In what ways is the Surface Stereo Imager "better" or different than human vision? What can it see on Mars that we cannot?
Our eyes can't pick up the longer wavelengths of infrared light but the imager can. Infrared is very important for figuring out the chemical composition of rocks and soil and so forth. Plus, having infrared means we can take advantage of different lighting situations. The imager can also see polarized light, just like those polarized sunglasses that eliminate glare. This allows us to do analyses of aerosols and dust composition in the atmosphere. We also use other filters to look at the sun to get direct readings of how much sunlight is reaching the surface. This is very important because Phoenix is solar-powered. We can tell just how clear the atmosphere is and know how much energy the solar panels will get that day. We can get very high accuracy humidity readings, too, so we can tell how much water vapor is in the air.
Has the Surface Stereo Imager done what it was supposed to do so far? Any glitches?
The imager is all day, every day. In general, we shoot about 150 to 200 images daily and all the other science teams really rely on it. Before the robotic arm digs anywhere, it has to know where the ground is. We need to know when the arm is moving and where we left it at the end of the day. The geology and chemistry people need multispectral images so they know where the most interesting place to dig is. There have been some communication problems—not with the imager per se; they have been more on the sense of that we can't quite always get the images we've commanded back from Mars. They have to be relayed through one of the satellites we have in orbit around Mars, and then there's a communications delay [of 15 minutes] as they're beamed back to Earth. There are literally hundreds of things that have to go right to get a picture, and sometimes 98 out of 100 go right, and it's not quite the right 98 for us to have that image back home.But that's what you expect, and it's hard to be down about it. If I don't get my pictures today, I will get them tomorrow morning. I still have an instrument that's working and happy and a spacecraft that's working and happy. Phoenix is beating its little heart out to find cool things for us to look at on Mars.