Data Set Overview
    =================
      This document describes how the MRO Mars Climate Sounder (MCS)
      Derived Data Record (DDR) was generated, including data sources
      and destinations. The document is intended to provide sufficient
      information to enable users to understand the MCS DDR data product.
      The users for whom this document is intended are scientists who
      will analyze the data, including those associated with the Mars
      Reconnaissance Orbiter (MRO) Project and those in the general
      planetary science community.
 
      This document addresses the Mars Reconnaissance Orbiter Derived
      Data Record (DDR) data, and how the data are processed, formatted,
      labeled, and uniquely identified. This document discusses standards
      used in generating the product and software that may be used to
      access the product. The data product structure and organization is
      described in sufficient detail to enable a user to fully utilize
      the DDR data product.
 
      This data set consists of tables and supporting documentation from
      the final analysis of the Derived Data Record (DDR) and details how
      the DDR data set was derived from the Mars Reconnaissance Orbiter
      (MRO) Mars Climate Sounder (MCS) Reduced Data Records (RDR).
 
      The scientific goals, measurement objectives, and observational
      strategies for the DDR dataset are discussed in MCCLEESE ET Al 2006
      and the INSTRUMENT.CAT file accompanying this data set. Detailed
      information addressing processing of the DDR data set can be found
      in KLEINBOEHL 2008.
 
      MCS is an atmospheric sounder that makes one measurement every
      2.048 seconds, containing science, engineering and housekeeping
      data, whenever the instrument is powered on. The instrument
      operates in a single data-taking mode and observational
      flexibility is provided by actuators that allow telescope
      boresights to be directed over a range of 270 degrees in azimuth
      and elevation.
 
      Each instrument packet contains one measurement. The MCS DDR
      contains time-ordered, calibrated data for the entire MCS
      mission, starting with the initial instrument power-on in the MRO
      mapping orbit at 16:00 UT on 24th September 2006. The data are
      organized by UTC in monthly archive volumes, with 6 four-hour ASCII
      tables per day accompanied by detached headers. Each table row
      contains one measurement, and each column contains one calibrated
      science, engineering or housekeeping parameter.
 
      The MCS DDR contains all the profiles processed by the MCS science
      team. Gaps in the data set are only evident from discontinuities in
      the timing of table rows (see Data Coverage and Quality section).
      For convenience these are presented in the same table format with
      -9999 indicating time slots where data are not taken.  Geometry
      information is not provided for soundings when the instrument is
      slewing and a value of -9999 is used in all geometry fields.
 
 
      Data Product Acquisition
      ------------------------
        The MCS software collects 192 sixteen-bit science measurements
        from the focal plane interface electronics every 2.048 seconds,
        along with associated instrument engineering and housekeeping
        measurements. The science and housekeeping data are organized
        into data packets that are transmitted to the spacecraft at the
        same 2.048-second spacing. The data packets are downlinked to the
        MRO Ground Data System (GDS) and placed into the Raw Science Data
        Server (RSDS). MCS software queries the data from the RSDS and
        assembles them into EDR data tables, each covering a 4 hour time
        period.  The data in the EDR tables are then calibrated to
        produce the RDR tables.
 
        TBD
 
        Each MCS DDR data table will be variable in size; typically
        5-6 MB for each 4 hour time period; the volume of the DDR data
        product will be approximately 36 MB per day; 1 GB per month.
 
 
      Data Product Generation and Flow
      --------------------------------
        The MCS DDR data products, generated by the MCS Instrument Team
        at JPL, are constructed from the MRO/MCS RDR data and formatted
        according to the MRO/MCS DDR SIS. Meta-data derived from fields
        in the DDR, will be used to populate the PDS label.
 
        MCS science and engineering telemetry are transferred to the MRO
        Project RSDS. Once transferred, the MCS software automatically
        processes the telemetry into Level 0 EDR data products. The MCS
        EDR data products are re-processed into RDR data products.  The
        DDR data products are generated from the RDR data products and
        then archived locally at the MCS operation center. After an
        initial 6 month data validation period, the MCS team assembles
        the DDR data products and ancillary files into archive volumes
        and transfers the assembled volumes to the PDS Atmospheres Node.
        An archive volume consists of one month of data.  Volumes are
        delivered approximately every 3 months.
 
        The MCS DDR archive will be made available via data releases
        scheduled at three month intervals as specified in the Mars
        Reconnaissance Orbiter Project Data Archive Generation,
        Validation and Transfer Plan
 
 
      Data Processing Level
      ---------------------
        This document uses the Committee on Data Management and
        Computation (CODMAC) data level numbering system to describe the
        processing level of the DDR data product. MCS DDR data products
        are considered CODMAC Level 5, equivalent to NASA level 2. The
        DDR data files are generated from CODMAC Level 4 or Resampled
        Data, which are the time-ordered instrument science data.
 
 
      Changes from Previous Versions
      ------------------------------
        The following section describes the changes between the various
        versions of the archived volumes. This archive, regardless of
        version number, contains the changes listed below:
 
        Version 2:
        1. Modified measurement selection and fixed minor bugs.
 
        Version 3:
        1. Improved topography calculation to get a better estimate of the
           Mars horizon during small rolls (up to 9 deg limb angle).
        2. Optimized detector selection for temperature retrieval to achieve
           improved altitude resolution.
        3. Modified detector selection for temperature, dust, and water ice
           retrieval to better accommodate calibration uncertainties
           (particularly in low radiances) that occur during limb-staring
           (when the instrument is pointed at the limb with a fixed
           elevation angle for an extended period of time).
 
        Version 4:
        1. MCS Frames kernels changed to modify a fixed instrument tilt
           identified in off-track limb observations. The tilt of 0.431
           degrees was applied about an axis in the S/C XY plance inclined
           at 25.8 degrees to the S/C X-Axis. The elevation rotation in the
           Frames kernel was changed from -0.203 degrees to -0.030 degrees
           to compensate for the effect of the tilt change. The overall
           effect of these changes is to improve limb pointing in the
           vertical to better than 0.02 degrees in both in and off-track
           observations.
 
 
    Processing - Level 1 to Level 2
    ===============================
      Level 1 to 2 data processing can be divided into three phases.
 
      1.  Pre-processing.
      2.  Atmospheric profile retrieval.
      3.  Post-processing.
 
 
      Pre-Processing
      --------------
        Pre processing takes the MCS level 1 data (calibrated radiances and
        geometry) as its input and performs the following functions.
 
        1.  Selects groups of 5 contiguous limb-viewing measurements.
        2.  Uses radiance, roll, freeze and geometry tests to reject problem
            data.
        3.  Uses MOLA altimetry maps to assign surface altitude to
            measurements.
        4.  Outputs a data file with input needed by the profile retrieval
            software.
 
 
      Atmopheric Profile Retrieval
      ----------------------------
        Atmopheric profile retrieval is the most complex element of the
        MCS level 1 to level 2 processing suite. Its primary functions
        are to:
 
        1.  Read and average groups of 5-limb measurements with geometry.
        2.  Select average radiance measurements used for profile retrievals.
        3.  Retrieve profiles of temperature, dust and water ice as a
            function of pressure from radiances using a modified Chahine
            method.
        4.  Output results of profile retrieval in a form suitable for the
            post-processing software.
 
 
      Post-Processing
      ---------------
        Post-processing applies quality control to the retrieved profiles and
        outputs level 2 products suitable for input to the PDS. Its chief
        functions are to:
 
        1.  Read relevant data output by the Profile Retrieval software.
        2.  Select good profile retrievals based on radiance residual
            criteria for the pressure, temperature, dust, and water ice
            retrievals considered seperately.
        3.  Calculate parameters needed for Level 2 data set.
        4.  Output formatted level 2 data for each good profile set.
 
 
      All three phases of level 1 to level 2 data processing are described in
      more detail below (see [KLEINBOEHL 2008]).
 
 
    Data
    ====
      The MCS DDR is represented by a single PDS labeled table.  Each
      table is accompanied by a full PDS detached label with the same
      name except for suffix *.LBL. The PDS label completely describes
      the format and contents of the table.
 
      The naming convention for the tables and detached headers follow
      the time-organization of the data itself and use the following
      naming convention:
 
         yyyymmddhh_DDR.TAB; where:
 
              yyyy = year in which the data was acquired
                mm = month of the year in which the data was acquired
                dd = day of the month in which the data was acquired
                hh = hour of the day in which the data was acquired
 
      Note that the hour is UT (to within the nearest second) at the start
      of the coverage of the data contained in the file.  There are six
      possible values for hour.
 
      The first data after powering on in September 2006 are:
 
       - 2006092416_DDR.LBL:   The PDS label that describes the DDR data
       - 2006092416_DDR.TAB:   The actual DDR data formatted into a PDS
                                 TABLE object
 
 
    Ancillary Data
    ==============
      Ancillary data is used to generate the geometry fields in the MCR
      DDR product. This data comes from the navigation team and is
      assumed to be the best available. The following SPICE NAIF Kernels
      are used:
 
        1. Sclk to Scet kernel (sclk)
        2. Leap Seconds kernel (lsk)
        3. Frame reference kernel (fk)
        4. Planetary constants kernel (pck)
        5. Spacecraft ephemeris kernel (spk)
        6. Pointing kernel (ck)
 
 
    Coordinate System
    =================
      All positions and vectors in the MCS DDR product files are
      specified in Areocentric spherical coordinates.
 
 
    Software
    ========
      The MCS DDR products are formatted as columnar ASCII data; and as
      such, they can be read and manipulated by standard, public-domain
      software. For this reason, no special utilities are provided.
 
      The MCS DDR products are standard PDS-labeled tables that can be
      viewed with NASAView, an application developed by the PDS and
      available for a variety of computer platforms from the PDS web
      site.
 
 
    Archive Format
    ==============
      The individual archives were delivered to the PDS Atmospheres
      node as gzipped tar files via ftp.  Once validated they are
      available online with the archive volume structure.

Overview
    ========
      Since MCS is a limb sounding instrument, the location of the
      measurements is slightly complex geometrically.  For any given
      detector, the vertical resolution is defined by the appropriate
      weighting function (see Kleinboeul et al) and is approximately 5
      km. The horizontal weighting function is controlled by the
      spherical atmosphere and is approxmately xxx km along the look
      direction (full-width half-max), centered at the tangent point.  In
      moderately opaque (either due to aerosols or the temperature
      structure), this may be biased closer to the instrument than the
      tangent point, but since excessive opacity prevents the measurement
      from being used, this is a small effect.  The width perpendicular
      to the look direction is controlled by the horizontal fields of
      view and is approximately 8 km [TBV].
 
 
      Quality Flags
      -------------
        The tangent point for each detector (or layer) is closer to the
        instrument than the one below it.  This results in a shift of xxx
        km between the surface and a view at 80 km altitude along the
        line of sight.  To help with this issue (and indicate the look
        direction) the altitude latitude and longitude are given for each
        pressure surface of the retrieval(columns 13, 14, and 15 in DDR
        part 2).  While the views of the two MCS telescopes overlap,
        those of the individual arrays do not.  This results in an
        effective observation region of ~100 km wide perpendicular to the
        line of sight.
 
        We have also included a simple location for the profile
        (Profile_lat and Profile_lon, columns 13 and 14 in DDR 1) for
        applications where the exact viewing geometry and profile shape
        are not relevant.  These are also useful for searching for
        profiles in specific profiles.
 
        The timestamp on each profile (columns 2, 3, and 4 of the DDR 1
        record) is the mean of the time of the limb soudnings (from the
        RDR dataset) used for the retrieval.  The limb soundings used are
        always consecutive (thus at 2 second intervals), but the number
        may vary from 4 to 6 (the current version always uses 5
        soundings).  This time is used to determine the L_s and orbit
        number of the profile.
 
        Likewise, the Solar_lat, Solar_lon, Solar_zen, Profile_lat,
        Profile_lon, Profile_rad, Profile_alt and Limb_ang (columns 9,
        10, 11, 13, 14, 15, 16, and 17) are the mean of the relevant RDR
        field for the limb soundings used in the retrieval. The latter 5
        are thus the geometry for the instrument boresight tangent point
        (see the RDR for further description).  The LTST (column 12) is
        derived from the averaged fields for convenience.
 
 
    Data Coverage and Quality
    =========================
      TBD
 
 
    Limitations
    ===========
      TBD
 
 
    Review
    ======
      This archival data set was examined by a peer review panel prior to
      its acceptance by the Planetary Data System (PDS). The peer review
      was conducted in accordance with PDS procedures.
 
      Prior to creation of the final version of the archival data set,
      key elements of the archive were distributed for preliminary
      review.  These included electronic versions of example PDS labels,
      CATALOG files, and Software Interface Specifications (SISs).
      These materials were distributed to PDS personnel, the experiment
      investigator, and others, as appropriate.