PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2023-03-01, S. MURCHIE edited" RECORD_TYPE = STREAM OBJECT = DATA_SET DATA_SET_ID = "MRO-M-CRISM-5-RDR-VNIRHYPERSPECTRAL-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "MRO CRISM VNIR HYPERSPECTRAL REDUCED DATA RECORD V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = {"TABLE", "IMAGE"} START_TIME = "N/A" STOP_TIME = "N/A" DATA_SET_RELEASE_DATE = 2023-03-01 PRODUCER_FULL_NAME = "SCOTT MURCHIE" DETAILED_CATALOG_FLAG = "N" ARCHIVE_STATUS = "IN QUEUE" CITATION_DESC = "Murchie, S., Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars VNIR Hyperspectral Reduced Data Record, MRO-M-CRISM-5-RDR-VNIR-HYPERSPECTRAL-V1.0, NASA Planetary Data System, 2023." DATA_SET_TERSE_DESC = "VNIR Hyperspectral Reduced Data Records for VNIR hyperspectral image cubes for CRISM (Compact Reconnaissance Imaging Spectrometer for Mars)." ABSTRACT_DESC = "This dataset contains CRISM VNIR Hyperspectral Reduced Data Records (VRDRs). VRDRs are organized into 30 subdirectories named by the Mars Chart containing the VRDR, e.g. MC01. Latitude and longitude limits of Mars Charts are given in the CRISM Data Product SIS and Data Archive SIS. A VRDR consists of several or more strips of VNIR hyperspectral mapping data mosaicked into a map tile. Thus a map tile is constructed from a large number of TRDRs. The mosaic is uncontrolled (accepting existing pointing data resulting in minor image mismatch at seams within a mosaic). The tile contains three images: Lambert albedo summary products DDR data corresponding to Lambert albedo, augmented with additional positional information The VRDR also contains one text file, listing the wavelengths present. Each file has a separate label. For every latitude or longitude in a VRDR, there is a value of Lambert albedo corrected for atmospheric and photometric effects, plus all the information needed to provide traceability to the source data. A global pattern of 1964 tiles each approximately 5 by 5 degrees in size is used, forming the major data product for VNIR hyperspectral mapping observations. Multiple VRDR tiles are in each of the 30 subdirectories." DATA_SET_DESC = " Data Set Overview ================= This volume contains portions of the CRISM VNIR Hyperspectral Reduced Data Record (VRDR) Archive, a collection of multiband images from the Compact Reconnaissance Imaging Spectrometer for Mars on the Mars Reconnaissance Orbiter spacecraft. Images consist of map-projected data corrected to units of Lambert albedo plus a text file listing the wavelengths present. Additional image data have had further corrections applied. Each image or text file is stored with a PDS label. This volume also contains an index file ('imgindx.tab') that tabulates the contents of the volume, ancillary data files, and documentation files. It may also contain browse images in PNG or IMG format, and HTML documents that support a web browser interface to the volume. For more information on the contents and organization of the volume set refer to the aareadme.txt file located in the root directory of the data volumes. Parameters ========== CRISM observing scenarios are constructed using a set of key variables ('configurations') which include the following. (All are selectable separately for the VNIR and IR detectors. Only a subset of the configurations are used to generate VRDRs.) Image source: Image data may be generated using digitized output from the detector, or using one of up to seven test patterns. Only data from the VNIR detector are included in a VRDR. Pixel binning: Pixels can be saved unbinned or binned 2x, 5x, or 10x in the spatial direction. No pixel binning in the spectral direction is supported. Data with 5x or 10x pixel binning are used in the generation of VRDRs. Row selection: All detector rows having useful signal can be saved, or alternatively an arbitrary, commandable subset of rows can be saved. VNIR hyperspectral mapping have also been collected using 107 VNIR channels 10x binned, or 92 channels 5x binned for a VNIR hyperspectral equivalent of VNIR+IR multispectral data. Those data are included in the VRDRs by extracting the 92 wavelengths that are common to both operating modes. Shutter position: Open, closed, or viewing the integrating sphere. The shutter is actually commandable directly to position 0 through 32. In software, open=3, sphere=17, closed=32. NOTE: during integration and testing, it was discovered that at positions <3 the hinge end of the shutter is directly illuminated and creates scattered light. Position 3 does not cause this effect, but the other end of the shutter slightly vignettes incoming light. Only data in which the shutter is open, and at position 3, may be processed to a VRDR. Pointing: CRISM has two basic gimbal pointing configurations and two basic superimposed scan patterns. Pointing can be (1) fixed (nadir-pointed in the primary science orbit) or (2) dynamic, tracking a target point on the surface of Mars and taking out ground track motion. Two types of superimposed scans are supported: (1) a short, 4-second duration fixed-rate ('EPF-type') scan which superimposes a constant angular velocity scan on either of the basic pointing profiles, or (2) a long, minutes-duration fixed-rate ('target swath-type') scan. Only fixed nadir-pointed data are processed to a VRDR. Processing ========== The CRISM data stream downlinked by the spacecraft unpacks into a succession of compressed image frames with binary headers containing housekeeping. In each image, one direction is spatial and one is spectral. There is one image for the VNIR focal plane and one image for the IR focal plane. The image from each focal plane has a header with 220 housekeeping items that contain full status of the instrument hardware, including data configuration, lamp and shutter status, gimbal position, a time stamp, and the target ID and macro within which the frame of data was taken. These parameters are stored as part of an Experiment Data Record (EDR), which consists of raw data. The data in one EDR represents a series of image frames acquired with a consistent instrument configuration (shutter position, frame rate, pixel binning, compression, exposure time, on/off status and setting of different lamps). Once data are assembled into EDRs, they are calibrated into TRDRs. Image data are converted to units of radiance using level-4 and level-6 CDRs, and analog housekeeping items in the text file (voltages, currents, and temperatures) have been converted into physical units using a level-6 CDR. Both files share a common label. The calibration algorithms are discussed at length in the CRISM Data Products SIS. A TRDR may also contain separately labeled multiband images in which radiance has been processed to one of the following: radiance in units of (W / (m^2 sr micron)) I/F (radiance divided by (pi * solar flux at 1 AU * heliocentric distance^2)), During construction of VRDRs, additional values generated from I/F include: Lambert albedo, and a set of derived spectral parameters (summary products) that provide an overview of the data set. The summary products include Lambert albedo, and key band depths or spectral reflectance ratios. To create Lambert albedo or most summary products, estimated corrections for photometric effects are applied to the I/F data. Information on physical properties and illumination conditions of the site observed in the EDR or TRDR is maintained in a Derived Data Record or DDR. There are 14 layers in each DDR: Solar incidence angle relative to areoid, at the same planetary radius as surface projection of pixel, units degrees. Emission angle relative to areoid, at the same planetary radius as surface projection of pixel, units degrees. Solar phase angle, units degrees. Areocentric latitude, units degrees N. Areocentric longitude, units degrees E. Solar incidence angle relative to planetary surface as estimated using MOLA shape model, units degrees. Emission angle relative to planetary surface as estimated using MOLA shape model, units degrees. Slope magnitude, using MOLA shape model and reference ellipsoid, units degrees. Slope azimuth, using MOLA shape model and reference ellipsoid, units degrees clockwise from N. Elevation relative to MOLA datum, units meters. TES thermal inertia, units J m^-2 K^-1 s^-0.5. TES bolometric albedo, unitless. Spare. Spare. The sequence of processing that creates an MRDR from the above products is as follows: (a) EDRs are assembled from raw data. (b) The radiance multiple band images in TRDRs are created from EDRs and Calibration Data Records, or CDRs, using a calibration algorithm discussed at length in an Appendix in the CRISM Data Products SIS. Briefly, a measurement of bias is subtracted from shutter-closed dark measurements, images of the interior of the integrating sphere taken with the shutter in an intermediate position, and scene data taken in the appropriate open position. Electronics artifacts are removed as detailed in the Data Product SIS, and the data are linearized. Dark measurements accompanying each the sphere and scene data are averaged by wavelength to improve signal-to-noise ratio, and scaled spatially to the dimensions of the scene and sphere data. Dark measurements are subtracted from both the scene and sphere measurements. The sphere measurements are averaged by wavelength to improve signal- to-noise ratio, and scaled spatially to the dimensions of the scene data. The scene and sphere measurements are divided by their respective exposure times. The scene data are divided by the sphere data, both now in units of corrected DN per second, to yield a unitless result, which is multiplied by a ground-calibration-derived model of integrating sphere spectral radiance, to yield scene spectral radiance. (c) Gimbal positions are extracted from the EDR housekeeping and formatted as a gimbal C kernel. (d) Using the gimbal C kernel and other SPICE kernels, DDRs are created. The surface intercept on the MOLA shape model is calculated for each spatial pixel (sample at the reference detector row). The angles of this pixel relative to the equatorial plane and reference longitude constitute the latitude and longitude of the pixel. For that latitude and longitude, solar incidence, emission, and phase angles are determined at a surface parallel to the areoid but having a radius from planetary center equivalent to that of the surface intercept of the shape model. Solar incidence and emission are also determined relative to the shape model itself. Using the latitude and longitude of the surface intercept of each spatial pixel, MOLA elevation is retrieved from a global elevation map and resampled into CRISM sensor space using nearest neighbor resampling. (e) Radiance is converted to I/F by dividing by (pi * solar flux at 1 AU * heliocentricdistance^2)). Solar flux is maintained in a level 4 CDR, and solar distance is written in the label to the radiance image. (f) I/F is converted to Lambert albedo to allow rapid identification of new ROIs and to quickly assess the information content of targeted observations. Some or all of the following corrections may be made: I/F is divided by cosine of the solar incidence angle The estimated contribution to and attenuation of the signal by atmospheric aerosols is normalized to a target value. (g) After the corrections discussed below are performed, TRDRs are map projected into VRDRs using the latitude and longitude information in the DDRs. Because of the mosaicked nature of an VRDR, the following protocol was used in VRDRs: A correction was used to correct for photometric effects, that does not attempt to correct for aerosol effects. This processing follows that applied to CRISM MRDRs, after removal of corrections that are specific to IR data. The photometric correction uses a Lambert assumption: IOF_corrected = IOF_uncorrected / cos(theta) where theta is the solar incidence angle. The photometric correction is calculated for each spatial pixel and is applied uniformly to all spectral channels. The spatial pixel specific incidence angle information is derived from the 'INA at areoid' band (incidence angle with respect to the Mars areoid) in the CRISM DDR (Derived Data Record) associated with the observation and segment under consideration. FILTERING TO REDUCE NOISE: The Ratio Shift Correction (RSC) procedure is the primary filtering process for VNIR hyperspectral mapping data. Within a given spectral band, a spatial column corresponds to a single detector element. The Ratio Shift Correction characterizes residual bias of each detector element through the evaluation of inter-column (or cross- track shifted) ratio statistics relative to a cross track model. Modifying the complexity of the underlying cross track model allows the RSC procedure to address high frequency column striping or low frequency banding while retaining real scene cross-track variability. NORMALIZATION OF STRIP-TO-STRIP RESIDUALS: At this stage of processing there are significant residual differences in I/F between overlapping strips of mapping data due to several effects: systematic errors in radiometric calibration between strips; and the presence of atmospheric dust and ice opacities different that the target values of dust opacity = 0.2, and ice opacity = 0.0. The residuals are only somewhat notable in Lambert albedo, but the magnitudes are in family with real spectral variations for many of the mineralogical spectral indices represented as summary products. To remediate these interstrip differences, an optimization procedure is performed in which derived values of surface reflectance are corrected to the values in the closest to ideal data among the mapping strips, using the millions of overlap and proximity relations in the map. Prior to optimization, the millions of areas of intersection and close proximity are identified. The differences between each such pair of strips is analyzed using graph theory, and the best-fit gain and offset describing the differences are recorded. Of course, each such solution will have some systematic error. In the optimization procedure, overall error is minimized (and the data set is optimized) by applying the gains and offsets in a weighted fashion, anchoring the output values to that part of the data which is closest to ideal. Those 'anchor' strips have the attribute of low dust opacity in the data as acquired as recorded in [MONTABONEETAL2015] data. This correction to Lambert albedo is propagated among all strips. Data ==== DATA DESCRIPTION: There is only one data type associated with this volume, the VNIR Hyperspectral Reduced Data Records or VRDRs. A VRDR consists of mosaicked, map-projected VNIR hyperspectral TRDRs. All data are represented as 32-bit real numbers. The VNIR hyperspectral map RDR contains three multiple-band images at 654 pixels/degree. The first multiple-band image is map-projected Lambert albedo. Only data from the VNIR detector are included. The size of the multiple-band image varies between map tiles. A typical multiple-band image might have 3072 pixels in the latitude direction, a comparable number of pixels in the longitude direction, and 92 pixels in the wavelength dimension, representing each of the selected channels in MSV mode. The second multiple-band image contains map-projected data from DDRs associated with a strip of multispectral data, used to derive Lambert albedo. Additional layers are present that are specific to individual VNIR hyperspectral strips used to assemble the tile, and are thus not contained in the DDR. This additional information provides traceability back to the source TRDRs: Solar longitude, units degrees Solar distance at time of measurement, units AU (versions 1,3) VNIR observation ID of constituent measurement The VNIR ordinal counter carried through from the source scene EDRs The VNIR column number carried through from the TRDR used to populate the MRDR; this identifies the VNIR wavelength calibration at the spatial pixel of the MRDR The ordinal number of the frame from the source VNIR TRDR; this together with column number, observation ID, and ordinal counter provides traceability back to a spatial pixel in a source EDR Time of day, hhmm.ss The third multiple-band image contains map-projected summary products. The list file, in ASCII format, contains wavelengths of each layer in the I/F and Lambert albedo images. A suite of mineral indicators and other measures of spectral shape and reflectivity, collectively called spectral summary parameters, is calculated from the Lambert albedo data. Formulations use the spectral summary parameter library of [VIVIANO-BECKETAL2014] which was developed to better detect the surprisingly large range of minerals found by CRISM and to reduce false positives. The bands in the SU image cube are given below along with a brief description of their significance. Users are referred to Table 3-12 of the CRISM Data Product SIS for detailed formulations and caveats. R770 = 0.77-micron reflectance (higher value more dusty or icy) RBR = Red/blue ratio (higher value indicates more nanophase iron oxide or sky illumination) BD530_2 = 0.53-micron band depth (higher value has more fine-grained crystalline hematite) SH600_2 = 0.6-micron shoulder height (select ferric minerals esp. hematite, goethite, or a compacted texture) SH770 = 0.77-micron shoulder height (select ferric minerals, less sensitive to BD920_2) BD640_2 = 0.64-micron band depth (select ferric minerals, esp. maghemite, but obscured by VNIR detector artifact) BD860_2 = 0.86-micron band depth (select crystalline ferric minerals, esp. hematite) BD920_2 = 0.92-micron band depth (crystalline ferric minerals and low-Ca pyroxene, or LCP) RPEAK1 = Reflectance peak 1 near 0.77 microns (<0.75 suggests olivine, 0.75 pyroxene, >0.8 dust) BDI1000VIS = 1-micron integrated band depth; VNIR wavelengths (olivine, pyroxene, or Fe-bearing glass) Ancillary Data ============== There is one type of ancillary data provided with this dataset: 1. The BROWSE directory contains browse images in PNG and IMG Format. See BROWINFO.TXT for more details. Coordinate System ================= Areocentric latitude and longitude, incidence, emission, and phase angles are derived from spacecraft attitude, gimbal position, pixel location, and MOLA shape model of Mars. The detailed procedure is described in the documentation on DDRs. The adopted projection convention is planetocentric, positive east, using the 2000 IAU prime meridian and pole of rotation. The projection varies in 5 degree latitude bands, using EQUIRECTANGULAR equatorward of 65 degrees latitude and POLAR STEREOGRAPHIC poleward of 65 degrees latitude. For the latitude band projected equirectangularly, the center latitude of projection is the equatorward boundary of each band to minimize distortion. For the latitude bands projected polar stereographically, the center of projection is the pole. In the north polar region, 0 longitude is down, and in the south polar region 0 longitude is up. The planet is divided into 1964 non- overlapping tiles, 654 pixels/degree. Their longitude width increases poleward to keep tiles approximately the same in area. Media/Format ============ The CRISM archive is made available online via Web and FTP servers. This is the primary means of distribution. Therefore the archive is organized as a set of virtual volumes, with each data set stored online as a single volume. As new data products are released they are added to the volume's data directory, and the volume's index table is updated accordingly. The size of the volume is not limited by the capacity of the physical media on which it is stored; hence the term virtual volume. When it is necessary to transfer all or part of a data set to other media such as DVD for distribution or for offline storage, the virtual volume's contents are written to the other media according to PDS policy, possibly dividing the contents among several physical volumes." CONFIDENCE_LEVEL_NOTE = " Confidence Level Overview ========================= All of the uncertainties in the constituent TRDRs and DDRs are propagated into the VRDRs. These are summarized below. - Water-ice clouds remaining in the data create residuals in VNIR spectral slope and color. - Real variations between adjacent mapping strips occur due to migration of dust and sand between the times of measurement of the strips of data. - Because of the fact that inter-strip normalization of residuals was performed over finite areas, small changes in Lambert albedo or summary products my occur across tile boundaries. Limitations =========== None." 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