MRO CRISM Multispectral Reduced Data Record (MRDR4)

Instrument: Compact Reconnaissance Imaging Spectrometer for Mars

PDS3 Data Set ID: MRO-M-CRISM-5-RDR-MULTISPECTRAL-V1.0DOI: 10.17189/1519437

PDS4 Bundle: urn:nasa:pds:mro_crism_mrdrDOI: 10.17189/3gnq-5m91

For more information about CRISM products, go to the CRISM Product Primer.

For more information about MRDR4s, see the CRISM Data Product SIS.

A map-projected Multispectral Reduced Data Record (MRDR) consists of several or more strips of multispectral survey data (or hyperspectral survey data downsampled to multispectral survey wavelengths) mosaicked into a map tile. MRDR4 is a PDS4 version of the version 4 MRDR product. A map tile is constructed from a large number of TRDRs. The mosaic is uncontrolled (accepting existing pointing data with image mismatch at seams generally less than one ~180-m pixel). A global pattern of 1,964 such tiles has been developed, forming the major data product for multispectral survey observations. Each tile may contain data in units of I/F extracted from a TRDR, plus Lambert albedo, summary products, and the DDR data used to generate them. So, for every latitude or longitude in an MRDR4, there is both an I/F and/or Lambert albedo and the information providing traceability between the two values. The MRDRs also include text files having information on the wavelength of the layers of the Lambert albedo and/or I/F multiband images.

An MRDR4, as shown in the figure, contains up to five multiple-band images at 256 pixels/degree (v1,v3) or 327 pixels/degree (v4), and one list file containing wavelengths of the multispectral data.

The first multiple-band image, if present, 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 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 serves as a backup to the Lambert albedo image if it is not present, or for when Lambert albedo processing was in early development.

The second multiple-band image, if present, is geometrically identical to the map-projected I/F multiple-band image, except that the data have been processed using the ADR binary tables and other subsequent steps as described in Appendix P3 CRISM Data Product SIS to Lambert albedo (the estimated surface contribution to reflected I/F, divided by cos i).

The third and fourth multiple-band images, if present, contains map-projected data from the DDRs associated with strips of multispectral data, used to derive I/F from radiance. One file corresponds to the I/F image, and one file corresponds to the Lambert albedo image (the component image strips may be fewer in the Lambert albeo file). In each of these, 11 additional layers are specific to individual multispectral strips used to assemble the tile, and are not contained in source DDRs.

  • .Solar longitude, units degrees,

  • Solar distance at time of measurement, units AU

  • VNIR OBSERVATION_ID of constituent measurement

  • IR OBSERVATION_ID of constituent measurement

  • The VNIR OBSERVATION_NUMBER carried through from the source scene EDRs,

  • The IR OBSERVATION_NUMBER carried through from the source scene EDRs,

  • The VNIR LINE_SAMPLE carried through from the temporary TRDR used to populate the MRDR, this identifies the VNIR wavelength calibration at the spatial pixel of the MRDR

  • The IR LINE_SAMPLE carried through from the temporary TRDR used to populate the MRDR, this identifies the IR wavelength calibration at the spatial pixel of the MRDR,

  • The LINE_SAMPLE from the source TRDR, this together with column number, observation ID, and ordinal counter provides traceability back to a spatial pixel in a source EDR,

  • The LINE from the source IR TRDR

  • The LINE from the source VNIR TRDR

The fifth multiple band image contains map-projected summary products from multispectral data.

The listfile, in ASCII format, contains wavelengths of each layer in the Lambert albedo and I/F images.

Three versions of MRDRs have been released, with version numbers loosely keyed to calibration version numbers of input TRDRs. Which multiband images are present differ with version depending on the development status of the processing pipeline. Versions 1 and 3 have included content from TRDRs of mapping data having the corresponding version numbers. Summary product values at a given column within a strip are normalized to their along-track values as a first order correction for optical artifacts. There are no corrections for stochastic noise or inter-strip residuals due to calibration artifacts or differences in atmospheric opacity. V1 contains all five multiband images; V3 contains updated uncorrected I/F and the corresponding derived data.

Version 4 uses v3 radiometric calibration, but adopts a different approach to populating map tiles with strips of mapping data. For individual input mapping strips, the remediation of systematic optical and calibration artifacts is included at the input strip level (adapted from v3 TERs and MTRDRs). Prior to tile assembly, corrected I/F values for Lambert albedo and summary product files are subjected to a normalization procedure to minimize differences between overlapping strips of mapping data, using as reference data acquired under clear atmospheric conditions early in the mission when the IR detector was operated at its coldest with the least noise. Appendix P3 in CRISM Data Product SIS provides further detail. Version 4 has been migrated to comply with the PDS4 standard. As this is the ultimate version of MRDRs, only Lambert albedo, corresponding derived data, and summary product multiband images are present.

CRISM MRDR4 products have the following file names:

Tnnnn_MRRtt_aahooo_res_v.IMG (with detached PDS label)

where:

nnnn = tile number with 0000 at the south pole, increasing spiraling northward

tt = product subtype

IF = I/F

AL = Lambert albedo

SU = summary products

DE = derived products for I/F

DL = derived products for Lambert albedo

WV = list of wavelengths and wavelength ranges of radiance and I/F images

aa = planetocentric latitude of center of the tile

h = hemisphere

N = north latitude

S = south latitude

ooo = east longitude of center of the tile

Res = nnnn, in map-projected pixels per degree, e.g. 0256 pixels per degree modified in the final delivery to 0327 pixels per degree

v = version, 0-9, a-z

 

Differences by Versions

V1 MRDRs were built using TRR1 mapping strips, and a preliminary version of the radiometric transfer corrections stored in ADRs. All five multiband images are present, and the MRRSU files use older formulations of summary products. MRRAL and MRRSU files retain uncorrected interstrip residuals; MRRSU files suffer from unfiltered stochastic noise. MRRIF files are available to create custom products using derived information in the MRRDE file and CAT. V1 MRDRs have been supersede by V3 MRDRs.

V3 MRDRs were built using TRR3 mapping strips. The MRRIF and MRRDE multiband images are present, representing coverage from 2012. MRRIF files can be used to create custom products using derived information in the MRRDE file and CAT. MRRAL, MRRDL, and MRRSU files are not present.

V4 MRDRs are built using TRR3 mapping strips, and the refined version of the radiometric transfer corrections stored in ADRs. All reflectance data are corrected to Lambert albedo using the optimization procedures described above, and the MRRSU files use current formulations of summary products. In MRRAL and MRRSU files interstrip residuals and stochastic noise are minimized using the IKF filter and optimization. The MRRDL files provide observing conditions and traceability to source observations. MRRIF and MRRDE files are not present.

In ODE, MRDR4 products have the following Product IDs:

TNNNN_MRRTT_AAHOOO_RES_V