Data Set Information
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| DATA_SET_NAME |
MRO CRISM MAP-PROJECTED TARGETED REDUCED DATA RECORD V1.0
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| DATA_SET_ID |
MRO-M-CRISM-5-RDR-MPTARGETED-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : This volume contains the CRISM Map-projected Targeted Reduced Data Record (MTRDR) archive, a collection of multiband image cubes derived from targeted (gimbaled) observations acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter (MRO) spacecraft. The primary MTRDR product (IF) consists of spectral reflectance (I/F) data corrected for photometric, atmospheric, and instrumental effects, that has been map-projected in accordance with MRO project standards, with an associated text file that contains wavelength information (WV) for each spectral band. For observations for which both VNIR (S-detector) and IR (L-detector) hyperspectral image cubes were acquired, the data from the VNIR detector has been spatially registered and concatenated to the IR data to form a full spectral range image cube that is map-projected with bad bands removed. The MTRDR product set also includes a spectral summary parameter (SU) image cube calculated using an updated version of the CRISM spectral summary parameter library [VIVIANO-BECKETAL2014], a refined spectral summary parameter (SR) image cube which is a noise-remediated version of the SU product, a series of browse product (BR) spectral content visualizations which are composed of thematically related summary parameters, a set of data processing information (IN) maps that illustrate spatial/spectral residuals related to the VNIR/IR spectral concatenation and empirical atmospheric correction, and a map-projected version of the IR (L-detector) Derived Data Record (DE) for the subject targeted observation. The DE multiband image contains the same information as the DDR for the IR part of the observation (photometric angles, MOLA topography, etc.) except that it is in map-projected form. The constituent products can be identified by the filename/product ID activity string prefix and the product type string: CCCNNNNNNNN_XX_AAAAAD_TTTV CCC : Class Type (e.g. FRT, HRL, HRS) NNNNNNNN : Hexadecimal observation ID XX : Hexadecimal observation segment counter AAAAA : Activity string - composed of a 2-character prefix followed by 3-digit macro ID. The 2-character prefix describes the contents of the file, and includes IF - Corrected I/F SU - Spectral summary parameters SR - Refined spectral summary parameters BR - Browse product IN - Data processing information DE - Derived data product WV - Wavelength information for the corrected I/F image The 3-digit macro ID identifies the instrument macro that was being run to collect the central scan part of the observation that was processed and is represented in the product D : sensor ID (S : VNIR; L : IR; J : Joined (VNIR + IR)) TTT : Product type string MTR - Map-projected Targeted Reduced Data Record, or MTRDR V : Version number In the MTR data product set the version number (V) is the radiometric calibration version number inherited from the source TRDRs, and the product type string (TTT) is MTR for Map-projected Targeted Reduced Data Record. For browse product (BR) files, the 3-digit macro ID is replaced with a 3-character product identifier. All MTRDR image data have been map-projected in accordance with MRO project standards. The image data are stored as multi-band images (.IMG) with associated PDS labels (.LBL) and ENVI headers (.HDR). The wavelength information is stored in text files (.TAB) also with associated PDS labels (.LBL). The browse products (BR) are stored in the Portable Network Graphics (.PNG) format with alpha channel transparency, referenced by the associated PDS labels (.LBL). MTRDR browse products also include the scaled data values of the .PNG file in a PDS image file (.IMG) and have an associated ENVI header file (.HDR), allowing the user to load the PDS image file into the ENVI software application. Processing : The Map-projected Targeted Reduced Data Record (MTRDR) data processing pipeline produces both TERs and MTRs. It integrates a series of standard and empirical spectral corrections, spatial transforms, parameter calculations, and renderings in the generation of a high level suite of analysis and visualization products. The TER/MTR data processing flow is illustrated in Figure 2-9a in the CRISM Data Product SIS and the TER/MTR data processing pipeline is described in detail in the CRISM Data Product SIS Appendix P1. The CRISM TERs and MTRs are paired data product types where an MTR is a map-projected version of a TER. The only exception to pairing of the products is that the MTR suite contains a DE product which is a map-projected version of the IR (L-detector) DDR associated with the source targeted observation. All of the TER products are in the IR (L-detector) sensor space, so the same map-projection transformation is used to generate all of the MTRs for a given source targeted observation. The bands in the MTR SU, SR, BR, and IN products match the TER precursors (and the bands in the MTR DE product match the DDR precursor). The TER IF products also contain all the channels in the source VNIR and IR TRDRs, whereas spectral channels with questionable radiometry ('bad bands') are not propagated from the TER IF to the MTR IF product (thus there are fewer spectral channels in the MTR spectral image cube as compared to the TER precursor). The TER/MTR data processing procedures through the generation of the MTR product set are summarized below. Detailed descriptions are provided in Appendix P1 of the CRISM Data Product SIS. Steps 1 through 10 describe processing done during generation of a TER and steps 11 through 13 describe post processing and map projection that is conducted to transform that to an MTR. 1. Lambertian Photometric Correction (PHT) The spectrum of each spatial pixel is divided by the cosine of the incidence angle at that pixel. 2. Modified 'Volcano Scan' Atmospheric Correction (ATM) (IR only) The spectrum of each spatial pixel is divided by an empirically derived atmospheric transmission spectrum scaled to match the depth of the 2000-nm CO2 absorption. The correction is derived from CRISM nadir-pointed observations crossing the full range of relief of Olympus Mons. To account for small wavelength shifts of the IR detector over the mission, the 'best' out of a series of temporally variable corrections is selected from a menu based on minimizing the residual from the correction. In addition, not all parts of the 2000-nm CO2 absorption - actually an overlapping series of narrower absorptions - scale the same with path length. An additional correction of the resulting artifact near 2070 nm is superimposed to mitigate the artifact. 3. Ratio Shift Correction (RSC) (IR only) A statistically robust 'destriping' procedure is applied to the ATM-corrected image cube to mitigate the reintroduction of spatial column-oriented residuals, as viewed in IR detector space. These originate from spurious values in either ground calibration data or flight scene or calibration data, and were filtered out of the IF version of the source TRDR in a statistically robust fashion. However some are reintroduced at a low level when the empirically based ATM correction is applied. An analogous procedure to that used in the IF version of the source TRDR is reapplied to correct reintroduced artifacts. 4. Empirical Geometric Normalization (EGN) Systematic brightness variations in the along-track direction of a CRISM targeted observation result from the continuously varying observation geometry (gimbal motion) that is used to take out along-track motion of the field of view. The variable phase angle and atmospheric path lengths that result from this procedure modulate the fractions of radiance at sensor that are contributed by the surface and atmosphere as a function of wavelength. The effects are characterized as a function of the continuously variable observation geometry along-track, and normalized to the geometry at the frame of the observation which is closest to nadir. 5. Empirical Smile Correction (ESC) Spectral smile is an optical artifact whereby a single wavelength does not translate uniquely to a single row of detector elements on either the VNIR or IR detector. As a result, the wavelength of a single detector row - which translate into a single band of a multiband image file - drifts up and down across the field of view. Where at-sensor radiance changes as a function of wavelength, the sampled radiance also therefore systematically changes. Spectral smile effects are mitigated using a fit of along-track-averaged cross-track variation in radiance that is constrained to have a form consistent with spectral smile effects. Cross-track variation is normalized to the 100-colunm wide strip near the center of the detector that corresponds to the reference wavelength sampling vector (also called the 'SW' CDR, in the CDR directory of the CRISM EDR archive). 6. VNIR/IR Sensor Space Transform (XFM) The focal lengths of the VNIR and IR parts of the CRISM instrument are slightly different, resulting in about a 1 percent difference in pixel scale. Post-processing is required to register the two parts of the data set; however, how they map onto Mars' surface is known very accurately. The corrected VNIR spectral data are remapped into the correct location in IR sensor space based on the known surface intercepts of each spatial pixel, using a nearest-neighbor sampling. The spectral concatenation of the transformed corrected VNIR data and the corrected IR data results in a fully corrected, full spectral range data product (a TER IF image cube, accompanied by a TER WV wavelength table). 7. Data Processing Information Generation (INF) Residuals from the joining of the VNIR and IR data around 1000 nm and from correction for atmospheric CO2 around 2000 nm are parameterized in the IN image cube, to identify for data users the wavelengths and spatial locations of data artifacts. There is also traceability back to line and sample coordinates in the source VNIR and IR image cubes. The bands in the IN product consist of: 'VNIR/IR Spectral Continuity Residual' - the difference in corrected I/F between the VNIR and IR data at the wavelength of the join. 'VNIR/IR Spatial Gradient Residual' - the difference in the sampling effects between the VNIR and IR, which can create a spectral artifact, measured as the dot product of the normals to a brightness gradient fitted to 3x3 spatial pixel kernels at wavelengths above and below that of the join. 'ATM Correction Spectral Shift Artifact' - a measure of the magnitude of a ringing-like artifact of correction for the atmospheric CO2 band near 2000 nm that arises when the IR wavelength calibrations of the source IR data and the IR data used to derive the atmospheric correction spectrum are slightly misaligned, typically by a fraction of a nanometer. 'VNIR Sample' - sample coordinate of the VNIR part of the TER spectrum in the source VNIR TRDR. 'VNIR Line - line coordinate of the VNIR part of the TER spectrum in the source VNIR TRDR. 'IR Sample' - sample coordinate of the IR part of the TER spectrum in the source IR TRDR. 'IR Line' - line coordinate of the IR part of the TER spectrum in the source IR TRDR. 'VNIR/IR Offset' - the difference in meters between the centers of the corresponding pixels of the VNIR and IR source products projected onto the Martian surface. 'VNIR/IR Mask' - a boolean indicator of which pixels are populated from the VNIR and IR source products, where 0 : populated and 1 : not populated. 8. Spectral Summary Parameter Generation (SUM) A suite of mineral indicators and other measures of spectral shape and reflectivity, collectively called spectral summary parameters, is calculated from the TER IF data using the revised and expanded spectral summary parameter library of [VIVIANO-BECKETAL2014] and stored in the SU product. The bands in the SU and refined summary parameter (SR) 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 compacted texture) SH770 : 0.77-micron shoulder height (select ferric minerals, less sensitive to LCP than SH600_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) BDI1000IR : 1-micron integrated band depth; IR wavelengths (crystalline Fe2+ silicates) R1330 : IR albedo BD1300 : 1.3-micron absorption associated with Fe2+ substitution in plagioclase OLINDEX3 : Broad absorption centered at 1 micron (olivine strongly >0, also Fe-phyllosilicate) LCPINDEX2 : Broad absorption centered at 1.81 micron (pyroxene is strongly +; favors LCP) HCPINDEX2 : Broad absorption centered at 2.12 microns (pyroxene is strongly +; favors HCP) VAR : 1.0-2.3-micron spectral variance ISLOPE1 : Spectral slope 1 (from 1.185 to 2.530 microns; ferric coating on dark rock) BD1400 : 1.4-micron H2O and -OH band depth (hydrated or hydroxylated minerals) BD1435 : 1.435-micron CO2 ice band depth BD1500_2 : 1.5-micron H2O ice band depth ICER1_2 : CO2 and H2O ice band depth ratio BD1750_2 : 1.75-micron H2O band depth (gypsum or alunite) BD1900_2 : 1.9-micron H2O band depth (hydrated minerals except monohydrated sulfates) BD1900r2 : 1.9-micron H2O band depth (hydrated minerals except monohydrated sulfates) BDI2000 : 2-micron integrated band depth (pyroxene) BD2100_2 : 2.1-micron shifted H2O band depth (monohydrated sulfates) BD2165 : 2.165-micron Al-OH band depth (pyrophyllite, kaolinite-group minerals) BD2190 : 2.190-micron Al-OH band depth (beidellite, allophane, imogolite) MIN2200 : 2.16-micron Si-OH band depth and 2.21-micron H-bound Si-OH band depth (doublet; kaolinite) BD2210_2 : 2.21-micron Al-OH band depth (Al-OH minerals) D2200 : 2.2-micron dropoff (Al-OH minerals) BD2230 : 2.23-micron band depth (hydroxylated ferric sulfate) BD2250 : 2.25-micron broad Al-OH and Si-OH band depth (opal, Al-OH minerals) MIN2250 : 2.21-micron Si-OH band depth and 2.26-micron H-bound Si-OH band depth (opal) BD2265 : 2.265-micron band depth (jarosite, gibbsite, acid-leached nontronite) BD2290 : 2.29-micron Mg,Fe-OH band depth / 2.292-micron CO2 ice band depth (Mg-OH and Fe-OH minerals, Mg carbonate, and CO2 ice) D2300 : 2.3-micron dropoff (hydroxylated Fe,Mg silicates strongly >0) BD2355 : 2.35-micron band depth (chlorite, prehnite, pumpellyite, carbonate, serpentine) SINDEX2 : Inverse lever rule to detect convexity at 2.29 microns due to 2.1- and 2.4-micron absorptions (hydrated sulfates strongly >0) ICER2_2 : 2.7-micron CO2 ice band MIN2295_2480 : Mg Carbonate overtone band depth and metal-OH band MIN2345_2537 : Ca/Fe Carbonate overtone band depth and metal-OH band BD2500_2 : Mg Carbonate overtone band depth BD3000 : 3-micron H2O band depth (adsorbed and bound H2O and ice) BD3100 : 3.1-micron H2O ice band depth BD3200 : 3.2-micron CO2 ice band depth BD3400_2 : 3.4-micron carbonate band depth CINDEX2 : Inverse lever rule to detect convexity at 3.6 micron due to 3.4- and 3.8-micron carbonate absorptions R440 : 0.44-micron reflectance R530 : 0.53-micron reflectance R600 : 0.60-micron reflectance IRR1 : IR ratio 1 (R880/R997; aphelion ice clouds >1, seasonal ice clouds and dust <1)) R1080 : 1.08-micron reflectance R1506 : 1.51-micron reflectance R2529 : 2.53-micron reflectance BD2600 : 2.6-micron H2O band depth IRR2 : IR ratio 2 (R2530/R2210; aphelion ice clouds vs. seasonal ice clouds or dust) IRR3 : IR ratio 3 (R3500/R3390; aphelion ice clouds vs. seasonal ice clouds or dust) R3920 : 3.92-micron reflectance, evaluated from the 5 'good bands' closest in wavelength to 3920 nm 9. Refined Spectral Summary Parameters (SRE) The majority of the parameter bands are filtered using a variant of the filtering algorithm used on IR TRDR I/F image cubes, to mitigate spurious noise structure that remains and is accentuated in the summary products. The noise remains because the filtering applied to the TRDRs uses a conservative threshold for calling an outlying pixel 'noise' and interpolating through it, to avoid altering the actual information content of the data. Low-magnitude noise that 'leaks though' TRDR processing appears larger in some of the summary products prior to filtering because their dynamic range is typically small compared to the I/F data. 10. Browse Product Generation (BRS) Browse products are greyscale or RGB composites of 1 or 3 thematically related summary products remapped to 8 bits that allow for a quick assessment of the information content of the source spectral data TER IF image cubes). The MTRDR browse product set consists of three data files and a detached PDS label file. The label file contains the metadata and pointers to the three data files. The three data files are 1) an IMG file containing the browse product image as a three-band PDS IMAGE object; 2) a PNG file containing the browse product image in the Portable Network Graphics file format (three bands and an alpha transparency channel); and 3) a HDR file associated with the IMG file which stores file format (and map projection information) in the ENVI header format. This allows users of the ENVI image processing software to readily read in the image data. The SOURCE_PRODUCT_ID keyword in the PDS label links the browse products to the source MTRDR. The following formulations are used. Abbreviation : TRU Name : True color R Component : R600 G Component : R530 B Component : R440 Additional description: An enhanced natural color representation of the scene composed of spectral channels across the visible spectrum. Contrast greater than the human eye would see. Abbreviation : VNA Name : VNIR albedo R Component : R770 G Component : R770 B Component : R770 Additional description: Reflectance at 770 nm as a proxy for VNIR albedo and may be used to correlate spectral variations with morphology. Abbreviation : FEM Name : Fe Minerals R Component : BD530_2 G Component : SH600_2 B Component : BDI1000VIS Additional description: Mafic minerals appear blue, nanophase ferric oxides red, and dust-coated mafic rocks or lithified dust yellow/green. Abbreviation : FM2 Name : Fe minerals, v2 R Component : BD530_2 G Component : BD920_2 B Component : BDI1000VIS Additional description: Mafic minerals appear blue, crystalline hematite green or yellow, and nanophase ferric oxides red. Abbreviation : TAN Name : Tandem R Component : R2529 G Component : IRA B Component : R770 Additional description: Enhanced visible to infrared false color representation of the scene, incorporating spectral data from both (VNIR and IR) detectors. Abbreviation : IRA Name : IR albedo R Component : R1300 G Component : R1300 B Component : R1300 Additional description: Reflectnace at 1330 nm as a proxy for IR albedo and may be used to correlate spectral variations with morphology. Abbreviation : FAL Name : False color R Component : R2529 G Component : R1506 B Component : R1080 Additional description: Red to orange coloration is typically characteristic of olivine-rich material, blue/green colors are often indicative of clay mineralogy, green colors may indicate carbonate, and gray/brown colors often indicate basaltic material. Abbreviation : MAF Name : Mafic mineralogy R Component : OLINDEX3 G Component : LCPINDEX2 B Component : HCPINDEX2 Additional description: Olivine and Fe-phyllosilicate share a 1000-1700 nm bowl-shaped absorption and will appear red in the MAF browse product. Low- and high-Ca pyroxene display an additional ~2000-nm absorption and appear green/cyan and blue/magenta respectively. Abbreviation : HYD Name : Hydrated mineralogy R Component : SINDEX2 G Component : BD2100_2 B Component : BD1900_2 Additional description: Polyhydrated sulfates have strong 1900 nm and 2400 nm absorption bands, and thus appear magenta in the HYD browse product. Monohydrated sulfates have a strong 2100 nm absorption and a weak 2400 nm absorption band, and thus appear yellow/green in the HYD browse product. Blue colors are indicative of other hydrated minerals (such as clays, glass, carbonate, or zeolite). Abbreviation : PHY Name : Phyllosilicates R Component : D2300 G Component : D2200 B Component : BD1900r2 Additional description: Fe/Mg-OH bearing minerals (e.g., Fe/Mg-phyllosilicate) will appear red, or magenta (when hydrated). Al/Si-OH bearing minerals (e.g., Al-phyllosilicates or hydrated silica) will appear green, or cyan (when hydrated). Blue colors are indicative of other hydrated minerals (such as sulfates, glass, carbonate, or water ice). Abbreviation : PFM Name : Phyllosilicates with Fe and Mg R Component : BD2355 G Component : D2300 B Component : BD2290 Additional description: Red/yellow colors indicate the presence of prehnite, chlorite, epidote, or Ca/Fe carbonate, while cyan colors indicate the presence of Fe/Mg-smectites or Mg-carbonate. Abbreviation : PAL Name : Phyllosilicates with Al R Component : BD2210_2 G Component : BD2190 B Component : BD2165 Additional description: Red/yellow colors indicate the presence of Al-smectites or hydrated silica, cyan colors may indicate the alunite, and light/white colors indicate the presence of kaolinite group minerals. Abbreviation : HYS Name : Hydrated silica R Component : MIN2250 G Component : BD2250 B Component : BD1900r2 Additional information: Light red/yellow colors indicate the presence of hydrated silica, whereas cyan colors indicate Al-OH minerals. Additionally, jarosite will appear yellow. Blue colors are indicative of other hydrated minerals (such as sulfates, clays, glass, carbonate, or water ice). Abbreviation : ICE Name : Ices R Component : BD1900_2 G Component : BD1500_2 B Component : BD1435 Additional information: CO2 frost or ice displays a sharp 1435-nm absorption and thus appears blue in the ICE browse product. Water ice or frost has a strong 1500 nm absorption and thus appears green in the ICE browse product. Red colors are indicative of hydrated minerals (such as sulfates, clays, glass, carbonate, or water ice). Abbreviation : IC2 Name : Ices, v2 R Component : R3920 G Component : BD1500_2 B Component : BD1435 Additional information: CO2 frost or ice displays a sharp 1435-nm absorption and thus appears blue in the IC2 browse product. Water ice or frost has a strong 1500 nm absorption and thus appears green in the IC2 browse product. The 3920-nm spectral channel is a discriminator for icy vs. ice-free material with ices having a lower solar reflected and thermal emission radiance at this wavelength, so ice-free material appears red. Abbreviation : CHL Name : Chloride R Component : ISLOPE G Component : BD3000 B Component : IRR2 Additional information: Martian chloride deposits have a relatively positive near-infrared spectral slope and are comparatively desiccated, so chlorides appear blue in the CHL browse product. Yellow/green colors are indicative of hydrated minerals, especially phyllosilicates. Abbreviation : CAR Name : Carbonates R Component : D2300 G Component : BD2500H2 B Component : BD1900_2 Additional information: Blueish- or yellowish-white colors indicate Mg-carbonate, while red/magenta colors indicate Fe/Mg-phyllosilicate. Blue colors are indicative of other hydrated minerals (such as sulfates, clays, glass, or carbonate). Abbreviation : CR2 Name : Carbonates, v2 R Component : MIN2295_2480 G Component : MIN2345_2537 B Component : CINDEX2 Additional information: Red/magenta colors indicate Mg-carbonates, while green/cyan colors indicate Fe/Ca-carbonates. 11. Removal of Spectral Bad bands A canonical set of spectral 'bad bands' has been identified through the evaluation of a set of prototype TER IF data products. The identified 'bad bands' are not forwarded into the MTR IF image cube from the TER IF image cube. These bands are known and understood from previous work on CRISM data, and are: 10 wavelengths less than 436 nm (due to artifacts from the scattered light correction in high contrast scenes). 11 wavelengths between 631 and 710 nm (due to optical artifacts at the boundary between zones of the VNIR detector). VNIR wavelengths above 1010 nm and IR wavelengths below 1067 nm (leaving a gap equivalent to about 4.6 wavelength increments, due to various calibration artifacts at the VNIR/IR join). 21 wavelengths between 2654 and 2806 nm (due to optical artifacts at a zone boundary in the IR detector). 4 wavelengths above 3897 nm (due to low signal to noise ratio). 12. Generation of Map-Projection Transform A spatial transform that maps data in the IR (L-detector) sensor space into the designated map-projected space is calculated using the ESRI Projection Engine (PE) through the ENVI Application Programming Interface (API). The resulting Geographic Lookup Table (GLT) encodes the spatial transformation. CRISM MTRDRs employ Mars Reconnaissance Orbiter (MRO) map projection conventions - planetocentric latitude, positive east longitude, and the IAU 2000 prime meridian, pole of rotation, and equatorial and polar planetary radii. A rolling equirectangular projection with the reference latitude (center of map projection) at the 5 degree latitude increment in the equatorward direction is used for observations centered between -65 and 65 degrees north, and a north or south polar stereographic projection is used for observations poleward of that latitude range. The rolling equirectangular map projection uses a sphere with a radius equal to the IAU 2000 ellipsoid radius (Equatorial radius : 3396.190 km; Polar radius : 3376.200 km) at the reference latitude. The pixel scale of the map projection is equal to 18 meters per pixel, and the number of pixels per degree depends on the radius of the sphere evaluated at the reference longitude. That latitude and longitude at which each pixel is projected derives from the DDR of the source IR observation. The EQUIRECTANGULAR projection is based on the formula for a sphere. To eliminate confusion in the IMAGE_MAP_PROJECTION object all three radius keywords (A_AXIS_RADIUS, B_AXIS_RADIUS, and C_AXIS_RADIUS) have been set to the same value. The value recorded in the three radii keywords is the local radius at the CENTER_LATITUDE on the Mars ellipsoid. The CENTER_LATITUDE is the center of the projection, not the center of the observation. Using the local radius of the ellipsoid implies that the MAP_SCALE and MAP_RESOLUTION are true at the CENTER_LATITUDE. The POLAR STEREOGRAPHIC projections use the ellipsoid form of the equations. However, most cartographic processing software cannot support planetocentric coordinates for this projection with the ellipsoid equation. The fallback is to use the spherical equations. More detail is provided in the MTR_MAP.CAT catalog file. It is important to note that although projection is on a sphere, the latitude and longitude of each pixel takes Mars surface topography into account. When the DDR containing the latitudes and longitudes is being generated, gimbal positions are extracted from the table of housekeeping values accompanying the Experiment Data Record (EDR) and formatted as a gimbal C kernel. Using that and other MRO SPICE kernels, the surface intercept on the MOLA shape model is calculated for each spatial pixel (sampled at the reference detector row, closest to 2300 nm). 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. These values are also included in the DDR, and map projected in the DE MTRDR image cube. 13. Map-Projection The GLT is applied to the corrected I/F (IF), summary product (SU), refined summary product (SR), browse product (BR), and informational (IN) TER image products to produce the corresponding MTR data products. The GLT is applied to the source IR DDR to produce the DE MTR data product. The 14 image bands in the DE product come directly from the source DDR and include the following, all represented as 32-bit real numbers arranged in band-sequential format: a. Solar incidence angle relative to areoid, at the same planetary radius as surface projection of pixel, units degrees. b. Emission angle relative to areoid, at the same planetary radius as surface projection of pixel, units degrees. c. Solar phase angle, units degrees. d. Areocentric latitude, units degrees N. e. Areocentric longitude, units degrees E. f. Solar incidence angle relative to planetary surface as estimated using MOLA shape model, units degrees. g. Emission angle relative to planetary surface as estimated using MOLA shape model, units degrees. h. Slope magnitude, using MOLA shape model and reference ellipsoid, units degrees. i. Slope azimuth, using MOLA shape model and reference ellipsoid, units degrees clockwise from N. j. Elevation relative to MOLA datum, units kilometers. k. TES thermal inertia, units J m^-2 K^-1 s^-0.5. l. TES bolometric albedo, unitless. m. Local solar time, hours. n. Spare. Extras : The MTRDR EXTRAS directory contains one visualization for each processed observation that illustrates the spatial/spectral information content of the primary MTRDR I/F data product. All TER/MTRDR EXTRAS visualizations are Portable Network Graphics (PNG) format files. Detailed descriptions of the TER/MTRDR EXTRAS products are provided in the CRISM Data Product SIS Appendix P2. Limitations : None.
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| DATA_SET_RELEASE_DATE |
2016-03-04T00:00:00.000Z
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| START_TIME |
2016-03-04T12:00:00.000Z
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| STOP_TIME |
N/A (ongoing)
|
| MISSION_NAME |
MARS RECONNAISSANCE ORBITER
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| MISSION_START_DATE |
2005-08-12T12:00:00.000Z
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| MISSION_STOP_DATE |
N/A (ongoing)
|
| TARGET_NAME |
MARS
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| TARGET_TYPE |
PLANET
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| INSTRUMENT_HOST_ID |
MRO
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| INSTRUMENT_NAME |
COMPACT RECONNAISSANCE IMAGING SPECTROMETER FOR MARS
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| INSTRUMENT_ID |
CRISM
|
| INSTRUMENT_TYPE |
IMAGING SPECTROMETER
|
| NODE_NAME |
Geosciences
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| ARCHIVE_STATUS |
ARCHIVED_ACCUMULATING
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| CONFIDENCE_LEVEL_NOTE |
By design many of the sources of uncertainty in interpretation of the data relevant to calibrated data or TRDRs are reduced or eliminated in TERs and MTRs. Remaining issues of most concern to data users follow. (1) Variable spectral resolution In order to distinguish spectrally similar minerals that have different geological implications for their environments of formation, adequate spectral resolution is necessary. This requires sufficiently high density spectral sampling, as well as a sufficiently narrow full width half maximum (FWHM) of the instrument response in the spectral direction. This 'slit function,' the effective bandpass for a single detector element, represents the convolution of spectral sampling and the point-spread function in the spectral direction. CRISM's benchmark is distinguishing the minerals montmorillonite and kaolinite, which form in hydrothermal environments under different temperature regimes [SWAYZEETAL2003]. The requirements for this are (a) <20 nm FWHM and (b) sampling of the spectrum at this or smaller increments. CRISM's spectral sampling requirement is <10 nm/channel to provide oversampling, and the actual performance is better at 6.55 nm/channel. FWHM is 8 nm in the VNIR across the FOV. In the IR it increases from 10 nm at short wavelengths to 15 nm at the longest wavelengths at the center of the FOV, and broadens by about 2 nm at 0.8 degrees from the center of the field of view. Outside +/-0.9 degrees from the center of the field of view the telescope is slightly vignetted, so further degradation is expected at extreme field angles. Although the spectral sampling and resolution meet requirements, their variation across the field-of-view must be accounted for when comparing with rock and mineral analog spectra. The FWHM of the slit function is given for the reference columns of the source TRDR as part of the WV table accompanying the MTR. (2) Long-wavelength calibration uncertainty The responsivity correction at IR wavelengths 3000-3920 is suspected to contain low wavelength frequency errors, perhaps leading to a broad 'bump' centered near 3400 nm. This is currently under investigation and may be corrected in a future version of the IR radiometric calibration. (3) Residuals from correction of the 2000-nm CO2 gas absorption As described above, parts of many scenes contain a ringing-like artifact of using a correction for atmospheric gases derived from data where the IR wavelength calibration has drifted slightly. An indicator of parts of an image subject to this effect is included in the informational IN image cube. (4) Artifacts near 1 micron For reasons that are not well understood, the quality of the calibration of VNIR and IR data on either side of the 'join' near 1 micron drifts in time. The IN informational image cube contains indicators of where in an image this is most severe. The calibration of data away from the join is only suspect where elsewhere indicated. (5) Calibration residuals In MTR IF image products, wavelengths with routinely deficient radiometric calibration are omitted by design. However wavelengths that exhibit only intermitted artifacts, or artifacts that are corrected by ratioing to a spectrally blank material measured by the same detector column in the source observation, are included. These are: a. In some observations, there is a column-dependent artifact in the form of a broad dip near 1220 nm, whose origin is unknown. The artifact disappears when a spectrum containing it is ratioed to spectrally bland material within the same observation, in or near the source IR detector column. b. In some observations, there is a spike or trough at the boundary between the short and intermediate wavelength segments of the IR detector, near 1660 nm. The artifact disappears when a spectrum containing it is ratioed to spectrally bland material within the same observation, in or near the source IR detector column. c. The shape of the spectrum at 3100-3800 nm is suspect and there may be a broad, low 'bump'. (6) Scene-dependent opacity of dust and ice aerosols The processing that normalizes atmospheric effects does not attempt to remove scattering effects of dust and ice aerosols, only to normalize them to the effects at the nearest-to-nadir geometry in the scene in question. Scenes with high opacities of dust or ice, for example observed during global dust events, are by design excluded from the TER archive. Thresholds used were dust opacity (tau) > 1.39 and ice opacity (tau) > 0.28. However overlapping scenes within the archive may have different dust or ice loads below these limits, so overlapping spectra measured at different times may have distinct values. The effects will be greatest at shorter wavelengths, and in absorptions related to iron minerals. In addition some scenes are observed through a thin water ice haze. These will have characteristic weak ice absorption near 1500 and 2000 nm. (7) Summary product and browse product cautions Summary products and browse products are intended to provide rapid overviews of the content of CRISM hyperspectral data, and to convey spatial variations in mineral spectral signatures in a compact fashion. However they are not conclusive indicators of the presence of particular minerals; false positives and false negatives are not uncommon. Users are referred to Table 3-12 of the CRISM Data Product SIS for detailed caveats regarding false positives, and to [VIVIANO-BECKETAL2014] for an extended discussion of the topic. (8) Uncertainties in contents of the DE product. The major sources of uncertainty in the source DDRs arise from uncertainties in instrument pointing knowledge, from coverage of the MOLA data set, and from the scale of the Thermal Emission Spectrometer (TES) data. The formal pointing uncertainty for the CRISM gimbal plane is 1 mrad each in the spacecraft yaw(z), roll(x), or pitch/gimbal(y) axes. The formal uncertainty in reconstructed spacecraft attitude is similar. Uncertainty in CRISM's gimbal attitude is negligible, about 0.006 mrad. The formal error in projection onto a surface location depends on the angle of the gimbal and typically is of order several hundreds of meters. Experience during operations suggests that the actual errors are smaller than expected formal errors, so that typical error in surface location is about 200 meters. Latitude and longitude are described by the intersection of CRISM field of view with the MOLA shape model. Given the uncertainties in location of a point on the surface, expected uncertainty near the equator is of the order of 0.005 degrees. Uncertainties in incidence, emission, and phase angles relative to the areoid are similar. Errors in incidence and emission angle relative to the MOLA shape model are dominated by the lower sampling density of the shape model. MOLA points are typically a few hundred meters apart. This compares to CRISM's sampling scale of 18 meters per spatial pixel, for a full spatial resolution observation. In areas of smooth topography the errors are small, but in areas with topography that is rough at scales less than a few hundred meters, uncertainty is several degrees. The same uncertainties apply to slope magnitude. Errors in bolometric albedo and thermal inertia will have a large contribution from the different scales of the CRISM and TES data sets. The TES data from which these values are retrieved are sampled at 8 pixels per degree, yet depending on instrument configuration, the native spatial sampling of the CRSIM data set is 256-4096 pixels per degree. Thus in areas with heterogeneous surface properties, large errors in bolometric albedo and thermal inertia may occur.
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| CITATION_DESCRIPTION |
Seelos, F., Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars Map-projected Targeted Reduced Data Record, MRO-M-CRISM-5-RDR-MPTARGETED-V1.0, NASA Planetary Data System, 2016.
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| ABSTRACT_TEXT |
This volume contains the CRISM Map-projected Targeted Reduced Data Record (MTRDR) archive, a collection of multiband image cubes derived from targeted (gimbaled) observations of Mars' surface acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter (MRO) spacecraft. Post-processing attempts to represent the spectrum the instrument would have measured looking at the surface of Mars at a standard illumination geometry, in the absence of atmospheric gases, with aerosol scattering normalized to that at the geometry within the observation that is closest to nadir, in the absence of instrument artifacts. A series of value added products represent spatial variability in signatures of minerals of interest. The data are map projected using terrain models of the Martian surface. A companion Targeted Empirical Record (TER) archive contains mostly the same data in the sensor space of the IR detector to support map projection using future more accurate terrain models.
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| PRODUCER_FULL_NAME |
FRANK SEELOS
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| SEARCH/ACCESS DATA |
Geosciences Web Services
Mars Orbital Data Explorer
Geosciences Online Archives
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