When you start testing hardware is when you start finding problems, and we hit one this week. Believe it or not, it was with Mini-TES, which has been the smoothest-running part of the whole payload until now. It's a weird problem. The instrument works fine when it's lying on its side, but goes bad when we turn it rightside-up! The guys in Santa Barbara took it apart this week to figure out what's wrong, and it looks like they found the problem. It seems to be a simple one: some wires are routed wrong, in a way that pulls the mirrors a tiny bit out of line when the instrument is rotated. We should know for sure this week if that was the problem. If it is it's an easy fix, but it will have taken us three weeks to track it down and take care of it. Good thing Mini-TES was thirteen weeks ahead of schedule before this happened!

We're testing hardware now. It started this week, with vibration tests on an engineering model of our APXS instrument. An engineering model is a piece of hardware that is pretty much identical to what we're going to fly, but that we can test pretty severely to make sure the design is good. We took the APXS to a test facility in Berlin this past week, and shook in three different directions at levels more violent than anything we should see in flight. We've still got a little more shaking to do, but so far nothing has broken. The APXS uses a new design that we've never tested before, so it'll be real good to have this set of tests behind us.

Like everyone else, our focus this week was on the tragic events in New York, Washington and Pennsylvania. Our hearts go out to all who suffered. We'll resume our weekly news updates next week.

This was one of those weeks where so much was going on that it's hard to decide what to write about. We're getting into real hardware testing now, and things are starting to get intense. I guess the biggest events of the week were the final preparations for two critical tests. One is the first vibration test of our new APXS design. In a "vibe" test, you shake a piece of hardware to simulate the vibrations it'll experience during launch. (Read more about this on our science bite page.) We're going to vibe the APXS in Berlin next week, and they're working very hard over in Germany to get ready for it.

The other big test we prepared for this week is the first "thermal vacuum" test of our latest Mini-TES instrument. In a thermal vac test, you put the hardware into a chamber with no air in it to simulate space, and then run it through its paces at the kinds of temperatures it'll experience in flight. This one's going to happen in Santa Barbara, and they're working really hard there as well.

So it was a busy week. Next week should be a big one, as we run both tests and hope that everything works.

Our biggest problem this past week has been working out the details of how our Pancam and Mini-TES instruments will work together. The Pancam cameras sit right at the top of the tall mast at the front of the rover. The reason that the mast is so fat is that it also acts as a periscope. Mini-TES sits down inside the rover and uses some mirrors near the top of the mast to get almost the same view of the world that Pancam does.

It's that "almost" that's the problem. The Mini-TES mirrors actually sit a little bit below the Pancam cameras, so they don't quite have the same vantage point. Also, we couldn't get everything to fit inside the lander until we turned the Mini-TES mirrors around so that they look in exactly the opposite direction from Pancam. So this means that we have to swing the mast around 180 degrees to look at the same object with both instruments. The tricky part of all this is building the hardware and software so that when we tell Mini-TES to look at something that Pancam has already seen, we don't miss it, even by a little bit. We're making progress, but this one is going to keep us busy for awhile.
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The Critical Design Review is done. It was a long review and it made for a long week, but we've got it behind us now. Of all the things that we talked about at the review, the one that got the most attention was our schedule. It's tight. Missions to the planets aren't like other space missions. You can only launch when the alignment of the planets is right. Miss a launch opportunity to Mars and you have to wait 26 months for the next one. Our launches are in the summer of 2003. That's almost two years away, but two years is a very small amount of time for all the work we need to get done. So we're going to be watching our schedule very closely. One thing that's certain is that the pace isn't going to ease up at all, any time between now and the end of the mission.

We've been having a lot of reviews lately... projects like this one tend to attract a lot of attention! But this coming week is the review of all reviews: the Project Critical Design Review. It literally is the review of all our other reviews, actually. We've had reviews of just about everything you can imagine on this project, from some of the smallest electronic parts all the way up to the whole spacecraft. Every piece of the payload has been through it too, of course, most of them several times. And now it all comes together this week at a three-day review of the whole MER project. It's no fun... preparing for these reviews is a lot of work. But reviewers from outside the project bring a fresh perspective, and that means that they sometimes catch things that we don't. Once this review is behind us, though, we've got to really step on the gas. Assembly and test of the first spacecraft begins in February, just five and a half months from now.

We had a little bit of a scare this week. A problem popped up early in the week that looked pretty stupid, but maybe also real. Our payload includes several magnets, whose job it is to gather magnetic mineral grains from the martian atmosphere. We'll look at these minerals with the instruments, including our Mössbauer Spectrometer. The Mössbauer, as it turns out, is built with a fair amount of magnetic metal in it. This metal gets attracted to the magnet, of course, when we bring the instrument close to it.

Early in the week, some calculations suggested that the arm that the Mössbauer is mounted on might not be strong enough to pull the Mössbauer back off the magnet once it has touched it! Imagine going all the way to Mars, using the Mössbauer to look at the magnet sometime early in the mission, and then getting it stuck there. Not good. We spent a couple of days worrying about it before concluding that we can fix things by making a pretty simple change in the way the arm is controlled for that one maneuver.

Believe it or not, our biggest worry this week has been ghosts. Or, to be more specific, we've been worried about what are called "ghost images".

One of the most important jobs for our Pancam camera will be to take pictures of the sun. Part of the reason we're going to do this is to figure out how dusty the martian atmosphere is: the more dust there is in the sky, the darker the sun will look. The really important reason, though, is to figure out which way is north. Mars doesn't have a magnetic field, so we can't use a compass to figure out directions. Instead, we use Pancam to see where the sun is in the sky, and then use that information to work out which way is which.

Taking pictures of the sun isn't all that hard: we just have to give Pancam special dark filters. They're sunglasses for our rover, really. But even with the filters, all that sunlight can sometimes bounce around inside the camera in funny ways, creating the "ghost images" we were worried about. But after lots of good work by the optics experts at JPL this week, we've concluded that it shouldn't be a problem. So we're not afraid of ghosts any more.
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It's CDR time. CDR stands for Critical Design Review, and it's a pivotal event in the life of any space mission. No project team does its work without a lot of help. MER is no exception; in fact, we seem to be getting more help than most. A Critical Design Review can be one of the most helpful events of all. At a CDR, we bring together a panel of outside experts, and we have them go over everything we're doing. Their questions can cover anything from the detailed design of the smallest component to the overall health of the project. Actually, we don't have just one CDR, but a whole series of them, culminating in the Flight System CDR this coming week (that's a review of the whole spacecraft, including the instruments), and the Project CDR a couple of weeks after that. We've spent months getting ready for this, and we're really hoping it's going to go well.

It's always something. We just came across a dumb little problem that could have caused a lot of headaches in the months ahead. There are an awful lot of cameras on this rover... ten on each. Most of them are in pairs, but how do we keep them all straight? In going through our documents this week, we realized that there was a lot of potential for confusion. There's one pair of cameras on the front of the rover, pointing forward. Another pair is on the back, pointing backward. Four more are on top of a rotating mast. So how do we name the cameras in each pair? Camera 1 and camera 2? If so, which is which? Port and starboard, like on a ship? If so, then what about the ones that rotate? It sounds trivial, but this is the kind of thing that can lead to wiring mistakes and all kinds of other goofups if you're not careful. We decided to keep it simple... name the cameras in each pair left and right, as if they were eyeballs in somebody's head. That way it's clear which is which, no matter which direction the cameras point. So three years from now when you see a martian picture from the rover's "Left Rear Hazcam", there shouldn't be any question about which camera really took the picture.

Mini-TES 2 is now a real instrument! Well, maybe not quite, but we're getting there. We hooked the electronics up to the optics and the motor last week. It still has a long way to go, of course. Right now the electronics boards are "fanned out", which means that they're hanging out where they're easy to get to, rather than tucked neatly inside the Mini-TES box where they belong. And we still have more pieces to put inside the box before the instrument is really done. Most importantly, there's enormous amount of testing that still has to happen. But what was just a bunch of parts a few months ago is now starting to look very much like a real scientific instrument.
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