PDS: Data Set Information

Data Set Information
DATA_SET_NAME	MRO CRISM TARGETED REDUCED DATA RECORD V1.0
DATA_SET_ID	MRO-M-CRISM-3-RDR-TARGETED-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION	Data Set Overview : This volume contains portions of the CRISM Targeted Reduced Data Record (TRDR) Archive, a collection of multiband images from the Compact Reconnaissance Imaging Spectrometer for Mars on the Mars Reconnaissance Orbiter spacecraft. Images consist of data calibrated to units of radiance or I/F plus a text file with housekeeping information, and optionally image data to which further corrections have been applied. Image data are in sensor space and non-map-projected. The data are stored with PDS labels. 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 represent 'scene' data, as indicated by the keyword MRO:ACTIVITY_ID. Only scene data that are aimed at planetary objects are processed to TRDRs. Only those configurations that affect the contents or dimensionality of a TRDR are discussed below): 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 detector are processed to a TRDR. 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 any pixel binning configuration may have a corresponding TRDR, but the pixel binning configuration will affect the dimensionality of the TRDR. Row selection: Detector row selection. All detector rows, sampling different wavelengths, having useful signal can be saved. Alternatively an arbitrary, commandable subset of rows can be saved. The number of rows with useful signal is 545, 107 in the VNIR and 438 in the IR, and these subsets of VNIR and IR detector rows are used for hyperspectral observing. Prior to 10 Dec 2006 the nominal number of rows for multispectral mode was 73, 18 in the VNIR and 55 in the IR. On 10 Dec 2006 an extra channel was added to the VNIR for calibration purposes, for a total of 19. For each detector, there are four options of channel selection to choose from rapidly by command: hyperspectral (545 total channels), multispectral (73 total channels prior to 10 Dec 2006, 74 total channels on and after 10 Dec 2006), and two sets of expanded multispectral (84 and 92 channels prior to 10 Dec 2006, 85 and 93 channels on and after 10 Dec 2006). New options are set by uploading a data structure to the DPU. On 12 Jan 2010, the smaller of the two expanded multispectral channel selections was replaced with the largest value supportable at a 15 Hz frame rate, all 107 VNIR channels and 155 IR channels; most of the IR channels are contiguous from 1.8-2.55 ?m to cover key mineral absorptions. Calibration lamps: 4095 levels are commandable in each of two lamps at each focal plane, and in two lamps in the integrating sphere. All lamps can be commanded open-loop, meaning that current is commanded directly. For the integrating sphere only, closed loop control is available at 4095 settings. For closed loop control, the setting refers to output from a photodiode viewing the interior of the integrating sphere; current is adjusted dynamically to attain the commanded photodiode output. Note: lamps reach maximum current at open- or closed-loop settings <4095. Only data for which the calibration lamps are off may be processed to a TRDR. 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 TRDR. 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. Pointing configuration affects the contents but not the dimensionality of a TRDR. 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, or a Targeted Reduced Data Record, or TRDR, the 'calibrated' equivalent of an EDR. The data in one EDR or TRDR represent 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). Each frame has dimensions of detector columns (spatial samples) and detector rows (wavelengths, or bands). The multiple image frames are concatenated, and are formatted into a single multiple-band image (suffix .IMG) in one file, plus a detached list file in which each record has housekeeping information specific to one frame of the multiple-band image (suffix .TAB). The text file is based on the 220 housekeeping items. Five of the items are composite in that each byte encodes particular information on gimbal status or control. These separate items are not broken out, except for the gimbal status at the beginning, middle, and end of each exposure, from which gimbal position is broken out (3 additional items). The housekeeping is pre-pended with 10 additional frame-specific items useful in data validation, processing, and sorting, for a total of 233 items per frame. Further information can be found in the data product SIS in the DOCUMENT directory. The multiple-band image has dimensions of sample, line, and wavelength. The size of the multiple-band image varies according to the observation mode but is deterministic given the macro ID. A typical multiple-band image might have XX pixels in the sample (cross-track) dimension, YY pixels in the line (along-track) dimension, and ZZ pixels in the wavelength dimension, where: XX (samples) : 640/binning, where 640 is the number of columns read off the detector, and binning is 1, 2, 5, or 10; YY (lines) : the number of image frames with a consistent instrument configuration; and ZZ (bands) : the number of detector rows (wavelengths) whose read-out values are retained by the instrument. 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 an Appendix in the CRISM Data Product SIS. A TRDR may also contain separately labeled multiband images in which radiance has been processed to one of the following: I/F (radiance divided by (pi * solar flux at 1 AU * heliocentric distance^2)), Lambert albedo, or a set of derived spectral parameters (summary products) that provide an overview of the data set. The summary products include Lambert albedo at key wavelengths, or key band depths or spectral reflectance ratios. To create Lambert albedo or most summary products, estimated corrections for atmospheric, photometric, and thermal effects are applied to the I/F data using corrections given in ADRs. The formulations for all of the summary products have been validated using data from Mars Express/OMEGA. The sequence of processing that creates a TRDR is as follows: (a) EDRs are assembled from raw data. (b) The radiance multiband images in TRDRs are created from the EDRs and Calibration Data Records, or CDRs, using a calibration algorithm discussed at length in an Appendix in the CRISM Data Products SIS. (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, TES bolometric albedo and thermal inertia are retrieved from global map products, and resampled into CRISM sensor space using nearest neighbor resampling. The same procedure is used to retrieve MOLA elevation, and the local slope magnitude and slope azimuth of the MOLA elevation model. (e) Optionally, 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) Beginning with version 3 of TRDRs, additional processing is applied to I/F multiband images to remediate the effect of noise in the flight data and propagated noise from ground and flight calibrations. The IR multiband image only is processed using an iterative kernel filter. A kernel with settable, typical dimensions of 3x3x5 spatial x spatial x spectral pixels is used to identify afflicted pixels using a Grubbs test for outliers; an outlying value is replaced by interpolation linearly in the spatial direction and using a 2nd degree polynomial in the spectral direction. Both the VNIR and IR multiband images are then processed using the ratio shift correction, which searches for values from detector elements that are systematically high or low and using a ratio to nearby pixels attempts to remove systematic error. Testing on a variety of multiband images shows that most systematic errors propagated from calibration files are removed, and the spurious data values due to elevated IR detector operating temperatures are greatly reduced in number and magnitude. (f) Optionally, I/F is converted to Lambert albedo. 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 or removed, and the estimated attenuation of the signal by atmospheric gases is removed. The thermal emission from longer IR wavelengths is removed. MRO:ATMO_CORRECTION_FLAG and MRO:THERMAL_CORRECTION_MODE indicate whether such corrections have been performed. CRISM data products are described in greater detail in the Data Product Software Interface Specification and the Data Archive Software Interface Specification in the DOCUMENT directory. Details of DN to radiance conversion : FLIGHT AND GROUND CALIBRATION DATA: ---------------------------------- All calibration matrices are stored in 'calibration data records' or CDRs, separate from the main algorithm coded in software. There are two general classes of calibration matrices, those derived from ground data and updated infrequently, and those that represent highly time-variable properties of the instrument. Examples of the former include the constants needed to uncompress data, correct non-linearity, or correct bias for effects of detector or focal plane electronics temperature. Examples of the latter include bias and IR thermal background, which depend on detector and spectrometer housing temperature respectively. There are two formats for storing the values in the matrices, distinguished by the levels of processing. Level 6 CDRs, or CDR6s, are tabulated numbers in ASCII format, and level 4 CDRs, or CDR4s, are images each derived from a collection of flight or ground calibration measurements. Calibration matrices that are highly time variable are measured inflight, and include the following. For the VNIR detector bias is measured directly, with the shutter closed and at the same integration time as accompanying measurements of Mars. For the IR, shutter-closed measurements also include thermal background. The bias is therefore measured for the IR detector by taking data at several integration times and extrapolating to zero exposure. The step function, a discontinuity in measured bias at some detector row, is modeled deterministically as a function of integration time. Currently, the default is to take a VNIR bias measurement with every observation and IR bias observations several times daily. IR thermal background is the response of the IR detector to 'glow' of the inside of the instrument predominantly at >2300 nm. The change in spectrometer housing temperature that perturbs thermal background by the equivalent to read noise is about 0.02K, whereas the spectrometer housing is predicted to change by several degrees over the course of an orbit. Therefore shutter-closed IR measurements are taken interspersed within all observations, at an interval of approximately once per 3 minutes. To correct any given frame of scene data, temporally adjacent shutter-closed measurements are used. The onboard integrating sphere serves as the radiance reference against which CRISM's radiometric responsivity as a system is pegged. Multiple measurements are conducted daily. The signal from the sphere is adequate at wavelengths greater than 560 nm; at shorter wavelengths a fixed responsivity derived from ground calibrations is used. The integrating sphere provides sufficient signal for a preliminary 'flat-field' correction of IR data, but not VNIR data. Pixel-to-pixel variations in VNIR detector responsivity are measured monthly using bland regions of Mars. Co-temporal IR measurements of the same bland regions are used to derive a secondary flat-field correction for IR data; in practice this is thought mostly to reduce propagated artifacts from ground and flight calibrations. RADIOMETRIC CALIBRATION: Radiometric calibration to units of radiance involves uncompressing data, correcting instrument artifacts, subtracting bias and background, dividing by exposure time, and converting of the result of these steps to units of radiance by comparing against a radiometric reference. This approach explicitly uses measurements of the internal integrating sphere. A simplified form of the equation to reduce measurements to units of radiance, using ground and flight calibration measurements, is: RD(x,lambda) : M(x,lambda,Hz)( ( K(x,lambda,Hz)( D14lambda( DN(x,lambda,TV,TW,TI,TJ,T2,Hz,t) ) - BiaT(x,lambda,TV,TW,TI,TJ,Hz,t) ) / t - Bkgd(x,lambda,TI,T2,Hz) - Scat(x,lambda,TV,TI,T2,Hz) ) / RST(x,lambda,TV,TI,T2,T3,S) ) Subscripts define the variables on which calibration coefficients depend, and include the following: x is spatial position in a row on the focal plane, in detector elements. lambda is position in the spectral direction on the focal plane, in detector elements. Hz is frame rate, and implicitly includes with it compression configuration including wavelength table and binning mode TI, is IR detector temperature in degrees K. TV is VNIR detector temperature in degrees K. T2, is spectrometer housing temperature in degrees K. T3 is temperature of the integrating sphere in degrees K. TJ is IR focal plane board temperature in degrees K. TW VNIR focal plane board temperature in degrees K. t is integration time in seconds. s is choice of sphere bulb, side 1 (controlled by IR focal plane electronics) or side 2 (controlled by VNIR focal plane electronics). Discussion of the various instrument effects being corrected is including in the 'Confidence Level Note' below. All of the input temperatures come from instrument housekeeping, and are monitored by the focal plane electronics. Temperatures are corrected for electronics noise by substituting for temperatures, currents, and voltages in the image headers the corresponding values at the same spacecraft time from the low-speed telemetry stored in 'ST' CDR6s. This step is performed because the low-speed telemetry maintains a fixed timing relative to instrument current variations on 1-second cycles, whereas the image headers do not; this makes the electronics noise more easily calibrated in the low-speed telemetry. The raw digital values are corrected for effects of frame rate and variable current loads, including lamps and coolers, using additive and multiplicative coefficients maintained in the 'HD' CDR6, and then scaled to physical units using other coefficients maintained in the 'HK' CDR6. The terms in the equation and their sequential application are as follows: Data decompression. D14lambda converts from raw 8- or 12-bit DNs to 14-bit DNs. This is accomplished by inverting the 12-to-8-bit LUT using the 'LI' CDR6, then dividing by the gain and adding the offset used onboard, whose values are contained in the 'PP' CDR6. Bias subtraction. BiaT(x,lambda,TV,TW,TI,TJ,Hz,t) is detector bias derived as described above from flight measurements, and stored as a 'BI' CDR4. For the VNIR, it is just a decompressed shutter-closed measurement. For the IR, it is the zero-exposure intercept of the pixel-by-pixel fit of 14-bit DN to exposure time in the bias measurements, added to the bias step function stored in the 'BS' CDR6. Bias is corrected for changes in focal plane electronics and detector temperature since the time of bias measurement, using telemetered detector and electronics temperature and the 'DB' and 'EB' CDR6's respectively. Electronics artifacts correction. K(x,lambda,Hz) applies detector ghost and detector nonlinearity corrections. This is actually a composite of distinct steps. The correction for detector ghosts subtracts the scaled, bias- removed DN from each quadrant from every other quadrant of the detector. Scaling coefficients are stored in the 'GH' CDR6. The nonlinearity correction scales bias- and ghost-removed DN to account for nonlinearity in detector response. Detector- averaged scaling coefficients are stored in the 'LI' CDR6. Pixel-dependent nonlinearity at higher frame rates can be corrected using images of bland regions of Mars taken at the same frame rate. A non-uniformity matrix, or flat-field, the 'NU' CDR4, is constructed from several thousand frames of different scenes along-track that are averaged to remove non-uniform illumination of the surface due to topography, and the spatial image at each wavelength is normalized by its mean value. Background subtraction. Bkgd(x,lambda,TI,T2,Hz) is a 'BK' CDR4 constructed by applying the D14, BiaT, and K corrections to a shutter-closed IR measurement interspersed with Mars measurements. The actual background subtracted from a scene measurement is a time-weighted average of preceding and subsequent 'BK' shutter-closed measurements, to allow for the continuous variation of IR thermal background as spectrometer housing temperature changes. Scattered light subtraction. Scat(x,lambda,TV,TI,T2,Hz) is the stray light subtraction, and includes two components. The first component is glare from the gratings, which produces a low level of light at a distance of tens or more of pixels from a source. For the VNIR detector, this component of scattered light is measured directly at each row of the detector as the mean level in the scattered light columns at a given row. The locations of the scattered light and scene pixels are stored in the 'DM' CDR4. It is then extrapolated across the detector using a function based on signal at the shortest wavelengths (UV), which is dominated by scatter. The shape of he function varies as a function of wavelength. For the IR detector, transient bad pixels render this correction noisy so instead this correction was derived using a bland, dusty scene on Mars, applying the correction both to the scene and to the accompanying sphere measurement. The extrapolation across the field of view uses a function resembling that at the longest VNIR wavelengths. The correction was then median filtered and multiplied into the sphere radiometric model. Given the derivation of the IR scattered light correction, it is most accurate for uniformly illuminated scenes. The second component of scattered light is the second-order light leaked through zone 3 of the IR order sorting filter. This is removed by scaling and subtracting the measured signal at second order wavelengths from the measured first-order signal in zone 3. For each detector row (wavelength), which second- order rows to use and their weightings are stored in the 'LL' CDR4. Responsivity correction using sphere data. RST(x,lambda,TV,TI,T2,T3,S) is spectral responsivity derived from onboard sphere calibration images. It is calculated by processing a sphere measurement through the aforementioned steps with two exceptions, and dividing by exposure time to create an 'SP' CDR4. The exception is that the background image is taken looking into the unilluminated sphere instead of with the shutter closed, in order to subtract out the blackbody radiation of the sphere's structure. The 'SP' product is corrected for non-reproducibility in shutter position by measuring the 'peak' in sphere DN/ms near VNIR detector row 232, and scaling a multiplicative correction stored in the 'SH' CDR4 by the magnitude of that peak. The SP CDR4 is divided by the sphere spectral radiance model stored in the 'SS' CDR4 to derive a snapshot of instrument responsivity. The model uses as an input the choice of sphere bulb. Normally the bulb controlled by the IR focal plane electronics is used. M(x,lambda,Hz) applies the detector mask in the 'DM' CDR4, flagging non-scene data (e.g. scattered light and masked pixels) with a value of 65535. This is a standard value for missing or 'bad' (saturated) data. Converting radiance to I/F. RD(x,lambda) is the observed spectral radiance in W/m2/steradian/um at the instrument aperture, and is the output of the preceding steps for a scene measurement. That radiance may be converted to I/F by dividing by squared solar distance (stored in EDR and TRDR labels) and the solar irradiance model stored in the 'SF' CDR4. That model is itself derived convolving a predicted solar spectrum with the measured center wavelength (stored in the 'WA' CDR4) and spectral bandpass (stored in the 'SB' CDR4) of every detector element. Data : DATA DESCRIPTION: There is only one data type associated with this volume, the Targeted Reduced Data Records or TRDRs. The TRDR consists of the output of one of the constituent macros associated with a target ID that contains scene data (Mars or other). Not all EDRs are processed to TRDR level; those containing bias, background, sphere, or focal plane lamp data are processed instead to CDRs. Only scene EDRs are processed to the TRDR level. The TRDR contains one or more multiple-band images (suffix .IMG). One matches the dimensions of the multiple-band image of raw DN in an EDR, except that the data are in units of radiance. The size of the multiple-band image varies according to the observation mode but is deterministic given the ID of the command macro used to acquire the data. Appended to the multiple-band image is a binary table of the detector rows that were used, as selected by the wavelength filter. This is a one-column table, with each row containing one detector row number expressed as a 16-bit unsigned integer values, most significant bit first. Other multiple-band images may contain I/F, Lambert albedo, or derived summary products. The I/F and Lambert albedo images, if present, parallel the structure of the radiance image except lack the list file. The summary products image has the same spatial dimensions, but a different dimension in the spectral direction and it lacks that table of row numbers. Each of these three multiple-band images has its own label. There are 45 summary parameters, as follows: SURFACE PARAMETERS: from Lambert albedo NAME: R770 PARAMETER: 0.77 micron reflectance FORMULATION : R770 RATIONALE: rock/dust ratio NAME: RBR PARAMETER: red/blue ratio FORMULATION : R770 / R440 RATIONALE: rock/dust ratio NAME: BD530 PARAMETER: 0.53 micron band depth FORMULATION : 1 - (R530/(aR709+bR440)) RATIONALE: crystalline ferric minerals NAME: SH600 PARAMETER: 0.60 micron shoulder height FORMULATION : R600/(aR530+bR709) RATIONALE: select ferric minerals NAME: BD640 PARAMETER: 0.64 micron band depth FORMULATION : 1 - (R648/(aR600+bR709)) RATIONALE: select ferric minerals, especially maghemite NAME: BD860 PARAMETER: 0.86 micron band depth FORMULATION : 1 - (R860/(aR800+bR984)) RATIONALE: select ferric minerals NAME: BD920 PARAMETER: 0.92 micron band depth FORMULATION : 1 - ( R920 / (aR800+bR984) ) RATIONALE: select ferric minerals NAME: RPEAK1 PARAMETER: reflectance peak 1 FORMULATION : wavelength where 1st derivative:0 of 5th order polynomial fit to R600, R648, R680, R710, R740, R770, R800, R830 RATIONALE: Fe mineralogy NAME: BDI1000VIS PARAMETER: 1 micron integrated band depth; VIS wavelengths FORMULATION : divide R830, R860, R890, R915 by RPEAK1 then integrate over (1 - normalized radiances) RATIONALE: crystalline Fe+2 or Fe+3 minerals NAME: BDI1000IR PARAMETER: 1 micron integrated band depth; IR wavelengths FORMULATION : divide R1030, R1050, R1080, R1150 by linear fit from peak R between 1.3 - 1.87 microns to R2530 extrapolated backwards, then integrate over (1 - normalized radiances) RATIONALE: crystalline Fe+2 minerals; corrected for overlying aerosol induced slope NAME: IRA PARAMETER: 1.3 micron reflectance FORMULATION : R1330 RATIONALE: IR albedo NAME: OLINDEX (prior to TRDR version 3) PARAMETER: olivine index FORMULATION : (R1695 / (0.1R1050 + 0.1R1210 + 0.4R1330 + 0.4R1470)) - 1 RATIONALE: olivine will be strongly +; based on fayalite NAME: OLINDEX2 (beginning with TRDR version 3) PARAMETER: olivine index with less sensitivity to illumination FORMULATION : (((RC1054 ? R1054)/RC1054) * 0.1) + (((RC1211 ? R1211)/(RC1211) * 0.1) + (((RC1329 ? R1329)/RC1329) * 0.4) + (((RC1474 ? R1474)/RC1474) * 0.4) RATIONALE: olivine will be strongly positive NAME: LCPINDEX PARAMETER: pyroxene index FORMULATION : ((R1330-R1050) / (R1330+R1050)) ((R1330-R1815) / (R1330+R1815) RATIONALE: pyroxene is strongly +; favors low-Ca pyroxene NAME: HCPXINDEX PARAMETER: pyroxene index FORMULATION : ((R1470-R1050) / (R1470+R1050)) ((R1470-R2067) / (R1470+R2067) RATIONALE: pyroxene is strongly +; favors high-Ca pyroxene NAME: VAR PARAMETER: spectral variance FORMULATION : find variance from a line fit from 1 - 2.3 micron by summing in quadrature over the intervening wavelengths RATIONALE: Ol & Px will have high values; Type 2 areas will have low values NAME: ISLOPE1 PARAMETER: -1 spectral slope1 FORMULATION : (R1815-R2530) / (2530-1815) RATIONALE: ferric coating on dark rock NAME: BD1435 PARAMETER: 1.435 micron band depth FORMULATION : 1 - ( R1430 / (aR1370+bR1470) ) RATIONALE: CO2 surface ice NAME: BD1500 PARAMETER: 1.5 micron band depth FORMULATION : 1 - ( ((R1510+R1558)0.5) / (aR1808+bR1367) RATIONALE: H2O surface ice NAME: ICER1 PARAMETER: 1.5 micron and 1.43 micron band ratio FORMULATION : R1510 / R1430 RATIONALE: CO2, H20 ice mixtures NAME: BD1750 PARAMETER: 1.75 micron band depth FORMULATION : 1 - ( R1750 / (aR1660+bR1815) ) RATIONALE: gypsum NAME: BD1900 PARAMETER: 1.9 micron band depth FORMULATION : 1 - ( ((R1930+R1985)0.5) / (aR1857+bR2067) ) RATIONALE: H2O, chemically bound or adsorbed NAME: BDI2000 PARAMETER: 2 micron integrated band depth FORMULATION : divide R1660, R1815, R2140, R2210, R2250, R2290, R2330, R2350, R2390, R2430, R2460 by linear fit from peak R between 1.3 - 1.87 microns to R2530, then integrate over (1 - normalized radiances) RATIONALE: pyroxene abundance and particle size NAME: BD2100 PARAMETER: 2.1 micron band depth FORMULATION : 1 - ( ((R2120+R2140)0.5) / (aR1930+bR2250) ) RATIONALE: monohydrated minerals NAME: BD2210 PARAMETER: 2.21 micron band depth FORMULATION : 1 - ( R2210 / (aR2140+bR2250) ) RATIONALE: Al-OH minerals NAME: BD2290 PARAMETER: 2.29 micron band depth FORMULATION : 1 - ( R2290 / (aR2250+bR2350) ) RATIONALE: Mg,Fe-OH minerals (at 2.3); also CO2 ice (at 2.292 microns) NAME: D2300 PARAMETER: 2.3 micron drop FORMULATION : 1 - ( (CR2290+CR2320+CR2330) / (CR2140+CR2170+CR2210) ) (CR values are observed R values divided by values fit along the slope as determined between 1.8 and 2.53 microns - essentially continuum corrected)) RATIONALE: hydrated minerals; particularly clays NAME: SINDEX PARAMETER: Convexity at 2.29 microns due to absorptions at 1.9/2.1 microns and 2.4 microns FORMULATION : 1 - (R2100 + R2400) / (2 R2290) CR values are observed R values divided by values fit along the slope as determined between 1.8 - 2.53 microns (essentially continuum corrected)) RATIONALE: hydrated minerals; particularly sulfates NAME: ICER2 PARAMETER: gauge 2.7 micron band FORMULATION : R2530 / R2600 RATIONALE: CO2 ice will be >>1, H2O ice and soil will be about 1 NAME: BDCARB PARAMETER: overtone band depth FORMULATION : 1 - ( sqrt [ ( R2330 / (aR2230+bR2390) ) * ( R2530/(cR2390+dR2600) ) ] ) RATIONALE: carbonate overtones NAME: BD3000 PARAMETER: 3 micron band depth FORMULATION : 1 - ( R3000 / (R2530(R2530/R2210)) ) RATIONALE: H2O, chemically bound or adsorbed NAME: BD3100 PARAMETER: 3.1 micron band depth FORMULATION : 1 - ( R3120 / (aR3000+bR3250) ) RATIONALE: H2O ice NAME: BD3200 PARAMETER: 3.2 micron band depth FORMULATION : 1 - ( R3320 / (aR3250+bR3390) ) RATIONALE: CO2 ice NAME: BD3400 PARAMETER: 3.4 micron band depth FORMULATION : 1 - ( (aR3390+bR3500) / (cR3250+dR3630) ) RATIONALE: carbonates; organics NAME: CINDEX PARAMETER: gauge 3.9 micron band FORMULATION : ( R3750 + (R3750-R3630) / (3750-3630) * (3920-3750) ) / R3920 - 1 RATIONALE: carbonates ATMOSPHERIC PARAMETERS: from I/F NAME: R440 PARAMETER: 0.44 micron reflectance FORMULATION : R440 RATIONALE: clouds/hazes NAME: IRR1 PARAMETER: IR ratio 1 FORMULATION : R800 / R1020 RATIONALE: Aphelion ice clouds vs. seasonal or dust NAME: BD1270O2 PARAMETER: 1.265 micron band FORMULATION : 1 - ( (aR1261+bR1268) / (cR1250+dR1280) ) RATIONALE: O2 emission; inversely correlated with high altitude water; signature of ozone NAME: BD1400H2O PARAMETER: 1.4 micron band depth FORMULATION : 1 - ( (aR1370+bR1400) / (cR1330+dR1510) ) RATIONALE: H2O vapor NAME: BD2000CO2 PARAMETER: 2 micron band FORMULATION : 1 - ( R2010 / (aR1815+bR2170) ) RATIONALE: atmospheric CO2 NAME: BD2350 PARAMETER: 2.35 micron band depth FORMULATION : 1 - ( (aR2320+bR2330+cR2350) / (dR2290+eR2430) ) RATIONALE: CO NAME: IRR2 PARAMETER: IR ratio 2 FORMULATION : R2530 / R2210 RATIONALE: aphelion ice clouds vs. seasonal or dust NAME: BD2600 PARAMETER: 2.6 micron band depth FORMULATION : 1 - ( R2600 / (aR2530+ bR2630) ) RATIONALE: H2O vapor NAME: R2700 PARAMETER: 2.70 micron reflectance FORMULATION : R2700 RATIONALE: high aerosols NAME: BD2700 PARAMETER: 2.70 micron band depth FORMULATION : 1 - ( R2700 / (R2530(R2530/R2350)) ) RATIONALE: CO2; atmospheric structure (accounts for spectral slope) NAME: IRR3 PARAMETER: IR ratio 3 FORMULATION : R3750 / R3500 RATIONALE: aphelion ice clouds vs. seasonal or dust Note : 'a', 'b', 'c', 'd', 'e' in band depth formulations represent fractional distances between wavelengths wavelength; for example, given BD(c), a band depth at a central wavelength 'c' with nearby continuum points defined at shorter and longer wavelengths 's' and 'l': BD(c) : 1 - R(c) / (aR(s) + bR(l)), where a : 1 - b and b : (lambda(c) - lambda(s)) / (lambda(l) - lambda(s)) DATA DIMENSIONALITY: The size of the multiple-band image varies according to the observation mode but is deterministic given the ID of the onboard macro the generated the data. A typical multiple-band image might have XX pixels in the sample (cross-track) dimension, YY pixels in the line (along-track) dimension, and ZZ pixels in the wavelength dimension, where: XX:640/binning, where binning is 1, 2, 5, or 10, and dark is the number of masked and scattered light pixels YY:the number of frames of data taken by the macro, and ZZ:the number of rows (wavelengths) that are retained by the instrument. The data in a TRDR do not have optical distortions removed. In one column, the projection onto Mars' surface may vary by as much as +/-0.4 not-binned detector elements in the XX dimension depending on position in the FOV (distortions are worst at the edges of the VNIR and IR FOVs). For a single wavelength, its location in the ZZ direction may vary by as much as +/-1 not-binned detector elements depending on wavelength and position in the XX direction (distortions are worst at the short- and long- wavelength ends of the IR detector). To correct for optical distortions, multiband images may be resampled in the spectral or spatial direction. Three types of resampling may have occurred: (a) resampling in the wavelength direction, as coded in the PS CDR; (b) resampling in the spatial direction, to remove differences in spatial scale with wavelength or band, using the CM CDR; and (c) VNIR data may be rescaled to match the slightly different magnification of the IR spectrometer, also the CM CDR. A resampled TRDR is distinguished by values of the keywords MRO:SPATIAL_RESAMPLING_FLAG, MRO:SPATIAL_RESCALING_FLAG, and MRO:SPECTRAL_RESAMPLING_FLAG. Ancillary Data : There are various types of ancillary data provided with this dataset: 1. Each hyperspectral targeted (gimbaled) observation TRDR IF data product has one browse product in a directory structure that parallels that of the TRDR directory. See BROWSE/BROWINFO.TXT for further details. 2. The TRDR EXTRAS visualizations are Portable Network Graphics (PNG) format files that depict the geometry and structure of CRISM hyperspectral targeted observations. See EXTRAS/EXTRINFO.TXT for further details. Coordinate System : The cartographic coordinate system used for the CRISM data products conforms to the IAU planetocentric system with East longitudes being positive. The IAU2000 reference system for Mars cartographic coordinates and rotational elements was used for computing latitude and longitude coordinates. Media/Format : The CRISM archive will be made available online via Web and FTP servers. This will be the primary means of distribution. Therefore the archive will be organized as a set of virtual volumes, with each data set stored online as a single volume. As new data products are released they will be added to the volume's data directory, and the volume's index table will be updated accordingly. The size of the volume will not be 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 will be written to the other media according to PDS policy, possibly dividing the contents among several physical volumes.
DATA_SET_RELEASE_DATE	2007-06-08T00:00:00.000Z
START_TIME	1965-01-01T12:00:00.000Z
STOP_TIME	N/A (ongoing)
MISSION_NAME	MARS RECONNAISSANCE ORBITER
MISSION_START_DATE	2005-08-12T12:00:00.000Z
MISSION_STOP_DATE	N/A (ongoing)
TARGET_NAME	MARS
TARGET_TYPE	PLANET
INSTRUMENT_HOST_ID	MRO
INSTRUMENT_NAME	COMPACT RECONNAISSANCE IMAGING SPECTROMETER FOR MARS
INSTRUMENT_ID	CRISM
INSTRUMENT_TYPE	IMAGING SPECTROMETER
NODE_NAME	Geosciences
ARCHIVE_STATUS	ARCHIVED - ACCUMULATING
CONFIDENCE_LEVEL_NOTE	Confidence Level Overview : There is a number of sources of uncertainty in the interpretation of TRDRs including: (A) Stochastic noise Random noise in the data due to statistical uncertainties in counting photons. This is manifested as noisy calibrated data. Noise is most significant in darker areas. Typically, the signal to noise ratio at <2500 nm is 400 in bright areas and 200 in dark areas, in the constituent observations, before pixel binning. (B) Optical distortions Optical distortion can affect spectra of small-scale features. In one column, the projection onto Mars' surface may vary by as much as +/-0.4 not-binned detector elements in the XX dimension depending on position in the FOV (distortions are worst at the edges of the VNIR and IR FOVs). For a single wavelength, its location in the ZZ direction may vary by as much as +/-1 not-binned detector elements depending on wavelength and position in the XX direction (distortions are worst at the short- and long-wavelength ends of the IR detector). In other words, different wavelengths include slightly different combinations of signal from spatially adjacent pixels, so that compositional interpretations of features near the scale of a pixel are weakly wavelength-dependent. Also, wavelength drifts across the field of view. Compositional interpretations based on exact wavelengths of absorptions may thus be weakly spatially dependent. The resampling approach outlined above can remove much of this uncertainty. (C) 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. (D) Calibration artifacts There are several instrument artifacts that are corrected in the calibration pipeline. Residual errors in the corrections will introduce systematic errors into the data. Optical Effects: (1) The boundary of zones 1 and 2 of the VNIR order sorting filter is a joint between two distinct glasses with different indices of refraction. When illuminated during detector-level tests, it was found to cause significant (>10%) scattered light at shorter wavelengths (<670 nm). This was correcting by replacing the VNIR focal plane assembly with the flight spare, onto which a narrow black stripe was painted to shadow the joint. The black stripe attenuates the light from 610-710 nm and causes a dip in response at those wavelengths. In the processed data, the are two major effects: signal to noise ratio is decreased, and non-reproducibility of the exact position of the shutter when observing the sphere causes shifting of the shadow in the wavelength direction. Measurement and correction of this effect are discussed below. (2) The spectrometer slit - which defines the mapping of wavelengths to detector rows as well as the spatial FOV - is mounted on a curved surface whose axis of curvature is parallel to the wavelength direction. The slit assembly is fixed with pins through holes whose diameters are oversized to provide margin for fastening the assembly. During instrument-level vibration testing, the slit assembly shifted in the wavelength direction by the tolerance in the hole diameters, shifting wavelength calibration by about 15 nm in both the VNIR and IR. Additional shifting of the slit assembly during and after launch is thought to have occurred. Wavelength calibration is observed to shift with major thermal excursions of the optomechanical assembly, at a magnitude of up to +/- 1 nm. This shift has been quantified and can be calibrated out using measured positions of Martian atmospheric gas absorptions, as recorded in the 'WS' CDR. (3) Shutter position irreproducibility - To illuminate the spectrometer slit's full 2.12 degree field of view, CRISM's telescope illuminates a circular region of slightly larger diameter surrounding the slit. The base of the shutter, on the hinge end, just protrudes into the illuminated area. At position 0, originally intended as the 'open' position, the reflective rear surface of the shutter provides the detectors an unbaffled view of the scene approximately 1 degree from the center of the field of view in a cross-slit direction, creating an out-of-focus 'ghost' image of that location. Moving the shutter through successive steps redirects the angle from which the ghost image originates to further from the center of the FOV. At position 3, the angle from which the ghost image originates is baffled by the telescope, and the ghost disappears. To remediate the ghost image, the open position of the shutter is defined in software to position 3. There is a small (about 0.1 degree) non-reproducibility in the angle at which the sphere is viewed and the fact that, unlike the external scene, the spectrometer's view of the sphere is vignetted by the sphere's aperture. With a slight shift in shutter position, the cone of sphere light entering spectrometer optics shifts. The filling of the dual zone gratings changes slightly, decreasing responsivity at long VNIR wavelengths and short IR wavelengths. Also, the shadow of the black strip on the VNIR order-sorting filter zone boundary shifts, creating a distinctive trough and peak pattern at detector rows 222-235 (approximately 605-690 nm). Because this effect is characteristic as a function of wavelength, it is correctable. Ratios of different sphere observations during ground calibration are used to create a multiplicative correction to a sphere image as a function of wavelength, that is maintained in a level 4 CDR. In flight data to be corrected, the magnitude of the peak near VNIR row 235 is measured. The correction is scaled by the magnitude of the peak, and it is multiplied by the data. The VNIR row 235 peak is used to scale the corrections for both the VNIR and IR. Errors in this correction would lead to high or low values especially at 600-700 nm, with the error being systematic within a group of observations processed using a single sphere observation, but random between such groups of observations. Put differently, the systematic errors would change every few orbits. To the limits of measurement error, the small irreproducibility of shutter position at the 'open' position has no measurable effect on external scene data. (4) IR 2nd order leakage: Zone 3 of the IR order sorting filter admits up to 3% of the 2nd order light from the grating, at wavelengths 1400-1950 nm, that falls at detector rows whose nominal wavelengths are 2800-3900 nm. The leakage peaks at a nominal wavelength of 3400 nm. Due to the falloff of both the solar spectrum and the Martian reflectance spectrum with increasing wavelength, the relative magnitude of the leakage to the signal in zone 3 is enhanced so that it becomes tens of percent of the total signal in that wavelength range. Ground testing provided sufficient data for an empirical correction for this effect, in which scaled values of signal at second-order wavelengths are subtracted from first-order (nominal) wavelengths. The correction is maintained in a level 4 CDR. Errors in this correction would be manifested in processed data as a negative positive additive component to the values from 2760-3920 nm, centered and strongest at 3400 nm. Electronics Ghost: Both detectors, but especially the VNIR detector, are subject to a weak ghost image of any illuminated spot into its corresponding location in every other of the four 160-column quadrants of the of the 640-column detector. This is a small effect at the <1% level, and is removed by scaling the image of each quadrant by an empirically determined value that is nonlinearly related to signal level, and then subtracting the scaled quadrant image from that of every other quadrant. The scale factors are maintained in a level 6 CDR. To the uncertainties in measurement, each of the four quadrants in a detector behaves only slightly differently. There is a minimal effect of frame rate, but ghost magnitude is apparently unaffected by detector temperature. Errors in this correction could be manifested as anomalously dark or bright spots exactly one-fourth of the detector width away (160 samples, 80 2x-binned samples, 32 5x-binned samples, or 16 10x-binned samples. IR 'Bad Pixels': The IR detector is operated at cryogenic temperature to minimize dark current and bias level of the detector. As the MRO mission has progressed, the setpoint for the IR detector has been raised to lessen the wear on the mechanical coolers that maintain IR detector temperature. With increasing detector temperature, not all pixels accrue an elevated bias level or dark current - the latter of which adds noise due to its electron counting statistics - at the same rate. The most susceptible pixels, within which effective SNR or available dynamic range are adversely impacted, are 'bad pixels.' Beginning with version 3 TRDRs, and improved approach to filtering is applied to I/F cubes to interpolate over bad pixels are interpolated over. VNIR Calibration Versions : Version 0 was the first version of VNIR radiometric calibration applied to flight data. Five major sources of inaccuracy and image artifacts were identified. The first arose from the method by which scattered light from the grating was extrapolated from scattered light columns across the scene. A simple linear interpolation was applied, and this underestimated the total scattered light within the scene. When this procedure was applied to ground calibration data to derive a model for sphere radiance, results include an unrealistically red spectral slope. When applied to flight measurements of Mars and the integrating sphere, results include residual cross-track (along-slit) color variations. The second problem arose from the choice of which sphere bulb to use as the primary calibration source. Originally it was the bulb controlled by the VNIR focal plane electronics. However, for unknown reasons, this bulb yields much greater scatter from the grating than does the bulb controlled by the IR focal plane electronics. Residuals within the shadow of zones 1 and 2 of the wavelengths order sorting filter led to a large negative artifact at 600-700 nm. The third problem arose from low light levels in the sphere at <560 nm. That is, measured sphere signal levels are low enough that they introduced systematic noise at short wavelengths into observations calibrated using them. The fourth problem arose from propagated statistical errors in sphere measurements used to calibrate the data. That is, corrections for all of the artifacts outlined above require a series of algebraic operations each of which propagates small errors or effects of noise. The sphere data require more corrections, and at lower-signal wavelengths the residual errors at each detector element are manifested as a spuriously high or low value at the corresponding wavelength and spatial position. This can appear as wavelength-dependent striping in the along-track direction. Fifth, it was discovered that the bias varies image to image, leading to striping in the cross-track direction in processed data. Version 1 used an arbitrary scaling across of scattered light from the grating across the field of view, in an attempt to remediate the first two effects. It proved unsuccessful, and was abandoned after validation of the first observations to which it was applied. Version 2 addresses and largely corrects each of the five major problems with version 0. First, there is a more sophisticated extrapolation from the scattered columns. At short wavelengths, the distribution is measured from measured signal at UV wavelengths. The detector is nearly unresponsive to UV signal from Mars, so in most regions the nominally UV wavelengths instead provide a measure of the scattered light at the corresponding position along the slit. This gradually transitions with longer wavelength to a linear extrapolation between the scattered light columns, as with version 0. This correction is applied both to ground calibration data used to derive the sphere radiance model, and to flight scene and sphere data. Second, the sphere bulb controlled by the IR focal plane electronics is used as the primary radiometric reference, because the lower scattered light from it is more easily corrected and leaves lesser artifacts at low-signal wavelengths. Third, calibration of the data is handled differently at <560 nm and at >560 nm. At longer wavelengths, sphere measurements and the sphere radiance model traceable to ground measurements are used to determine a snapshot of detector responsivity, and apply that to scene data to derive radiance. This is appropriate because of temperature dependence of optical throughput, especially the beamsplitter, at >560 nm. At shorter wavelengths, responsivity is derived directly from ground calibration measurements, and low-signal sphere data are not used. The approach has consistently yielding nearly identical, continuous results at the wavelengths at which the two approaches overlap, about 530-600 nm. Fourth, to eliminate propagation of statistical errors in processing of sphere data, the sphere-derived responsivity at each wavelength is averaged. Correction for spatial nonuniformity occurs using a Mars flat-field calibration and the NU CDR derived from it. Fifth, to remove frame-to-frame variations in bias, an additive correction is applied to each frame while still in units of DN, to make the physically masked columns at the edge of the detector zero after dark subtraction. There are two alternate versions of VNIR version 2 specifically for special types of observations. The bland Mars scenes used to measure non-uniformity are processed to version 9 TRDRs. The version 9 processing is the same as version 2 except it doesn't include the non-uniformity correction. Deimos, Phobos, and any other pointlike or compact targets like stars are processed to version 8 TRDRs. The major difference in the processing for such scenes is that within-scene scattered light from the grating is much less, so the correction for intra-scene scattered light is skipped. The VNIR version 8 processing uses special version 8 'SS' and 'NU' CDR4s. Version 3 is the current version of the VNIR calibration, released in late 2010. The most substantive change from version 2 is an improved correction for shutter mirror irreproducibility. Version 7 replaces version 9 for bland Mars scenes. Version 6 replaces version 8 for Phobos and Deimos. For I/F cubes - but not radiance cubes - the ratio shift correction was introduced to further reduce the magnitude of propagated artifacts of ground calibration. (The radiance cube is a 'control' in case the ratio shift correction introduces its own artifacts.) Known Issues with VNIR Radiometric Calibration : Version 3 has been validated using observations of the MER Spirit and Opportunity landing sites, with PANCAM measurements that were modeled at the top of the atmosphere using CRISM viewing geometry and solar longitude. Four artifacts or data quality concerns remain. (a) Radiance at <410 nm is typically low, because there is not much signal at those wavelengths and they are most susceptible to artifacts from scattered light subtraction. (b) Some artifact at the wavelengths of the filter zone boundary. In some parts of the field of view at sharp brightness contrasts it extends to 644-684 nm. (c) Scenes with large coverage by ice, especially near either edge of the field of view, have more significant artifacts from the scattered light correction because, unlike typical Martian soils, ice has significant UV reflectance and that decreases accuracy of the correction. Typical effects may include degradation at wavelengths below 480 nm and above 1010 nm. (d) Due to spectral smile, mineralogic absorptions located where instrument response varies steeply with wavelength exhibit variation with field angle. This is most prominent with Fe mineral absorptions near 900 nm. IR Calibration Versions : Version 0 was the first version of IR radiometric calibration applied to flight data. Five major sources of inaccuracy and image artifacts in version 0 are known. The first originated from inadequacy of the bad pixel correction. On ground, three types of bad pixels were observed: hot with high dark current, dead with no response, and noisy. Based on that the bad pixel correction was planned to use dark measurements to identify bad pixels. Inflight, a new type of bad pixel was identified, whereby a detector element abruptly develops high dark current, then abruptly returns to normal. At least 2 percent of pixels, and probably more, display this behavior at some time. This was manifested as sharp, wavelength-dependent striping in the along-track direction in image data. The second problem originated from incomplete correction of bad pixels in ground calibration measurements used to derive the sphere radiance model. This was manifested as diffuse, wavelength-dependent striping in the along-track direction in image data. The third problem was spuriously high radiances near the boundaries of the order sorting filters, especially at 1630-1680 and 2690-2770. A lesser spuriously high radiance occurred at 1800 nm. Spuriously high values also occurred at <1050 nm. The fourth problem was 'bumps' in radiances at 1370 and 1850 nm, water vapor in the beam and adsorbed water on ground calibration sources was under-corrected. The fifth problem was that the correction for leaked second order light at >2700 nm was not implemented in version 0. Version 1 partially corrected problems with version 0 but did not close out known IR calibration issues. First, within-scene bad pixels were identified were interpolated over. For each scene, the entire scene was collapsed to one median frame matching the layout of the detector. Then a median filter was run in the spatial direction. The difference between the median image and the filtered median image was calculated, and detector elements having more than a 1.4 standard deviation difference were identified as bad pixels. These were replaced throughout the scene by the average of the adjacent non-bad pixels at the same wavelength. Second, artifacts in the sphere radiance model were removed using a Mars flat-field calibration and the NU CDR derived from it. However this is not done within strong atmospheric absorptions near 1400, 1600, 2000, and 2700 nm because spectral smile would introduce new artifacts. Third, systematically high radiances at the filter zone boundaries were corrected by smoothing the sphere radiance model. Fourth, the 'bumps' in radiances at 1370 and 1850 were corrected by performing an approximate atmosphere removal on bland, dusty terrain at the summit of Olympus Mons. The magnitude of the 'bumps' was estimated, and the appropriate multiplicative correction to the sphere model to remove them was applied. Version 2 added six further corrections for outstanding issues identified in version 1. First, in version 1, incomplete correction for water vapor in the spectra of ground calibration sources had introduces a 'bump' in radiance at 2550-2650 nm. This wavelength is on the edge of a strong 3-micron absorption in Mars; spectrum, so Olympus Mons observations could not be used to estimate a correction. Instead this artifact was corrected using observations of Deimos, which lacks a 3-micron band. The magnitude of the 'bump' was estimated, and the appropriate multiplicative correction to the sphere model to remove them was applied. Second, smoothing of the sphere radiance model that had been used in version 1 was performed in an attempt to correct anomalously high derived Mars radiances in the 2 channels closest in wavelength to 2700 nm. Third, in version 2 leaked second order light at >2700 nm was corrected. This was performed by subtracting scaled radiances from one-half the wavelength using the 'LL' CDR4s. Fourth, in version 1, the bad pixel correction had been set to too sensitive a threshold, so that abrupt brightness boundaries often triggered the bad pixel correction, leading to aliasing at those boundaries. The threshold for identifying a bad pixel in the median-scene image was increased from 1.4 to 2.4 standard deviations in version 2. Fifth, slight misalignment of the instrument aperture with the ground calibration source introduced systematic error into the sphere radiance model. This preferentially affected wavelengths below 1500 nm, and in version 1 scene radiances it had introduced a broad, sigmoidal-shaped bump centered near 1400 nm. For version 2, this effect was modeled using grating theory, and a one-time correction for it was applied to the sphere radiance model. Sixth, in version 1, no attempt had been made to remove scattered light from the grating at IR wavelengths, either in scene data or in observations of the internal integrating sphere. The effect was overestimation of IR scene radiance at <1900 nm. In version 2, the correction was introduced. However, unlike the VNIR correction for grating scatter, for the IR detector transient bad pixels render a correction of this form noisy. Instead this correction was derived using a bland, dusty scene on Mars, applying the correction both to the scene and to the accompanying sphere measurement. The extrapolation across the field of view uses a function resembling that at the longest VNIR wavelengths. The correction was then median filtered and multiplied into the sphere radiometric model. Given the derivation of the IR scattered light correction, it is most accurate for uniformly illuminated scenes. There are two alternate versions of IR version 2 specifically for special types of observations. The bland Mars scenes used to measure non-uniformity are processed to version 9 TRDRs. The version 9 processing is the same as version 2 except it doesn't include the non-uniformity correction. Deimos, Phobos, and any other pointlike or compact targets like stars are processed to version 8 TRDRs. The major difference in the processing for such scenes is that within-scene scattered light from the grating is much less, so the correction for intra-scene scattered light is skipped. The IR version 8 processing uses special version 8 SS CDR4s. Version 3 is the current version of IR radiometric calibration, released in late 2010. There are several improvements over version 2. First, the effects of shutter mirror position irreproducibility were found to vary with each sphere measurement, that was in turn applied to a group of scene measurements. That group was in many cases systematically too high or low in radiance at 1000-1700 nm. Instead, each sphere measurement is corrected using as a measurement of the shutter mirror effect the shape of the VNIR zone boundary artifact. This approach was found to yield greatly improved reproducibility of different TRDRs covering the same scene. Second, the estimation of leaked 2nd order light at IR wavelengths near 3100-3300 nm was improved. The algorithm used in version 2 had propagated an artifact at the zone 1 - zone 2 filter boundary near 1630 nm, where the leakage was being estimated, to 3180 nm, where the leakage was being removed. Interpolation of the leakage correction over a wider band at the zone 1 - zone 2 boundary was found to greatly reduce the artifact near 3180 nm. Third, the correction for atmospheric water vapor in ground calibration measurements was modified to further reduce spectral artifacts near 1850 and 2550 microns. Fourth, the width of the band near 2000 nm within which flat-fielding is not applied was increased, to remove distortions in Mars' atmospheric CO2 absorption near 1830 nm. For I/F cubes - but not radiance cubes - the ratio shift correction and iterative kernel filter were introduced to further reduce the magnitude of propagated artifacts of ground calibration and noise in flight data. (The radiance cube is a 'control' in case the ratio shift correction and iterative kernel filter introduce their own artifacts.) Known Issues with IR Radiometric Calibration : Due to spectral smile, mineralogic absorptions located where instrument response varies steeply with wavelength exhibit variation with field angle. This is most prominent at the edge of atmospheric gas absorptions near 1400 and 2000 nm. 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. Summary of VNIR and IR 'bad channels' : The following channels can be routinely excluded: VNIR: wavelengths less than 410, 644-684, greater than 1023 nm IR: wavelengths less than 1021 nm, 2694 and 2701 nm, and greater than 3924 nm The following channels may be 'degraded' and their quality is observation-dependent. Caution is recommended but the data may be valid. VNIR: Wavelengths less than 442 nm (due to artifacts from scattered light correction in very contrasty scenes) Wavelengths greater than or equal to 970 nm (radiances are observed to misalign with IR radiances; the reason is uncertain but may be related to uncorrected effects of beamsplitter temperature) IR: Wavelengths less than 1047 nm radiances are observed to misalign with IR radiances; the reason is uncertain but may be related to uncorrected effects of beamsplitter temperature) Wavelengths 2660-2800 nm (the reason is uncertain but may be due to problems with correction of water vapor in measurements of the ground calibration sources) The shape of the spectrum at 3100-3800 nm is suspect and there may be a broad, low 'bump'. Review : This archival data set will be examined by a peer review panel prior to its acceptance by the Planetary Data System (PDS). The peer review will be conducted in accordance with PDS procedures. Data Coverage and Quality : For each observation, every EDR is compared against frame-by-frame predictions of commanded instrument state. The results of the comparison are written as a data validation report that accompanies the EDRs for that observation. In the case of a hardware or configuration discrepancy (shutter position, lamp status or level, pixel binning, frame rate, channel selection, power status of detectors), processing of the image data to TRDR level does not occur in order to avoid introducing invalid results, and DDRs are not created. Also, missing frames or portions of frames are replaced with a value of 65535 (this cannot be a valid data value). That portion of the EDR is not further processed, and it also is propagated to a value of 65535 in all layers of the TRDR. Only a subset of instrument configurations represent 'scene' data, as indicated by the keyword MRO:ACTIVITY_ID. Only scene data aimed at planetary targets have corresponding TRDRs. Limitations : None.
CITATION_DESCRIPTION	Murchie, S., Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars Targeted Reduced Data Record, MRO-M-CRISM-3-RDR-TARGETED-V1.0, NASA Planetary Data System, 2006.
ABSTRACT_TEXT	This dataset is intended to include IR and VNIR data from the CRISM instrument on MRO, processed to several different levels. The core structure parallels that of an EDR with a multiband image and a text file containing frame-specific housekeeping information for each of the concatenated image frames in the multiband image. However the image data has been 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. A TRDR may also contain separately labeled multiband images in which radiance has been processed to I/F (radiance divided by (pi * solar flux at 1 AU * heliocentric distance^2)), Lambert albedo, or a set of derived spectral parameters (summary products) that provide an overview of the data set. The summary products include Lambert albedo at key wavelengths, or key band depths or spectral reflectance ratios. To create Lambert albedo or most summary products, estimated corrections for atmospheric and photometric effects are applied to the I/F data.
PRODUCER_FULL_NAME	SCOTT MURCHIE
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