Data Set Overview : All level zero accelerometer data are packaged by periapsis number for each aerobraking orbit. Each orbit is identified by a file with name Pyyy where where 'yyy' is the three digit periapsis number. Level 0 accelerometer data are provided every 1.0 seconds during an interval of time that generally assures 60 seconds of data before and after the spacecraft passes through the 170 km altitude 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-4 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 2-4 contain the 1.0 second acceleration for the second beginning at the time stamp. The body y direction in approximately into the wind.  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-4 array. The first column is time as described above. The next 4 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.  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. AACSDEFN. 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 ws 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 above the noise level. Accelerometer bias clearly drifts with temperature during the pass, but the change is well below 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 ODY 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, or time lags between various data streams.