Data Set Information
DATA_SET_NAME MGN V RDRS 5 GLOBAL DATA RECORD TOPOGRAPHIC V1.0
DATA_SET_ID MGN-V-RDRS-5-GDR-TOPOGRAPHIC-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : Global Topographic Data Record (GTDR). The range to surface is derived by fitting altimeter echoes from the fan-beam altimetry antenna as a function of time to Hagfors' radar backscatter model templates. The ranges are subtracted from the spacecraft radial coordinate (derived from Doppler tracking), yielding measurements of planetary radius. The data are filtered to remove low-frequency errors in the in-plane elements of each spacecraft orbit, and then re-sampled into sinusoidal, Mercator, and north and south polar stereographic projections at a resolution of about 5x5 kilometers per pixel. A fifth image contains estimates of the absolute accuracy of the radius values in each pixel of the sinusoidal projection. This is derived by taking the root mean square of (a) the statistical accuracy anticipated from the template fitting and (b) the systematic errors estimated from the in-plane element filtration. Note that this is the absolute topographic accuracy -- relative errors are much smaller, about 10-15 meters in relatively flat areas. Except in the radius error image, each GTDR pixel is represented by a 16-bit integer. In sinusoidal images, pixels lying outside the domain of the projection are set to zero. In all images, pixels with unknown or unmeasured values are also set to zero. The remaining values are related to the planetary radius by the following equation: DN : (RADIUS ) - 6039999. In the radius error image, each pixel is represented by an 8-bit integer. Pixels lying outside the domain of the projection are set to zero, as are all pixels with unknown or unmeasured values. The remaining values are related to the radius error by the following equation: DN : (RADIUS-ERROR * 0.2) + 1. See: Software Interface Specification Document (Peter G. Ford, 1991, Global Altimetry and Radiometry Data Records, MIT-MGN-GxDR SIS Version 2.3, 40 p.) that is included on the GxDR CD-ROMs. Note: There exist photoproducts that are identified as GxDRP (where x is E (Emissivity), S (Slope), RE (Reflectivity), or T (Topography)) however, they are not generated from the digital GxDR products. They are instead produced from the Magellan ARCDR (Altimetry and Radiometry Composite Data Record) data files. Processing Level Id : 5 Software Flag : N Processing Start Time : 1991-06-24T20:11:00.000 Processing Stop Time : 1992-12-04T00:55:49.000 Parameters : 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 : METER Sampling Parameter Name : PIXEL Sampling Parameter Unit : METER Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 9282 Sampling Parameter Interval : 4641 Minimum Available Sampling Int : N/A Noise Level : UNK Source Instrument Parameters : Instrument Host ID : MGN Data Set Parameter Name : PLANETARY RADIUS Instrument Parameter Name : RADAR ECHO POWER Important Instrument Parameters : 1 Processing : Processing History ------------------ Source Data Set ID : MGN-V-RDRS-5-CDR-ALT/RAD-V1.0 Software : MGMMAP Product Data Set ID : MGN-V-RDRS-5-GDR-TOPOGRAPHIC-V1.0 Software 'MGMMAP' ----------------- The MIT Altimetry and Radiometry Mapping Software (MGMMAP) reads Altimetry and Radiometry Composite Data Records (ARCDRs), and generates an image of a specified data field i a specified map projection. Each footprint datum is added with a weight and horizontal extent proportional to the appropriate ARCDR elements. This software will be released t Magellan Data Management Archive Team (DMAT) upon the completion of the nominal mission. Software Name : MGMMAP Software Type : N/A Software Release Date : N/A Node ID : N/A Cognizant Engineer : DR. PETER G. FORD Software Access Description : N/A
DATA_SET_RELEASE_DATE 1992-01-15T00:00:00.000Z
START_TIME 1990-09-15T04:22:14.871Z
STOP_TIME 1992-09-14T02:27:41.936Z
MISSION_NAME MAGELLAN
MISSION_START_DATE 1989-05-04T12:00:00.000Z
MISSION_STOP_DATE 1994-10-12T12:00:00.000Z
TARGET_NAME VENUS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MGN
INSTRUMENT_NAME RADAR SYSTEM
INSTRUMENT_ID RDRS
INSTRUMENT_TYPE RADAR
NODE_NAME Geosciences
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Overview : UNK
CITATION_DESCRIPTION Ford, P. G., MGN V RDRS 5 GLOBAL DATA RECORD TOPOGRAPHIC V1.0, MGN-V-RDRS-5-GDR-TOPOGRAPHIC-V1.0, NASA Planetary Data System, 1992
ABSTRACT_TEXT This data set contains the Magellan Global Topographic Data Record (GTDR). The range to surface is derived by fitting altimeter echoes from the fan-beam altimetry antenna as a function of time to Hagfors' radar backscatter model templates. The ranges are subtracted from the spacecraft radial coordinate (derived from Doppler tracking), yielding measurements of planetary radius. The data are filtered to remove low-frequency errors in the in-plane elements of each spacecraft orbit, and then re-sampled into sinusoidal, Mercator, and north and south polar stereographic projections at a resolution of about 5x5 kilometers per pixel.
PRODUCER_FULL_NAME PETER G. FORD
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