Week Ending March 29, 2003
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...
Week Ending March 22, 2003
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...
Week Ending March 15, 2003
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.
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.
Week Ending March 8, 2003
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
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.
Week Ending March 1, 2003
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
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.
Week Ending February 22, 2003
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
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
Week Ending February 15, 2003
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
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.
Week Ending February 8, 2003
We passed another big milestone this week -- our very last
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
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.
Week Ending February 1, 2003
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.
Week Ending January 25, 2003
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.
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
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 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.
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.
Week Ending January 11, 2003
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 Ending January 4, 2003
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