The Athena payload for the MER-2 rover is done.

At some point you have to be prepared to say goodbye to your hardware on a project like this, and that time is just about here. We have taken the last data we'll ever take on this planet with the instruments on the MER-2 rover. We stowed everything for launch this week. The mast is locked down tight against the rover deck now, and the arm is tucked up against the front end of the rover. Our instruments have been turned off, and they're going to stay that way for awhile. The next time we talk to them, the rover will be in deep space, on its way to Mars. And the next time we move the arm or the mast, or take any real pictures, we'll be down on the martian surface.

That's MER-2. MER-1 is still very busy, taking pictures, driving around, and going through its last bit of testing in Florida before we stow that one for launch too. But in another week or so, everything we've worked on for the past seven years is going to be ready to head into space.

Nine weeks until we launch...

We've just been through two of the toughest weeks we've had in the past couple of years.

Problem number one was with our Moessbauer spectrometer. Each Moessbauer instrument is like four instruments in one... four separate sensors that each return data. When we got them to Florida, the MER-1 Moessbauer looked fine, but one of the four sensors on the MER-2 Moessbauer had gone totally dead. We spent almost a week troubleshooting it, and we finally traced the problem to one tiny electronic part, called a resistor, that had failed. We managed to figure out why it failed, and we confirmed that the problem shouldn't affect any of the other sensors. Roberta Cerda flew out from JPL, put the broken hardware under a microscope, and fixed it. She is a true artist with a soldering iron, and the instrument is now ready to go.

Problem number two was with our APXS instrument, and this one looked even worse. Six hours into a test at JPL, the MER-1 APXS just plain died. Or at least it sure looked like it had. It suddenly stopped working, and when we made some quick measurements it was clear that a short circuit had developed somewhere inside the instrument. That kind of thing can be fatal for flight hardware, and most of us were pretty convinced we were going to have to fly one of our spare instruments. But Ralf Gellert didn't give up on it. He took the instrument apart, and he found the problem. A tiny sliver of aluminum, probably stripped from a small screw, had gotten wedged in just the wrong part of the instrument and caused the short. That's why we do tests, to find that kind of problem. The instrument wasn't damaged, and when he took the sliver out everything started working fine again. You can bet we inspected the inside of the instrument really carefully to make sure there was nothing else like that inside it! So that one's ready to go too.

When problems like this happen a year or two before launch, it can be easy enough to deal with them. But when they happen now, with both spacecraft at Cape Canaveral, it's a different story. We really dodged a couple of bullets this week.

Ten weeks to go...

This week marked one of the most important milestones since we started this thing more than seven years ago. The second MER rover and its Athena payload arrived in Florida.

Since the summer of 1999 we've been putting weekly news updates on this web site. We've had a lot of ups and downs over that span, including some times when it looked like maybe we weren't ever going to get our payload to the launch pad at all. And now, after years of effort by hundreds of scientists and engineers, everything is at Cape Canaveral. It's an incredible feeling. This picture, taken by Goestar Klingelhoefer, shows the last of the trucks rolling through the gate at Kennedy Space Center... with me on my cell phone giving the news to the folks back home.

We're now less than eleven weeks away from our first launch.

Every now and then you catch a lucky break. We caught one this week that we still don't completely understand, but we'll take it. Our Rock Abrasion Tool (also known as the RAT) uses diamond grinding heads to wear away at martian rocks. Even though diamonds are the hardest materials known, they can still wear out, and we've been very concerned about how long the RAT grinding heads will last on Mars. We've done a lot of testing in the laboratory, and it looked like the RAT would do fine if martian rocks are soft. If the rocks turn out to be really hard, though, it seemed that the RAT would make it through just a handful of grindings before wearing out.

The big question, of course, was how things would work under the very cold, dry, low-pressure atmospheric conditions on Mars. We put a RAT into a test chamber recently, took it to real martian conditions for the first time, and got a very pleasant surprise. The rate at which our diamond-studded teeth wear away slowed way down! We're still figuring out why, but it turns out that when you put this martian RAT into its natural environment, its teeth don't wear down nearly as fast. So we should be able to grind into as many rocks as we want to on Mars, no matter how hard they turn out to be.

Thermal vac testing of MER-1 is almost over. It's been quite an experience. Back in December, when we put the MER-2 rover into a thermal vacuum chamber and ran it under martian conditions, it was quite a struggle. We got all the data we needed, but a lot of things also went wrong. The worst of them was the "speckle" problem in the right Pancam camera, which we finally killed off in a test on MER-2 last week.

For MER-1, though, thermal vac testing this past week has gone much more smoothly. Everything has gotten better over the past couple of months: hardware, software, and people. There was no speckling in the Pancam on this rover. We got tons of Mini-TES data, and the data showed that this instrument is just as good as the one on MER-2, or even a tad better. And we did the first full-up test at martian temperatures of the fix to the Moessbauer Spectrometer problem that turned up months ago. The Moessbauer data looked great, so that one is behind us now too.

As in the last test, two of the real standouts were the Instrument Deployment Device — also known as the rover's arm — and the Microscopic Imager that it carries. Here's a sequence of five Microscopic Imager pictures, taken as the arm slowly moved the camera to bring things into focus. Pretty cool, huh? Now imagine what it'll be like next January when this same camera is taking close-up pictures of martian rocks.

It's that time again: Thermal-vac testing, this time for the MER-1 rover. Before each rover goes to Mars, we have to put it through all its paces under martian conditions. This means putting into a big "thermal vacuum" chamber, pumping the air out, cooling the walls down, and filling the chamber with a little bit of very cold gas to simulate the martian atmosphere. We then make the rover do just about every trick it knows, including operating all of the science instruments.

We did this with the MER-2 rover back in December, and it was a pretty exhausting experience. Thermal vac runs 24 hours a day until it's over, and MER-2 thermal vac went on for something like ten days and nights. MER-1 has just gone into the chamber as I'm writing this, and the action should continue all this coming week. The first big hurdle will be to make sure that the Pancam "speckle" problem that hit us on MER-2 is really gone. And after that, we'll just rock around the clock until all the tests are done.

This week we put to rest what may have been the worst remaining problem that stood between us and launch.

This one was looking very nasty for awhile. Back in December, we put the whole MER-2 rover into a big thermal chamber and took it down to cold martian temperatures. Almost everything worked right, but one thing was very, very wrong. When the rover got really cold, the pictures from one of our two Pancam cameras got bad. In fact, they were worse than bad, they were terrible. Imagine a TV picture with static so bad you can barely tell what you're looking at. That's what some of them were like. It only happened in that one camera, and it went away as soon as we warmed things up a bit. But it was pretty scary, because we didn't know what was wrong.

We chased this one for a long time. The breakthrough came a few weeks ago, when Leo Bister at JPL took a really careful look at the cables that run to all the cameras at the top of the rover's mast. Something just didn't seem quite right to him, and when he dug into it he realized that we had built the cable wrong. That cable has a bunch of pairs of wires in it, with the pairs of them carefully twisted together. Problem was, the wrong wires had been paired up when they were twisted, letting signals from the camera become contaminated by signals in other wires. It was the kind of thing that would get worse when the cable got cold, and it was also the kind of thing that could really mess up a picture.

This had to be it, but you can't be sure until you test. We built some new cables, replaced the old ones, and late last week we put the whole rover back into the chamber again, cooled it down, and held our breath. It worked. Every picture was clean and flawless, even at the coldest temperature. It was a huge relief, and a nice piece of detective work by Leo.

We passed another big milestone this week -- our very last vibe tests. Vibration tests are some of the scariest things you do to space flight hardware. It's a torture test: You bolt your instrument to a machine that shakes it as hard as the rocket will shake it when you launch it, or even harder. Sometimes the instrument survives the test, and sometimes it doesn't.

These were the final vibe tests for our flight APXS instruments. We should have done these tests many months ago, of course, but sometimes things don't work out the way you'd like them to. Several months ago we discovered a very bad mistake that we had made in part of the APXS that detects alpha particles. This "alpha mode", as we call it, is essential for detecting important elements like carbon, and it simply wouldn't have worked on Mars the way we originally built it. At least we found the problem in time! But it meant that we had to go out and get new and improved alpha detectors, put them in the instrument, and then do all the testing months later than we originally wanted to.

If we hadn't passed the tests this week, we would have been stuck flying our spare APXS instruments. The spares are okay in most respects, but their alpha detectors won't work right because of the design mistake we made. So it was with enormous apprehension that we shipped the APXS flight instruments, with the fixed alpha mode included, to Berlin for their final vibe tests. They both passed beautifully, and soon they'll be ready to go on the rovers. It's an enormous relief.

The space program is a lot like a family, and our family experienced a terrible loss this week. We'll return to Mars news next week. For now our thoughts and prayers are with the loved ones of the astronauts who lost their lives in the Columbia tragedy.

Time is getting short, and we're killing off problems as fast as we can. We just got another one.

This was a strange one. During a test we did back in December, something odd happened to our APXS instrument. During a two-hour test, the instrument somehow got reset -- that is, it got turned off and back on again -- seventeen times. That kind of thing isn't good, and if it happened on Mars we'd lose data, just like you can lose data on your computer if it gets turned off before you've saved something. We couldn't figure out what was wrong, and it looked like it could be a real problem.

After a lot of sleuthing, the answer became clear. During the same two hours that we were testing the APXS, the rover engineers were testing the rover's power system. That means they were working with things like the batteries, the electronics that run them, and so forth. And during that time, what we learned was that they had sent seventeen different commands to the power system. That was the clue we needed to solve the mystery. When we dug in deeply, we discovered that there is a nasty bug in the rover design: every time somebody sends a command to the power system, it inadvertently turns the APXS and the Mössbauer Spectrometer off and back on again! It's such a goofy bug we didn't believe it at first, but that turned out to be the problem. We're fixing it with a change to the software, and next month when we do the same test with APXS on the other rover, we're expecting it to behave itself.

Week Ending January 18, 2003

There's been so much news lately that we never got around to posting what's probably the coolest data product of all from the MER-2 rover testing we did back in December. Here it is. The image on the left is one taken by the rover's navigation camera, or Navcam. The Navcams are black-and-white cameras, with a wider field of view than Pancam has. On Mars, we'll use them mostly to figure out where to drive the rovers. In this picture, you can see a special target that was built for this test by Dick Morris, one of our team members from Johnson Space Center in Houston. It's got a bunch of thin slabs on it, each cut from a different kind of rock.

The cool thing is the stuff on the right. This is an image of the same target, but put together with data from our Mini-TES instrument. Mini-TES can sense what each rock is made of, and the "false colors" of the pixels in the image show the variation in the composition of the rocks on the target.

But there's more in the Mini-TES data than you can see in just a simple image. For every pixel in that image, we have more than just a false color... we have a complete infrared spectrum to really tell us in detail what the rock is made of. This plot shows a spectrum for each of the rocks on the target. All those wiggles and squiggles, to a trained spectroscopist, are the distinctive fingerprint of a rock type. We did this as a "blind" test, meaning that the real compositions of the rocks on that target are known only to Dick, and he's not telling. But with data this good, they won't be unknown to the rest of the team for long.

At this stage in a project, it's all about working out the little details, making sure we'll be ready to ship the rovers to the Cape when the time comes. And there sure are a lot of details! One of the ones we took care of this week involves our magnet experiment. To do the magnet experiment when we get to Mars, we'll use the Pancam cameras every few days to take a look at the magnets that are mounted on the rover. Once we see enough martian dust sticking to the magnets, we'll look at them with the APXS and the Mössbauer Spectrometer to find out what the magnetic stuff in the dust is made of.

It's simple, but to do that experiment we need to know which direction to point the cameras so that the magnets will be in the field of view. It'd be easy to just wait until the rovers on Mars to figure it out, but time then will be even more precious than it is now. So we swung the cameras around to where we thought the magnets ought to be, and took a few pictures. In the first one, we missed! In the second one we at least managed to get both magnets in the frame (they're the two round things on the right side of the picture). They're not centered, but it's good enough for now. We can center them up better once we get to Mars.

And if you see off-center magnet pictures after we land a year from now, you'll know we didn't have time to make it pretty, and decided to just go with what we learned this week!

For weeks now, we've been chasing a nasty problem with our Mössbauer Spectrometer. There may finally be a light at the end of the tunnel.

The problem's not the instrument... the instrument works just fine when we test it by itself. But the Mössbauer Spectrometer comes in two parts. One part is the "sensor head", which is out at the end of the rover's arm, and the other is the electronics, deep inside the rover body. The two parts are connected by a long and complicated cable, and it's the cable that's been the problem.

The thing you'd want to do is simply replace the cable with one that works better, but that turns out not to be so simple. Half of the cable -- the part of it that's inside the rover -- is fairly easy to replace, and we've done that already. It helps, but it doesn't solve the problem. The other half of the cable, which runs up the arm, is very, very difficult to replace. We'd essentially have to take the whole arm apart to do it, and nobody wants to do that to a piece of flight hardware that's been assembled and tested, and that works beautifully.

So what to do? A team of very talented electrical engineers, both in Germany and at JPL, has been working on that problem for a couple of months now. The solution appears to be to add a tiny little electronics board to the outside of the sensor head. This board improves the signal that runs up the arm enough that the cable can handle it. We tested it this week at JPL with one of our two flight instruments, and it worked. We still have to confirm that it works with the other one, and we also have to make sure that it works at martian temperatures. But the solution to one of our toughest problems now may be in sight.

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