PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = " STEVEN GAISER 2006-07-06; initial version; R. Joyner, 2008-05-12, additional info; D. Kass, 2012-10-04, additional info; A. Kleinboehl, 2017-08-14, additional info; A. Kleinboehl, 2024-12-10, additional info " OBJECT = DATA_SET DATA_SET_ID = "MRO-M-MCS-5-DDR-V6.2" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "MRO MARS CLIMATE SOUNDER LEVEL 5 DDR V6.2" DATA_SET_TERSE_DESC = "The MCS atmospheric profiler detects vertical variations of temperature, dust, water ice, and water vapor concentrations in the Martian atmosphere. Derived Data Records (DDRs) in the form of Level 2 data products (retrieved geophysical profiles) are generated from the RDRs" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = TABLE ARCHIVE_STATUS = "LOCALLY ARCHIVED" START_TIME = 2006-09-24T16:00:00.000 STOP_TIME = NULL DATA_SET_RELEASE_DATE = 2008-05-22 PRODUCER_FULL_NAME = "DANIEL J. MCCLEESE" DETAILED_CATALOG_FLAG = "N" CITATION_DESC = "McCleese and Schofield, MRO MARS CLIMATE SOUNDER LEVEL 5 DDR V6.2, NASA Planetary Data System, MRO-M-MCS-5-DDR-V6.2, 2006." ABSTRACT_DESC = "NULL" DATA_SET_DESC = " 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 MCCLEESEETAL2007 and the INST.CAT file accompanying this data set. A mission overview and spacecraft and orbit characteristics are found in ZUREKANDSMREKAR2007 and in the INSTHOST.CAT and MISSION.CAT files. Detailed information addressing processing of the DDR data set are found in KLEINBOEHLETAL2009, KLEINBOEHLETAL2011 and KLEINBOEHLETAL2017. 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, atmospheric profile 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. 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). Fields that are not available for a specific profile contain -9999. 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. The individual records from the RDR tables observing the limb and surface are sorted and grouped, based on the geolocation of the observations. Groups of five limb viewing records are combined with pairs of on-planet views. Geophysical quantities are retrieved from each group of RDR records using spherical radiative transfer. These quantities are used to interpolate geophysical gradients which are then combined with the original groups of RDR records. Geophysical quantities are re-retrieved using two-dimensional limb radiative transfer. The resulting DDR records are placed into data tables. 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, are 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. 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). 4. 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 plane 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. 5. Added a single-scattering approximation to the radiative transfer for the calculation of limb radiances (see KLEINBOEHLETAL2011). The surface contribution to the scattering term is based on observed on-planet radiances when available, otherwise it is based on a surface temperature climatology. Version 3: 1. On-planet observations within a 2 degree great circle distance of the profile location of a limb measurement are selected if available. They are used in combination with the limb measurement for a surface temperature retrieval, a near surface atmospheric temperature retrieval and the atmospheric temperature profile in the lowest 20 km. Channel B1 (31.7 microns) is used to determine the surface temperature. Depending on the atmospheric opacity and viewing angle, either A1 (16.5 microns) or A1 and A2 (15.9 microns) are used for the atmospheric temperature retrievals. These are nadir-like views and the corresponding weighting functions are broader than the ones for limb views and have ~10 km vertical resolution. The algorithm meshes the two types of weighting functions. An overview on results obtained with this version is given in MCCLEESEETAL2010. 2. The radiance residual criteria for profile acceptance were slightly modified to be partly based on the absolute radiance and not just the NER. This avoided rejecting otherwise good profiles on the day side equatorial regions (where the warm atmosphere and surface create large radiances). These profiles will have somewhat larger uncertainties associated with them, reflecting the quality of the radiance fit. 3. Finally, the opacity criteria were tuned so the algorithm would better recognize when the limb path is too opaque for temperature sounding. Version 4: 1. The retrieval code was modified to execute a retrieval with climatological surface pressure in case at the end of a retrieval that included pressure as a retrieved quantity the criteria for a successful retrieval were not met. This leads to a significant improvement in retrieval coverage compared to previous versions. The climatological pressure is based on Viking Lander 1, adjusted for elevation. In Level 2 data files, profiles with retrieved pressure are marked with P_QUAL=0, while profiles with climatological pressure are marked with P_QUAL=9. Intercomparisons of this version with other datasets are found in SHIRLEYETAL2015 and HINSONETAL2014. 2. The representation of the polar CO2-ice cap was improved. It is now based on a circular, pole-centered fit to day/night temperature differences in the MCS B1 channel. 3. The selection of detectors for temperature retrieval has been optimized to be more conservative in the presence of large aerosol opacities. In addition, on-planet radiance measurements in channel A3 (15.4 microns) are now used for atmospheric temperature retrievals in high aerosol conditions. This extends the vertical range of temperature profile retrievals to lower altitudes by adding information comparable to a T15 temperature. On-planet radiance measurements in channels A2 and A3 can now also be included in the atmospheric temperature retrieval over CO2-ice if sufficient atmospheric opacity is present, extending the vertical range to lower altitudes. 4. The vertical coverage of aerosol profile retrievals has been extended. In addition, the climatological surface temperatures during the 2007 dust storm was adjusted to be more representative of conditions during a global dust storm. This yields a significantly better retrieval coverage during dust storm conditions. Version 5: 1. The main upgrade of this version is the use of two-dimensional limb radiative transfer for profile retrievals in a second pass of the retrieval process. The approach provides a correction of horizontal gradients along the line-of-sight of a limb view. Horizontal gradients in temperature, pressure, and dust and water ice extinction are characterized along the line-of-sight through information from neighboring measurements. The derived gradients are represented by means of two-dimensional radiative transfer in the forward model of the retrieval. Retrievals using two-dimensional radiative transfer are not performed for limb viewing directions deviating by more than 2 degrees in azimuth from the nominal 0 and 180 degrees of in-track measurements (those with OBS_QUAL values other than 0, 1 or 7). In Level 2 data files, the OBS_QUAL flag of profiles retrieved with two-dimensional radiative transfer is incremented by 10. Two-dimensional radiative transfer has been shown to greatly reduce biases in temperature and aerosol opacity caused by observational geometry, predominantly in the polar winter regions. A detailed description of the procedure together with examples is found in KLEINBOEHLETAL2017. 2. Furthermore, the derivation of the climatological surface pressure used in the retrieval was updated in order to use a scale height based on averages from radio science measurements. Version 6: 1. The primary upgrade of this version is the use of a method for retrieving aerosol profiles from MCS limb measurements that combines information from mid- and far infrared spectroscopic channels. The use of far infrared channels enables aerosol profile retrievals from limb measurements that typically reach about a scale height deeper into the atmosphere than would be possible using mid-infrared channels only. As in earlier versions of the algorithm, retrieval of dust extinction profiles is based on limb observations in MCS channel A5. If at a given tangent altitude the line-of-sight of the limb measurement in channel A5 reaches an optical depth > 1.9 the algorithm will invoke limb measurements of channel B1. Then B1 detectors will replace A5 detectors at altitudes below which channel A5 reaches an optical depth > 1.2. B1 detectors are selected for retrieval below the transition altitude as long as their line-of-sight optical depth stays below 1.9 and the surface contribution in their field-of-view stays below 10%. B1 is not used for aerosol retrieval in the winter polar vortex region where CO2 ice is likely to be present. Similarly, retrieval of water ice extinction profiles is based on limb observations in MCS channel A4. If at a given tangent altitude the line-of-sight of the limb measurement in channel A4 reaches an optical depth > 1.9 the algorithm will invoke limb measurements of channel B2. Then B2 detectors will replace A4 detectors at altitudes below which channel A4 reaches an optical depth > 1.2. B1 detectors are selected for retrieval below the transition altitude as long as their line-of-sight optical depth stays below 1.9 and the surface contribution in their field-of-view stays below 10%. In some cases the use of channel B2 might not be sufficient to allow a water ice retrieval down to the lowest scale height. This occurs occasionally within the aphelion cloud belt. In this case the retrieval can select channel B1 in addition to channels A4 and B2. The use of this channel for water ice only occurs under the condition that it is not used for dust retrieval and only in the equatorial region between 40S and 40N and in the aphelion season between Ls=0 and 180. Analogously to the other transitions to channels with less opacity, a transition is triggered when detectors are reevaluated and channel B2 reaches an optical depth > 1.9. Then B1 detectors will replace B2 detectors at altitudes below which the B2 channel reaches an optical depth > 1.2. Further details of this process, as well as retrieval examples, are given in KLEINBOEHLETAL2024. Even if a detector of a far infrared channel is used for retrieval at a given tangent altitude, the aerosol extinction will still be reported for the center frequency of the nominal retrieval channel for that aerosol in the mid-infrared (A5 for dust, A4 for water ice). Conversion of the extinction in the far infrared channel to the reference extinction in the mid-infrared channel is done using the empirical extinction efficiency ratios in Table 1. These ratios were derived empirically from MCS limb measurements as described in KLEINBOEHLETAL2024. For dust, a single conversion factor is used in all atmospheric conditions. For water ice it turned out that the observed variability in extinction efficiencies required the use of different conversion factors depending on geographic location and local time. For latitudes > 50N polar parameters are used. For latitudes between 80S and 40N at daytime, daytime equatorial parameters are used. Due to the sun-synchronous orbit of MRO with equator crossing times around 3 am and 3 pm local mean solar time, the time period when local true solar time (LTST) is between 9 am and 9 pm is considered daytime. For latitudes between 80S and 40N at nighttime, nighttime equatorial parameters are used. At latitudes between 40N and 50N the conversion parameters are interpolated in latitude between polar and the relevant daytime or nighttime equatorial parameters. At latitudes > 80S, the conversion parameters are interpolated in local time between daytime and nighttime equatorial parameters as the local time changes rapidly at these high latitudes due to the near-polar orbit of MRO. Information on whether a combination of mid- and far infrared channels or only mid-infrared channels were used for dust or water ice profile retrievals is provided in the DUST_QUAL and H2OICE_QUAL flags, respectively. Table 1: Extinction efficiency ratios between far infrared and mid-infrared MCS aerosol channels derived empirically (unless otherwise noted). From KLEINBOEHLETAL2024. _____________________________________________________________________ Aerosol type Channel pair Atmospheric conditions Extinction (center frequencies) efficiency ratio _____________________________________________________________________ Dust B1(316 cm-1) / A5(463 cm-1) n/a 0.504 _____________________________________________________________________ B2(254 cm-1) / A5(463 cm-1) n/a 0.299 (2) _____________________________________________________________________ Water ice B2(254 cm-1) / equatorial belt, day 0.327 A4(843 cm-1) equatorial belt, night 0.486 polar north 0.375 _____________________________________________________________________ B1(316 cm-1) / equatorial belt, day 0.123 (1) A4(843 cm-1) equatorial belt, night 0.229 (1) polar north 0.161 (1) (2) _____________________________________________________________________ (1) Derived from Mie calculations. (2) Not used for retrieval in current version. 2. The extended vertical range of retrievals enabled by the use of far infrared channels allows us to derive a column optical depth from the retrieved aerosol extinction profile by integrating the extinction profile from the surface to the highest retrievable altitude. Due to the limb sounding geometry of the MCS profile measurement, the lowest retrievable altitude in a profile can be a notable distance above the surface, depending on the aerosol loading of the atmosphere. For deriving dust column optical depth, the dust profile is extended homogeneously mixed below the lowest retrievable altitude, and this extension is included in the vertical integration in order to bridge the gap between the lowest retrievable altitude and the surface. For an aerosol column to be reported, it is required that the minimum retrievable altitude is within 15 km of the surface. This distance threshold is raised to 25 km in large-scale regional dust storms, and 35 km in global dust events as defined in Table 2. For reporting a dust column, it is additionally required that at the minimum retrievable altitude the dust extinction (at 463 cm-1) is larger than the water ice extinction retrieved simultaneously (at 843 cm-1). Dust and water ice columns are reported in the fields DUST_COLUMN and H2OICE_COLUMN, respectively. Reported column optical depths are not normalized to surface pressure. If for a particular measurement a dust column is reported, a surface pressure will also be reported in the field P_SURF. If this surface pressure is based on a pressure retrieval in the middle atmosphere, extrapolated to the surface, the flag P_QUAL will be set to 0 and an uncertainty associated with this surface pressure will be reported. If the reported surface pressure is only based on surface pressure climatology, flag P_QUAL will be set to 9 and no uncertainty associated with this surface pressure will be reported. While the retrieved surface pressure is not expected to be of sufficient quality for scientific studies, it is provided in order to put the user in the position to calculate a normalized dust column selfconsistently with the surface pressure that was used in the retrieval. Table 2: Start and end times of Global Dust Events and large-scale regional dust storms based on 200 K temperature contour at the 50 Pa pressure level at daytime in retrieval version 6. Peak times are based on peak temperatures at 50 Pa at daytime. Parameters of B-storms are only given for completeness, they do not trigger any modifications in the retrieval or quality control. From KLEINBOEHLETAL2024. ____________________________________________________________ Mars Year Storm Start Ls Peak Ls End Ls ____________________________________________________________ 28 A (1) 221.5 231 259.5 B 252.3 265 266 GDE 266 (2) 275 323.4 29 A 231.3 241 265.9 B 259.9 275 292.6 C 311.3 317 323.6 30 A 234.9 247 263 B 257.2 269 292.6 C (3) 316.8 323 329.6 31 A 209.2 213 237 B 248.4 263 287.4 C 312 319 325.1 32 A 218.3 227 247 B 254.9 263 292.6 C 311.3 313 326.3 33 A 217.8 223 241 B 249.9 269 291.5 C 324 327 341.9 34 GDE 188.8 211 270 (4) B 260.3 267 (4) 291.2 C 320.5 325 336.5 35 A 226.5 237 259 B 257.6 267 293.7 C 316.1 321 329.8 36 A 219.6 227 259 B 255.4 265 297.9 C 310.5 315 330.2 ____________________________________________________________ (1) Event may actually consist of two individual storms. (2) The formal 200 K contour start is Ls = 266; however, the atmosphere was already quite dusty so to properly capture the early activity, the actual retrieval considers the GDE to start at Ls = 262, such that the transition to the higher cutoff altitude and modified uncertainty calculation occurs starting at Ls = 260. (3) Storm defined based on a 197 K temperature contour. (4) Ls was estimated due to data gap. Errors for the derived column quantities are estimated based on the errors derived for independent individual layers of an aerosol profile. The total error of the aerosol column is calculated through a root-sum-square of the error in these layers from the surface to the maximum retrievable altitude. During global or large-scale regional dust storms, the lowest detector that is useable for limb retrieval may be at a sufficiently high altitude to lead to a large error based on the formal error estimate above. A correction to the uncertainty in the dust column optical depth is provided for these conditions, assuming that the homogeneously mixed extrapolation of the dust profile does not contribute to the uncertainty of the column. The correction considers the variability of the dust surrounding a particular measurement. The resulting error then represents a value based on the dust variation in time and space on a larger scale. This process is applied to the global dust storms as well as the A-storm in MY29 and the C-storms in MY34 and 36 in Table 2. Details on these error estimates can be found in KLEINBOEHLETAL2024. 3. Surface brightness temperature measurements from MCS are based on channel B1 because this channel has the least aerosol absorption. The characterization of the aerosol profile and column from the limb measurement allows the separation of the contributions of the surface and the atmosphere that contribute to the top-of-the-atmosphere temperature observed in channel B1. Surface brightness temperatures are retrieved using nadir/off-nadir radiative transfer that accounts for the contribution of dust and water ice aerosol based on the results of the limb retrieval as well as a climatological distribution of water vapor, assuming a surface emissivity of one. Errors in retrieved surface brightness temperature are based on a root-sum-square of the signal-to-noise in channel B1 and the quality of the fit. Retrieved surface brightness temperatures are reported if the fit is of sufficient quality and both dust and water ice columns are reported. If one or both aerosol columns are not reported, we evaluate the impact of that aerosol type on the retrieved surface brightness temperature based on the uncertainty in the aerosol and surface/atmosphere temperature contrast and report surface brightness temperature if the aerosol effect is less than 2 K. The error is then based on a root-sum-square of the original error and the uncertainty caused by the aerosol. Details on these retrievals can be found in KLEINBOEHLETAL2024. Processing - Level 1 (RDR) to Level 2 (DDR) =============================== RDR to DDR data processing can be divided into three phases: 1. Pre-processing. 2. Atmospheric profile retrieval. 3. Post-processing. For atmospheric profiles that are derived using two-dimensional radiative transfer in a second retrieval pass, the following steps are added to this procedure: 4. Interpolation. 5. Atmospheric profile retrieval with 2D radiative transfer. 6. Post-processing of profiles with 2D radiative transfer. Pre-Processing -------------- Pre-processing takes the MCS level 1 (RDR) data (calibrated radiances and geometry) as its input and performs the following functions: 1. Selects groups of 5 contiguous limb viewing measurements. 2. Selects groups of up to 2 contiguous on-planet measurements. 3. Uses radiance, roll, freeze and geometry tests to reject problem data. 4. Uses MOLA altimetry maps to assign surface altitude to measurements. 5. Outputs data files with input needed by the profile retrieval software. Atmospheric Profile Retrieval ----------------------------- Atmospheric 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 as well as accompanying on-planet measurements when available. 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 assuming spherical symmetry and 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 separately. 3. Calculate parameters needed for Level 2 data set. 4. Output formatted level 2 data for each good profile set that is not included in the retrieval with 2D radiative transfer. These three phases of level 1 to level 2 data processing are described in more detail in KLEINBOEHLETAL2009. Interpolation ------------- The interpolation is part of the 2D radiative transfer algorithm and derives interpolated fields of temperature, pressure, and dust and water ice extinction along the MRO orbit. It performs the following functions: 1. Ingest a suitable number of profiles retrieved with spherical symmetry along the MRO orbit that passed the quality control of the post-processing. 2. Derive interpolated fields of temperature, pressure, and dust and water ice extinction vs. altitude and distance along the MRO orbit track. 3. Outputs data files with line-of-sight gradients of these fields for the second pass of the atmospheric profile retrieval. Atmospheric Profile Retrieval with 2D radiative transfer -------------------------------------------------------- A second pass of atmospheric profile retrievals is performed with the same functions as described above. The first guesses and constraints are unchanged. Only the assumption of spherical symmetry is dropped. Instead, horizontal gradients in temperature, pressure, and dust and water ice extinction along the line-of-sight of the limb views is taken into account based on the results of the interpolation code. Post-Processing of profiles with 2D radiative transfer ------------------------------------------------------ Post processing of profiles retrieved with 2D radiative transfer is performed with the same software as described above, using the same quality criteria. It outputs formatted level 2 data for each good profile set. The interpolation approach and the atmospheric profile retrieval with 2D radiative transfer is described in more detail in KLEINBOEHLETAL2017. If the error in the dust column optical depth is adjusted in conditions of high dust loading this adjustment is performed after nominal retrievals for a sufficient time period are completed. 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 are used to generate the geometry fields in the MCS 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. All coordinates follow the MRO mission convention and use north latitude and east longitude. 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. " CONFIDENCE_LEVEL_NOTE = " Overview ======== The MCS philosophy has been to perform a series of careful quality control checks to make sure the retrieved results fit the observed radiances and not report places where they do not fit and/or are otherwise determined to be incorrect. This involves both the removal of complete profiles that are problematic and of individual regions of profiles that are otherwise well retrieved. This is not perfect, but the overall confidence level is high. Geometry and Resolution Description ------------- MCS is primarily a limb sounding instrument. For nominal limb scans MCS views the forward limb in the direction of spacecraft movement along the orbit track. For any given detector, the vertical resolution is defined by the appropriate weighting function (see KLEINBOEHLETAL2009) and is approximately 5 km. The horizontal weighting function is controlled by the spherical atmosphere and is approximately 250 km along the look direction (full-width half-max), centered at the tangent point. In moderately opaque conditions (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. The tangent point for each detector (or layer) is closer to the instrument than the one below it. This results in a shift of ~200 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 locations. The timestamp on each profile (columns 2, 3, and 4 of the DDR 1 record) is the mean of the time of the limb soundings (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. Quality Flags ------------- The quality flag (column 1) has limited meaning for the RDR records. A value of 0 indicates present and completely valid data; a value of 1 indicates a record header line; a value of 4 indicates the unpacking software had an issue with the time interpolation. The GQUAL field describes the quality of the geometry calculation of the instrument pointing of the RDR records used for each retrieval. Only radiances with adequate pointing are used for retrievals, however the field is used to flag cases where the geometry was manually corrected. See the MCS_DDR1.FMT for details. The RQUAL field describes the quality of the radiance calibration. The flag is not implemented yet, so for now it's always 0. The remaining quality fields primarily defined the coverage of the retrieval. P_QUAL is 0 in case of a successful pressure retrieval and 9 in case climatological pressure was used. T_QUAL indicates the vertical coverage of the temperature profile, DUST_QUAL, H2OICE_QUAL, and CO2ICE_QUAL indicate whether mid- and far infrared channels or only mid-infrared channels were used for aerosol retrieval and whether aerosol column quantities are reported (see MCS_DDR1.FMT for the meaning of each value). OBS_QUAL primarily defines the direction of the observation relative to the spacecraft (or velocity vector). This primarily identifies profile populations in local time. An OBS_QUAL value of 1 indicates a limb staring observation, which may have the limitations described below. The OBS_QUAL flag of profiles retrieved with two-dimensional radiative transfer is incremented by 10. SURF_QUAL is not used at present. Data Coverage and Quality ========================= The MCS detector array is usually placed on the limb to observe from the surface to over 80 km. In order to avoid detectors that overlap with the surface, the lowest limb detectors used are between 5 km and 10 km. The lowest part of the atmosphere is also often too opaque in the limb path. This is especially true for the aerosol channels. The retrieval uses on-planet observations (where the detectors were pointed at the surface) to retrieve the temperature down to the surface. On-planet views are not always available (or useable) and thus some of the profiles are terminated before reaching the surface due to the opacity in the limb path. This is the case for all aerosol profiles. The opacity and surface contribution also increases the uncertainty in the retrieved results near the surface. This is reflected in the error bars. Through most of the atmosphere, the MCS retrievals are very good (as reflected in the uncertainty terms in the dataset). Aerosols do reach undetectable levels fairly low in the atmosphere, but the temperatures usually extend to 80 km or above, although the signal at the top of the atmosphere is often quite low and results in larger uncertainties. The exception is in the cold polar night. The rapid decrease in density and often cooler temperatures result in running out of signal at slightly lower altitudes. The vertical coverage of the MCS profiles was somewhat compromised during the limb staring period (February 9, 2007 through June 18, 2007). During this period, the limb was not tracked around the orbit and was allowed to drift up and down. This resulted in covering approximately 0 km to 50 km in the southern hemisphere and 15 km to 80 km over the north pole (while the array extended to even higher altitudes, there is insufficient signal for routine retrievals). The poorer calibration during this time results in increased uncertainty at higher altitudes in the profiles as well as more overall uncertainty in the aerosol profiles. Starting September 2010 MCS has been performing regular limb scans with the instrument pointed perpendicular or at an angle to the orbit track. This was done in order to enhance the local time coverage of the MCS measurements (see KLEINBOEHLETAL2013). Views perpendicular to the orbit track cause the limb profile to be offset from the orbit track by about 1.5 hours in local time at low latitudes; this offset increases towards higher latitudes. For limb viewing directions deviating more than 2 degrees from the orbit track typically no accompanying on-planet measurements are available so no retrievals of surface quantities are performed and temperature profiles tend to terminate higher in the atmosphere than for nominal in-track measurements. The MCS team generally advocates for continuous global coverage, however MRO is a multi-purpose orbiter. A number of global and regional interruptions/gaps exist in the dataset. Many of the gaps are due to spacecraft or instrument activities and anomalies. These include instrument (MCS or other) calibrations, routine targeted imaging by the MRO cameras and telecommunications with landed missions. In addition, a number of larger gaps (24 hours to 3 months) exist due to spacecraft issues and the MCS pointing anomalies. With the landing of the Curiosity rover on August 6, 2012, MRO became the primary relay orbiter for this rover. MCS cannot perform measurements during relay passes, which creates a persistent data gap in the vicinity of the rover location (4.59S,137.44E). Only occasional measurements are available, either during scheduled campaigns for coordinated observations with the meteorological instruments on the rover or because relay passes were dropped. These measurements are typically limb-only and do not have accompanying on-planet views. With the landing of the Perseverance rover on February 18, 2021, MRO became the primary relay orbiter for this rover. MCS cannot perform measurements during relay passes, which creates a persistent data gap in the vicinity of the rover location (18.44N,77.45E). Only occasional measurements are available, either during scheduled campaigns for coordinated observations with the meteorological instruments on the rover or because relay passes were dropped. These measurements are typically limb-only and do not have accompanying on-planet views. Limitations =========== The altitude provided with the MCS observations (column 13 of the DDR 2 record) is based on the reconstructed knowledge of the spacecraft and instrument pointing. While this is adequately determined for MCS to be able to track the limb and select measurements the calculated altitude relative to the surface (or radius to the center of Mars) is only approximate. The uncertainties in the overall pointing is <= 3 km at the limb of Mars. The relative positions of the fields of view are significantly more accurate and the altitudes of the individual pressure surfaces relative to each other are accurate to <= 100 m. In the region where on-planet views are used to extend the temperature profile to the surface (the lowest 5 km to 25 km depending on channel selection), the vertical weighting function starts to resemble a nadir weighting function with a vertical resolution approaching 10 km. During times when there is significant aerosol (dust, water ice or CO2 ice) in the atmosphere at or above ~30 km, the limb is opaque in the 15 micron CO2 band in the region where MCS does its pressure retrieval. In these cases, a pressure retrieval is not possible and geophysical parameters are retrieved and reported based on a pressure profile derived from a climatological surface pressure and the hydrostatic equation. 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. " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = MARS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = MRO INSTRUMENT_ID = MCS END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_MISSION MISSION_NAME = "MARS RECONNAISSANCE ORBITER" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLEINBOEHLETAL2024" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLEINBOEHLETAL2017" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SHIRLEYETAL2015" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HINSONETAL2014" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLEINBOEHLETAL2013" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLEINBOEHLETAL2011" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "MCCLEESEETAL2010" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLEINBOEHLETAL2009" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "MCCLEESEETAL2007" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "ZUREKANDSMREKAR2007" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END