Data Set Information
DATA_SET_NAME MARS EXPRESS MARS MARSIS REDUCED DATA RECORD SUBSURFACE V1.0
DATA_SET_ID MEX-M-MARSIS-3-RDR-SS-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : Level 1b data are further processed to produce Level 2 data, i.e. data which have been calibrated, range-compressed and corrected for ionosphere distortion. Auxiliary information for Level 2 data is not modified, and thus the volume of auxiliary data accompanying Level 2 data is the same as for Level 1b data. Scientific data, however, are converted from 1-byte integer counts from the analogue-to-digital converter of the instrument to 4-byte real voltages, producing an increase of science data volume by a factor of four. Parameters : MARSIS data are organized into groups of echoes called frames. A frame contains one or more echoes, with or without on-board processing. Each echo, depending on the kind of processing it underwent, is recorded either as a time series of signal samples, or as the complex spectrum of the signal itself produced by means of a FFT. Scientific data in a frame are complemented by a set of ancillary data, produced by the instrument and recording parameter values used in pulse transmission, echo reception and on-board processing. Processing : The primary task of Level 2 data processor is the Range Compression of the Marsis collected echoes during the subsurface modes (except for the SS2 Mode) and transmitted to the ground. These data are only compressed in azimuth on board (Doppler Filters output). Since these data have been distorted by the Ionosphere, we cannot use an ideal reference function (the ideal chirp) for range compression. Therefore we shall use the Contrast Method and/or the Front Surface Reflection (FSR) Method to estimate the Ionospheric distortion and to calculate a complex correction to modify the Ideal Reference Function in order to optimize the compressed signal. Note that the data related to the SS2 Mode will not be processed by the Level 2 processor, because they will be transmitted to the ground already compressed in time and also after a multi looking procedure. The Level 2 processor could elaborate the same data more times, using the information elaborated during the mission on the ionosphere and the instrument. This will signify a progressive improvement of the Level 2 data product. The Level 2 processing can be resumed in these steps : -| Data Decompression -| Ionospheric Dispersion Correction (Contrast Method and/or FSR Method) -| Range Compression Level 2 data distribution to the Co-Is and to the Mars Express mission archive is performed by ASDC. It is required by ESA that data products are delivered in batches of six-months worth of data within six months from the last data take (i.e. one year after the beginning of that particular data collection period), but it is necessary that level 1b processing be completed in a much shorter period, to allow enough time for level 2 data processing and data analysis within the MARSIS team before the expiration of the data proprietary period (which is the same six-month time span). Data : The MARS EXPRESS MARS MARSIS REDUCED DATA RECORD SUBSURFACE V1.0 Data Set contains subsurface-sounding data from the MARS EXPRESS MARS MARSIS EXPERIMENT DATA RECORD V1.0 Data Set that have been uncompressed, calibrated and, except for data acquired using the SS2 mode, range-processed after correcting for the distortion of the transmitted signal caused by the ionosphere. Geometric information needed to locate observations in space and time is also provided in the Data Set. The list of RDR data Products is : SSx_TRK_CMP_RDR : On-board processed Subsurface Sounding data Where x stands for a number between 1 and 5 RDR Data Products are made by two files, each of which contains a PDS binary TABLE object preceded by a PDS attached label describing its structure. The first file, called Frame file (FRM) contains the instrument data proper, organised into individual frames. Each frame corresponds to a record in the file, which is also a row in the PDS binary TABLE object into which frames are organised. A Data Product contains all frames acquired using the same instrument mode in tracking (TRK) state during a single orbit. . The second file constituting an RDR Data Product is called a Geometry file (GEO), and contains one record, corresponding to one line of the PDS binary TABLE object into which data are organised, for every frame in the corresponding FRM file. Columns of the table contain the values of parameters describing the geometry of observation for the corresponding frame. Ancillary Data : Each frame of MARSIS data (with the exception of frames stored in flash memory) carries a 228 byte header of ancillary data, containing necessary information for subsequent analysis of the data and further processing. The exact content of the ancillary data depends on instrument mode. Coordinate System : Locations on the surface of Mars are expressed in planetocentric coordinates. Longitude is comprised in the range 0 - 360 degrees. Software : Marsis data products can be read by the PDS software NASAView, which reads a PDS label and displays the associated image or table. NASAView has been tested on both EDR and RDR data products. Media/Format : The standard distribution format for the data is transfer through Internet from the Planetary Science Archive of ESA, which can be accessed at the following URL: http://www.rssd.esa.int/psa
DATA_SET_RELEASE_DATE 2007-11-30T00:00:00.000Z
START_TIME 2005-06-01T12:00:00.000Z
STOP_TIME 2005-12-31T12:00:00.000Z
MISSION_NAME MARS EXPRESS
MISSION_START_DATE 1997-10-31T12:00:00.000Z
MISSION_STOP_DATE N/A (ongoing)
TARGET_NAME MARS
PHOBOS
TARGET_TYPE PLANET
SATELLITE
INSTRUMENT_HOST_ID MEX
INSTRUMENT_NAME MARS ADVANCED RADAR FOR SUBSURFACE AND IONOSPHERE SOUNDING
INSTRUMENT_ID MARSIS
INSTRUMENT_TYPE RADAR
NODE_NAME Planetary Science Archive
ARCHIVE_STATUS ARCHIVED_ACCUMULATING
CONFIDENCE_LEVEL_NOTE Review : These data have been reviewed by the instrument team and are of the highest quality that can be generated at this time. Science results based on these data have been published in journals. The dataset is currently being reviewed by the Plannetary Science Archive of ESA. Data Coverage and Quality : Data in this dataset have been acquired only in the last six months of the nominal mission, because of the delay in the deployment of the MARSIS antenna. Because of this, coverage is limited mainly to southern latitudes. Data quality in a data product label is indicated through the DATA_QUALITY_ID element, and measures the integrity of the telemetry stream from the instrument. The permitted values of DATA_QUALITY_ID are the following: -1: percentage of corrupted data not available 0: no corrupted data 1: less than 2% corrupted data 2: less than 5% corrupted data 3: less than 10% corrupted data 4: more than 10% corrupted data Limitations : There are no known limitations at this time.
CITATION_DESCRIPTION Picardi, G. et al. MARS EXPRESS MARS MARSIS REDUCED DATA RECORD SUBSURFACE V1.0 MEX-M-MARSIS-3-RDR-SS-V1.0, Dipartimento INFOCOM, 2005.
ABSTRACT_TEXT This dataset contains the Level 1b data that have been processed to produce calibrated echoes of subsurface reflections: thus, they are the data set of choice for geological analysis of the structure and layering of the Martian subsurface.
PRODUCER_FULL_NAME GIOVANNI PICARDI
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