Surface Stereo Imager (SSI)

built by the University of Arizona

SSI will serve as Phoenix's "eyes" for the mission, providing high-resolution, stereo, panoramic images of the martian arctic. Using an advanced optical system, SSI will survey the arctic landing site for geological context, provide range maps in support of digging operations, and make atmospheric dust and cloud measurements.

The two lens SSI is a higher resolution upgrade of the imager used for Mars Pathfinder, which returned more than 17,000 stereo images. Image Credit: SSI Team, University of Arizona.
Situated atop an extended mast, SSI will provide images at a height two meters above the ground, roughly the height of a tall person. SSI simulates the human eye with its two optical lens system that will give three-dimensional views of the arctic plains. The instrument will also simulate the resolution of human eyesight using a charged-coupled device that produces high density 1024 x 1024 pixel images. But SSI exceeds the capabilities of the human eye by using optical and infrared filters, allowing multispectral imaging at 12 wavelengths of geological interest and atmospheric interest.

SSI has a 12-position color filter wheel ranging through optical to infrared wavelengths. Image Credit: SSI Team, University of Arizona.

Looking downward, stereo data from SSI will support robotic arm operations by producing digital elevation models of the surrounding terrain. With these data, scientists and engineers will have three-dimensional virtual views of the digging area. Along with data from the TEGA and the MECA, scientists will use the three-dimensional views to better understand the geomorphology and mineralogy of the site. Engineers will also use these three-dimensional views to command the trenching operations of the robotic arm. SSI will also be used to provide multispectral images of samples delivered to the lander deck to support results from the other scientific instruments.

Senior Engineer, Roger Tanner, examines the SSI mast flown on the Mars Polar Lander. Image Credit: SSI Team, University of Arizona.

Looking upward, SSI will be used to estimate the optical properties of the martian atmosphere around the landing site. Using narrow-band imaging of the Sun, the imager will estimate density of atmospheric dust, optical depth of airborne aerosols, and abundance of atmospheric water vapor. SSI will also look at the lander itself to assess the amount of wind-blown dust deposited on spacecraft. Deposition rates provide important information for scientists to understand erosional and atmospheric processes, but are critical for engineers who are concerned about the amount of deposited dust on the solar panels and associated power degradation.

SSI is being built by a team at the University of Arizona, led by Mr. Chris Shinohara. This team was responsible for designing and building the Imager for the Mars Pathfinder, which provided the first ever stereo images of Mars. The team also developed the Surface Stereo/Science Image that flew on the ill-fated Mars Polar Lander.