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.


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 by cleaning, merging and time-ordering the
packets. Duplicate data are deleted, missing packets are padded out,
and the data are organised by orbits. Data are then sorted by
instrument data types and instrument modes, and provided with
spacecraft position, velocity and attitude information.

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, but they are
uncalibrated.


Data
====

The list of EDR data Products is:

E_AIS           Active Ionosphere Sounding data frames with geometry
information

E_CAL           Data frames acquired in Calibration mode with geometry
information

E_RXO           Data frames acquired in Receive Only mode with
geometry information

E_SSx_ACQ_CMP   On-board-processed Subsurface Sounding data in
Acquisition state, with geometry information

E_SSx_TRK_CMP   On-board-processed Subsurface Sounding data in
Tracking state, with geometry information

Where 'x' stands for a number between 1 and 5.

EDR Data Products consist of two binary files, each of which contains
a PDS binary TABLE object, and a single detached PDS label describing
their 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.

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. Columns of the table contains the values of
parameters describing the geometry of observation for the
corresponding frame.


Ancillary Data
==============

No Ancillary data are provided.


Coordinate System
=================

Locations on the surface of Mars are expressed in planetocentric
coordinates. Longitude increases to the East and 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.


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.cosmos.esa.int/web/psa/psa-introduction


Confidence Level Overview
=========================

This data set contains all data for the Mars Express MARSIS for the
interval described above. Every effort has been made to ensure that
all data returned by the spacecraft is included and that processing is
accurate.


Review
======

The MARSIS EDR data have been reviewed internally by the Mars Express
MARSIS team prior to release to the PDS. The data set has been also
peer reviewed by the PSA.


Data Coverage and Quality
=========================

All data in the stated interval are included, to the best of our
knowledge and attempts to determine completeness. The instrument was
operated only briefly during cruise for periodic instrument health.
The late deployment of the MARSIS antenna allowed the start of science
operations only six months before the end of the nominal mission.

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.

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.