Data Set Information
DATA_SET_NAME PIONEER 12 VENUS ORBITING RADAR DERIVED RADAR IMAGES V1.0
DATA_SET_ID P12-V-ORAD-5-RADAR-IMAGE-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set consists of five VICAR2 format images of Venus derived from Pioneer Venus radar altimeter measurements. Data are presented in simple cylindrical projection format. The radius image contains 1440 lines (latitude) and 2880 samples (longitude), and the others contain 1024 lines and 2048 samples. The images are as follows: (1) An image of Venus radii corrected for atmospheric delay, using the results of Kliore et al., 1985, and further corrected for orbit element estimation errors. This image represents version 3.0 of the official Project Magellan topography database. (2) Venus microwave brightness temperature, in degrees Kelvin, derived from the Pioneer Venus radar altimeter planet radiance (PC) and space radiance (SC) measurements, as follows: the dataset was divided into 1 degree latitude intervals. For each interval, the average SC reading was taken to represent a measurement of the 3K cold sky. The average PC values from lowland regions were interpreted as measuring an average temperature of 735K with an emissivity of 88%. The brightness_temperature is therefore given by (735*0.88*(PC-)+3*(-PC)) /(-). (3) Venus surface radar-derived Fresnel reflectivity, from radar altimeter measurements, derived by analyzing the time-sampled radar echo profile according to Hagfors' Law of near-normal-incidence scattering from a quasi-specular surface. The radar-derived Fresnel reflectivity is related to the (complex) surface bulk dielectric constant E by ((sqrt(E)-1)/(sqrt(E)+1))**2. The radar-derived Fresnel reflectivity is derived by analyzing the time-sampled radar echo profile according to Hagfors' Law of near-normal-incidence scattering from a quasi-specular surface. (4) Venus surface radar-derived Fresnel reflectivity corrected for diffuse scattering from radar altimeter and side-looking backscatter measurements. A correction is made to the radar-derived Fresnel reflectivity to account for that fraction of the incident radar beam that is reflected by sub-wavelength-sized scatterers. This component was estimated, where possible, from the Pioneer Venus radar side-looking imaging mode, and modeled by the phenomenological function g*a*R*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. R is the true radar-derived Fresnel reflectivity. The correction is only made 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. (5) Venus RMS average surface slopes at meter scale, from radar altimeter measurements, derived by analyzing the time-sampled radar echo profile according to Hagfors' Law of near-normal-incidence scattering from a quasi-specular surface where the specific radar cross section varies with the scattering angle t according to 0.5*R*C*(cos(t)**4+C*sin(t)**2)**(-1.5), where R is the radar-derived Fresnel reflectivity and the average slope, S (in radians), is related to the Hagfors constant C by S:1/sqrt(C). Processing Level Id : 5 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 : PIXEL Sampling Parameter Unit : N/A Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A 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 : PIXEL Sampling Parameter Unit : N/A Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A 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 : PIXEL Sampling Parameter Unit : N/A Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A 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 : PIXEL Sampling Parameter Unit : N/A Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A 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 : PIXEL Sampling Parameter Unit : N/A Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A 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 : The radius data have been corrected for spacecraft timing errors, orbit determination errors, and for atmospheric delay. The brightness temperature, reflectivity, and corrected reflectivity data have been corrected for spacecraft timing errors, receiver filter response factors, and for atmospheric attenuation. Considerable systematic errors remain in these three images, due principally to residual spacecraft timing errors. The RMS surface slope data contain no known systematic errors, beyond those made by the assumption that the Venus surface scatters according to Hagfors' law.
CITATION_DESCRIPTION Ford, P. G., PIONEER 12 VENUS ORBITING RADAR DERIVED RADAR IMAGES V1.0, P12-V-ORAD-5-RADAR-IMAGE-V1.0, NASA Planetary Data System, 1988
ABSTRACT_TEXT This data set consists of five VICAR2 format images of Venus derived from Pioneer Venus radar altimeter measurements. Data are presented in simple cylindrical projection format. The radius image contains 1440 lines (latitude) and 2880 samples (longitude), and the others contain 1024 lines and 2048 samples.
PRODUCER_FULL_NAME PETER G. FORD
SEARCH/ACCESS DATA
  • Geosciences Web Services
  • Geosciences Online Archives
    		•