the serendipitous measurement of the totalsolar EUV flux. The latter is an important parameter because solar EUV isthe main source of ionization and heating for the Venusian thermosphereand ionosphere. The method is discussed by Brace et al., (1988).The pe current measurements are taken just before PVO leaves the solarwind and enters the magnetosheath (usually an hour or two beforeperiapsis). This approach provides the solar EUV flux that the Venusthermosphere received just before the periapsis measurements. Themaximum value of the spin modulated Ipe is taken because it correspondsto a probe orientation perpendicular to the Sun when the maximum areaof the probe is exposed to the Sun. Ipe is proportional to the intensity ofthe ionizing component of solar radiation, so it is possible to derive thetotal solar EUV (and far UV) flux. Ly alpha contributes approximately halfof the Ipe while nearly all of the rest is produced by radiation between 200A and 1200 A which ionizes, excites and dissociates thermosphericneutrals.This file contains the daily average value of the photoelectron emissioncurrent, Ipe, from the radial probe, usually measured about 1 hr beforeperiapsis. The Ipe values are given in units of 10-9 amperes. The datacover the interval from 1979 through early 1992 when periapsis got lowenough to cause photoelectric yield changes that have not been fullyresolved and corrected for appropriately. The data provided cover orbits1 to 4800. After orbit 4800, when PVO began to enter the atmosphere, theLangmuir probe could no longer be kept clean, and as a result the yieldchanged. For further details, contact Walt Hoegy at GSFC code 914,(301) 286-3837 or email hoegy@mite.gsfc.nasa.gov.The daily Ipe measurements can be converted into the total solar EUV flux(VEUV) using the following the equation given by Brace et al., (1988), VEUV = 1.53 x 1011 Ipe (photons/cm2/s)VEUV represents the total solar flux, weighted by the known wavelength-dependent yield of the collector. A standard Hinteregger solar EUV/UVspectrum is assumed to derive the coefficient, but the measurement isrelatively insensitive to this assumption over the typical range ofvariations in the solar spectrum.The VEUV data have been useful in the study of solar EUV effects on the ionproduction and electron heating rates in the Venus ionosphere. VEUVvariations have been correlated with changes in the density andtemperature of the ionosphere (Elphic et al., 1984), the height of the bowshock (Alexander et al., 1985, Russell et al., 1988), and changes in thedensity and temperature of the thermosphere (Mahajan et al., 1990). OBJECT = DSPARMINFO SAMPLING_PARAMETER_NAME = N/A SAMPLING_PARAMETER_RESOLUTION = N/A MINIMUM_SAMPLING_PARAMETER = N/A MAXIMUM_SAMPLING_PARAMETER = N/A SAMPLING_PARAMETER_INTERVAL = N/A MINIMUM_AVAILABLE_SAMPLING_INT = N/A SAMPLING_PARAMETER_UNIT = N/A DATA_SET_PARAMETER_NAME = PHOTOELECTRON CURRENT NOISE_LEVEL = UNK DATA_SET_PARAMETER_UNIT = AMPERES / 10**9 END_OBJECT = DSPARMINFO
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| DATA_SET_RELEASE_DATE |
1993-10-01T00:00:00.000Z
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| START_TIME |
1978-12-05T12:00:00.000Z
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| STOP_TIME |
1992-01-18T11:59:59.999Z
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| MISSION_NAME |
PIONEER VENUS
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| MISSION_START_DATE |
1968-06-01T12:00:00.000Z
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| MISSION_STOP_DATE |
1992-10-07T12:00:00.000Z
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| TARGET_NAME |
VENUS
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| TARGET_TYPE |
PLANET
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| INSTRUMENT_HOST_ID |
PVO
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| INSTRUMENT_NAME |
ELECTRON TEMPERATURE PROBE
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| INSTRUMENT_ID |
OETP
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| INSTRUMENT_TYPE |
PLASMA INSTRUMENT
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| NODE_NAME |
planetary plasma interactions
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| ARCHIVE_STATUS |
ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
The Ipe measurements themselves are made with an absolute accuracy of 1to 2%, depending upon where the current falls within the decade range ofthe ranging electrometer. The absolute accuracy of the measurements isalso limited by our knowledge of the photoelectric yield of the radialprobe collector, and our assumption that a Hinteregger standard EUV/UVspectrum is correct. We estimate a 10% absolute accuracy in the total EUVflux and a 1 to 2% relative accuracy or precision provided by the accuracyof the current measurements themselves. See Brace et al.(1988) fordetails of the method.
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| CITATION_DESCRIPTION |
Theis, R. F., PVO VENUS ELECT TMP PROBE RESAMP SOLAR EUV 24 HR AVG VER 1.0, PVO-V-OETP-4-SOLAREUV-24HRAVG-V1.0, NASA Planetary Data System, 1993
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| ABSTRACT_TEXT |
The Solar EUV Daily Values File. This file gives the magnitude of thephotoemission current from the radial probe, Ipe, (in units of 10-9 amps).Ipe dominates the ion current measurements outside the Venusianionosphere, making possible the serendipitous measurement of the totalsolar EUV flux. The latter is an important parameter because solar EUV isthe main source of ionization and heating for the Venusian thermosphereand ionosphere.
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| PRODUCER_FULL_NAME |
DR. ROBERT F. THEIS
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| SEARCH/ACCESS DATA |
Planetary Plasma Interactions Website
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