Clementine HiRes Data Processing

Statement of Work

Malin Space Science Systems (MSSS) will create overlapping and/or strip mosaics of the Clementine HIRES images. HIRES images were systematically acquired poleward of 50° latitude, at each pole, and on each orbit. The HIRES instrument had a field of view of 0.4° by 0.3° ; the swath width near the poles was about 10 km in the apoapsis hemisphere and about 5 km in the periapsis hemisphere. Thus, overlapping coverage (using data from both months) only exists for latitudes above about 82° . At a resolution of 1/1024 degrees/pixel (29.6 meters/pixel) the two polar mosaics will fit on a single CD-ROM. The remainder of the systematic HIRES data form non-overlapping strips. MSSS will produce calibrated, registered image strips, at the average resolution of the strip, using a sinusoidal map projection. The total volume of these strip mosaics will be about 18 GB, or 28 CD-ROMs.

Construction of mosaiced products from Clementine data will be performed systematically, and MSSS will initially concentrate its efforts on automated mosaicing techniques. The U. S. Geological Survey is using a hybrid approach (both automated and manual) to construction of the UVVIS mosaics and MSSS will interact closely with and benefit from this effort, which already is receiving NASA support. For each area to be mapped, the processing steps required are:

  1. Locate all images covering the area to be mosaiced. The EDR archive CD-ROMS will be stored in a CD-ROM jukebox to allow unattended access.

  2. For each image:

    1. ) Decompress from JPEG to standard image format.

    2. ) Apply calibration to convert the image to physical units. This calibration makes use of pre-launch and in-flight calibration information to correct for variations in detector response, interpolate bad pixels, and remove instrument noise. It then applies knowledge of the exposure time, gain and offset state, filter, and lighting geometry to produce a 32-bit image in physical units, normalized to a reference lighting geometry.

  3. Register overlapping images to one another and to the highest resolution USGS global image mosaic available as a reference. This registration will be done automatically, to sub-pixel precision, using a moving-window cross-correlation maximization algorithm. The registration will occur in image coordinates rather than map-projected coordinates to minimize the effects of errors in the SPICE information; errors in the SPICE will result in mispositionings of pixels on the planet's surface. Should the USGS mosaic prove to be of insufficient resolution for HIRES mosaic registration, select portions of the intermediate resolution LWIR data will be mosaiced and registered to the USGS mosaic to then act as a base for the HIRES data.

  4. Compute the dynamic range of each mosaic and convert to 8-bit form, recording the conversion factors to return to physical units. Cosmetic adjustment of residual brightness level mismatches between adjacent images will also be performed at this point, and recorded so that conversion back to physical units will be unaffected.

  5. Map-project all mosaics. Experiments have shown that use of the currently-available SPICE data results in image mismatches on the order of 10 pixels. Refinement of the SPICE data will be done using cross-correlation between overlap regions in adjacent images, between a feature catalog of control points and the images, and between the images and the base image to be produced by USGS.

Summary of Processing and CD-ROM Volumes to be Produced

      Description            Total Size   CPU Usage (Months)  Number of CD-ROMs

 1/1024 HIRES polar mosaics     640 MB            0.4                  1
 HIRES strip mosaics             18 GB           12.5                 28

 Total                          ~19 GB           13                   29

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