Data Set Information
DATA_SET_NAME MRO MARS SHARAD 5 3D V1.0
DATA_SET_ID MRO-M-SHARAD-5-3D-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This archive contains 3D radar volumes produced from data acquired by the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) instrument, which uses a 15-25 MHz radio signal to probe up to several kilometers through low-loss materials like the polar layered deposits, and up to a few hundred meters in typical geologic materials. Reflections occur where there are significant changes in the dielectric permittivity among layered deposits, occurring over lateral scales of at least a few kilometers. Radar volumes are produced using a consistent set of synthetic-aperture radar processing parameters described in the accompanying User's Guide (see 3D_PROCESSING in the DOCUMENT directory). In the DATA directory, each 3D radar volume consists of an amalgamation of data collected over many SHARAD tracks crossing a given projected area. Each 3D volume contains values of the radar backscatter power, strength, or amplitude arranged in an ARRAY with either time delay or depth on the fastest varying (Z) axis, the projection X coordinate on the slowest varying axis, and the projection Y coordinate on the intermediately varying axis. The label file for each 3D volume contains information about the axes sampling intervals, projections, and data scaling. In the BROWSE directory, there are a series of JPEG-format images excerpted from each volume, showing 2D radargrams for every 100th sample in the X and Y directions and a radar time-delay or depth slice (map view with values at all X and Y locations) for every 25th sample in the Z (time delay or depth) dimension. The name of each browse image contains the corresponding X, Y, or Z index value. Each JPEG image has an accompanying label file. Processing : SHARAD transmits a linear frequency-modulated chirp signal with a bandwidth of 10 MHz (15-25 MHz frequency). Data processing is described in detail in the accompanying User's Guide (see 3D_PROCESSING in the DOCUMENT directory). In brief, the received signals are range-compressed by convolution with a model for the transmitted waveform, then processed using synthetic aperture radar techniques to improve the signal-to-noise performance. An empirical model for ionospheric delay effects is applied to bring the vertical registration among crossing tracks into better agreement. To prepare the data for 3D processing, a demigration process is applied to each input 2D radargram that effectively repositions reflectors to their zero-offset positions, resulting in a product that is similar to an unfocused radargram. The data are then assembled into a 3D binning grid, with a grid-cell size of 475 m by 475 m in an appropriate projection. A spatial interpolation process is applied, and the data are imaged in a 3D migration step that repositions reflectors from the locations where they were recorded to their two surface and subsurface positions. Data : As of 2021, the 2D radargrams read into the 3D processing contain 32-bit values that correspond to arbitrary units of received signal power. That may change in future products, since there is an interest in retaining amplitude information through the 3D processing step. Thus, the 3D data volumes in this archive may be presented in radar backscatter power, strength, or amplitude. The label file for each 3D volume will specify the data type in use for that volume. The vertical axis will be either delay time, with a resolution of 37.5 nanoseconds, or depth with a resolution of 5 meters. These values represent approximately a factor of two in oversampling with respect to the resolution dictated by the 10-MHz bandwidth of the transmitted chirp signal. Coordinate System : The coordinate system is specific to each 3D data volume, with the Planum Boreum and Planum Australe volumes using planetocentric, polar stereographic projections centered on each pole. See the label files for details. Please see 3D_PROCESSING.PDF in the DOCUMENT directory for more information.
DATA_SET_RELEASE_DATE 2021-04-13T00:00:00.000Z
START_TIME 1965-01-01T12:00:00.000Z
STOP_TIME N/A (ongoing)
MISSION_NAME MARS RECONNAISSANCE ORBITER
MISSION_START_DATE 2005-08-12T12:00:00.000Z
MISSION_STOP_DATE N/A (ongoing)
TARGET_NAME MARS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MRO
INSTRUMENT_NAME SHALLOW RADAR
INSTRUMENT_ID SHARAD
INSTRUMENT_TYPE RADAR
NODE_NAME Geosciences
ARCHIVE_STATUS ARCHIVED - ACCUMULATING
CONFIDENCE_LEVEL_NOTE Review : This data set was examined by a peer review panel in accordance with PDS procedures. Data Coverage and Quality : See 3D_PROCESSING.PDF in the DOCUMENT directory. Limitations : See 3D_PROCESSING.PDF in the DOCUMENT directory.
CITATION_DESCRIPTION Putzig, N. E., Foss II, F. J., Campbell, B. A., Perry, M. R., Phillips, R. J., Mars Reconnaissance Orbiter Shallow Radar 3D Data, MRO-M-SHARAD-5-3D-V1.0, NASA Planetary Data System, 2021.
ABSTRACT_TEXT This dataset contains three-dimensional volumes of radar sounding data for Mars collected by the SHARAD instrument on the Mars Reconnaissance Orbiter. Each 3D radar volume consists of an amalgamation of data collected over many SHARAD tracks crossing a given projected area. Each 3D volume contains values of the radar backscatter power, strength, or amplitude arranged in an array with either time delay or depth on the fastest varying (Z) axis, the projection X coordinate on the slowest varying axis, and the projection Y coordinate on the intermediately varying axis. The label file for each 3D volume contains information about the axes sampling intervals, projections, and data scaling.
PRODUCER_FULL_NAME NATHANIEL E. PUTZIG
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