MRO CRISM Multispectral Reduced Data Record (MRDR)

Instrument: Compact Reconnaissance Imaging Spectrometer for Mars

PDS Data Set ID: MRO-M-CRISM-5-RDR-MULTISPECTRAL-V1.0

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

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

A map-projected Multispectral Reduced Data Record (MRDR) consists of several or more strips of multispectral survey data mosaicked into a map tile. Thus a map tile is constructed from a large number of EDRs. The mosaic is uncontrolled (accepting existing pointing data often resulting in mismatch at seams within a mosaic). A global pattern of 1,964 such tiles has been developed, forming the major data product for multispectral survey observations. The tile contains data in units of I/F extracted from a temporary TRDR, plus Lambert albedo, summary products, and the DDR data used to generate them. So, for every latitude or longitude in an MRDR, there is both an I/F and all the information providing traceability to a companion I/F corrected for atmospheric, photometric, and thermal emission effects. The MRDRs also include text files having information on the wavelength of the layers of the Lambert albedo and I/F multiband images and on the SPICE metakernels used for map projecting the image data.

An MRDR, as shown in the figure, contains up to five multiple-band images at 256 pixels/degree, and up to two list files.

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 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.

The second multiple-band image is geometrically identical to the map-projected I/F multiple-band image, except that the data have been processed using the ADR binary tables to Lambert albedo (the thermally-corrected estimated surface contribution to reflected I/F, divided by cos i).

The third and fourth multiple-band image 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. In each of these, 11 additional layers are specific to individual multispectral strips used to assemble the tile, and are thus not contained in the 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 the TRDR associated with ta strip of multispectral data.

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

CRISM MRDR products have the following file names:

Tnnnn_MRRtt_aahooo_0256_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

v = version, 0-9, a-z

In ODE, MRDR products have the following Product IDs:

TNNNN_MRRTT_AAHOOO_0256_V