Abstract. The Surface Stereo Imager (SSI), a stereoscopic, multispectral camera on the Mars Polar Lander, is described in terms of its capabilities for studying the Martian polar environment. The camera's two eyes, separated by 15.0 cm, provide the camera with range-finding ability. Each eye illuminates half of a single CCD detector with a field of view of 13.8 ø high by 14.3 ø wide and has 12 selectable filters between 440 and 1000 nm. The f/18 optics have a large depth of field, and no focusing mechanism is required; a mechanical shutter is avoided by using the frame transfer capability of the 528 x 512 CCD. The resolving power of the camera, 0.975 mrad/pixel, is the same as the Imager for Mars Pathfinder camera, of which it is nearly an exact copy. Specially designed targets are positioned on the Lander; they provide information on the magnetic properties of windblown dust, and radiometric standards for calibration. Several experiments beyond the requisite color panorama are described in detail: contour mapping of the local terrain, multispectral imaging of interesting features (possibly with ice or frost in shaded spots) to study local mineralogy, and atmospheric imaging to constrain the properties of the haze and clouds. Eight low-transmission filters are included for imaging the Sun directly at multiple wavelengths to give SSI the ability to measure dust opacity and potentially the water vapor content. This paper is intended to document the functionality and calibration of the SSI as flown on the failed lander. IntroductionThe [Boynton et al., this issue]. Operationally, the SSI stereoscopic imagery was designed to maintain a virtual environment needed to create command sequences for the arm and RAC. This range map can be augmented by RAC images in locations inaccessible to SSI, such as underneath the lander. Periodic images of the arm will serve to verify its true location compared to its commanded location. Images taken of the lander deck and solar panels will be valuable as troubleshooting guides when performance of various subsystems degrades.The scientific objectives for SSI fall into several broad categories: geomorphology, mineralogy, and atmospheric studies. Geomorphology, as always, is governed by the choice of landing site. The polar layered terrain affords the rare opportunity to learn the stratigraphic history of this circumpolar geologic unit. Local landforms are likely to show fine-scale layering that is likely to have been depositional in origin, but later modified by strong winds. Unlike the Viking Landers 1 and 2 and Pathfinder sites, few, if any, rocks are expected. Defining the role of ices in the formation of the layers is a prime goal for SSI. To aid in the study of the layers, the camera's multispectral imaging mode will be used. Subtle color differences between layers may indicate a different ice fraction, changes in particle size, or composition changes. We will compare the spectra to those obtained at the distant Pathfinder site to check for variations in the globally distributed d...

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The rebuilding of St Giles-in-the-Fields between 1730 and 1734 is one of the least known but most significant episodes in the history of Georgian church design, standing at a crucial crossroads of radical architectural change and representing nothing less than the first Palladian-Revival church to be erected in London in the eighteenth century (Fig. 19).

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