Mars Exploration Rovers Update: Spirit Breaks Driving Record -- Again, and Meets the Stone Council
Posted by A.J.S. Rayl
13-02-2004 11:00 CST
Opportunity Completes Survey of Outcrop
The Mars Exploration Rovers are really starting to 'show their stuff' on the Red Planet. Despite a couple of technological hiccups earlier in the week, the twin robot field geologists are getting down and dirty in the Martian soil.
"We have two very busy rovers on the surface of Mars," reported Art Thompson, a member of the rover flight team, at the news conference Thursday.
Yesterday -- or "yestersol" as the MER teams members like to say, Spirit set yet another new driving record at Gusev Crater, and Opportunity completed her study of the outcrop at Meridiani Planum, returning the data scientists need to create a "base map" of the area.
During the next few sols, Spirit will continue her trek to Bonneville Crater, while Opportunity finishes her study of the small crater in which she landed.
The Latest From Gusev Crater
Just last Tuesday, Spirit set a new record for the longest one-day drive by a rover on Mars -- cruising 23-feet (7 meters) to break the record set by Sojourner in 1997. Yesterday, she broke that record by adding 80 feet (24.4 meters) to her odometer. That brings Spirit's total mileage to 188 feet (57.4 meters). Before roving on, the rover took images of White Rock and the area around it with her microscopic imager (MI) and panorama camera (PanCam).
The drive was a leisurely one, taking two hours and 48 minutes. But Spirit was on her own, testing out her autonomous navigation system, and moving in a way to avoid hazards. Just like she was supposed to, the rover stopped when she recognized an obstacle, the cluster of rocks that was the day's intended destination, Stone Council.
"The report card on Spirit is she's in outstanding health right now," Thompson announced. "Since Sol 33, or for the past seven days, Spirit has been a fully functional science platform. We have absolutely no adverse effects from the [recent] memory problems."
During the last three successful days of driving, Spirit took "a bunch of images" that scientists are using to create what they call "a goodness map," said Thompson. The 'goodness map' tells them and the rover where it is safe to traverse -- green and yellow areas are passable, while orange and red are areas to avoid.
Spirit did experience a 'burp' in operations last Wednesday, her 38th day on Mars, when the cold Martian temperatures caused her high-gain antenna (HGA) to stall. That meant she was unable to return data during the morning high-gain communication window. The high-gain antenna is how the rovers return high volumes of data direct to Earth via receiving dishes in the Deep Space Network (DSN). "We were not able to get the master sequence on board as planned and it took a while to figure out what had happened," said Thompson.
As it turned out, the MER engineers were able to relatively quickly conclude that the rover's high-gain antenna was not pointed toward Earth, and that her orientation after the previous sol's drive -- 45 degrees to the northeast -- apparently had caused her camera mast to cast an early-morning shadow on the HGA's elevation actuator. That shadow caused it to be just cold enough to make the actuator -- the mechanism that makes the HGA move -- stall during its calibration. Hence, the antenna failed to point to Earth.
As the morning wore on, the shadow disappeared and the actuator was back to working normally. "We were successful at commanding a low gain session," confirmed Thompson, "and later on a high gain session, so we were/are basically back on track."
To alleviate the problem in the future, the team has decided to perform these calibrations late in the afternoon, as opposed to early morning. "The antenna basically gets to re-zero its pointing and then when it wakes up in the morning it has a fresh pointing direction," explained Thompson. "We have a group that's supposed to look forward to what the orientation of the vehicle is and anticipate these types of events," he added. "We missed this one and it basically costs us a morning."
The afternoon link with the Mars Odyssey orbiter, however, sent down previously acquired images of the rocks Adirondack and White Boat and a miniature thermal emission spectrometer (Mini-TES) observation of the depression drilled by the rock abrasion tool (RAT) on Adirondack.
Spirit is currently in a routine of performing daily "touch and go" maneuvers -- inspecting the soil immediately surrounding her with the instruments on her arm, then stowing her arm and driving onward, toward Bonneville Crater.
Discovering which way the wind blows
The MER mission is in full swing now, and everything is going on simultaneously. While the rovers are roving, collecting and returning their research and the data is rushing in from the DSN, the orbiters, and direct HGA communications, the science team is planning day-by-day where to go tomorrow, and the engineers are figuring out best paths for the rovers to take, and other team members are analyzing the data as it's coming in.
The atmospheric scientists, for example, have already uncovered new findings about the winds on Mars from a mini-TES observation taken by Spirit that was coordinated and correlated with an observation from the thermal emission spectrometer (TES) on board Mars Global Surveyor (MGS) done at the same time.
Although the mini-TES that both rovers carry was designed primarily to record the thermal spectra of various rocks and soils to determine the types and amounts of minerals that they contain, it can also obtain and measure surface and atmospheric temperatures.
Just as the rover has twice done with the European Space Agency's orbiter, Mars Express, Spirit looked up with her mini-TES as MGS looked down with TES and together they measured a section of the atmosphere, top to bottom. The TES on MGS "tells us the temperature looking down from orbit toward the surface, but it doesn't do a very good job in the bottom 5 kilometers of the atmosphere," explained atmospheric scientist Don Banfield, a rover science team collaborator from Cornell University. "On the other hand, Mini-TES sitting on the bottom looking up can do a great job from the bottom up to about 5 kilometers, so they're very complementary and they're adding data to each other in a very good way," he added.
"In the past, with Viking and Pathfinder data, we had temperatures about a meter and a half off the surface, but with the rovers we can use the mini-TES to look at the thermal emission of the atmosphere and then get a temperature profile of the [lower] atmosphere, and this is a much richer data set than we've had before," Banfield noted.
What the atmospheric scientists have found in this "richer data set" is that the temperature changes rapidly in the lower atmosphere in the morning. In mid-morning, the air temperature at about the height of an eight-story building swings up and down by as much as 7 degrees within a minute. "This is a significant change of temperature. If you turned your thermostat on Earth up by 7 degrees you would notice the difference, and if you lived on Mars you would notice the difference there too," Banfield pointed out.
"Down near the surface you see these cold blobs of air and warm blobs of air intermittently passing above the rover," Banfield elaborated. "Up higher in the atmosphere, it is slowly getting warmer, but down near the surface you've got this interesting variability. What we think is going on here is that ground is warming up from the sunlight, then the ground transmits its heat to the atmosphere at the bottom, the atmosphere gets warm -- and hot air rises on Mars just as it does on Earth. That rising air goes up to something like 100 meters at 10 in the morning and then it gives its heat up to the atmosphere slowly warming up the rest of the atmosphere. Then, there's a cold blob that will come after that. Basically, you're watching the over-turning, the 'boiling' of the atmosphere as it's warming up in the morning," he explained.
"If you look at something around 24 minutes after 10 o'clock there, you can see there's an upward trend that's sort of evidence that these are warm blobs that are moving upwards with time -- so it's convection, moving heat away from the surface that the Sun has deposited down on it," he elaborated.
These temperature spikes are "not really a big surprise," Banfield said. "We see this on the Earth. Out in desert you have warm blobs of air move past you -- they're called thermals and we see them on Earth all the time. What's interesting about these is that we can see them on Mars. And, when we look at them and see the subtleties of them -- how warm they are, how fast they happen, how quickly they rise, we'll understand a lot better about the dynamics of the winds on Mars and how they couple down to the surface and how the winds mix down and move sand grains and lift dust."
The team plans to repeat the experiment, as early as tomorrow, in a different patch of atmosphere.
Scientists are interested in better understanding the atmosphere of Mars for two main reasons: the winds of Mars can threaten safe landings, and because the atmosphere -- and the winds in particular -- are a major cause of geologic change on the planet right now. By observing the details of these changes, scientists can improve their models for understanding Mars' winds. In other words, the more they learn, the better they will be able to get spacecraft down safely, and the better they will be able to understand what's happening geologically on Mars now.
"You may remember there was some concern when we tried to get the rovers down through the Martian atmosphere about whether we could safely deposit them to the surface and [a major] concern was about the wind shears that we would see in the atmosphere," Banfield reminded. "We didn't have very good data on the atmosphere prior to this, but the MER rovers are giving us good profiles of the temperature structure of the atmosphere and that's going to help us maybe in the future put rovers safer on the ground on Mars," he said.
Better understanding of Mars' winds is also important for interpreting some features the scientists are seeing on the surface of Mars. "We've been talking a lot about water on Mars in the past, but wind is currently the important agent of change on Mars," Banfield pointed out. "We have dunes that we see and dust devils that we have seen and dust storms that can be global, so wind is currently a very important thing on Mars. Just to bring it down to the most simple terms, understanding how the winds mixed down to the surface -- or how the rubber meets the road -- is what we're trying to do with the MER rovers," he added.
"This is very novel data and we think it's going to allow us to much better constrain the models that were used to understand the winds that were a danger at the Gusev and Meridiani sites -- and the fact that we're seeing these temperature profiles will really allow us to get these models better for future efforts at Mars," Banfield summarized.
Although the MER team has been on the lookout for dust devils, both at Gusev and Meridiani, they have yet to spot any. "We're keeping vigilant -- every time a hazard camera image comes down, that's a good place to look for them and we haven't seen anything yet," Banfield informed. "We did have a bit of false alarm this morning that turned out to be a dust smudge on one of the cameras."
Appearing before the Stone Council
The Spirit team woke up its rover today, her 40th day on Mars, to Louis Armstrong's "What a Wonderful World," which proved to be a good omen. After utilizing mini-TES to record the spectra on the soil surrounding her at Waypoint Charlie, and completing some pre-drive imaging with the panoramic camera, the rover embarked on the 2.95-foot (90-centimeter) drive toward a collection of rocks called Stone Council.
The drive lasted less than five minutes, so Spirit had plenty of time to take some pictures of several rocks with the PanCam, and complete a mosaic of the area in front and to the left of itself.
Tomorrow, Spirit will be repositioned in front of one of the members of Stone Council, a flaky rock called Mimi, in preparation for placing her instrument deployment device on that rock during the weekend.
The current plan calls for Spirit to stay at Stone Council for at least a day, conducting studies with her robotic arm and collecting in situ measurements. Then, the robot geologist will once again rove off toward Bonneville Crater, which is still 340 meters or more than two football-field lengths away.
In coming weeks, the MER scientists and engineers -- who are continually working on "maximizing" the rover's ability to drive distances in any given sol, according to Thompson -- plan for Spirit to drive right up to the rim of Bonneville, and peer inside. They hope that will give them good views of the formation and layers that could reveal the geologic history and the potential role of water at the Gusev site.
The Latest From Meridiani Planum
At Meridiani Planum, Opportunity has been on a three-day tour of the outcrop, taking pictures and measurements to build what geologists call a "base map." The tour will also help the science team decide what specific spots they want to target for more thorough investigation with their science instruments.
Yesterday evening -- or 'yestersol' as the team often says -- Opportunity climbed to Waypoint Charlie, where she is slated to complete her initial survey of the outcrop Opportunity Ledge today. The team 'divided' the rock outcrop into three sectors, delineating them according to military tradition -- Alpha, Bravo, Charlie.
On Opportunity's agenda for today is a PanCam image looking toward the top of the crater and a "touch and go" around the outpost area Charlie -- where she will deploy and use her MI and Mössbauer spectrometer, then stow her arm and drive to the next location.
Scientists and engineers, in the meantime, are reviewing the data collected along Opportunity Ledge this week to target a few 'return' trips to the most interesting science locations along the outcrop for more thorough examination.
Although the flight team was having some troubles with Opportunity slipping in the soil earlier this week, those problems have resolved, and chalked up to a matter of learning and adjusting to the soil and how the rover moves through the soil, said Thompson. "We did experience some significant slippage when we first attempted to drive up the rim of the crater," he recalled. "We performed a dry sand slippage study and we've since corrected the way we drive due to the results of that study. Now when we attempt to drive up the slope, we intentionally overdrive and when we drive down the slope and we under drive," he explained. "We've done three 4 to 60 meter drives in the last three sols and we're off less than a quarter of a meter, so I think we pretty much understand the slippage problem."
Revealing more than meets the eye
The science team is already getting glimpses of what's on the surface and what's happening to the surface of Meridiani Planum through the pictures taken by the microscopic imager (MI). For one thing, recent MI pictures indicate that windblown sand is eroding Opportunity Ledge.
Mark Lemmon, science team member from Texas A&M University, College Station, said that taking a series of images with the MI at slightly different distances from the target allows the team to create a three-dimensional view of the terrain and the outcrop. "There's much more than meets the eye in these images," he said, as he displayed more MI pictures at the news briefing.
"The MI has a depth of field of about 4 millimeters -- if it's in the wrong place by just 4 mm, an in focus image turns to a out of focus, blurry image, " Lemmon explained. Therefore, they try to take a series of five images for every target of interest. "The series of five is taken for a primary purpose -- making sure that one is in focus," he said. The reason some parts of an image are in focus in one image from the series, while other parts are in focus in others images in the series is because "we're not looking at a flat surface, but a surface with a lot of topography on it," he explained.
What the scientists can do and have done -- is unite the in-focus elements of each picture in the series and create anaglyphs that present a three-dimensional view of the outcrop and the terrain of the crater floor. "By looking at where we have good focus and where we don't, we can get information out of the image and we can turn that info into a different way of looking at Mars," Lemmon said.
The MI pictures of the floor of the crater in which Opportunity now sits have been particularly revealing. "The floor of the crater is just an exciting place, very different from what we've seen on Mars before," noted Lemmon, as he displayed a picture that showed in exquisite detail fine-scale sand grains, irregular shaped particles that appear to be coming down from the outcrop, and "the most spectacular thing we're seeing," the rounded spherules. "They've been called blueberries, because they are relatively blue compared to the background coming out of the outcrop," he informed. These spherules, Lemmon added, "are actually more like a BB in size, less than 5 mm or so typically."
The team can also "go beyond the anaglyphs" and "push the process a little bit more" to create "depth maps" to study the Martian terrain "up close and personal," Lemmon continued. "Basically, these are the highest resolution topographic maps that we've taken of another planet."
Now, they're turning those high resolution topographical maps into little motion pictures that reveal the terrain in great detail. "We're gathering as much information about the things we're looking at as we possibly can," Lemmon said.
A slight miscalculation = a slight delay
Opportunity 'hiccupped' Wednesday, her 18th day on Mars, that set her arrival to Waypoint Charlie back by a day. The wrist on her arm would not point as far vertically as the engineering rover's wrist did on Earth during a model test the night before. Because of this, Opportunity was unable to stow her arm, and as a result did not move on to her next target. The rover also automatically stopped using her mast due to the fact that she believed a requested pointing position was in an area beyond its limits.
"One of our ground modeling tools did not accurately reflect how we should have placed the instrument on the ground and we tried to swing the instrument down underneath us and we failed out in that drive," explained Thompson. "It was a ground-tool modeling problem that we didn't catch. We should have moved it over the top. Basically [the problem] was a wrist positioning actuation that we didn't model correctly and that caused us not to complete the master sequences plan."
The MER engineers solved both problems the same day and Opportunity pulled up to Waypoint Charlie safe and sound yesterday.
It can be tricky trying to maneuver a robotic arm from 93 million miles away. "It's not just this place on Mars, it's using the instrument, the whole system and understanding the positioning of the IDD, depending on where the rock or soil is, how far out in front and exactly where we want to place it on the target -- vertically or horizontally or some angle," Thompson explained. And even though a group of engineers and scientists have spent years practicing how to do this and even though "they're pretty darn good at it," he said, "we missed this one on Sol 18."
The immediate plan for Opportunity at Meridiani Planum is to continue with a drive over to an area just beyond Waypoint Charlie called Sand Patch that "appears to have a higher hematite concentration," said Thompson.
Hematite is an iron oxide -- which on Earth usually forms in processes involving water -- and it is the mineral that lured the team to Meridiani Planum. Orbital surveys indicate the area is rich with hematite -- at least the signature of hematite is coming through loud and clear in orbital data, but the scientists have yet to figure out where those rich deposits are. Of course, Opportunity is still in the confines of the tiny crater into which the rover rolled, and the strongest readings are coming from outside the crater, as MER lead scientist Steve Squyres has previously noted on several occasions.
Knowing more about the hematite distribution on Mars will help the scientists characterize the past environment and unravel the mystery of whether that environment ever boasted a body of water and provided favorable conditions for life.
This weekend, Opportunity will prepare for 'trenching,' and perhaps even complete the operation at Sand Patch, said Thompson. By spinning one of her front wheels while keeping the others stationary, the rover will dig -- or "trench" -- a shallow hole in the ground so that scientists can see what's below the surface.
"On Sol 21 [Saturday] we'll perform the pre-trench operations with the IDD [instrument deployment device], and then on Sol 22 [Sunday] we'll actually trench, where we try to dig a small trench and back up. On Sol 23 [Monday], we'll stick the IDD instrument arm into the trench. Then on Sol 24 [Tuesday] we hope to drive to an interesting place called El Capitan," offered Thompson.
"We're going back to El Capitan, because it has color differences and variation in it that we can see," Wendy Calvin, one of the science team members, said. "There's some interesting morphology and structure in terms of the layers in the rock, so we're going to go back and pursue those in high-resolution detail. Sand Patch is a new name on me, [but] this sandbar spot was chosen because we think we're going to be in a higher hematite region and so we're hoping to trench through then whatever's on the surface causing the hematite [signature]. Phil Christensen showed early on that we can see the hematite signature on the surface, but not in the airbag smash marks, so if we can trench through this upper layer than has the hematite signature and get to a lower layer that doesn't have it, and then do IDD work on it with the alpha particle x-ray spectrometer and the Mössbauer spectrometer, then we'll know more about what is causing that hematite signature in the infrared."
The long-term plan for Opportunity is still being debated. "We saw some preliminary high-resolution images from Malin Space Science Systems that Mike Malin brought in . . . PROTOs to get us at 50 centimeter resolution," Calvin informed. "He's starting to image spots outside the crater to feed into our long-term planning, so we had a big meeting about which general direction we should head once we get out. But those images are still coming down. There are still some spots outside the crater we'd like to get more high-resolution images on before we really make a decision."
Student Programs Tap Into Mars Rover Adventures
Public interest in the MER mission appears to remain fairly high, and that may be due in part to the fact that many teachers across the country are using this mission to teach science and to get students interested in science and math.
With the rovers now on Mars, students can and are learning science in a fun way. Following a steady downward trend in science and math scores across the nation, the rovers appear to be helping to get students to take an interest in those two basic subjects. As part of its educational outreach goals, NASA has endorsed and helped sponsor various programs involving its various Mars missions in hopes of inspiring the next generation of space explorers.
On the dais at the news conference to talk about the variety of educational program that are being offered in conjunction with the various missions to Mars were Sheri Klug of Arizona State University and JPL, who coordinates Mars education programs for kindergarten through high school; Wendy Calvin, rover science team member from University of Nevada, Reno; and the student she is mentoring, 16-year-old student Shannon Theissen.
"This is a very special time -- for the first time we have landed on Mars during school time," noted Klug. "And we are tying in classrooms from around the country and across the U.S., in lots of different ways, from classrooms down to a personal level."
In working to coordinate real mission science with science being taught in schools, "we want the students to learn about the next place we're going, the future places like Mars, which is so intriguing and interesting that it brings them into the science and makes them want to learn more," Klug continued.
"It's been an amazing experience for the students, and we're grooming them with the real stuff," Klug pointed out. "This is not baby stuff. It's the real science -- and the students have access to the tools the scientists are using in real time. We're teaching them the authentic science and letting them do the science -- and as a result they can see themselves as scientists in the future because they understand the process of science through these types of participation in these programs."
With a host of missions to the Red Planet coming up in the near future, Klug noted "Mars is going to be in the curriculum for the long term."
A few of these Mars educational programs allow a select number of students first-hand opportunities to work with the scientists at JPL. The Athena Student Intern Program, which Calvin and Theissen are a part, gives students (chosen by their teachers) the chance to be mentored for a week by one of the MER scientists. Red Rover, The Planetary Society's student astronaut program offers two students (who win an essay contest) the opportunity to take part in rover activities each week.
"Where I was in high school 20-25 years ago, and where I ended up in a career is not someplace I would have ever thought I would have been and I saw this as a good opportunity to show kids that you could end up some place you never thought you might have at 15 or 16," said Calvin of her decision to become a mentor.
There are also a number of programs that draw in entire classrooms across the country, utilizing the same data NASA scientists do in their curriculums:
- The Mars Exploration Student Data Team -- which involves 54 teams and more than 700 students in 25 states - analyzes orbital data from Odyssey to assist the rover team on weather and dust storm prediction.
- The Mars Student Imaging Project has given some 3800 students to date the opportunity to use a camera onboard Odyssey to take their own images of Mars and learn how to map craters and volcanoes.
- Imagine Mars -- a national arts, sciences and technology initiative - has K-8 students working together to design a Mars community.
A program called Rover Quest that debuts on the web this week, will offer lesson plans for teachers framed around real data coming down to the scientists at JPL.
"When I came here I was not expecting to actually be able to work with the scientists -- I thought I'd be put aside and kind of come as they want me to," said Theissen, a junior at Silver Stage High School, one of 13 schools participating in the Athena Student Intern program that pairs selected students with researchers on the rover missions. "But I actually got the experience to work with the scientist - Wendy has been an awesome mentor -- and we've actually gotten to work with her on the computers. She showed us how to use the programs and it's really awesome."
Her experience, Theissen said, made her realize that "you don't have to be a scientists or an engineer" to be working for JPL or NASA. "There are many different jobs and everybody can be part of this -- and if you want to be part of it follow your dreams."One of the most important aspects of these educational programs is the "reaching out," Calvin noted. "As we are reaching out in Nevada to small communities and small towns, people in the middle nowhere, not doing anything can get to participate in a once-in-a-lifetime opportunity to participate with two rovers working on Mars. This is the real stuff."
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