Software Interface Specification for HiRISE Reduced Data Record ...

At this point in the processing the EDR-validation step occurs (see Section 4.3).
To continue the pipeline processing the reconstructed SPK and CK SPICE
kernels [17], providing information about the observing viewing geometry and
spacecraft ephemerides, need to be retrieved from the NAIF Node though
HiROC’s HiSPICE subsystem. Reconstructed SPICE kernels are generally
provided to the MRO science teams one to two weeks after the observation was
acquired. The HiGeomInit pipeline extracts the spacecraft ephemeris kernel
(SPK) and C-matrix pointing kernel (CK) data from the SPICE files and transfers
the data to the CCD image files for geometry processing by the pipelines that
follow. Additionally HiGeomInit populates the observation geometry table with
viewing geometry and coordinate metadata. See [4] for more information about
the contents of the observation geometry table. The RedGeom and ColorGeom
pipelines perform geometric processing on individual CCD images (see Section
4.1.2). The RedMosaic and ColorMosaic pipelines mosaic the projected CCD
images to form an observational image (see Figure 4.1.1). Additionally these
pipelines create RDR-product browse and thumbnail jpeg images for HiRISE and
PDS Imaging Node web-based distribution services. The last pipeline step,
RDRgen, creates the JPEG2000 image accompanied by a PDS detached label
and populates the RDR product table with information about the product.
Following a final validation step the EDR and RDR products are releasable to the
PDS and science community.
4.1.1 Radiometric Calibration Correction
The radiometric calibration-correction procedure is described here at a high level.
A detailed description will be provided in a future HiRISE calibration paper. The
radiometric calibration correction is performed on each individual HiRISE channel
file (EDR) correcting for instrument offset, dark current, gain, then converting to
I/F reflectance.
The first step in the calibration, carried out by the ISIS hiclean program, corrects
for instrument dark current and offset. The hiclean program uses the ancillary
calibration data (dark and mask pixels) [3] that accompany the science data to
compute corrections in both the column (sample) and row (line) directions. The
mask pixels, positioned at the start of the instrument output, provide dark current
information for each column. The dark pixels, positioned at the end of each
image row, capture the time dependent dark current and offset instrument drift.
The ISIS hical program then applies an intra-channel B0 (additive dark current
matrix) and A0 (multiplicative gain matrix) correction for each column in the
image array. The hical then converts the pixel values to I/F (intensity/flux, I/F = 1
for a 100% ideal lambertian reflector viewed normal to the surface) as described
below:
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