Data Set Overview : MARSIS Level 1b data products consist of the data produced by the instrument reconstructed from the scientific telemetry, sorted by instrument state and data type, and provided with spacecraft position, velocity and attitude information. Any other spacecraft telemetry relevant for calibration and processing (e.g. temperature of the receiver) is also be included.   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 : Level 1b processing starts from the telemetry data, as produced by the C&DH system on the spacecraft and passed to the telemetry subsystem: data are still in the form of transfer frame packets organised by contacts or ground tests data. Processing starts by cleaning, merging and time-ordering the packets. This means that duplicate data have been deleted, missing packets are padded out, and the data are organised by days (or orbits). Data then need to be sorted by instrument data types and instrument modes.  MARSIS Level 1b processing orders data in a useful way for the intended users (i.e. radar scientists) and applications (i.e. quick look to monitor hardware performance and higher-level processing), altering and manipulating them as little as possible to avoid the risk of introducing errors and, at the same time, including all necessary information from all relevant sources. Level 1b data are in scientifically useful form, i.e. individual spectra. These data are still uncalibrated.  MARSIS Level 1b data products consist of the data produced by the instrument reconstructed from the scientific telemetry, sorted by instrument state and data type, and provided with spacecraft position, velocity and attitude information. Any other spacecraft telemetry relevant for calibration and Processing (e.g. temperature of the receiver) is also be included.  Level 1b processing requires the acquisition of MARSIS scientific telemetry and any relevant spacecraft auxiliary data from the Mars Express Data Disposition System (DDS) in ESOC, and of SPICE kernels describing the spacecraft state and attitude from the Auxiliary Data Conversion System (ADCS) in ESTEC.  Both instrument telemetry and ancillary data are stored at the PI processing facility as they accumulate over the course of the mission, to provide the capability to reprocess data in case of errors or to accommodate new information referring to existing data sets.  Level 1b 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 EXPERIMENT DATA RECORD V1.0 Data Set contains scientific telemetry generated by the instrument, edited to remove duplications, zero-padded for missing packets, and correlated with geometric information needed to locate observations in space and time. No other kind of processing is applied to the data.  The list of EDR data Products is :  AIS_EDR : Active Ionosphere Sounding data frames with geometry information. CAL_EDR : Data frames acquired in Calibration mode with geometry information. RXO_EDR : Data frames acquired in Receive Only mode with geometry Information. SSx_yyy_CMP_EDR : On-board processed Subsurface Sounding data (either in Acquisition or Tracking state) with geometry information SSx_yyy_IND_EDR : Individual Echoes from Subsurface Sounding data (either in Acquisition or Tracking state). SSx_yyy_UNC_EDR : Uncompressed Subsurface Sounding data (either in Acquisition or Tracking state). SSx_yyy_RAW_EDR : Raw Subsurface Sounding data (either in Acquisition or Tracking state). Where x stands for a number between 1 and 5, while yyy stands either for ACQ or TRK.  AIS_EDR, CAL_EDR, RXO_EDR and SSx_yyy_CMP_EDR Data Products is 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, exactly in the same format (bit by bit) as they were produced by the instrument. 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 the same instrument state and after the same type of on-board processing during a single orbit. The second file constituting an EDR 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.  Subsurface data from Individual Echoes are the unprocessed version of data that are also down-linked in processed form. A frame of Individual Echoes consists of a variable number of raw echoes, because, to produce a constant along-track ground resolution, synthetic aperture (Doppler) processing performed on board requires a number of echoes that increases with altitude of the spacecraft. The Data Product consists in just one file containing a PDS header and the data themselves, because any additional geometric information would just duplicate similar information already provided in SSx_yyy_CMP_EDR GEO data files. File names contain the first ten digits of the spacecraft clock count corresponding to the time at which data were acquired.  Each record in a file contains a single unprocessed echo, preceded by auxiliary data and by a counter starting from 0 and increasing by one at each new echo. Echoes are ordered according to the time at which they were collected. Ancillary information is produced once per frame, and is thus the same for all echoes in a file: this duplication has been deemed necessary to simplify the data structure as much as possible.  The number of echoes required in Doppler processing is a function of frequency, as well as of spacecraft altitude. In a dual-frequency mode, the exact number of echoes collected at each frequency is contained in the Ancillary data and echoes within a frame are ordered by frequency before being ordered in time.  Subsurface UNC data are the uncompressed version of data that are also down-linked in fully processed form. Because they are structured exactly as CMP data, the only difference being the compression of individual echo samples from 4-byte IEEE real numbers to 1-byte integers, it has been chosen to produce one Data Product per orbit, just as for CMP data. The Data Product consists in just one file containing a PDS header and the data themselves, because any additional geometric information would just duplicate similar information already provided in SSx_yyy_CMP_EDR GEO data files. File names contains the four-digit number of the orbit at which data were acquired. The structure of UNC Data Products is identical to the one used in CMP FRM files. Because UNC data are down- linked through a dump of the flash memory, rather than through the scientific telemetry of the instrument, they do not come with a full set of ancillary data  Subsurface Raw Data are the unprocessed version of data that are also down-linked in processed form. A frame of Raw Data consists of a variable number of raw echoes, because, to produce a constant along- track ground resolution, synthetic aperture (Doppler) processing performed on board requires a number of echoes that increases with altitude of the spacecraft.  Because of this, it has been chosen to produce one Data Product per each frame of Raw Data, rather than one per orbit, similarly to Individual Echoes. The Data Product consists in just one file containing a PDS header and the data themselves, because any additional geometric information would just duplicate similar information already provided in SSx_yyy_CMP_EDR GEO data files. File names contain the first ten digits of the spacecraft clock count corresponding to the time at which data were acquired.  The structure of RAW Data Products is identical to the one used in IND files. Because RAW data are down-linked through a dump of the flash memory, rather than through the scientific telemetry of the instrument, they do not come with a full set of ancillary data.   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. There are four major structure types of the ancillary data : acquisition, tracking / individual echoes for subsurface modes, calibration / receive only and active ionosphere   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

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.