Week Ending June 29, 2002
We've just gotten the first
pictures taken by our Microscopic Imager, and they're fantastic!
The picture that you see shows the surface of a rock, and covers an
area about 3 centimeters (a little over an inch) across. You can
see features in the images down to considerably less than 100
micrometers in size... less than the width of a human hair. It's
really exciting to start seeing data like this, and we can't help
but think what it's going to feel like the first time we see Mars
at this scale.
Week Ending June 22, 2002
What a week... the APXS is done and
Pancam is taking pictures!
After a huge amount of work over in Germany, Rudi and Ralf came over
with two completed APXS instruments this week. The electronics boards
for each one are the ones that are actually going to Mars, and the
team at JPL should start working with them sometime this week. The
sensor heads -- the part that goes out on the arm -- that they brought
over are spare units. We can fly these spares if we have to, but
we're planning on flying sensor heads that are still back in Germany
and about to begin months of testing. If all that testing goes
well, we'll swap the spare sensor head with the flight units sometime
in the fall.
And the Pancam pictures are beautiful! We just got the first Pancam
put together early last week, and it took a perfect picture the first
time we pushed the button. Amazing. This one is an engineering model, so
it's not going to Mars either. But the flight cameras are identical
to it, and those will be coming together over the next few weeks. As
soon as we have some good pictures from those, we'll put 'em on this
web site for the world to see.
Week Ending June 15, 2002
We have finally finished torturing Mini-TES.
Before you can put anything on top of a rocket, you have to test it to make sure it can withstand all the rigors of
spaceflight. It's necessary, but that doesn't mean it's fun. Over the past couple of weeks, we've finally finished
doing all the testing we need to do on Mini-TES. It's scary stuff. The week before last, we did a test where we
simulate what happens when you fire a "pyrotechnic" device on the rover. These are little explosive devices that
are used to do things like release the instrument arm or the camera mast right after we land. They're very small
explosions, but they're explosions nonetheless, and we have to make sure that when we fire them off we won't hurt
Mini-TES. We simulated it, and nothing broke.
Just as scary was the test that simulates landing. Even though our lander is cushioned by airbags, it still hits the
martian surface pretty hard. So, of course, we have to make sure Mini-TES can survive that too. We don't do this by
putting it in a lander and dropping it... we do it by putting it into a giant centrifuge, and spinning it until it
feels stresses even worse than what it'll feel on landing. We survived that too, thank goodness, and the torture
testing of Mini-TES is now over.
Except, of course, next year when we put 'em both on real rockets and send them off to Mars...
Week Ending June 8, 2002
We had a breakthrough in the development of our RAT this week. RAT stands for Rock Abrasion
Tool, and it's what we'll use to grind the dusty and weathered
surfaces off of martian rocks, exposing fresh rock underneath.
It works well, and the RAT can grind about half a centimeter
into even very hard rock. The problem, though, is that
sometimes the dust created by all that grinding winds up
filling the hole. And that's not exactly where we want dust
to be, since the whole point of the RAT is to expose the
clean rock underneath.
So what to do? We're running out of time, and big design changes are out of the question at this point.
The guys at Honeybee Robotics
went to work on it, and came up with a simple solution that
sounded like it ought to work: A new brush built into the
RAT. The RAT already has a part that revolves slowly as
the grinding takes place, and if we mounted a brush to this
part and then spun it for awhile after the grinding was
done, we figured that maybe that would do the trick. Turns
out that it does. On Thursday we ran a test that was a
duplicate of one we had done several weeks ago that had
filled the hole with dust. The new brush cleared things right
out, producing a nice clean rock surface. And it's a good
thing it worked, too, since we've got to start bolting
RATs onto rovers in not too many more weeks. It doesn't
matter how clever you are if you run out of time before
you run out of ideas.
Week Ending June 1, 2002
Our focus this week has been the mad rush to finish up our first set of APXS instruments and get them delivered
to JPL. This is a complicated business, because we have so many
instruments to build. On the one hand, JPL needs some instruments right away, to start putting them into the rovers and testing the whole system to see if it works. On the other hand, each APXS that we're actually going to fly to Mars requires many, many months of testing back in Germany before it's ready to fly. JPL needs instruments
now, but the flight instruments have to stay in Germany until
sometime this fall.
So what do we do? We build twice as many instruments. Right now, Rudi and Ralf are scrambling to finish up the first set of instruments,
which should go to JPL next week. These will go onto the rovers
temporarily. Then, after a day or two to catch their breath, Rudi
and Ralf will start assembling the next pair... the ones that'll
actually go to Mars. These will be tested over a long work-filled
summer in Mainz, and then get delivered to JPL and swapped with
the other ones sometime this fall.
It's twice as many instruments, and an awful lot of work, but
it's the only way to do it when the schedule is so tight.
Week Ending May 25, 2002
The big news this week has been all about Mini-TES.
The tin whisker problem that we had a few weeks ago now seems
to be officially behind us. We had to do a pretty scary repair job on
Mini-TES 2 to fix this, but it looks like the fix worked. We just
finished putting the instrument through some pretty thorough "thermal
vacuum" testing in Santa Barbara, subjecting it to the
same kinds of temperatures it will experience on Mars. The
news was as good as it possibly could have been -- even
after the repairs, the instrument works as well as it ever
did. So Mini-TES 2 now has a clean bill of health.
Of course, things are never simple. Mini-TES 2 may be
healthy, but we've known for awhile that we're also going
to have to do a little bit of repair work on Mini-TES 1,
and the time for that has come. This isn't nearly
as big a deal as the tin whisker job was; we just have to
put one new wire in, to make the design a little safer
and more reliable than it is now. But you have to do that
sort of thing very carefully, which means a trip to Santa Barbara. So
Mini-TES 2 heads back down the coast, Mini-TES 1 heads back up the
coast, and we keep sweating just a little bit.
Week Ending May 18, 2002
We're finally building cameras! It seemed like this day would
never come, but it's finally here. Most parts of our two
cameras -- Pancam and the
Microscopic Imager, have been
coming along fine. The electronics, though, have been giving
us fits. We were still troubleshooting problems as recently
as a week ago, but Arsham and the rest of the camera
electronics guys at JPL have been doing a great job, and now
seem to have chased down the last major problems and killed
So now it's time to build a lot of hardware. The first
batch of cameras, which are being put together now, will
be what we call Engineering Models. They're essentially
identical to the flight cameras, but instead of sending
them to Mars we test the heck out of them, to make
absolutely certain that the design is sound. We should
have them in our hands this coming week. If all goes
well, the real flight cameras -- the ones that really
go to Mars -- will start coming together in a little
over a week.
Week Ending May 11, 2002
Good news and bad news on the cameras this week. The good news is
that we finally seem to have our electronics boards built. This has
been an epic struggle, with one set of boards after another having
some kind of problem that has made it impossible for us to fly
them. We've finally got a good set of boards now -- ones that are
good enough to go to Mars.
That's the good news. The bad news is that we're still having
little problems with the electronics. They're not serious
problems, or at least they don't seem to be. In fact, we're pretty
sure we could fly things just as they are, and still take some
very good pictures. But things still aren't quite right, and
"not quite right" is not where we want to be for something as
important as our cameras.
The problem now isn't the boards. The problem is somewhere in all
the dozens of little electronics parts that go on the boards.
We're going to find it, probably within the next few days. But
we're going to feel an awful lot lot better if we can find it,
and fix it, sooner rather than later.
Week Ending May 4, 2002
The surgery on our Mini-TES
2 instrument is over, and it seems to have gone well. We had
to do this to fix the "tin whiskers" problem that I wrote about
last week. It was
a pretty scary operation. The guys in Santa Barbara had to
open up the instrument, and then cut into the steel outer
shell of one of the parts on the inside. The critical trick
was to keep from getting little metal shavings loose inside
the instrument -- those could be even worse than the tin
whiskers we're trying to prevent! They cut into it nice
and clean, and on Friday they coated the inside of the part
with a spray-on plastic that should solve the whisker problem.
We're not done yet, though. When you do something that
severe to a piece of flight hardware, you have to do a lot
of testing afterwards to make sure that nothing bad happened.
So now we're in for more
vibration testing, more thermal testing, and so forth.
We're not out of the woods yet, but at least the really
scary part seems to be over.
Week Ending April 27, 2002
We've uncovered a very troubling problem with Mini-TES 2: we're afraid that it might grow whiskers.
What we have learned, just recently, is that one of the electronic parts
that we used deep inside Mini-TES 2 was made using some pure tin. And pure
tin, it turns out, can do some very strange things. What it does, under
certain conditions, is develop microscopic "whiskers"... tiny needle-like
growths of metal that protrude out from the tin surface. They're nasty
things to have inside a sensitive piece of electrical equipment. If
they grow too far, or if they break off and start rattling around, you
can get a short circuit. And then poof, no more instrument.
So what do we do? The thing to do, it turns out, is to open up the
part that has the tin in it, and then coat the inside with a kind of
spray-on plastic. That'll help keep tin whiskers from growing, and
also will hold any ones that do grow in place so they can't cause
You can imagine that cracking open an instrument that we thought was
all done is not exactly high on the list of things we'd like to do!
But we have to do it, and Mini-TES 2 is back up in Santa Barbara now,
ready to undergo a little minor surgery.
Week Ending April 20, 2002
So much happened this week that it's impossible to pick one thing to
write about. The electronics boards for the APXS
passed their vibration tests in Berlin. We finished fixing the problem
with the Mössbauer spectrometer
sensor heads that popped up during their vibration tests last month.
The motors that we've been waiting months for that go in the
RAT finally arrived. A problem came
up in our camera electronics board that's going to cost us another
two or three week delay that we can barely afford. And we discovered
a problem with one of the electronic parts inside Mini-TES 2 that we haven't figured out how to
fix yet. It was quite a week! We're hoping for a slightly calmer
one this week, but we're not counting on it.
Week Ending April 13, 2002
When the schedule starts to get tight on a project like this, sometimes you
have to start making some tough choices. And our schedule is getting
very tight indeed.
There's a small problem in the electronics of our cameras, and its result
is that the pictures are a little bit more "noisy" than we'd like them to
be. Imagine a TV picture with some "static" in it. The static is there in
our cameras at a level far too low for the eye to see, but we know it's
Being fussy scientists and engineers, we'd love to get rid of that little
bit of noise. And we know how to do it. But the changes we'd have to make
would take something like five to ten days. And our camera schedule
is so tight now that any time we take to make the cameras a little bit
better will come out of the time we need for critical testing over the
coming months. So we have a choice: a little more noise than we'd like,
or five to ten days out of our schedule. There's a saying in this business
that "better is the enemy of good enough". And when the schedule is as
tight as ours is, "good enough" starts to look pretty good.
Week Ending April 6, 2002
We're working on a little design change to the RAT
that should make a big difference in how it works.
The Rock Abrasion Tool (a.k.a. "the RAT") is very good at grinding
through rock. But all that grinding makes some rock dust, and the
dust tends to get all over things. A problem that we've been worried
about is that there might be some dust left on the rock surface after
the RAT is done grinding away at it. Two of our instruments --
the APXS and the
Mössbauer Spectrometer -- wouldn't be
bothered by this. But the Microscopic
Imager takes close-up pictures, and those pictures could
be pretty useless if there's lots of dust on the rock.
The old design of the RAT has two grinding wheels. What we've found
after lots of testing is that the RAT works just about as well with
one wheel as it does with two. So we're keeping one grinding wheel,
but considering replacing the other with a brush that whisks away
the dust, keeping the surface clean and beautiful. There's still
more testing to be done, but if it works it should make for some
great closeup pictures of the insides of martian rocks.