MRO CRISM Limb Data Record (LDR)

Instrument: Compact Reconnaissance Imaging Spectrometer for Mars

PDS Data Set ID: MRO-M-CRISM-6-LDR-V1.0

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

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

A Limb Data Record (LDR) accompanies each observation scanned across Mars’ limb, and includes information on the tangent height of each pixel above Mars’ surface and photometric angles to analyze the measured radiances. Once limb scan image data are assembled into EDRs, calibrated into TRDRs, and reconstructed pointing is available, LDRs are created for the data. There is one LDR per VNIR TRDR or scene EDR, and one LDR per IR TRDR or scene EDR. It has the same spatial dimensions as the corresponding scene EDR or resulting TRDR. The LDR is indexed to the wavelength bands of EDRs and TRDRs that are closest to 610 nm (VNIR) or 2300 nm (IR).

There are 15 layers in the LDR, all represented as 32-bit real numbers.

  • Solar incidence angle at the areoid, units degrees,

  • Emission angle at the areoid, units degrees,

  • Phase angle, units degrees

  • Planetocentric latitude at the tangent point of the line of sight, units degrees N,

  • Longitude at the tangent point of the line of sight, units degrees E,

  • Solar incidence angle at a surface intercept relative to a MOLA shape model, units degrees,

  • Emission angle at a surface intercept relative to a MOLA shape model, units degrees,

  • Elevation at the tangent point of the line of sight, units meters relative to areoid

  • Elevation at the tangent point of the line of sigh, units meters relative to the MOLA shape model,

  • Local Solar Time, units hours,

  • Ephemeris Time of observation, seconds past noon January 1, 2000”

  • Sub-solar planetocentric latitude, units degrees N,

  • Sub-solar longitude, units degrees E,

  • Sub-spacecraft planetocentric latitude, units degrees N,

  • Sub-spacecraft longitude, units degrees E.

CRISM Observing Modes Used

Mode

Pointing

Description

Coverage

Atmospheric (hyperspectral)

Limb scans

Limb scan measurements (LMBs)

Spatial pixels 10x binned; ~200 m vertical sampling)

2 orbits every 2 months

Contents of each type of CRISM observation

Class of observation

Frame rate, Hz

Activity

Pixel binning

#

Wavelengths

Frames (typical)

Limb scan (LMB)

3.75

Individual scans

10

Variable

545

540

Dark sets

10

Same

545

12

CRISM LDR products have the following file names:

LMBnnnnnnnn_mm_DEbbbc_LDRv.IMG (with detached PDS label)

where:

nnnnnnnn = observation ID, unique for the whole CRISM mission, expressed as a hexadecimal number

mm = ordinal counter carried through from the source EDR ID, expressed as a hexadecimal number

bbb = macro #

c = sensor ID

S = VNIR

L = IR

v = version, 0-9, a-z

In ODE, LDR products have the following Product IDs:

LMBNNNNNNNN_MM_DEBBC_LDRV