Data Set Information
DATA_SET_NAME P12 V ORBITING RADAR RESAMPLED ALTIMETER/RADIOMETER V1.0
DATA_SET_ID P12-V-ORAD-4-ALT/RAD-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set consists of groups of measurements made by the Radar Mapper experiment on the Pioneer Venus Orbiter spacecraft. The measurements were made during each approximately 12-second spacecraft rotation period for a period of 32 minutes on either side of periapsis, when the range to the surface was less than about 4500 kilometers. During those 12 seconds, up to 8 measurements were made: (a) cold-sky received calibration when the antenna pointed to the zenith, (b) 'early' imaging, when the antenna pointer at an angle of between 10 and 40 degrees from nadir, (c) planetary thermal noise temperature when the antenna pointed to the nadir (d) one altimetry measurement, or (d-g) four altimetry measurements, and (h) 'late' imaging, when the antenna again pointed at an angle of between 10 and 40 degrees from nadir, but on the other side from 'early' imaging. The decision to make one or four altimetry measurements depended on the spacecraft altitude -- one measurement was made above 700 kilometers, four below. Also, the imaging modes were only enabled below 700 kilometers and only generated useful results below 550 kilometers. This data set contains results from the altimetry and radiometry measurements. Each record describes the data collected during a single 12-second roll period. If 4 altimetry measurements were made at that time, the individual results have been averaged. Processing Level Id : 4 Software Flag : N Processing Start Time : 1988-12-01 Processing Stop Time : 1988-12-01 Parameters : Data Set Parameter 'BRIGHTNESS TEMPERATURE' ------------------------------------------- The kinetic temperature of an ideal blackbody which, if observed with the spectral response of the instrument spectral channel in question would yield the observed radiance. Data Set Parameter Name : BRIGHTNESS TEMPERATURE Data Set Parameter Unit : KELVIN Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 0.001 Sampling Parameter Interval : 12 Minimum Available Sampling Int : 12 Noise Level : N/A Data Set Parameter 'PIONEER-VENUS FRESNEL REFLECTIVITY CORR' ------------------------------------------------------------ For the Pioneer-Venus Orbiter Radar (ORAD) measurements, a correction to the Fresnel reflectivity that accounts for the fraction of the incident radar beam that is reflected by sub-wavelength-sized scatterers. This component was estimated, where possible, from the ORAD side looking radar imaging mode, and modeled by the phenomenological function g*a*Rf*cos(t)**1.5, where t is the scattering angle, g : 2.69 is a fitted geometrical factor, and a is the fraction of the surface covered by diffusely-scattering material. Rf is the true Fresnel reflectivity, and may be reconstructed from Fresnel reflectivity + Fresnel reflectivity correction. This correction is only available for that portion of the altimetric dataset that is also covered by side-looking imaging data, i.e. from about 15 degrees south to 45 degrees north latitude. Data Set Parameter Name : PIONEER-VENUS FRESNEL REFLECTIVITY CORR Data Set Parameter Unit : DIMENSIONLESS Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 0.001 Sampling Parameter Interval : 12 Minimum Available Sampling Int : 12 Noise Level : N/A Data Set Parameter 'PLANETARY RADIUS' ------------------------------------- Radial distance from center of planet or satellite to given location on the surface. Data Set Parameter Name : PLANETARY RADIUS Data Set Parameter Unit : KILOMETER Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 0.001 Sampling Parameter Interval : 12 Minimum Available Sampling Int : 12 Noise Level : N/A Data Set Parameter 'RADAR-DERIVED FRESNEL REFLECTIVITY' ------------------------------------------------------- The Fresnel reflectivity of a surface derived by modeling backscatter cross-section as a function of surface RMS slope and Fresnel reflectivity. This value is related to the (complex) surface bulk dielectric constant E by ((sqrt(E)-1)/(sqrt(E)+1))**2. Data Set Parameter Name : RADAR-DERIVED FRESNEL REFLECTIVITY Data Set Parameter Unit : DIMENSIONLESS Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 0.001 Sampling Parameter Interval : 12 Minimum Available Sampling Int : 12 Noise Level : N/A Data Set Parameter 'RADAR-DERIVED RMS SLOPE' -------------------------------------------- The RMS average surface slope derived from radar measurements. Horizontal length scales that correspond to RMS slope estimates vary from many times the radar wavelength at small (220 deg) radar incidence angle observations (so called quasi-specular regime) to approximately the radar wavelength at larger incidence angles. Data Set Parameter Name : RADAR-DERIVED RMS SLOPE Data Set Parameter Unit : RADIAN Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 0.001 Sampling Parameter Interval : 12 Minimum Available Sampling Int : 12 Noise Level : N/A Source Instrument Parameters : Instrument Host ID : P12 Data Set Parameter Name : BRIGHTNESS TEMPERATURE Instrument Parameter Name : RADIANCE Important Instrument Parameters : 1 Instrument Host ID : P12 Data Set Parameter Name : PLANETARY RADIUS Instrument Parameter Name : RADAR ECHO POWER Important Instrument Parameters : 1 Instrument Host ID : P12 Data Set Parameter Name : RADAR-DERIVED RMS SLOPE Instrument Parameter Name : RADAR ECHO POWER Important Instrument Parameters : 1 Instrument Host ID : P12 Data Set Parameter Name : RADAR-DERIVED FRESNEL REFLECTIVITY Instrument Parameter Name : RADAR ECHO POWER Important Instrument Parameters : 1 Instrument Host ID : P12 Data Set Parameter Name : PIONEER-VENUS FRESNEL REFLECTIVITY CORR Instrument Parameter Name : RADAR ECHO POWER Important Instrument Parameters : 2 Processing : N/A
DATA_SET_RELEASE_DATE 1988-12-01T00:00:00.000Z
START_TIME 1978-12-05T12:00:00.000Z
STOP_TIME 1981-03-23T12:00:00.000Z
MISSION_NAME PIONEER
PRE-MAGELLAN
MISSION_START_DATE 1978-05-20T12:00:00.000Z
1968-11-09T12:00:00.000Z
MISSION_STOP_DATE 1992-10-08T12:00:00.000Z
1988-07-27T12:00:00.000Z
TARGET_NAME VENUS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID P12
INSTRUMENT_NAME ORBITING RADAR
INSTRUMENT_ID ORAD
INSTRUMENT_TYPE RADAR
NODE_NAME Geosciences
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Overview : This data set includes corrections for timing errors, orbit determination errors, and for atmospheric delay and attenuation. There remain severe systematic errors in the planetary radius and Fresnel reflectivity parameters, the former due to a combination of spacecraft timing and orbit determination errors, the latter to spacecraft timing errors alone.
CITATION_DESCRIPTION Pettengill, G. H., P12 V ORBITING RADAR RESAMPLED ALTIMETER/RADIOMETER V1.0, P12-V-ORAD-4-ALT/RAD-V1.0, NASA Planetary Data System, 1988
ABSTRACT_TEXT This data set consists of groups of measurements made by the Radar Mapper experiment on the Pioneer Venus Orbiter spacecraft. The measurements were made during each approximately 12-second spacecraft rotation period for a period of 32 minutes on either side of periapsis, when the range to the surface was less than about 4500 kilometers. During those 12 seconds, up to 8 measurements were made: (a) cold-sky received calibration when the antenna pointed to the zenith, (b) 'early' imaging, when the antenna pointer at an angle of between 10 and 40 degrees from nadir, (c) planetary thermal noise temperature when the antenna pointed to the nadir (d) one altimetry measurement, or (d-g) four altimetry measurements, and (h) 'late' imaging, when the antenna again pointed at an angle of between 10 and 40 degrees from nadir, but on the other side from 'early' imaging.
PRODUCER_FULL_NAME GORDON H. PETTENGILL
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