Martian Chronicles I
Seeing Flight Hardware
Three spacecrafts are now hurtling toward the Red Planet to look for evidence that it might once have been wet enough to sustain life. Orbital projections of where Europe’s Mars Express and the two NASA Mars Exploration Rovers (MER) are right now, can be continuously monitored over their half-year journeys. Experiments performed by the MERs will help to determine whether water might have once existed in volume on the red planet. The two Mars Exploration Rovers are targeting what imagery indicates might have been ancient dry lake beds and other geologically interesting sites in early 2004.
The Martian Chronicles series gives an inside view of what it takes for scientists to deliver such a complex mars mission. The journal entries are from Cornell’s Steve Squyres, the Principal Investigator for the Mars Exploration Rovers’ scientific package called Athena. The chronicles begin sequentially from the beginning of July 1999, four years before launch, and will culminate in the dramatic landing of the twin rovers on Mars in January 2004. The expected mission time roaming the red planet is ninety days, from January to April.
The chronicles include an insider’s view of hardware tests and site selection, to problem solving and science planning on the surface of another planet.
July 9, 1999
This week starts a new feature on the site: A summary of the major events of the past week. We’re into one of the exciting phases of APEX now, with flight hardware being built and tests underway.
The big event of this past week has been "thermal vac" testing of the Mini-TES flight instrument — putting it into a vacuum chamber in Santa Barbara and running it through the kinds of temperatures we’ll see on Mars. We got a little bit of a scare at first… the instrument was performing beautifully at warm temperatures, but not nearly so well as it got colder. Some troubleshooting tracked the problem down, though, and it was easily fixed by changing just one part – a resistor – in the electronics. All in all, an elegant bit of sleuthing by the guys at Raytheon.
July 16, 1999
We’re deep into our test program. Mini-TES is still in the thermal vacuum chamber in Santa Barbara, and we’re working to confirm that the fix we made last week worked. The most important event of this past week was that the Mössbauer spectrometer design has finally passed its vibration test in Germany. This was a big deal, because a wire inside the instrument had broken the first couple of times we tried it. The team in Darmstadt figured out a change that fixed the problem, and now we have a design that we’re confident will be able to withstand the rigors of launch.
Credit: NASA JPL
July 23, 1999
This week we did our second big operations test with the FIDO rover. This one was in the "Mars yard": a gigantic rock-filled sandbox at JPL. In two days of work, we simulated the first 12 martian days (or "sols") of the Athena Rover’s mission. Commanding the rover in the blind, we selected rocks for investigation, and then drove the rover into the precise positions necessary to sample them. These tests are crucial to learn how to operate the vehicle once we get to Mars, and they’re also a ton of fun!
August 6, 1999
Sorry about missing last week’s report… things have been a little busy lately. Mini-TES has spent the better part of the last two weeks in continued thermal vacuum testing in Santa Barbara, making sure we’ve really chased down all the problems. As of this weekend, it looks like we’ve finally got it. The big news of this past week came from the Mössbauer Spectrometer. Uwe and Bodo from Darmstadt brought the first copy of the Mössbauer electronics to JPL this week, and when we hooked them up to the rest of the APEX electronics, everything worked! It doesn’t always happen that way…
August 20, 1999
APEX hardware is starting to come together very quickly now. The most important event of the week (and one of the most important APEX events to date) was that Mini-TES has now been delivered. The instrument was shipped from Santa Barbara to JPL, and is ready now to begin integration with the rest of the APEX flight hardware once it arrives.
|The new Pancam design has a camera bar that contains Pancam and Navcam (navigation camera) heads. A "visor" changes the elevation of the cameras so the rover can look up or down.|
Credit: Cornell University
The Pancam flight cameras are coming together quickly now, too, and should look like real cameras within another few weeks. And calibration of the APXS instrument continues in Germany… a months-long process that has been going on round-the-clock since June.
August 27, 1999
Lots of hard work this week. It’s time to start getting our instruments ready to "talk" to the lander once it’s built… to exchange commands and data in the same way that they will when we get to Mars. We had worked most of this out over the past several weeks, but there was one interface — the one that lets Pancam talk to the spacecraft — that wasn’t working. Several of the APEX electronics and software hotshots hopped a plane to Denver early this week, and spent a very long day there with the Lockheed Martin lander team tracking down the problem. They got it, and as of this week all of the APEX interfaces to the spacecraft are tested and ready to go.
September 3, 1999
The Mars 2001 Project is making progress toward picking a landing site. Back in June, there was a landing site workshop in Buffalo. Dozens of Mars scientists attended, and something like sixty or so possible sites were discussed. Lots of these sites would have been good scientifically, but there’s also the issue of lander safety, which is essential. Since the workshop, the Mars Global Surveyor spacecraft (which is orbiting Mars now) has put a lot of effort into taking high-resolution pictures of prospective sites. Many of them, it turns out, are too rugged for the lander to be able to land safely. But some of them look pretty good, and it’s now down to a "short list" that MGS will inspect even more carefully over the next few months. The general landing area needs to be picked by the end of the year. After that, there’ll plenty of time to fine-tune the location of the final site.
September 10, 1999
Little troubles here and there this week. The good news is that the engineering model for the APEX Mössbauer Spectrometer has been delivered to JPL. The bad news is that it isn’t working yet… or rather, that it isn’t talking properly to the rest of the APEX electronics. We don’t think it’s a big problem, mostly because we got an earlier version of the Mössbauer to work just fine. But it’s one of those things that you have to track down and fix, which ought to keep some of the team busy for the next few days. Meanwhile, we’ve hit a little bump in the road with the APXS, too, having to spend a week going in and changing some temperature-correction hardware and software that we thought was working right months ago. This is the reason that you put margin in your schedule! The instrument’s doing fine overall, though, and we’re still on track to deliver it to the Marie Curie rover early next month.
September 17, 1999
We had a wild week, with lots going on. On APEX, the Mössbauer problem from last week was fixed, and we’re making good progress toward assembling the flight versions of both the Mössbauer Spectrometer and the Pancam cameras. Over in Germany, the flight APXS instrument underwent the final refurbishment of its electronics, and is now almost completely calibrated. We should ship it to JPL to be put onto the Marie Curie rover in just a few weeks.
|A simulated image of the new Mars rover carrying the Athena science instruments.|
On Athena, the big news of the week was the System Requirements Review… the first big formal review of the Mars Sample Return Project. This is the review where you make sure you’ve got all your requirements straight — in other words, where show that you understand the job that you’re supposed to do. It went well, and the next big one will be the Preliminary Design Review, coming up in December.
September 24, 1999
This was a very bad week for Mars exploration. On Thursday, we got the news that the Mars Climate Orbiter spacecraft had been lost during its orbit insertion maneuver. Apparently the spacecraft was sent too close to the planet as a result of a navigation error. The friction with the martian atmosphere at that altitude — only about 57 kilometers above the surface — would have been enough to destroy the spacecraft.
This is a setback for the Mars program, though not a crippling blow. One of the reasons that NASA is sending so many spacecraft to Mars now is that it keeps the loss of any one spacecraft from causing serious damage to the program. And when you do things as hard as flying missions to Mars, mistakes and accidents will happen. APEX and Athena should not be impacted by the loss of MCO. But our hearts go out to the MCO Project family… we know how hard they worked on their spacecraft and their instruments, and we know how deeply they feel this loss.
October 1, 1999
We hit a little snag with Pancam this week. The flight electronics for one of the cameras were put together and worked beautifully. When we put the second set together, however, there was some ugly noise in the images — stripes across the pictures like static in a bad TV picture. A little work by Enrique Villegas, our Pancam electronics whiz, showed that this was caused by the fact that the detector for that camera had been damaged — probably by a little accidental jolt of static electricity somewhere along the line. We’re still not sure how it happened, but this is the reason you always make sure you have spares of critical components! We have a good number of flight-quality detectors, so we’ve popped one of them onto a new Pancam electronics board, and we’re back in business.
October 8, 1999
It looks like we’re closing in on a landing site for APEX. There was a big workshop down in Houston this week, and now we seem to be down to just two candidate regions. One is a place on the rim of the Isidis Basin. This one is in some of Mars’ oldest terrain, and is in an area with lots of small valleys and gullies that indicate that water once flowed there. It also has some spectacular topography, which could make for a very scenic landing. The other is a smooth, flat plain that has been found from orbit to have a lot of the mineral hematite present.
|Gray hematite (above) is found in three places on Mars: Meridiani Planum, Aram Chaos and Valles Marineris.|
Credit: Amethyst Galleries, Inc.
Hematite normally forms in the presence of liquid water, so this is another place that may have once been warm and wet, and that is very different from almost everything else on the planet. There’s still plenty of time to study these two places before the Project has to decide, but it’s great to have two sites this exciting that we might go to.
October 15, 1999
We had a real up-and-down week. The up part was that the APXS is now integrated into the Marie Curie rover! This whole operation took about a week, and went better than we could have imagined. The down part is that we ran into a bunch of annoying little problems on Pancam, including a motor that has to be replaced, a couple of devices called photodiodes that we wired in backwards by mistake, and the discovery that we have to redesign the sunshades a little bit. None of these are big deals, but they all worked to slow down what otherwise would have been one of our best weeks ever.
October 22, 1999
The flight Mössbauer Spectrometer is coming together now. The electronics boards are all assembled and tested. They work fine, although we’ll have to replace one part once it gets to JPL with a similar part that can survive all the radiation that we’ll encounter in space. The other part of the instrument, the sensor head, is lagging behind a little bit, but should be ready near the end of November.
The other news this week was that we just completed our second operations test with the FIDO rover in the Mars yard. We set this one up as a truly "blind" test, with the operations team in a windowless room in the JPL robotics lab, far from the Mars yard and interacting with the rover just as we’ll have to do it on Mars. Each time we do this we learn more and more, and this was probably our most successful test to date.
October 29, 1999
No big news this week…just lots of little odds and ends. Mini-TES and APXS are tucked away in storage at JPL, waiting for the other instruments to show up. Mössbauer is coming together in Germany, with the latest arrival being the special microcomputer chip the instrument needs to survive in the radiation environment of space. And Pancam is in pieces at JPL, getting fixed up for the next big round of calibration, which should start in two weeks. The biggest excitement of the week was getting our first look at the Mars 2001 lander. There’s a long way to go, but it’s great to finally be seeing the real flight hardware!