Martian Chronicles III: Furious Pace
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 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 Mars.
February 26, 2000
Well, this week was a good one for a change. We still have the problem with the Pancam cable, but all of the other instruments have now passed the electromagnetic cleanliness tests with flying colors. We still don’t know when we’re going to fly, or on what spacecraft, but the instruments are going to be ready to go when the opportunity arises.
|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
March 10, 2000
Well, after lots of thought and analysis, we’ve decided to take the easy way out of that problem that we found in the Pancam cable a few weeks back. It was a sophisticated cable called a "flexprint", and the elegant solution would have been to correct the design problems, build another one, and make it work. The easy way, though, is just to replace it with conventional cabling… in other words, plain old wires. It’ll be a little heavier than the old design, but it’s easy, it’s cheap, and we know it’ll work. And at this stage of a project, sometimes you just go with what you know will work!
March 17, 2000
Despite the uncertainty about when we’re going to fly, testing goes forward. This week, the focus has been on the Marie Curie rover.
|A simulated image of the new Mars rover carrying the Athena science instruments.|
It carries our APXS instrument, and this week it has been in "thermal vac" testing, experiencing the temperatures and pressures it’ll see on the way to Mars and on the martian surface. We expected this test to go pretty well… after all, Marie Curie is a copy of the Sojourner rover that did so well on Mars Pathfinder. Still, it’s always nerve-wracking when you do something like this to a piece of hardware you’ve worked so hard on. The test isn’t over yet, but so far the APXS has behaved like a champ, and we’re keeping our fingers crossed.
March 24, 2000
We had a great week. There is a lot of news, but the big event for us was the first real full-up test of Pancam. It’s together in all its glory now, in the Spacecraft Assembly Facility at JPL, and on Thursday and Friday the past week we took our first real panoramic images with it. It’s going to take a lot of time to put them together to make a true panorama, but even a quick first look suggests it’s going to be really good.
March 31, 2000
Well, the event we’ve been expecting has finally happened… the Mars ’01 Lander mission has been cancelled. Even though we expected it, and even though it’s the right thing for NASA to do, it still isn’t easy to take. We’ve been working on our hardware for years now, and to have our ride to Mars disappear just twelve months before launch is hard.
It sure isn’t as hard as what happened to the Mars Polar Lander team, though.
Space exploration is an unforgiving business. "One strike and you’re out", as Tom Young put it when his committee reported last week on what has been wrong with the Mars program. After everything that has happened, what’s best for the nation’s space program, and what’s best for us, is to wait.
Wait a little bit while NASA comes up with a more reliable way to land hardware on Mars. Wait a little bit to take a good hard look at our own work, and to make sure that we’ve done as good a job as we need to in a one-strike-you’re-out business. We think our stuff is about as good as it could possibly be, but another good hard look at everything we’ve done sure won’t hurt.
So we’ll wait. Right now, we don’t even know when we’ll fly. With Mars launch opportunities only every 26 months, the summer of 2003 looks like our next reasonable shot at it. NASA has told us to finish up our instruments, and that they’ll fly them as soon as they can. So all we can do now is keep pushing. We’ll be ready when the time comes.
May 6, 2000
This week was devoted to final preparations for the APEX operations tests on May 10-12. The key event was putting the radioactive sources into the Mössbauer spectrometer.
|The Mössbauer Spectrometer electronics. |
Credit: Johannes Gutenberg University
In order to work, the Mössbauer has to carry two tiny flecks of cobalt-57… one deep inside the instrument, and one at the business end of the sensor head that shines gamma rays onto the rock or soil we’re studying. Bodo Bernhardt came over from Germany and put the sources in late in the week, so now the Mössbauer’s all set.
A few tweaks to the Mini-TES software Monday and Tuesday, and by Wednesday morning we should be ready to go.
May 20, 2000
Things are going at a furious pace now. We have about seven weeks until the big review at which NASA will decide whether or not we’ll fly in 2003. We’re doing what seems like a thousand things at once: wrapping up work on the instruments, figuring out what changes we’ll need to make to fly on this new rover, and working out how we’ll use the rover to do the science we need to do.
The FIDO rover test that finished up this past week has been a huge help in our planning, since it gave us our first good chance to operate a real rover in a real unknown environment. Now that the test is over, we’ve been told where it was: in the mountains outside of Ely, Nevada. We learned a lot about the geology of the site with the rover, and a lot more about how to use a rover to do exploration.
May 27, 2000
The biggest effort of this past week has been processing all the data that we took during the test of our instruments that we conducted on May 10-12. We’ve still got a lot more work to do, but the results so far have been pretty spectacular. We’ll put a bunch of data up on the site soon, but here’s one teaser for now. It’s a 360-degree Pancam panorama of the "high bay" — the big room in the Spacecraft Assembly Facility at JPL where we did the tests.
There are still a few odds and ends we need to fix up in this panorama, including mosaicking the frames together nicely so that the seams don’t show. But the main thing to note is the resolution: the actual resolution of this image is ten times what’s displayed here. That’s ten times as much detail both horizontally and vertically, meaning a hundred times as many pixels as you see in this image. That’s a lot of detail! More data, including some full-resolution views, will follow shortly.
June 2, 2000
We’re continuing to work with the data we collected during the tests we did with the Athena flight instruments last month. Here’s the same panorama that we showed last week. It’s reduced in resolution by a factor of ten in each direction so that it won’t be too enormous to download. In this version, there are some red boxes… click on them to see portions of the panorama at full resolution. The slight speckling you see in some of the images is there because we were running the cameras at high temperatures; that’ll be gone at martian temperatures. Now imagine a full martian panorama at this kind of resolution!
June 9, 2000
Here’s some more data from our tests last month. Click here first to see a Pancam image that shows part of the test facility at JPL, with some rock targets in the foreground. Then click in the red box to see a Mini-TES image of of the scene inside the box. For each and every pixel in that Mini-TES image, we have a complete infrared spectrum that tells us about the composition of the rocks. The image has been color-coded, with different colors representing different minerals: blue is hematite, pink is gypsum, orange is calcite, and so forth. We’ll use data like this on Mars to figure out what the rocks are made of from a distance, and to decide which ones to go look at in more detail. By the way, that’s a person sitting just to the left of the rock target in the Mini-TES image!
June 16, 2000
Here’s some more Mini-TES data from our tests last month. Last week we showed a Mini-TES image, color-coded to show the mineralogy of the rocks we were looking at. But Mini-TES produces much more than just images. Each "pixel" of a Mini-TES image is actually a complete, detailed infrared spectrum. Click here to see three examples of what Mini-TES data look like when you check them out in detail. And these are just the spectra for three pixels in the image… every other pixel has just as much information in it too. We can get a good idea of what the rocks around the rover are made of with Mini-TES, which lets us decide which ones to go and investigate in more detail with our other instruments.
August 6, 2000
It’s hard to imagine news that could be much better than what we’ve heard in the past week. We’re back in business again. After six months of uncertainty about our fate, NASA has now decided to fly the Athena payload to Mars on a big, capable rover. We launch in the summer of 2003, and we land in January of 2004. See last week’s press release for more details. So now we’re back to work.
Several of the instruments we built for the cancelled ’01 lander should be ready for this rover: Pancam, Mini-TES, and the Mössbauer are all good to go. But we need to do a new APXS, we have to work out the design details for the our Microscopic Imager, and we have to essentially invent the Rock Abrasion Tool (a.k.a. the RAT) from scratch. And there’s more.
Not only has NASA decided to fly us, but they may decide to fly two copies of everything… on two rovers! If that happens, the rovers will both be launched in ’03, and they’ll land on Mars within a few weeks of one another. And, obviously, if that happens we’ll have to build more copies of everything. At least we shouldn’t have to wait long for this decision… it may come within the next few days.
August 13, 2000
Another wild week. On Thursday, NASA announced that they plan to send not one but two rovers to Mars in 2003, both carrying identical copies of the Athena payload. This is great for the science, since it means we’ll be able to land the rovers in two very different places, doubling the science without doubling the cost.
|The Mössbauer Spectrometer sensor head.|
Credit: Johannes Gutenberg University
In the near term, though, it means we have a lot more work to do! We thought we were done building some of our toughest instruments. Not so. Now we have to get started on another Mini-TES, another Pancam, another Mössbauer, and so forth. The experience we gained building the first set should help immensely, and we’re hoping to avoid some of the little "adventures" we had the first time around. But it’s going to be a long haul.
August 27, 2000
This is an incredibly hectic time… which is why it has been two weeks since we’ve even been able to summarize here what’s been going on! We’re at the beginning phases of this project now, dealing with what seems like a million details of rover and mission design. The big event coming up in a couple of months is the mission’s Preliminary Design Review, or PDR. (We love acronyms in this business.)
The PDR is where we have to show that we don’t have any show-stoppers in front of us… that there’s a clear path from where we are to having a detailed design that will really work. So the big jobs now, before the PDR, are figuring out exactly what the whole rover and payload have to do, and then making the design decisions that will make it possible. Probably the biggest decision of the past two weeks was that we’ve decided to focus the Microscopic Imager just by moving the rover’s arm, rather than putting a complicated little focusing mechanism into the camera. But that’s just one decision among very many. We have a long, long way to go…
September 3, 2000
Our main focus this past week has been on the two newest pieces of our payload: The Microscopic Imager and the RAT (a.k.a. the Rock Abrasion Tool). The biggest issue lately has been figuring out how to make them work together. The RAT will grind away a circular area of rock, and then we’ll use the Microscopic Imager to look at it and see what’s inside the rock. The RAT needs to be able grind away an area as big as the MI’s field of view. The bigger this is the more we’ll see, but if it’s too big, the RAT has to be pretty big and heavy to get the job done.
After considering everything together, we came out with a RAT that grinds an area 47 millimeters in diameter, and a camera field of view that’s 42 millimeters across its diagonal — giving us 5 millimeters of wiggle room in case we can’t position the camera as accurately as we’d like. Just one of the hundreds of design decisions we’ve got to make before we’re ready to start building more hardware.
September 10, 2000
We’re in the part of the project where dozens of important design decisions are made every week. The biggest decision of this past week is that we’re probably going to build new Pancams for the 2003 mission, rather than using the ones that we already built for 2001. The 2001 cameras are great, but they require a fair amount of electrical power to keep them warm at night. We’re going to be building a whole lot of new cameras that don’t require heat anyway — cameras for navigation, and for detecting hazards. And as long as we’re building so many, it doesn’t take much additional effort to replace the Pancams we have now with new ones that’ll work just as well (or even better).
In the process we save electrical power, which will mean the mission will last longer. But it feels just a little sad to put aside those cameras that we worked so hard on for 2001.
September 16, 2000
One of the big issues we’re dealing with right now is filters for all the rovers’ cameras. For Pancam, we’re pretty much set. Pancam has a filter wheel for each camera, which means that each time we take a Pancam picture we can choose from among eight filters. The filter sets in the wheels are mostly different for each camera, and with two Pancams we get a total of fourteen different filters. That’s a lot. We picked a bunch of good filters for Pancam a couple of years ago, and we’re going to pretty much stay with them. None of the other cameras have filter wheels, though, so for each of them we have to pick one filter and stick with it.
|Each "eye" of the Pancam carries a filter wheel that gives Pancam its multispectral imaging capabilities.|
There are actually ten cameras on each rover: Two Pancams, two navigation cameras, four "hazard avoidance" cameras (two in the front and two in the back, to watch out for obstacles), the Microscopic Imager, and a sun camera for navigation. We’ve got about one more week to pick the filters for all of them, so we’ll be doing a lot of work over the next several days to investigate different possible filter choices and, we hope, to pick the best ones.
October 7, 2000
Things are happening so fast, and on so many fronts, that it’s almost impossible to keep track. Here are just two examples of the dozens of things we’ve been thinking about this past week. One is where to put the calibration target for Mini-TES. This target is what we look at with Mini-TES to figure out how well the instrument is working.
After some thought, we’ve decided to put it on the back side of the rover’s main radio antenna… the one we’ll use to talk to Earth. The nice thing about this is that putting target there doesn’t take up space on the rover’s solar array, which is our only source of electrical power. But the bad thing is that it means that we can’t look at the target and talk to Earth at the same time.
A second issue is how to protect the APXS from martian dust. We have a dust cover designed… it’s a set of doors on the front of the instrument that can open and close. But how to open and close the doors?
A separate motor would be complicated, so we want to just use the arm to press the doors against some surface, moving the doors. The new concept, courtesy of Steve Kondos at JPL, is a mechanism like the one in a ball-point pen… one click to open the doors, and another to close them. Clever idea… now all we have to do is design it!