Imager for Mars Pathfinder (IMP)

Description

The Mars Pathfinder Lander camera is a side-by-side charged-coupled device (CCD) stereo imager in a barrel-shaped housing which sits on top of an extendable mast that stretches 62 cm above its stowed position upon deployment and approximately 150 cm above the surface. There are two 12-position color filter wheels, one in each path of the stereo system. The camera is fully controllable in both elevation and side-to-side (azimuth) motion by stepper motors with gear heads, which provide a field 178 degrees in azimuth and +83 to -72 degrees in elevation. The optics do not require active focusing. The field of view for each eye is 14.4 degrees by 14.0 degrees and the resolution is six-tenths of a millimeter near the lander. The imager is f/18 with a focal length of 2.3 cm. The best focus of the camera is at 1.3 meters, the depth of field ranges from 0.5 m to infinity.

The stereoscopic system consists of 2 eyes covered by fused silica windows separated by 15.0 cm backed by two fold mirrors with one filter wheel and a set of three lenses in each optical path with a fold prism to place the images side-by-side on the CCD focal plane. The two filter wheels contain 24 filters total: fifteen are optimized for Mars geology (four for stereo geology), eight filters for atmospheric and solar studies including four solar filters, and one magnifying diopter filter. The spectral range is 440 to 1000 nm. The spectral channels are particularly sensitive to iron and pyroxene minerals. The CCD is a front-illuminated frame transfer array with 23 micrometer square pixels in two square 256 x 256 pixel frames. Each pixel has an instantaneous field of view of 0.98 milliradian. The signal-to-noise ratio is 350 and both lossy and lossless compressions were used to store and transmit images.

The imager returned 16,661 images, including frames to produce 360 degree panoramas of the landing site. The camera was used for science experiments, including filter-wheel spectral mapping of the landing site to determine the mineralogy of rocks and soil and to identify rocks as targets for further investigation. Spectral mapping was also used to study weathering processes and products in the dust, soil, and rocks of Mars. Images were taken of the surface to study phenomena which occur over time, such as deposition, dune formation and seasonal changes. Images were also taken of the sky, clouds, the Sun, Phobos, Deimos, some stars, and calibration targets on the lander. Frequent images were taken of the rover to support its operations. Two other investigations were associated with the imager. The magnetic properties experiment consisting of five magnets of different strengths was mounted on the lander. Over the course of the mission, images were taken of these magnets to study the accumulation of dust. A wind experiment consisting of three small wind socks mounted on a mast were also the targets of the imager on a regular basis.