| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This volume contains portions of the CRISM Multispectral Reduced
Data Record (MRDR) Archive, a collection of multiband images
from the Compact Reconnaissance Imaging Spectrometer for Mars on
the Mars Reconnaissance Orbiter spacecraft. Images consist of
map-projected data calibrated to units of corrected I/F plus a
text file listing the wavelengths present. Additional image
data have had further corrections applied. Each image or text
file is stored with a PDS label.
This volume also contains an index file ('imgindx.tab') that
tabulates the contents of the volume, ancillary data files, and
documentation files. It may also contain browse images in PNG
or IMG format, and HTML documents that support a web browser
interface to the volume.
For more information on the contents and organization of the
volume set refer to the aareadme.txt file located in the root
directory of the data volumes.
Parameters
==========
CRISM observing scenarios are constructed using a set of key
variables ('configurations') which include the following. (All
are selectable separately for the VNIR and IR detectors. Only a
subset of the configurations are used to generate MRDRs.)
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 10x pixel binning are used in
the generation of MRDRs.
Row selection: All detector rows having useful signal can be
saved, or 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. The nominal number of rows for
multispectral mode was 73, 18 in the VNIR and 55 in the IR prior
to 10 Dec 2006. On that date an extra channel was added to the
VNIR for a total of 19. One row in each detector is for calibration
Purposes. Mapping data have also been collected with extended
wavelength sets, all 107 VNIR channels and 155 IR channels, for
a partially hyperspectral equivalent of the multispectral data.
Those data are included in the MRDRs by extracting the wavelengths
that are common to multispectral operating mode.
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
an MRDR. Focal plane lamps are not used as part of the calibration
process, but the integrating sphere lamp controlled by the
IR focal plane is.
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 an MRDR.
Pointing: CRISM has two basic gimbal pointing configurations and
two basic superimposed scan patterns. Pointing can be (1) fixed
(nadir-pointed in the primary science orbit) or (2) dynamic,
tracking a target point on the surface of Mars and taking out
ground track motion. Two types of superimposed scans are
supported: (1) a short, 4-second duration fixed-rate ('EPF-type')
scan which superimposes a constant angular velocity scan on either
of the basic pointing profiles, or (2) a long, minutes-duration
fixed-rate ('target swath-type') scan. Only fixed nadir-pointed
data are processed to an MRDR.
Processing
==========
The CRISM data stream downlinked by the spacecraft unpacks into a
succession of compressed image frames with binary headers
containing housekeeping. In each image, one direction is spatial
and one is spectral. There is one image for the VNIR focal plane
and one image for the IR focal plane. The image from each focal
plane has a header with 220 housekeeping items that contain full
status of the instrument hardware, including data configuration,
lamp and shutter status, gimbal position, a time stamp, and the
target ID and macro within which the frame of data was taken.
These parameters are stored as part of an Experiment Data Record
(EDR), which consists of raw data. The data in one EDR
represents a series of image frames acquired with a consistent
instrument configuration (shutter position, frame rate, pixel
binning, compression, exposure time, on/off status and setting
of different lamps).
Once data are assembled into EDRs, they are calibrated into TRDRs.
Image data are converted to units of radiance using level-4 and
level-6 CDRs, and analog housekeeping items in the text file
(voltages, currents, and temperatures) have been converted into
physical units using a level-6 CDR. Both files share a common
label. The calibration algorithms are discussed at length in
the CRISM Data Products SIS.
A TRDR may also contain separately labeled multiband images in
which radiance has been processed to one of the following:
radiance in units of (W / (m^2 sr micron))
I/F (radiance divided by (pi * solar flux at 1 AU * heliocentric
distance^2)),
During construction of MRDRs, additional values generated from I/F
include:
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.
Information on physical properties and illumination conditions of
the site observed in the EDR or TRDR is maintained in a Derived
Data Record or DDR. There are 14 layers in each DDR:
Solar incidence angle relative to areoid, at the same planetary
radius as surface projection of pixel, units degrees.
Emission angle relative to areoid, at the same planetary
radius as surface projection of pixel, units degrees.
Solar phase angle, units degrees.
Areocentric latitude, units degrees N.
Areocentric longitude, units degrees E.
Solar incidence angle relative to planetary surface as estimated
using MOLA shape model, units degrees.
Emission angle relative to planetary surface as estimated using
MOLA shape model, units degrees.
Slope magnitude, using MOLA shape model and reference ellipsoid,
units degrees.
Slope azimuth, using MOLA shape model and reference ellipsoid,
units degrees clockwise from N.
Elevation relative to MOLA datum, units meters.
TES thermal inertia, units J m^-2 K^-1 s^-0.5.
TES bolometric albedo, unitless.
Spare.
Spare.
The TES data are in support for a correction for thermal emission
which is not included as part of MRDR processing.
The sequence of processing that creates an MRDR from the above
products is as follows:
(a) EDRs are assembled from raw data.
(b) The radiance multiple band images in TRDRs are created from
EDRs and Calibration Data Records, or CDRs, using a calibration
algorithm discussed at length in an Appendix in the CRISM Data
Products SIS. Briefly, a measurement of bias is subtracted from
shutter-closed dark measurements, images of the interior of the
integrating sphere taken with the shutter in an intermediate
position, and scene data taken in the appropriate open position.
Electronics artifacts are removed as detailed in the Data Product
SIS, and the data are linearized. Dark measurements accompanying
each the sphere and scene data are averaged by wavelength to
improve signal-to-noise ratio, and scaled spatially to the
dimensions of the scene and sphere data. Dark measurements are
subtracted from both the scene and sphere measurements. The
sphere measurements are averaged by wavelength to improve signal-
to-noise ratio, and scaled spatially to the dimensions of the
scene data. The scene and sphere measurements are divided by
their respective exposure times. The scene data are divided by
the sphere data, both now in units of corrected DN per second,
to yield a unitless result, which is multiplied by a
ground-calibration-derived model of integrating sphere
spectral radiance, to yield scene spectral radiance.
(c) Gimbal positions are extracted from the EDR housekeeping and
formatted as a gimbal C kernel.
(d) Using the gimbal C kernel and other SPICE kernels, DDRs are
created. The surface intercept on the MOLA shape model is
calculated for each spatial pixel (sample at the reference
detector row). The angles of this pixel relative to the equatorial
plane and reference longitude constitute the latitude and
longitude of the pixel. For that latitude and longitude, solar
incidence, emission, and phase angles are determined at a
surface parallel to the areoid but having a radius from
planetary center equivalent to that of the surface intercept of
the shape model. Solar incidence and emission are also
determined relative to the shape model itself. Using the
latitude and longitude of the surface intercept of each spatial
pixel, MOLA elevation is retrieved from a global elevation map
and resampled into CRISM sensor space using nearest neighbor
resampling.
(e) Radiance is converted to I/F by dividing by (pi *
solar flux at 1 AU * heliocentricdistance^2)). Solar flux is
maintained in a level 4 CDR, and solar distance is written in the
label to the radiance image.
(f) I/F is converted to Lambert albedo to allow rapid
identification of new ROIs and to quickly assess the information
content of targeted observations. Some or all of the following
corrections may be made:
I/F is divided by cosine of the solar incidence angle
The estimated contribution to and attenuation of the signal by
atmospheric aerosols is removed.
The estimated attenuation of the signal by atmospheric dust and
ice aerosols is corrected to a target value.
(g) After the corrections discussed below are performed,
multispectral TRDRs are map projected into MRDRs using the
latitude and longitude information in the DDRs. Because of the
mosaicked nature of an MRDR, the following protocol was used in
MRDR versions 1 and 3 to select between overlapping TRDRs for
inclusion in the MRDR:
If I/F is available but not Lambert albedo, the TRDR with
the lower incidence angle at the areoid is used
If Lambert albedo is available, then:
If both TRDRs have incidence angles >70 degrees, the one
with the lower incidence angle is used.
If one incidence angle is >70 degrees and one is <70,
the TRDR with i < 70 degrees is used.
If both incidence angles are <70 degrees, then the TRDR with
the lower 440-nm Lambert albedo is used.
For version 4, strips of mapping data are placed into the Lambert
albedo multiple band images such that the strip acquired under the
conditions of highest atmospheric opacity from [MONTABONEETAL2015]
data is placed first, and strips are then placed in order of
decreasing atmospheric opacity with the strip acquired under the
lowest atmospheric opacity is placed 'on top'. Only data acquired
during periods of atmospheric opacity <1.0 from
[MONTABONEETAL2015] are included, to limit the opacity whose
Effects are to be corrected as described below.
TIME DEPENDENCY OF THE APPROACH TO ATMOSPHERIC CORRECTION:
There are two alternative paths for correction of atmospheric
and photometric effects (the second path only applies to
version 4 MRDRs):
Mapping data acquired prior to May 2012 fall within the time range
of acquisition of gimbaled CRISM Emission Phase Functions, from
which retrievals provide a record of atmospheric dust opacity
sampled at CRISM's wavelength sampling and resolution as a
function of latitude, longitude, solar longitude, and Mars year.
MRO MARCI data provide retrievals of atmospheric water-ice
opacity also as a function of latitude, longitude, Ls, and Mars
year. For times when these opacities are present, using the
procedures described by [MCGUIREETAL2013], a full radiative
transfer model is used to correct I/F to a standard reference
photometric geometry with atmospheric contributions to I/F
normalized to a nadir geometry with a dust opacity of 0.2 and
an ice opacity of 0.0. Information on latitude, longitude, Ls,
and altitude are extracted from the header of the TRDR containing
the I/F data and the companion DDR. These data are used to
extrapolate to the best estimate of the atmospheric opacites
from CRISM and MARCI data. Then the photometric angles,
altitude, Ls, and wavelength plus the opacities extracted from
CRISM and MARCI data are used to interpolate wavelength-by-
wavelength to correct from I/F to Lambert albedo at i=30
degrees, e=0, g=30, dust opacity=0.2, and ice opacity=0.0
with no absorptions due to atmospheric gases. The Lambert
albedo becomes the basis to which mapping strips acquired
after May 2012 (when EPFs were no longer acquired) are corrected.
For mapping data acquired after May 2012, a two-step correction
is used that does normalize out atmospheric gas absorptions and
correct for photometric effects, but does not attempt to correct
for aerosol effects. This processing closely follows that
applied to CRISM TERs and MTRDRs. The first step is the
volcano scan atmospheric correction uses empirically derived
Mars atmospheric transmission spectra to correct CRISM IR
(L-detector) spectral reflectance data for atmospheric gas
absorptions (due primarily to CO2, H2O, and CO)
[MURCHIEETAL2009, MORGANETAL2011]. There are no significant
atmospheric gas absorptions over the CRISM VNIR wavelength
range, so this correction is not applied to VNIR (S-detector)
data. Detector column-specific reference atmospheric transmission
spectra (to accommodate spectral smile) are derived from a suite
of push-broom hyperspectral Flat Field Calibration (FFC) scans
over Olympus Mons and are matched to a given observation to
minimize high frequency residual spectral structure due to sub-nm
wavelength calibration variability across the wavelengths
affected by the 2000 nm CO2 absorption (1947 - 2066 nm).
The depth of the 2000 nm CO2 absorption is determined for the
spectrum of each spatial pixel in the image cube under
consideration, the selected reference transmission spectrum
is scaled to match according to the Beer-Lambert Law, and the
resulting model transmission spectrum is ratioed out of the I/F
data. The MRDR pipeline implementation of the volcano also
includes a CRISM-specific volcano scan patch (included in the
CRISM Analysis Toolkit v7.1+ available at the PDS Geosciences
Node) that is applied after the initial correction to reduce
the influence of varying path length and pressure broadening
in the derivation of the reference transmission spectra.
The second step for data corrected using the volcano scan is
application of a photometric correction using a Lambert
assumption:
IOF_corrected = IOF_uncorrected / cos(theta)
where theta is the solar incidence angle.
The photometric correction is calculated for each spatial
pixel and is applied uniformly to all spectral
channels. The spatial pixel specific incidence angle
information is derived from the 'INA at areoid' band
(incidence angle with respect to the Mars areoid) in the
CRISM DDR (Derived Data Record) associated with the
observation and segment under consideration.
FILTERING TO REDUCE NOISE (version 4 only):
72-channel I/F mapping strips are filtered for stochastic noise
and systematic noise and artifacts in two steps, respectively.
The first step to remediate stochastic noise is a simplified
version of the Iterative Kernel Filter used for noise
remediation in the I/F version of TRR3s. The second step to
remediate systematic effects is the Ratio Shift Correction also
applied during that filtering.
The Iterative Kernel Filter (IKF) procedure as applied to
multispectral data is a kernel based filtering algorithm that
models the information content of a given two dimensional
normalized data kernel as a multidimensional polynomial.
The model residuals are treated as a sample set and examined
for outliers using the Grubbs test. If an outlier is detected,
the corresponding pixel is removed from consideration and the
kernel model is iterated. Model iteration is terminated when
no further outliers are detected. The filtered value for the
target pixel at the center of the input kernel is then given
by a proximity weighted model of the kernel elements that were
not marked as outliers. The confidence level threshold for
the Grubbs test is conservative so the filter retains some
marginal noise. The IKF is applied primarily to IR data.
The Ratio Shift Correction (RSC) procedure as applied to
multispectral data is the primary filtering process for VNIR
data. Within a given spectral band, a spatial column
corresponds to a single detector element. The Ratio Shift
Correction characterizes residual bias of each detector
element through the evaluation of inter-column (or cross-
track shifted) ratio statistics relative to a cross track
model. Modifying the complexity of the underlying cross track
model allows the RSC procedure to address high frequency
column striping or low frequency banding while retaining real
scene cross-track variability.
NORMALIZATION OF STRIP-TO-STRIP RESIDUALS (version 4 only):
At this stage of processing there are significant residual
differences in I/F between overlapping strips of mapping
data due to several effects: systematic errors in radiometric
calibration between strips; inaccuracy in the assumption of
a wavelength-independent Lambert photometric function; for strips
processed to Lambert albedo, differences between the modeled and
actual atmospheric dust and ice opacities; for strips processed
using the volcano scan correction, the presence of atmospheric
dust and ice opacities different that the target values of dust
opacity = 0.2, and ice opacity=0.0; and differences between the
actual and modeled values of H2O vapor and CO due to seasonal
or meteorological variations. The calibration residuals are
only somewhat notable in I/F, but the magnitudes are in family
with real spectral variations for many of the mineralogical
spectral indices represented as summary products.
To remediate these interstrip differences, an optimization
procedure is performed in which derived values of surface
reflectance are corrected to the values in the closest to ideal
data among the mapping strips, using the millions of overlap and
proximity relations among the approximately 83,000 strips of
VNIR+IR data in the map. Prior to optimization, the millions
of areas of intersection and close proximity are identified.
The differences between each such pair of strips is analyzed
using graph theory, and the best-fit gain and offset
describing the differences are recorded. Of course, each such
solution will have some systematic error.
In the optimization procedure, overall error is minimized (and the
data set is optimized) by applying the gains and offsets in a
weighted fashion, anchoring the output values to that part of the
data which is closest to ideal. Those 'anchor' strips have the
following attributes: low IR detector temperature, as close as
possible to the minimum value used in flight; low solar incidence
angles; low dust opacity in the data as acquired as recorded in
[MONTABONEETAL2015] data; and the atmospheric corrections were
performed using the full radiometric model, not the volcano scan
correction. Note that only mapping strips corrected to
dust opacity=0.2 and ice opacity=0.0 using DISORT-traceable
procedures populate the anchor strips. Provided that there are
overlaps with such strips, the strips corrected with the volcano
scan approach effectively have their dust and ice opacities also
normalized to the target values. Thus correction to Lambert
albedo is propagated among all strips.
Data
====
DATA DESCRIPTION:
There is only one data type associated with this volume, the
Multispectral Reduced Data Records or MRDRs.
An MRDR consists of mosaicked, map-projected multispectral TRDRs.
All data are represented as 32-bit real numbers. The
multispectral map RDR contains up to five multiple-band images at
256 pixels/degree (versions 1 and 3) or 327 pixels/degree
(version 4) and one list file.
The first multiple-band image is map-projected I/F without
any further corrections applied, taken directly from the
TRDR associated with a strip of multispectral data.
Although in the TRDRs there are separate multiple-band images
for the VNIR and IR detectors, in this case the data are merged.
The size of the multiple-band image varies between map tiles. A
typical multiple-band image might have 1280 pixels (versions 1
and 3) or 1635 pixels (version 4) in the latitude direction,
a variable number of pixels in the longitude direction, and
approximately 72 pixels in the wavelength dimension, representing
each of the selected channels in multispectral mode. This type
of multiple-band image is present in version 1 and 3 MRDRs.
The second multiple-band image is geometrically identical to the
map-projected I/F multiple-band image (if present), except that
data have been processed to Lambert albedo. This type of multiple
band image is present in version 1 and 4 MRDRs.
The third multiple-band image contains map-projected data from
DDRs associated with a strip of multispectral data, used to
derive I/F from radiance. The file corresponds to mosaicked I/F.
11 additional layers that are specific to individual multispectral
strips used to assemble the tile, and are thus not contained in
the DDR. This additional information provides traceability back
to the source TRDRs:
Solar longitude, units degrees
Solar distance at time of measurement, units AU (versions 1,3)
VNIR observation ID of constituent measurement
IR observation ID of constituent measurement
The VNIR ordinal counter carried through from the source scene
EDRs
The IR ordinal counter carried through from the source scene
EDRs
The VNIR column number carried through from the TRDR
used to populate the MRDR; this identifies the VNIR wavelength
calibration at the spatial pixel of the MRDR
The IR column number carried through from the TRDR
used to populate the MRDR; this identifies the IR wavelength
calibration at the spatial pixel of the MRDR
The ordinal number of the frame from the source VNIR TRDR; this
together with column number, observation ID, and ordinal counter
provides traceability back to a spatial pixel in a source EDR
The ordinal number of the frame from the source IR TRDR
Time of day, hhmm.ss
This type of multiple-band image is present in version 1 and 3
MRDRs.
The fourth multiple-band image contains map-projected data from
DDRs associated with a strip of multispectral data, which has been
processed to Lambert albedo. The files correspond to the mosaicked
Lambert albedo. The same additional layers as in the third file are
also present. This type of multiple-band image is present in
version 1 and 4 MRDRs.
The fifth multiple-band image contains map-projected summary
products.
The list file, in ASCII format, contains wavelengths
of each layer in the I/F and Lambert albedo images.
A suite of mineral indicators and other measures of spectral
shape and reflectivity, collectively called spectral summary
parameters, is calculated from the Lambert albedo or I/F data.
Summary product multiple band images are included in version 1 and
4 MRDRs. Version 1 used formulations based upon the published
formulations of [PELKEYETAL2007]. Version 4 MRDRs used the
revised and expanded spectral summary parameter library of
[VIVIANO-BECKETAL2014] which was developed to better detect
the surprisingly large range of minerals found by CRISM and
to reduce false positives. The bands in the SU image cube are
given below along with a brief description of their significance.
Users are referred to Table 3-12 of the CRISM Data Product SIS for
detailed formulations and caveats.
R770 (versions 1, 4)
= 0.77-micron reflectance (higher value more dusty
or icy)
RBR (versions 1, 4)
= Red/blue ratio (higher value indicates more
nanophase iron oxide or sky illumination)
BBD530 (version 1), BD530_2 (version 4)
= 0.53-micron band depth (higher value has more
fine-grained crystalline hematite)
SH600 (version 1), SH600_2 (version 4)
= 0.6-micron shoulder height (select ferric
minerals esp. hematite, goethite, or a
compacted texture)
SH770 (version 4)
= 0.77-micron shoulder height (select ferric
minerals, less sensitive to LCP than SH600_2)
BD640 (version 1), BD640_2 (version 4)
= 0.64-micron band depth (select ferric minerals,
esp. maghemite, but obscured by VNIR detector
artifact)
BD860 (version 1), BD860_2 (version 4)
= 0.86-micron band depth (select crystalline
ferric minerals, esp. hematite)
BD920 (version 1), BD920_2 (version 4)
= 0.92-micron band depth (crystalline ferric minerals
and low-Ca pyroxene, or LCP)
RPEAK1 (versions 1, 3, 4)
= Reflectance peak 1 near 0.77 microns (<0.75
suggests olivine, 0.75 pyroxene, >0.8 dust)
BDI1000VIS (versions 1, 4)
= 1-micron integrated band depth; VNIR wavelengths
(olivine, pyroxene, or Fe-bearing glass)
BDI1000IR (versions 1, 4)
= 1-micron integrated band depth; IR wavelengths
(crystalline Fe2+ silicates)
IRA (version 1), R1330 (version 4)
= IR albedo at 1.3 microns, near peak between pyroxene
absorptions
BD1300 (version 4)
= 1.3-micron absorption associated with Fe2+
substitution in plagioclase
OLINDEX (version 1), OLINDEX3 (version 4)
= Broad absorption centered at 1 micron
(olivine strongly >0, also detects Fe-phyllosilicate)
LCPINDEX (version 1), LCPINDEX2 (version 4)
= Broad absorption centered at 1.81 micron
(pyroxene is strongly +; favors LCP)
HCPINDEX (version 1), HCPINDEX2 (version 4)
= Broad absorption centered at 2.12 microns
(pyroxene is strongly +; favors HCP)
VAR (versions 1, 4)
= 1.0-2.3-micron spectral variance; Ol & Px will
have high values; MGS/TES Type 2 areas will have
low values
BD1270O2 (version 1)
= O2 emission; inversely correlated with high altitude
water; signature of ozone
ISLOPE1 (versions 1, 4)
= Spectral slope 1 (from 1.185 to 2.530 microns;
ferric coating on dark rock)
BD1400H20 (version 1), BD1400 (version 4)
= 1.4-micron H2O and -OH band depth
(hydrated or hydroxylated minerals)
BD1435 (versions 1, 4)
= 1.435-micron CO2 ice band depth
BD1500 (version 1), BD1500_2 (version 4)
= 1.5-micron H2O ice band depth
ICER1 (version 1), ICER1_2 (version 4)
= CO2 and H2O ice band depth ratio at 1.43-1.5 microns
BD1750 (version 1), BD1750_2 (version 4)
= 1.75-micron H2O band depth (gypsum or alunite)
BD1900 (version 1), BD1900_2 (version 4)
= 1.9-micron H2O band depth (hydrated minerals
except monohydrated sulfates)
BD1900r2 (version 4)
= 1.9-micron H2O band depth (hydrated minerals
except monohydrated sulfates)
BDI2000 (versions 1, 4)
= 2-micron integrated band depth (pyroxene)
BD2100 (version 1), BD2100_2 (version 4)
= 2.1-micron shifted H2O band depth in monohydrated
sulfates
BD2165 (version 4)
= 2.165-micron Al-OH band depth
(pyrophyllite, kaolinite-group minerals)
BD2190 (version 4)
= 2.190-micron Al-OH band depth
(beidellite, allophane, imogolite)
MIN2200 (version 4)
= 2.16-micron Si-OH band depth and 2.21-micron
H-bound Si-OH band depth (doublet; kaolinite)
BD2210 (version 1), BD2210_2 (version 4)
= 2.21-micron Al-OH band depth (Al-OH minerals)
D2200 (version 4)
= 2.2-micron dropoff (Al-OH minerals)
BD2230 (version 4)
= 2.23-micron band depth
(hydroxylated ferric sulfate)
BD2250 (version 4)
= 2.25-micron broad Al-OH and Si-OH band depth
(opal, Al-OH minerals)
MIN2250 (version 4)
= 2.21-micron Si-OH band depth and 2.26-micron
H-bound Si-OH band depth (opal)
BD2265 (version 4)
= 2.265-micron band depth (jarosite, gibbsite,
acid-leached nontronite)
BD2290 (versions 1, 4)
= 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 (versions 1, 4)
= 2.3-micron dropoff (hydroxylated Fe,Mg
silicates strongly >0)
BD2350 (version 1), BD2355 (version 4)
= 2.35-micron band depth (chlorite, prehnite,
pumpellyite, carbonate, serpentine)
SINDEX (version 1), SINDEX2 (version 4)
= Inverse lever rule to detect convexity at 2.29
microns due to 2.1- and 2.4-micron absorptions
(hydrated sulfates strongly >0)
ICER2 (version 1), ICER2_2 (version 4)
= 2.7-micron CO2 ice band
BDCARB (version 1)
= 2.33, 2.53-micron Ca or Fe carbonate band
MIN2295_2480 (version 4)
= Mg Carbonate overtone band depth and metal-OH
band
MIN2345_2537 (version 4)
= Ca/Fe Carbonate overtone band depth and
metal-OH band
BD2500_2 (version 4)
= Mg Carbonate overtone band depth, or zeolite
BD3000 (versions 1, 4)
= 3-micron H2O band depth (adsorbed and bound
H2O and ice)
BD3100 (versions 1, 4)
= 3.1-micron H2O ice band depth
BD3200 (versions 1, 4)
= 3.2-micron CO2 ice band depth
BD3400 (version 1), BD3400_2 (version 4)
= 3.4-micron carbonate band depth
CINDEX (version 1), CINDEX2 (version 4)
= Inverse lever rule to detect convexity at 3.6
micron due to 3.4- and 3.8-micron
carbonate absorptions
R440 (versions 1, 4)
= 0.44-micron reflectance
R530 (version 4)
= 0.53-micron reflectance
R600 (version 4)
= 0.60-micron reflectance
IRR1 (versions 1, 4)
= IR ratio 1 (R880/R997; aphelion ice clouds >1,
seasonal ice clouds and dust <1))
R1080 (version 4)
= 1.08-micron reflectance
R1506 (version 4)
= 1.51-micron reflectance
R2529 (version 4)
= 2.53-micron reflectance
BD2000CO2 (version 1)
= 2-micron atmospheric CO2 band depth
BD2600 (versions 1, 4)
= 2.6-micron atmospheric H2O band depth
BD2700 (version 1)
= 2.7-micron atmospheric CO2 band depth
IRR2 (versions 1, 4)
= IR ratio 2 (R2530/R2210; aphelion ice clouds
vs. seasonal ice clouds or dust)
R2700 (version 1)
= high clouds above most atmospheric CO2
IRR3 (versions 1, 4)
= IR ratio 3 (R3500/R3390; aphelion ice clouds
vs. seasonal ice clouds or dust)
R3920 (version 4)
= 3.92-micron reflectance, useful in detecting ice-free
Regions at the poles
Ancillary Data
==============
There is one type of ancillary data provided with this
dataset:
1. The BROWSE directory contains browse images in PNG format.
See BROWINFO.TXT for more details.
Coordinate System
=================
Areocentric latitude and longitude, incidence, emission, and
phase angles are derived from spacecraft attitude, gimbal
position, pixel location, and MOLA shape model of Mars. The
detailed procedure is described in the documentation on DDRs.
The adopted projection convention is planetocentric, positive
east, using the 2000 IAU prime meridian and pole of rotation.
The projection varies in 5 degree latitude bands, using
EQUIRECTANGULAR equatorward of 65 degrees latitude and POLAR
STEREOGRAPHIC poleward of 65 degrees latitude. For the latitude
band projected equirectangularly, the center latitude of
projection is the equatorward boundary of each band to minimize
distortion. For the latitude bands projected polar
stereographically, the center of projection is the pole. In the
north polar region, 0 longitude is down, and in the south polar
region 0 longitude is up. The planet is divided into 1964 non-
overlapping tiles, 256 pixel/degree in versions 1 and 3,
and 327 pixels/degree in version 4. Their longitude width
increases poleward to keep tiles approximately the same in area.
Media/Format
============
The CRISM archive is made available online via Web and FTP
servers. This is the primary means of distribution.
Therefore the archive is organized as a set of virtual
volumes, with each data set stored online as a single volume. As
new data products are released they are added to the volume's
data directory, and the volume's index table is updated
accordingly. The size of the volume is not limited by the
capacity of the physical media on which it is stored; hence the
term virtual volume. When it is necessary to transfer all or part
of a data set to other media such as DVD for distribution or for
offline storage, the virtual volume's contents are written to
the other media according to PDS policy, possibly dividing the
contents among several physical volumes.
|
.png)
.png)
