I examined the documentation on Aug 17th and the data on Aug 20th. I note that some changes seem to have occurred to a few files between that work and your receipt of this review. That may affect the validity of my comments. The data that are included in this release seem to be of good quality, but much important ancilliary information is not included. I discuss some urgent points (address prior to release) that I believe are critical for any plausible use of the data, some useful points (address in a revision after release) that would help the user, and some minor points (address when convenient) that are mainly typos. I discuss some unusual features (possibly errors, possibly not) in the data in the useful points section. Urgent Points ============= Entry state, positions and orientations of IMUs and other reference frames, and measurement uncertainties What is the entry state? (3-component position and 3-component velocity in a clearly defined reference frame at a time that can be related to the times in the data files) Any use of the data that I can imagine will require this information. I doubt that it is classified, ITAR-sensitive, or otherwise restricted in any way. HIGHRATE data. What is the orientation of each of the three axes of each of the two IMUs with respect to the spacecraft/lander/backshell axes? References to any article that has diagrams of these axes would be very helpful. Again, it seems impossible to use the data without knowing this. TRANSFORMED data. What are the orientation of these axes with respect to the physical layout of the spacecraft? Are these orientations the same for transformations made to the entry capsule CM, to the lander CM, and to the backshell CM? Highrate data are either transformed to the entry capsule CM or to the rover/backshell CM. What are the positions of these three CMs? When are data transformed to one and when are they transformed to the other? The transformation is presumably based on the 3-component position of each IMU and its 3-axis orientation. Are these nominal positions and orientations available? This information will enable verification of whether the "nominal positions and orientations" are accurate. Errors. Most PDS data files have a column of uncertainties for each column of measurements. This volume does not. The accelerometer resolution and noise is discussed in CATALOG/INST.CAT, but the corresponding properties for the gyros are not. Neither are the gyro uncertainties discussed in Crisp et al. 2003. Some uncertainties need to be suggested for the gyros. Do the transformations (based on nominal properties, etc) introduce uncertainties? Since the CM and IMU positions are uncertain, they should do. Is there any reason to suspect instrument drift due to time, high g load, high heating, or anything else? Useful Points ============= TIRS and other events. A timeline of events that affect the EDL sequence (entry, parachute deployment, end of bridle unwinding, TIRS firing, RAD firing, bridle cut, first impact, roll-stop) would help users identify strange/corrupt data points without confusing them with parts of the nominal EDL sequence. I have plotted each data series to see if they look reasonable or not (smoothness, magnitude, periodicities, shape, etc), and all seem OK, but I have not had time to perform a reconstruction or any other analysis that would test that impression properly. I note that the gyro data continues to change after roll-stop. I presume that is the rotation of Mars with respect to J2000. If not, then something funny is happening. The delta-v series also continued to change after roll-stop. Prior to entry, MER is in free-fall, measures zero g on its accelerometers, has values of zero in its delta-v series, and is speeding up due to the gravitational acceleration of Mars. After landing, MER sits on the ground, measures 3.7 ms-2 acceleration, thus has steadily changing values in its delta-v series, but is not moving anywhere. This is very counter-intuititive. Should the documentation emphasise and explain what is happening here? Some data points seemed unusual to me (distinctly different from neighbours, etc). Some of them must correspond to interesting and known events during EDL, but some might correspond to unanticipated events during EDL and some might be instrument glitches. I list them here for your interest, referenced by row in their file, with row zero being the first in each file. 1HIGHRATE.TAB row 496 odd in BACKSHELL_IMU_DELTA_VEL_Y and BACKSHELL_IMU_DELTA_VEL_Z row 729 odd in ROVER_IMU_RATES_Y and ROVER_IMU_DELTA_VEL_Y Something major happens around rows 1522/1523 in ROVER_IMU_RATES_Y, ROVER_IMU_DELTA_VEL_X, ROVER_IMU_DELTA_VEL_Y, BACKSHELL_IMU_DELTA_VEL_X, BACKSHELL_IMU_DELTA_VEL_Y, and BACKSHELL_IMU_DELTA_VEL_Z. The clearest indication of this is in ROVER_IMU_RATES_Y. 1TRANSFORMED.TAB row 4697 odd in ROVER_IMU_QUATERNION_1,2,3,4 2HIGHRATE.TAB row 249 odd in BACKSHELL_IMU_DELTA_VEL_Y and BACKSHELL_IMU_DELTA_VEL_Z row 625 odd in ROVER_IMU_RATES_Y, ROVER_IMU_DELTA_VEL_Y, possibly BACKSHELL_IMU_DELTA_VEL_X as well. row 1526 (and over a few neighbouring timesteps) BACKSHELL_IMU_DELTA_VEL_X,Y,Z jump and timing seems to match with change in nature of oscillations in other data series 2TRANSFORMED.TAB row 4138 odd in BACKSHELL_IMU_ACCEL_Z only row 4923 odd in BACKSHELL_IMU_ACCEL_Z, possibly in BACKSHELL_IMU_ACCEL_Y Atmospheric reconstruction. The above comments relate to information necessary for a good trajectory reconstruction. The following are additional comments relevant for atmospheric reconstruction. What was the entry mass and area of each MER? These are needed in the drag equation. Is the MER aerodynamic database available yet? If so, where. If not, will it soon be available. If so, where? If not, why not? Can users get an acceptable substitute by using the Pathfinder database or some other database that is in the public domain? MINOR POINTS ============ AAREADME.TXT defines IMU as Inertial Mass Unit, not I Measurement U. Is the phrase IMU singular, plural, or both? I would expect it to be used as "one IMU, many IMUs". I eventually worked out that the lander was the bit that descended from the bridle and contained the rover, airbags, and some other stuff, but it took me a while to do so. Are entry vehicle, entry capsule, and entry shell synonymous? If so, pick one phrase and use it exclusively. If not, explain the differences. CATALOG/INST.CAT file: Each IMU is said to be 9cm by 9cm. The IMUs are 3D objects, not 2D objects. CATALOG/INST.CAT file: "Subsequent simultaneous backshell and lander" This line has a carriage return in it for no apparent reason. CATALOG/INST.CAT file: "Atmospheric entry occurred at a nominal height of 128 km". Entry is elsewhere defined as 3522.2 km radial distance. CATALOG/INST.CAT file (in calibration section) suggests that nominal cross-sectional area and angle of attack influenced the calculation of the accelerations. I don't see how that can be true. CATALOG/MER_INSTHOST.CAT: "was is referred to as MER-2". Either was or is. CATALOG/MER_INSTHOST.CAT: " not more than 100 W h of energy" Per hour, per sol, or per year? CATALOG/MER_INSTHOST.CAT: "engineering urposes" Urposes or purposes... CATALOG/MER_MISSION.CAT: "January 4, 2004" Are these (and other) dates UTC, PST, or some other time zone? The landing took place at different dates on UTC and PST, which has the potential to cause much confusion. CATALOG/MER_MISSION.CAT: "MOLA IAU 2000 frame" Spirit latitude quoted as 4.6S and as 14.6S. Which is it? CATALOG/MER_MISSION.CAT: " December 2003 special section in the Journal of Geophysical Research - Planets." Why not add a reference to the Garvin introduction article? JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. E12, 8060, doi:10.1029/2003JE002072, 2003 CATALOG/MER_MISSION.CAT: "bridle cut(6.5 m above" Insert a space. CATALOG/MER_MISSION.CAT: "contain H20 or OH" This looks like H-two-zero, not H-two-oh, to my eye. CATALOG/MER_MISSION.CAT: "long- range traverse" Delete space.