Data Set Overview
    =================
      All level zero accelerometer data are packaged by periapsis number for
      each aerobraking orbit.  Each orbit is identified by a folder with name
      Pyyy where 'yyy' is the three digit periapsis number. Level 0 y-axis
      accelerometer data are provided every 1.0 seconds during an interval of
      time that generally assures that the initial and final data points are
      taken at least 250 km above the surface of Mars.
 
 
    Parameters
    ==========
      Acceleration:        Units = m/s^2
                           Sampling Interval = 1 seconds
      Quaternions:         Units = dimensionless
                           Sampling Interval = 1 second
      Body rates:          Units = rad/s
                           Sampling Interval = 1 second
      Thruster on-times:   Units = sec (cumulative time thruster has fired)
                           Sampling Interval = various
      Orbital elements:    Units = various
                           Sampling Interval = once per orbit
 
    Data
    ====
     For each orbit, Level 0 data consist of four arrays in four files in
     folder Pyyy.  The array in 'ACCEL.TAB' is n-by-2 in size, where n is the
     number of seconds of data received during the aerobraking pass.  Column 1
     contains the time in UTC and follows the PDS format
     YYYY-DDDTHH:MM:SS.SSSZ where YYYY = four digit year, DDD = day of year,
     HH = hour, MM = minute, and SS.SSS = seconds.  T is a separator for date
     and time and the Z is the UTC Z.  Column 2 contains the 1.0 second
     y-acceleration for the second beginning at the time stamp.
 
     The array in 'RATEQUAT.TAB' is n-by-8 in size.  Column 1 is the time
     corresponding to the filtered rates and quaternions in the same UTC
     format as described for the acceleration above.  Columns 2-4 contain the
     angular rates about the x, y and z axes respectively.  Columns 5-8
     contain the quaternions.
 
     The third file, 'THRUSTER.TAB', is a k-by-9 array.  The first column is
     time as described above.  The next 8 columns are the cumulative reading
     of how long each thruster has been fired during the mission. Column two
     corresponds to thruster number one, column 3 with thruster 2, and so on.
     Column 9 corresponds with thruster 8.
 
     The fourth file, 'ORBELEM.TAB', is a 1-by-6 array of osculating elements
     at periapsis in the order semi-major axis (km), eccentricity, inclination
     (radians), longitude of the ascending node (radians), argument of
     periapsis (radians), and universal time of periapsis (seconds past
     J2000).
 
 
    Coordinate System
    =================
      Acceleration and rates are given in the MRO body system with the y-axis
      along the centerline of the bus, positive z on the same side of the bus
      as the high gain antenna and x completing the right hand system, ref.
      MROGNC2005. The quaternions define the orientation of the body axes with
      respect to the IAU Mars Centered Mars Equatorial at Time of Jan 1, 2000
      12:00.  Orbital elements are given relative to the IAU system.
 
 
    Timing
    ======
      The times in the data sets are UTC. For orbit calculations, ephemeris
      time was converted to UTC using the current ET-UTC conversion. No
      attempt was made during operations to synchronize the data types.

Confidence Level Overview
    =========================
     After the effects of rate filtering are included (see Limitations below),
     the confidence level for the rate and quaternion data is sufficient for
     reducing almost all the accelerometer data to the noise level. The only
     exception is during a thruster firing which can introduce spikes in the
     acceleration about 5 times the noise level. Accelerometer bias clearly
     drifts with temperature during the pass, but the change is about 1/5 of
     the noise level and no attempt was made to improve the calibration.
 
 
    Review
    ======
      All of the data types included in the level 0 product are utilized by
      the MRO operations to monitor the health of the spacecraft.  These data
      are reviewed in near real time to assure MRO performance.
 
 
    Data Coverage and Quality
    =========================
      Data coverage during an aerobraking pass varied as the orbital
      eccentricity decreased. Except for a few orbits, data were received
      throughout the mission for a sufficient time to cover the altitude range
      from periapsis to an altitude of 250 km.
 
 
    Limitations
    ===========
      Version 0 data are based on operational processing of the data. No
      attempt has been made to eliminate effects due to thruster firing,
      center of mass location errors, time lags between various data streams,
      or what appears to be an acceleration induced by fuel slosh.