Martian Chronicles XI: Feeling Real
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.
June 14, 2003
We’re flying. Spirit was launched on Tuesday and so far she’s behaving beautifully.
|Delta launch rocket for MER mission.
It’s always a little nerve-wracking when you put a new spacecraft out into space for the first time. It’s in the environment that it was designed for, of course, so you expect things to go reasonably well. Still, it’s not uncommon for problems to pop up, both big and small, when you first get it out there.
The good news is that Spirit has been a very sweet little spacecraft so far. The few problems that we have had have been very minor. All in all, we’ve had about as good a first week in space as you could ever hope for.
And it’s a good thing too, since we hardly have time to rest on our laurels. It’s almost time for our other rover, Opportunity, to leave the nest. Opportunity will take flight just after midnight next Wednesday, and it should be another spectacular show.
June 21, 2003
This was a good-news/bad-news week… Good news for Spirit and bad news for Opportunity.
The good news for Spirit is that we had a good TCM-1. "TCM" stands for "trajectory correction maneuver", and this was our first one. When we launch, the spacecraft is headed in the general direction of Mars, but it’s not on a path that will take it directly to the planet. There are several reasons for this, one of which is simply that the rocket by itself isn’t accurate enough to do that. The rocket’s main job is to get us going really fast, not necessarily to get us going precisely to Mars.
|Artist conception of dramatic airbag landing Credit: NASA.|
In a trajectory correction maneuver, we use tiny rocket thrusters on the spacecraft to give it a little nudge in just the right direction. We gave it its first nudge on Friday, and that nudge put us much, much closer to the path that’ll get us to Gusev Crater next January. Everything seems to have gone according to plan… "right down the pipe" as the space navigators like to put it.
The bad news was on Opportunity, which is still on the ground in Florida. Each Delta rocket has a little bit of insulation on the outside of it, to keep the rocket temperature just right as it rises through the Earth’s atmosphere. Unfortunately, the insulation on the Opportunity rocket is cracking in a few places. We know why it’s cracking, and we know how to fix it. But you have to do this sort of fix very carefully, and it’s going to take several days to get the job done right. So the launch date has slipped to Saturday night at the earliest. Just one of the things you have to deal with when you’re trying to get a precious piece of hardware like Opportunity safely on its way to Mars.
June 28, 2003
We’re waiting. The launch window for Opportunity opened almost a week ago, but right now we’re still on the ground in Florida. The problem is with our launch vehicle. It has a layer of insulation made out of cork, believe it or not that protects the skin of the rocket from being heated too much as it ascends through the dense lower part of the Earth’s atmosphere. Some of this insulation came unglued from the rocket’s skin, and they’ve got to replace it. This is pretty low-tech stuff, gluing cork to metal… sometimes even rocket science isn’t rocket science. But it’s got to be done right, and we can’t fly until everybody is 100% convinced that it’s safe to do so. They’re working as fast as they can out on the launch pad, and all we can do is be patient.
So we wait.
July 5, 2003
We’re still waiting. It’s been a long week in Florida, and Opportunity is still on the ground. The biggest problem we’ve had is the cork insulation on the outside of our launch vehicle. The glue they were using to keep the cork on wasn’t as sticky as they had hoped it would be. The problem is caused by liquid oxygen. Our rocket uses a lot of super-cold liquid oxygen, as the oxidizer that it combines with fuel to get its thrust. When the liquid oxygen is loaded into the tank inside the rocket, the skin of the rocket gets very cold, and it shrinks a little bit. When this happened, some of the cork was popping off the outside of the rocket because the glue holding it in place wasn’t sticky enough. They’ve switched to a better glue, and now the cork stays put. Problem solved.
|The early fiery entry of Beagle 2 probe into the thin Martian upper atmosphere at 12,000 miles per hour Credit: ESA|
But that wasn’t our only problem. The other one was that there is a crucial battery inside the rocket that died a couple of days ago. It’s been replaced, and once some tests are finished we’ll be ready to go. In fact, as I write this on Monday morning in Florida, we may be just 12 hours or so from launch if all goes well. The weather’s looking good. Cross your fingers…
July 7, 2003
The Mars rover Opportunity took flight this evening, at 11:18 PM Eastern time. We had a little excitement on our first launch attempt, when a problem with the liquid oxygen fill-and-drain valve on the first stage of the Delta II caused a hold with just seven seconds to go in the countdown. But the launch team did a fantastic job, recycling the vehicle for a second launch attempt about 40 minutes later. Our rocket the first Delta II Heavy gave us a perfect ride. Opportunity is in good shape, and on her way to Meridiani Planum.
July 12, 2003
We spent this week preparing for one of the first big events of the mission… the first cruise checkout sequence.
All of our science instruments were turned off at launch, and they’ve been off ever since then. Mars is where they’ll do their job, so there’s not much point in having them turned on all the way to Mars. But launch is a dangerous and violent event, and we want to take enough data during the cruise to Mars to be sure that the instruments survived the launch and are working properly. So this coming week we’re going to send commands to all the instruments on Spirit, turning them on and taking data.
|A view of Gusev Crater.
We’ve had to do a lot of work to prepare for this. We have what we call a "testbed" on the ground, which is a very accurate replica of the rover and all its instruments. Before you send any commands to a spacecraft this complicated, it’s a good idea to try them out on the ground first, and that’s what we’ve been doing, in the testbed, this week. Everything has looked okay, so we expect the commands to work properly once we send them to the spacecraft.
We don’t expect to see much in the data that we get back next week, of course, since the rover’s safely tucked inside the aeroshell. It’s dark in there, so the pictures from all the cameras, for example, will just be black. But even from black images we can tell whether or not the cameras are healthy, and that’s all we need to know. The pretty pictures and exciting spectra can come later. If everything’s in good shape, we’ll all breathe a sigh of relief. And if something’s gone wrong, we can start figuring out what to do about it now, instead of having to wait until we’re on Mars next January.
So fingers are crossed.
July 19, 2003
One down and one to go. We did an in-flight checkout of all the instruments on Spirit last week. This was the first time we had turned the payload on since launch, so it was a big event! Fortunately, things are looking good. Pancam, Mini-TES, Microscopic Imager and APXS are all looking completely normal. There’s one thing about the Mössbauer that looks a little funny, but we’re working on it and we don’t expect it to be a big problem on Mars. So we’ve got one good-looking payload on the way. We’ll do the same thing on Opportunity the week after next.
July 26, 2003
We’re getting ready to practice in a "sandbox." The "sandbox" is a facility at the Jet Propulsion Lab that contains martian-like dirt, rocks, simulated sunlight, and a replica of the rover. Much of our effort this week has been focused on preparations for a test that uses this facility to help us learn to command the rovers on Mars. The test is called PORT-3 Post-Launch Operations Readiness Test (formerly known as Surface Operations Readiness Test). We will operate a bank of computers in one building at JPL to drive the model of the rover in another building.
To prepare for PORT-3, the science team has been ironing out details in teleconferences, downloading software to practice, and building sequences. These sequences will command the rover in the sandbox to approach a rock target, position its arm near the target, and tell science instruments on the end of the arm to make contact with the rock.
|A simulated image of the new Mars rover carrying its science instruments.
It takes weeks to prepare for a test like this. But we’re doing our homework and we’ll be ready.
August 2, 2003
We’ve now completed checking out the science payload on Opportunity, so both rovers are done now. On Opportunity, all of the instruments look good. If each one operates on Mars exactly the way it’s operating in space today, we’ll get beautiful data from each and every one of them.
On Spirit, we’re still dealing with a problem with the Mössbauer spectrometer. We had thought that maybe the reason the Spirit Mössbauer data that we took a couple of weeks ago looked funny was simply that the instrument didn’t behave the same way in zero-g that it does on Earth. We know now that that’s not the case, since we just learned that the instrument on Opportunity is working just the way it did back on Earth. So something else is going on.
If we had to use the Spirit Mössbauer on Mars just like the way it’s behaving now, we’d get science data that’s not perfect but that’s still useable. We think that we may be able to improve the situation by reprogramming the way the instrument operates a bit. So that’s something that we’ll be looking at very hard in the coming weeks and months. We’ve got five months to get this worked out, and we’re going to take our time with it.
So: The bottom line is that out of our ten science instruments on the two rovers, nine are working well and the other one is going to keep us busy for awhile.
August 9, 2003
Wow, what a week! It’s been the biggest week by far since we’ve launched, and one of the biggest weeks since we started the project. As I write this, we’re four days into a five-day "Operations Readiness Test", or ORT. In an ORT, we simulate in as much detail as we possibly can the process of operating a spacecraft. And this is the very first ORT in the history of this project in which we have actually simulated the process of operating one of our rovers, with all its instruments, on Mars.
|Mars makes its closest approach this year in the last 50 millenia
Credit: NASA/JPL Viking
The rover isn’t on Mars, of course, But we do have a complete rover, very much like the real ones, in a giant indoor "sandbox" at JPL. The sandbox is full of rocks, and we’re driving the rover around and operating it exactly as we will on Mars next January.
It hasn’t all been smooth sailing. In fact, we’ve made a bunch of mistakes, some of them pretty significant. But that’s what an ORT is for. We’re using these tests to shake out all the bugs, to find all our weak spots, and to figure out how to fix everything so that once we get to Mars it’ll all work the way it’s supposed to.
Despite all the challenges and problems and mistakes of a "first ORT", I have to say that I’m incredibly proud of the job the team has done. We’ve taken beautiful pictures with Pancam and we’ve taken lots of data with Mini-TES. We’ve used the pictures to pick a rock target to drive to. (We named the rock "Brain", since that’s what it looks like.) We’ve driven the rover to the rock, and right now the rover is close enough that tomorrow we’re going to try to reach out and look at it with the Microscopic Imager, the APXS, and the Mössbauer. I don’t know if we’ll succeed or not driving rovers on Mars is the kind of business where you never know for sure if you’ll succeed. But these are very exciting times for our team.
August 16, 2003
We just completed a very successful ORT (Operations Readiness Test) and our instruments performed beautifully. We were able to maneuver the rover arm into the perfect position to examine something interesting on a "martian" rock in JPL’s giant indoor "sandbox." We’re extremely busy right now assessing our performance
August 23, 2003
Boy, it’s been a crazy couple of weeks. We’re still pulling together all the things we learned from our last operations readiness test, and already it seems like the next one is almost upon us. These things will be coming at us fast and furious between now and landing.
In the most recent one, we operated one of the rovers for five straight simulated martian days, or sols, in the big indoor Mars facility at JPL. It went amazingly well, considering it was the first time we’d ever tried it. Unknown to us, the engineering team down in the test facility had glued pennies to about half a dozen of the many rocks that are scattered about the scene. We first spotted a couple of them in Navcam images, and then we zeroed in on them with Pancam images. Deciding that they’d be interesting targets to go after (they had, after all, been put there to tempt us), we drove the rover over to one of them, reached the arm out, and got data on it with all of the arm-mounted instruments.
|While the exact nature of these tube-like structures is not known, one interpretation is that they may be microscopic fossils of primitive, bacteria-like organisms that may have lived on Mars more than 3.6 billion years ago.
This sounds deceptively simple, but in fact it was astonishing to have a machine as complicated as ours accomplish something that complex on the first try. What we’ve proven, for the first time, is that we can use some of our instruments to pick a small target from a distance, drive over to it, and investigate it in more detail with the other instruments.
Now we just have to practice this stuff over and over and over again until we get extremely good at it.
August 30, 2003
We’re starting to really put the RAT through its paces. We’ve tested the RAT extensively, of course, but so far that’s been mostly by itself on simple test stands, either at JPL or back at Honeybee Robotics in New York, where the RAT was built. We’ve also tested the Instrument Deployment Device (also known as the rover’s arm) quite a bit. But until the last week or so, we had really never had the chance to do a complete test in which we used a RAT on the end of an arm to grind into a real rock.
Well, we finally did it, and it worked… at least so far. For our first test, we mounted the RAT on the end of an arm and used it to grind into some limestone. We don’t really expect to find limestone on Mars, but it’s a nice soft rock that’s an easy one to start with. Things worked great. We got a nice hole about 4 millimeters deep, brushed free of dust so we could see it with all the other instruments. It was a big confidence builder!
But that’s not enough. What the RAT really needs to be able to do is grind into really hard, tough rock like basalt. We’ve done that with a RAT on its own, but we still need to try it with a RAT on an arm. So that’ll be our next test, and if it works it’ll be the proof we need that the RAT and the arm will really work together properly on Mars.
September 13, 2003
We’re into our next Operational Readiness Test now, and this one’s really different. In the last one, we were practicing the process of driving and doing science on the martian surface. In this one, we’re focusing on landing the spacecraft and getting the rover off the lander. As I write this, on the morning of Tuesday the 16th, we’re about to make decisions on whether or not to do some final trajectory correction maneuvers, or TCMs. A TCM is a maneuver you do with a spacecraft’s propulsion system to nudge it a little bit closer to your intended landing site. In this test, we’re simulating the landing of Spirit in Gusev crater, and the "landing" itself is planned for Friday evening. Between now and then is the TCM, and if we decide to do it, it’ll happen late tomorrow night. This is all starting to feel very real…
September 20, 2003
You might think it’d make your life easier if you could have an extra thirty-nine minutes every day. Believe me, it doesn’t. We’re more than a week into our latest operations readiness test now, and this business of living on Mars time really wears you down.
The martian day is longer than the Earth day, by 39 minutes. Our rovers are solar powered, and they don’t know or care if it’s daytime or nighttime on Earth. They only care about the time on Mars.
In this operations readiness test, we’re simulating the process of landing on Mars and getting the rover off the lander. As of today (Monday September 22nd) we’re in our fourth day on the martian surface. The rover’s day starts when it’s about 9:00 AM on Mars… which right now happens to come at about 6:00 PM Pacific time. Tomorrow it’ll be at 6:39 PM, the day after that it’ll be 7:18 PM, and so forth. So a lot of us are doing just what we’ll be doing next January… sleeping during the Earth daytime, and working through the Earth night. And even worse than that, the start times for our shifts are 39 minutes later every night than they were the night before. It’s like having jet lag all the time.