KPLO ShadowCam Calibrated Data

ODE: Moon

Mission: Korea Pathfinder Lunar Orbiter (KPLO)

PDS4 Bundle: urn:nasa:pds:kplo-shadowcamDOI: 10.17189/y89z-kt98

ShadowCam calibrated products are released as a 32-bit ISIS cube. Raw data are first decompanded into 12-bit digital numbers, then corrected using the calibration steps defined in the ShadowCam calibration paper (Humm et al., 2023), producing pixels in radiance units of W/m²/sr/μm. During this process, non-scene columns are removed, resulting in an image width of 3,072 pixels. The embedded ISIS header makes the files directly usable in ISIS and other PDS-compliant viewers, while also preserving essential metadata even if the detached XML label is missing.

Each calibrated product comes with three ancillary products to help view or evaluate the data without downloading or processing the original file.

Browse Image - scaled-down image with the largest dimension of 1,000 pixels in PNG format.
Full-resolution COG - pyramidal product in a 32-bit TIFF format complying with the Cloud Optimized GeoTIFF (COG) standard without the geographic header to allow fast browsing via web-based tools.
Histogram - CSV-formatted histogram data with the values divided into 256 bins.

Two additional types of ancillary products: smear maps and map-projected products were generated for each observation entirely on the Moon’s surface. These products are not generated for any non-Moon observations or for limb views.

Smear maps are data products that measure downtrack image smear in ShadowCam observations. They are generated using the same software that calculates line rate information, but instead of predictive SPICE used in planning, they rely on definitive SPICE. The image is divided into 100-meter bins, and each bin’s line rate is converted into the number of pixels of smear. This smear value can be positive or negative depending on whether the line rate is too high or too slow, though in most cases the absolute value is sufficient to understand the amount of smear. Two types of smear maps are produced: a shadowed smear map, which reports values only in shadowed regions where ShadowCam data are most reliable, and a full smear map that provides values across the entire scene. Both types are distributed in two formats: ISIS cubes and COGs. The data are stored in 32-bit format with map projection information included.

Map-projected products are provided for all ShadowCam lunar observations to make the data easier for users to work with. These products are created directly from the ISIS ShadowCam camera model without additional fine-tuning or control networks, so ground accuracy can vary. The projection process uses the best available topography data for the region, selecting from SLDEM, LOLA 60 m, or LOLA 30 m. Images with a center latitude within ±65° latitude are projected in equirectangular with the latitude of true scale set at the image center, while images closer to the poles use polar stereographic projection with the longitude of origin and latitude of true scale at the center to reduce distortion. The resolution is determined by the image center pixel scale projected onto the chosen topography. These map-projected products are released in COGs format for compatibility with GIS and web applications, with two versions available per observation: an 8-bit stretched COG created with a 0.5% contrast stretch (using 0 as NODATA), and a 32-bit COG containing calibrated radiance values with ISIS special pixels converted to NODATA.

ShadowCam Calibrated data products have the following file names:

tnnnnnnnnnsc(_***).ext

where:

t = target

M = Moon

E = Earth

C = non-Moon calibration

S = star

nnnnnnnnn = an approximate mission elapsed time (MET) in seconds

S = ShadowCam product

C = calibrated product

*** = ancillary product type

browse = Browse Image in png format

cog = Full-resolution COG - pyramidal product in TIFF format

hist = CSV-formatted histogram data

smear_full = full smear maps

smear_shadowed = shadowed smear maps

map_raw = raw map-projected COG products

map_stretched = stretched map-projected COG products

ext = the file extension

cub = ISIS cube files

png = browse image files

tif = COG - pyramidal product files

csv = text files

xml= PDS4 XML labels

In ODE, ShadowCam Calibrated data products have the following product IDs:

tnnnnnnnnnsc

More information about ShadowCam Calibrated data products can be found in:

Humm DC, Kinczyk MJ, Brylow SM, Wagner RV, Speyerer EJ, Estes NM, Mahanti P, Boyd AK, Robinson MS. Calibration of ShadowCam. J. Astron. Space Sci. 2023; 40(4):173-197. https://doi.org/10.5140/JASS.2023.40.4.173.