MER press briefing, February 6, 2004
Jennifer Trosper: Spirit status, on Wednesday we spent 3 hours to erase the flash, and 1 hour later in the day to reformat and restart the vehicle. Nerve-racking but the craft did exactly what we needed it to do and is up and running in great health. After that we moved quickly to science. On Thursday, Spirit woke up at 9am, we got data down fist thing and then we commanded craft to use the RAT to brush the rock. We and placed Mossbauer and APXS on the rock overnight. Today we'll place the RAT on the rock and actually grind. Thanks to the people that have been in crisis mode. (listed team members). I want to show an image (image of the instrument cluster on the IDD). It took us a few days to get the testbed testing done and in those two days we downlinked several images that were in flash and for this image we actually posed the arm to get the flag (on the side of the RAT) in the image. Yesterday morning right after we played the Spirit wake-up song, "back in the saddle again" we played a second song, "the star spangled banner", and it reminded me that it's not just about this team of people, it's about every person out there across the country that has contributed, so we'd like to dedicate this image to the American people.
Glen (Reeves?): I actually had a day off yesterday, not in crisis mode and I'm proud of that :D The story of how we got from crisis to relief is the story of a lot of people. First I want to talk about what went wrong and how we fixed it, then I'll turn it over to science team. The first part of the problem was that as we accumulated more files, we consumed more memory and we eventually ran out. Problem 2 was that our reaction to that was rather severe, we corrupted the file system. To get out we needed to pull as much data out of the flash as possible and then reformat. Consuming all the memory is a severe error. The craft did what it was supposed to do and reset itself. The number of files caused us to again, on each initialization, consume the same amount of memory, hitting the problem, and again resetting. It was sol 18 when we first got an idea of what was going on. It took us a couple of days to begin to get data because of communications problems. Over about 3 days we concluded that the system was in this reset loop. We had fortunately built into the system a mode called cripple mode that allowed us to boot without the flash. We thought if we could get into that mode we could stabilize the vehicle. On sol 21 we got into cripple mode and we got communications control back so we could go in and debug. Drawback about debugging a system that far away, if you can imagine the slowest ISP, compared to communications with the rover, I love my ISP :-) During this time, the throughput is fairly low and the most critical part of our activity was to capitalize on every single time we talked to the vehicle. We extracted the absolute most information we could get every time we talked to it. Once we concluded we could keep the vehicle stable in cripple mode, we got to debugging. Our theories proved out and we established that the filesystem onboard was for the most part intact. On the 27th we actually started to use the filesystem again and started downlinking as much data as possible. The file system, though, appeared to be corrupted. This meant that the manner for resetting was going to be to erase all the flash and reformat. We've done that. We're back to the beginning, we've established the state of the system like this many times before. We have a fresh system and we have a procedure in place to work around this problem indefinitely. There are some suggestions to make changes to the flight software to identify the problem more quickly.
Stephen Gorevan: My expectation was to report on the first use of the RAT as a grinding too. Instead, the first time use of the RAT was to brush. In the science discussions over the last few sols it became clear that this capability was available to us. Adirondack looked to be clean but in case there was a cemented coating, we decided to take the brush to remove loose material and to preserve a cemented coating which could tell us something about the history of the rock. This image shows the RAT's stainless steel bristles called the rock brush. It's primary purpose was to remove the grindings from the hole after a RATting. Many of us didn't expect to see a difference. Here is Adirondack before the brushing. Here is the part we brushed. This is a big surprise. All I could think to say, like Mohamad Ali, "This is the greatest interplanetary brushing of all time" ;-) 5 minutes of brushing and we think we have preserved any cemented coating that existed below the dust.
Ken Herkenhoff: Happy to be back up here talking about Spirit science activities and thanks to the engineering team who never stops surprising me. This photo is an MI picture before the target was brushed. It's in full sunlight, lighting from upper right. This is the post brushed image of the same area, same lighting. To my surprise there was a lot of dust there. You'll remember, that we chose this rock because in Pancam images we thought Adirondack was relatively dust free. You can see as we zoom out that some dust remains around the edge and a crack running diagonally from top left to bottom right is still filled with dust. We're seeing mineral crystals on the rock surface and we're very excited to see what continued RAT abrasion will tell us. Looks like a basalt and we're anticipating more data soon.
Matt Wallace: Opportunity is continuing to turn the crank and move forward. We've had a number of very productive days. We completed exercising the arm and the Mossbauer and APXS instruments. Yesterday we completed a 3.5 meter drive with several arcturns to the left, a turn to the right, a turn in place, and a drive forward. Today we sequenced a drive to approach the right-hand side of the outcrop and a target named "Snout". That was a 1.6 meter drive. We came up a little bit short on Snout and so we'll complete that approach tomorrow. Here are some front Hazcam images. (Animation of images moving us to the right side of the outcrop.) This last image shows the target, Snout. We're within half a meter of the target. The second set of images are some of my favorites, pointing in the other direction, rear Hazcam looking back at lander and its y-petal and progressing away from the lander. You can clearly see the tread marks from 6 wheels, the bounce marks, the other side of the outcrop that extends about halfway around the crater. Those are some framable shots, some good ones :) The plan for tomorrow is to move forward 30 or 40 cm. Prior to that we're going to do a "touch" before the "go" -- we'll deploy the IDD and take several of these MI pictures of the soil to continue to catalog the soil in this crater, then we'll re-stow the arm and drive forward to prepare for a full suite of instrument arm activities on Snout, the MI, the APXS and the Mossbauer. Then we'll start an arc along the bottom of the outcrop stopping at choice viewing areas and taking pictures plus dropping the arm down at a few places and taking additional data. Opportunity's in good shape. She's healthy and happy and continuing to do the job she was sent to do.
Q. Software problem similar in a way to what plagued Polar Lander in that you didn't test long enough to reveal problems? Other things lurking?
Glen: I've concluded a couple of things during this process. There was in some of our later tests an inkling of what was out there. During testing, we ran the system right up against the limit and here, the system was asked to perform above what it was capable of. The recovery possible because of what we put in place to be able to analyze and recover. So in that, it's not like Polar Lander.
Q. Can you draw any conclusions about the weather from this dust you're seeing on Adirondack?
Steve: The dust offered no resistance.
Ken: There's actually very little dust, maybe just a few microns. Almost completely removed except for little hollows. Little clumps of dust around the edges. It does look like it's sticking together but not strong enough to keep it from being brushed away rather easily.
Q. Big picture? will you be able to get into the ejecta blanket and get to Bonneville?
Jennifer: We finish RATting today and start driving tomorrow, best case. We're on west southwest side of the lander so we're gonna drive around the lander and head northeast. We do believe we can get there. Strategizing now and initial thinking is we'll start designating the traversebased on imaging, where we design the movement but at the end of each drive we'll turn on auto-navigation for the rover for a couple of meters. We'll extend that auto-navigation each day. Baby steps. Also, we've talked about 4 or 5 places we might stop.
Q. From MGS does it look like there's a rout you might actually get up to the edge and look in?
Jennifer: It does look like there's a path to get to the crater. We'll know better as we get closer. Unrelated but important, we did a demonstration with Mars Express for forward link commanding and return telemetry and it worked very well. International interplanetary communications network in place and functioning well.
Q. For Jennifer or Glen, you're keeping an eye on Spirit, what about Opportunity. For Matt, why did you fall short on getting to Snout?
Glenn: We believe that the issue on Spirit potentially exists on Opportunity so we put in place RAM monitoring and procedures to limit our activities if that amount of space gets low. Matt: We're not entirely sure why we fell short but pretty sure it's soil slippage. The rover is pitched up or back by almost 13° and if you look at some of the testing we've done relative to soil mechanics and capability, you get to 10 ° or so of pitch and you start to get some slip. Based on our ranging and correlating that to wheel tracks in the last couple of hours since we got the data, we're getting 10 to 20% of slip during these traverses. Once we better understand this we'll be able to accommodate that efficiently.
Q. Glenn, you mentioned there might be some kind of software patching to flight software, can you address that?
Glenn: The problem itself is actually that in the configuration of the vehicle we allowed it to consume more memory that it has. We could set a single configuration value to limit that. We're anticipating one to two days to get the information to the vehicle and the actual change would probably take an afternoon, if we did it. If we decide to do it we'll definitely do it for both vehicles but right now we have a good way to avoid the problem and I'm not sure we'll make the change.
Q. This dust seems to have a very sticky property. Stuck to rock and airbags. Electrostatic properties or chemical bonding?
Stephen: Not sure. Ken: Not sure. Certain minerals tend to aggregate better than others without electrostatic being involved. There may be a clay component that allows it to adhere more easily. We can't tell yet.
Q. Given that this rock was dirty when you thought it was clean does this skew things in terms of your ability to do mineral characterization from orbit.
Ken: We'll be taking into account this new data. We're going to continue with remote sensing for dust-free areas but it's looking like they will be difficult to find.
Q. On location of Opportunity, are you close to being found?
Matt: We know we're on Mars at a pretty cool site in a cool crater ;-) A lot of good work in the last 3-5 days, gathering a good amount of information and rather than me give you my interpretation, let's wait on the experts to get up here and give you the scoop. It's exciting and fun and it's coming.
Q. Question from a reader, one of the Opportunity photos, close to the lander, seemed to show some whitish streaks on the soil. Any chance it's frost?
Ken: Temperatures from mini-TES too high for frost, brighter streaks are not white, just brighter and redder, probably a little bit of dust.
Next news briefing will be Monday at 9am.