NASAball.gif Mars Orbiter Camera Images ames_logo.gif

MOC Images

These images are from the current Mars Global Surveyor's Mars Orbiter Camera (MOC), with resolutions ranging from ~2 to ~15 meters/pixel. They are the narrow-angle MOC images from the Orbital Insertion Phase (including Aerobraking-1, Science Phasing-1, and Science Phasing-2 Orbits), for the period Sept. 1997 to Sept. 1998. The images are from the MOC Decompressed Standard Data Product (DSDP) Archive, produced at Malin Space Science Systems, and released on CD-ROM and the Web by NASA's Planetary Data System (PDS). Newer MOC images will be soon be included.

Context Images

Accompanying each MOC image are "Viking context images" showing the MOC image in the context of its broader region. Medium-resolution (256 pixels/degree) images from the Viking Orbiters' Mosaiced Digital Image Models (MDIM) image set are used for these context images. Precise locations of the MOC images were attempted by matching physiographic features between the MOC and Viking images. Inhouse OpenGL-based software was used to translate MOC images from their nominal coordinates (and skew them if need be) to visually align features.

Where precise locations could not be ascertained, due to poor Viking image resolution, poor MOC image quality, and/or lack of sufficient physiographic detail, it is noted. Coordinates given for the MOC images are those after the MOC relocation, using the geoid used for calibrating the Viking images. The MOC relocations should never be used for quantitative analyses, as the visual placement is an inherently subjective process. In the context images, clicking will toggle between display of MOC image outline only, or outline plus MOC image.

Image Processing

In converting the MOC images from their native PDS format to browser-friendly JPEGs, "diffuse" histogram equalization was applied, whereby the histogram curve achieved after equalization was "diffused" or "smeared" by some image-specific amount to soften the constrast, to achieve some optimal level between unprocessed and fully-equalized. "Optimal" was generally defined in terms of overall image quality; some specific areas of the images may have been compromised in order to gain optimal contrast over the entire image. Or in some cases, contrast of the image as a whole may have been a bit compromised in order to see more detail in geologically-significant portions of the image. After histogram equalization, some sharpening was applied to the images as well.

There has (as yet) been no attempt made to eliminate the radiometric streak artifacts seen in some images that are due to the varying sensitivities and biases of each detector in the MOC's push-broom array. This may be addressed in the future.

JPEG images as shown have been corrected for both horizontal ("mirrored" vs. "normal") orientation, and vertical orientation (north is always up). To achieve the correct aspect ratios as specified in the cumulative index of the MOC images, the JPEG images were vertically-stretched. Note that the TIFF files are unprocessed, but have been corrected for horizontal orientation and aspect ratio. If your browser doesn't display TIFF files, you can download them directly to disk with your browser's "save link to disk" function (Netscape: "Save this Link as...", IE: "Download Link to Disk").

Online Image Processing

Online Java-based image processing is provided to enable individual user optimization; for example, one can bring out details in a shadowed crater rim at the expense of the brighter ejecta becoming saturated.

Included in the image processing functions is a Photoshop-like "Adjust Levels": a histogram curve is shown, with sliders which allow users to constrain or expand pixel levels. This histogram curve updates its profile in response to the other available processing functions as well. In the near-future, we hope to be able offer cropping, whereby users can crop an image and apply processing only to the cropped portion.

Image processing can be applied to the "small" or "medium" scale versions of each MOC image. Because of memory constraints, the medium versions of inherently large images may fail to load in the Java applet. You should use the small image version in these cases.

At present, there is no direct way of saving your custom-processed image to your local disk, although you may accomplish this by using your computer's screen-capture utility.

Browser Requirements:

Netscape and Internet Explorer (both v4.5 or greater) on Windows and UNIX platforms are required (versions 4.0 to 4.5 may work but have not been tested).

Macintosh users should use Internet Explorer (v4.5 or greater), since the Java applets use features which are not in the Java Development Kit (JDK) version 1.0, precluding their use with Netscape on the Mac.