HRSCview - A Web-based Mars Express HRSC Image Viewer

Greg Michael, Freie Universität Berlin

The High Resolution Stereo Camera (HRSC) on the ESA Mars Express spacecraft has been operating in orbit since January 2004. So far (April 2007), the camera has returned around 2 terabytes of image data, covering around 35% of the Martian surface in stereo and colour at a resolution of between 10 and 20 m/pixel. These data are publicly accessible through the ESA Planetary Science Archive.

Because the images are typically several gigabytes in size, and consist of several channels of differing resolutions, they can be cumbersome to download and require non-standard software for viewing and processing. For this reason, both for rapid scientific previewing and for general public interest, we have developed HRSCview - a joint website of the Freie Universität Berlin and the German Aerospace Center (DLR), which provides the ability to explore within the images up to full resolution with the data-subsetting, sub-sampling, stretching and compositing being carried out on-the-fly by the image server. This means regions of interest can be explored at full resolution without needing to download full data-product sets.

We had already developed similar tools for internal use using IDL, benefiting from its array-handling capabilities. ION (IDL On the Net) offered the possibility to repackage much of the same code into a web environment in a relatively simple manner, so that the additional design effort was mainly directed towards the user interaction with the software rather than the image processing. It was an important feature of ION-script that it operates with no additional software on the user side: an ordinary browser is sufficient.

The site can be explored at: http://hrscview.fu-berlin.de

The main features of HRSCview are:

• nadir, colour composite, elevation composite browsing
• an image footprint map, with direct navigation into images
• location selection by surface coordinates or orbit number
• perspective views
• direct switching between overlapping images at point of interest
• click off-the-edge of one image to move directly into adjacent coverage
• links to full data-products from product description pages

Figure 1: Footprint map

Figure 2: Elevation map

Figure 3: Perspective view

Questions or suggestions are welcome, and should be directed to Greg Michael (gregory.michael at fu-berlin.de)