Are you happy with the landing site?
I've seen the pictures of the surface we're going to land on from the MOC (Mars Orbiter Camera, an instrument aboard the Mars Global Surveyor) camera. It's going to be an interesting site. One thing we can be sure of for the Polar Lander mission, is that it will not look like either the Viking sites or the Pathfinder site.
What is the terrain going to be like?
We've taken a couple of dozen strips across this with the MOC camera. And of all these strips, you can hardly find two that look the same. Some are obviously linear, layered features. Others are curved features. Some are hills. Some are pitted terrain, it's called. In other words, there are chunks like potholes out of the ground everywhere. We're seeing every kind of terrain you can imagine. And some we didn't even know how to explain.
In this pitted terrain, how big are these potholes?
Oh, might be 30, 40 feet across. But it could be that they're transitions from one layer to the next. In other words, something's eaten away part of one of the upper layers. Exposed a lower one. I don't know. Nobody really understands the surface. So, we don't know what we're getting into. But it's going to be different. That we know for sure.
How is the landing of going to be different from the Pathfinder lander, which came down on airbags? What is the benefit of using thrusters?
We already know which direction north is going to be when we land, where the sun will be, and everything else. What we don't know is the slope of the surface we're going to land on. But we really have no way of knowing what it will be landing on. And it'll come down just as confidently on dangerous terrain as safe terrain. We could still land safely, but be cocked at an angle, and we don't get all the solar power we want.
There aren't any large views of peaks on the horizon or anything like that. But I hope we're perched nicely on a hill with view of the surrounding terrain and not 30 feet down in a pothole somewhere.
So if it's in the middle of a pothole, it won't necessarily get a whole lot of nice pictures?
Well, you never know where the real story on Mars is these days. Is it in looking at the distant views, or would a real closeup of the edge of a pothole be where all the stuff is? We're landing in layered terrain, and if we're in a pothole, maybe all the layers are right there visible for us. It might be the best place. It's really hard to say. We'll just take what we can get. We're taking our best choice in the landing site to be sure it's safe because obviously without the safe landing we've got nothing.
Is the camera on board the lander much different from the one that was on Pathfinder?
Oh, there are a few minor changes to make it more reliable, but it's the same design. The new camera on this mission is the robotic arm camera. We built that from scratch, and it's never flown before. We're testing that one out.
Who built the camera?
It's collaboration between the University of Arizona and the Max Planck Institute in Germany. We built parts, we sent them to Germany. The Germans built other parts and put them all together. Then they sent it back to us and we calibrated the thing. The Pathfinder camera cost $6 million to build from scratch, from blank paper. I think this camera, for Mars polar lander, cost $2.5 million. And now we're building two cameras. So the cost is dropping. We're building two cameras again for the '01 mission, and the cost is now under a million dollars.
How big is the robotic arm camera?
About three inches wide, four inches long.
Can you describe the mounting mechanism and where it is on this arm?
The arm is about the same size as a human wrist. If you think of the hand as the scoop of the robotic arm, the camera mounts on the bottom side of the wrist. That allows it to look into the trench, and not get in the way of digging -- which of course is not a good thing for a camera to be doing. In order to protect ourselves from all the dust that's likely to be drifting from the digging operation, we have put a protective window over the camera, and we only open it at those few seconds when we're taking an image. The rest of the time it's closed.
So you stop digging, open the camera, and take a picture.
Right.
Close the camera, then continue digging?
Continue digging, and we go down layer by layer.
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