Thursday, October 10, 2002. Open in New Window
My name is Michael Sims and I am from NASA Ames research center. I work in the center for Mars exploration and Computational Sciences Division. I have also been working on a number of missions over time. Both planning human missions and actively working on rover missions. What I am going to today is talk a little bit about Mars science and how it effects operations and how we do operations. Going to the first slide. Basically there is a relationship between the science that we are trying to do and the physical constraints that exist. Both constraints based on pure physics and contraints on how we know how to build things, engineering constraints. Although, if you look at a text book or you talk to someone who wants to be precise in how they say it, they will say you begin with the science constraints, you begin with the science objectives, and then that tells you what to do, and then you do the engineering. In fact, it doesn't work that way. In fact what we actually do in almost all circumstances is there's a dance, there's a dance between the science objectives that we're trying to do, the science goals that we have in mind, and the engineering and physics constraint that we know how to do and we know how to, actually, put it together into a system that we can send to a planetary surface and accomplish what it is we're up to. And you'll see that, you'll see that partly during the discussion today. So moving to the second slide, the topics that I'm going to talk about today are how missions occur. Really, what occurs for a mission to be set up, who proposes that, what makes one be chosen. I'm going to look at three missions. I'm going to look at Pathfinder briefly. I'm going to look at one current mission. Pathfinder was a mission that went to Mars in 1997, landed in 1997. I'm talk about one current mission called MER, Mars Exploration Rover which was designed to go to Mars in 2003 so we're going to launch next year and it consists of two rovers going to this planetary surface and then I'm going to talk about a possible future mission just as a way of giving you an indication of how missions are designed and specifically what it is we do when we're trying to build up a mission and trying to understand what we're going to do in a rover mission. And finally, I'm going to say something about the players and constraints on a rover and how that impacts the planetary operations we do, how that impacts the way we operate that rover. Now, I'm not actually going to talk about those topics in the order in which I listed them. The first thing I'm going to actually do is talk about Pathfinder and then I'm going to talk about MER and then I'm going to say something about constraints and how the science constraints impact a mission and then I'm going to go on finally to a future mission, a description of a possible future mission and finally I'll possibly come back and say something about constraints at the end.
So on the next slide which in my listing is slide 4, in 1997 we sent a spacecraft to Mars, and it landed in 1997, and it was calls Mars Pathfinder, it was part of the overall mission, and there was a particular small rover associated with that mission called the Sojourner Rover, and what you see in the image is a image of the Sojourner Rover sitting up, it's placed up against a rock, and you may or may not be able to see it, the resolution of the images you have. In this case and in some future ones you may not be able to see
it actually is in a stowed position as if it's up next to your chest, and then as it's deployed t moves straightforward, and there is some manipulation on the end so it contours to the shape of the object that it lies against. And on that arm there is one scientific device called an alpha x-ray proton spectrometer, and basically it allows us to understand the elemental composition of what it is that it's against, so we will be able to determine if that rock has nitrogen, or argon, whatever, and so the purpose of the APXS device, alpha x-ray proton spectrometer, is really to find the elemental things, and what we'll want to do is put that against the soils and put that against rocks. So that's one of the scientific [STRAO-UPLGTS] on that Pathfinder mission, and it was one of the scientific instruments that was on the rover itself.
Now, the landing -- the Pathfinder mission actually had two parts to it. There is what's normally called the lander, and it's been since named the Carl Sagan Memorial Lander, and the lander consisted, it actually had air bags that were sitting around the outside of it, and it came down to the surface, and it bounced around. After bouncing a number of times, more than our counters could count, more than 16 times, what it did is it eventually settled down, and at that point the air bags retracted, the pedals we want out and that was the lander. And a particular -- a camera system, called IMP, Imager for Mars Pathfinder, IMP, the IMP camera deployed, and so that means it stood up on a mast so it was standing up high, and there was a pair of stereo cameras, a right eye and a left eye, and those cameras were able to be rotated around the scene so you could look at various objects, and you could see it in stereo, so you could see it with the equivalent of one-eyed vision or the other eye, and by combining those, you could have the effect of getting a human sperption of stereo, or we were able to build three-dimensional models which described how far it was to objects and what the topography of the ground look like.
It's never -- it's usually not said quite this way, but almost always when you do a planetary mission. The primary instrument is the imaging because humans are such visual animals, when we see -- when we see what's on a surface we understand it much better than than we do when we don't so imaging is almost always a crucial part of the scientific mission. So in the case of the Mars Pathfinder, the IMP camera on the lander was the primary imager, and when you see images of the rover on the surface those images were taken by the camera on the lander. So very seldom do you see the lander itself except in computer-generated animation since it didn't look at itself.
The rover itself also had a pair of stereo cameras on it that were used for navigational purposes. They were very wide angle, and they were not particularly valuable scientifically, but useful in navigation.
There were other instruments associated with the mission. Let me just describe one more. Another instrument on the Pathfinder, and it was on the lander itself, was a wind sock, and what that was was a -- very much like the kind of wind sock that you'll see at an airport, which is just something that looks very much like a sock, and when the wind blows, it bellows out in a given direction and you can tell which way the wind is blowing, and so very late in the Pathfinder mission, a participating scientist was added to the mission who added a wind sock, so by using the camera to take pictures of that wind sock, we were able to tell what direction the wind was blowing, get some indication of the velocity of that wind.
Another element of Pathfinder mission that's true -- that was true previously, is true in any land mission on a planetary surface, particularly Mars since that's the one we're talking about, is that the period of the Mars day is not identical to the period of the Earth Day. And in order to give you a contrast with that, I will also bring up the lunar day. So on Mars the day -- on earth we all know the day is 24 hours long, right? And our seconds as a given unit described international convention as to a standard what a second is, and then we asked 60 seconds together and we get a minute and we add 60 minutes and we get an hour and we add 24 hours and we get a day. That's how we do the timekeeping on earth.
On Mars, as you might imagine, the day is not identical, so we do it in a different way. And if you just sort of keep those units more or less the same on earth, what you'll find is a single equivalent of a day, which we call on a planetary surfaceness a Sol, S-o-l, the equivalent of a day, the Sol is about 24 hours and about 39 minutes. So what that means is the day is a little longer on Mars.
If we go to the moon, the equivalent of that day is about, you know, 29 days long. So it's -- it's 30 times as long as it is on earth, whereas on Mars, it's just a tiny bit longer. So, on the moon, you would never try to sort of stretch out hours to make it fit 24 hours in that 30 days, or you would never try to stretch out seconds to make seconds fit inside of -- in the same way, stretch it out by a factor of 30 on the moon. It just would be unintuitive. Seconds and hours meaning totally different things. And it would be contrary --
Okay, great, thanks.
It would be contrary to the standards for -- that we use for physics, for those measurements. So we don't do that.
On Mars there is a tendency for people sometimes to do that simply because it's close enough they can get away with it, and it makes it easier to build clocks. But nonetheless, the day, the Sol, is longer. So what that means, as we go -- one day is 39 minutes longer, and most people can manage that without trouble. But your day as you progress along becomes 39 minutes longer each day. And over a period of time what you find is that you get an extension of -- it's as if your work shift is shifting 40 minutes each day. And it disturbs your sleep patterns, it gives you a whole new way of, you know, interacting with that, because you don't get up at eight o'clock every day, you get up at 8:41 day and then another 40 minutes later the next day, in order to make that work. And it's not necessarily an easy adjustment, but it's an adjustment we pretty much have to make on the Mars surface as a consequence of the additional time necessary.
Mars Pathfinder was an unusual mission in a number of ways, but one of the ways in which it was unusual was it was a primary example of the class of missions that we call -- that were designed to be cheaper, faster, and better, and it really did exemplify those characteristics, and in a way that not many missions before and few since have exemplified those attempts to do it.
So actually, if we try to draw patterns from how the science operations was done, or the operations were done in Mars Pathfinder, it's actually not -- it is an unusual mission in that sense. It was a very small team, a very small science operating team, and a very close-knit intimate interaction with the rover. Let me come -- I will come back and see more later about the something about the science operations, but in general, it was as I described, you have these periods of 90 minutes, or 40 minutes additional at the end of each extension on each day, so you would have meetings each day, and plan what you were going to do the next day.
Which brings me to -- let me just go on to the next mission -- sorry -- to the next mission, the MER 2003 mission. Again, we have the same sort of characteristics of the day being about half an hour longer every day, and in the case of MER we're going to have two rovers. And they're going to land a month or so apart in time, and they're going to be alive for about three months. So a good portion of the time you're going to have a large contingency of activities going on in parallel between the two rovers. So one of the things we try to do is to figure out how to operate that efficiently and effectively.
The 2003 rover is a much larger rover than the Pathfinder rover. It's a more capable rover in many, many ways, and it carries a fairly robust instrument suite that I'll say a few words about in a minute, but again, primarily the dominant instrument in this rover, as I will argue in all rovers, is going to be the imaging system, and it's a superb imaging system on the MER 2003 rover. It's an imaging system which is designed to have the visual fidelity, to have the visual acuity of the fume fulveal system. In the human, the very center of your vision system, you can see very accurately. And as you get a few degrees outside of that very center of your imaging, you don't see nearly as well. Your image is blurred, although your mind compensates for that, and it appears -- you don't notice that blurriness, effectively. But you don't -- your resolution is not as acute.
The MER rover imaging system was -- it's called PANCAM for panoramic camera. The PANCAM system was designed to be able to give you imaging at the resolution you can see if your fulveal portion of your eye, and the imaging which returns should be as good as you can see as you're there. I'm sure it won't quite be the point, it won't quite be that good, but it will be very, very good, so I think we're all going to be astonished by the quality of the imaging that we'll see.
And I'll say something about the other images in a moment.
On this slide there is a pointer to the -- to the Athena web site at Cornell. Athena is the name of the science team that proposed the MER 2003 rover, and in Cornell, the principal investigators, Steve Squires is at Cornell, so that's where the web site is.
On the next view graph, next slide you will -- you may be able to see -- if you're looking at this on the web you may not see it in high resolution, but that's okay, it won't matter for this part. But you should at least roughly see the outlines of the rover, and the rover consists of a set of solar panels sitting on the top which give it power in order for its operation. There is a mast -- in other words, a pole standing up that has on top of it a set of cameras and access for a particular spectral instrument, so there's a set of PANCAM cameras that I described earlier. The PANCAM cameras are again, those high resolution science cameras.
There's also a fair of nav, or navigation cameras that are sitting up there, that allow -- that are lower resolution and allow one to navigate in the terrain without -- and perceive objects that are around you. In the images -- if you can see this, there will be a robot I can arm associated with this, and on this robot I can arm there are several instruments. Et cetera it's again an alpha x-ray proton device. There's a Moss-Bauer instrument, and -- there's also an instrument on the vehicle called the minitest, and one of the things the minitest does is it takes -- it gathers spectral information in the thermal emission. In other words, when objects are at a certain temperature, they radiate -- they emit radiation, and their characteristics, spectral lines in that that are characteristic of the minerals that you're looking at, the Tess instrument, TES, it's a small one that fits on the rover, what the TES instrument is what those mineralogiesr as well. That is associated with the mast as well.
Again the rover in the MER case is a six-wheeled rover, and you can -- you may be able to see images of it there or you can find images on the web just by typing MER rover on Cal Google and you'll find lots of images.
The next view graph, I presume most of you will not be able to read during this talk, and that's fine, because I'm going to talk you through it. And if I spend the next half hour on this view graph and if I community to you something about what's going on in this view graph, I will have flished the main part of what I would like to do today, so I plan on lingering on it a while, and I realize you can't read it, but let me tell you what's there.
The view graph is a schedule chart, and it's a schedule for one day, one Sol, actually, in the process of managing the rover, one of the rovers. Okay, so this is only a chart for one of the rovers on the MER mission. And there are probably few things most of us would find more boring than a schedule chart. Nonetheless, I will try to sort of indicate what is valuable about it and what is interesting.
Across the bottom, there's a scale. Actually the scale is on the top, but as you move across from left to right, there are numbers on the top that begins with 12. Twelve should translate into noon to you, to 13, 13 hour. So it's one o'clock in standard U.S. time. And then that goes on to 23, and then it loops back around at 23 around zero, and zero being, you know, middle of the night.
Yes. And I actually don't -- oh, this is slide number 7. So if you're missing it, this is slide number 7. Thanks.
So, again, middle of the night is zero, in the middle, and then on the far right you get 11, and that corresponds to 11 o'clock.
So time just sort of marches across from left to right in this chart, and it repeats every day. The idea is that it repeats every day. There's a whole bunch of stuff on there that's designed to tell the operations team and the science team where they're supposed to be when, what it is you're supposed to be doing, and what it is you're supposed to have accomplished by a given time.
In the upper left of it there's something called DTE and that stands for "direct to earth." What that means is, if I go back a slide, if you look at the MER rover you may or may not be able to see, but there's sort of in the middle of it, just above the solar panels, there's a roundish sort of disc shape, cylinder shape, and there's a a pointer that points to it that says "high gain antenna." The high gain antenna, what it does is it communicates with earth, so it actually has to point, and it figures out where it is, and it points at earth, and it communicates by transmitting on a radio transmitter, it communicates back to earth, and that's what DTE means, it means direct communication with Earth. Okay, what that says is we have a bunch of data that's sitting on the rover, we're taking it, and we'll say something more later about where that data came from and what kind of data it is, but we've taken the data in this mission, and what we want to do now is transmit it back to Earth so those people can look at it, play with it, so you can put it on CNN. DTE is that process, okay, and in the time line, that's when it occurs.
If the look -- if you could see -- and again, it's not essential since I'll talk you through it -- but if you could see, directly below that what you will see is a category in black called telemetry processing. What telemetry processing means is that, okay, the data comes back to Earth, but it comes back in a form that's appropriate for communicating from across interplanetary surfaces so it's in packets, it's compressed in such a way that if we lost some of those packets we could still reconstruct most of what the image was, or most of what the data was. Once it arrives back at Earth, we have to sort of undo that, we have to process that data, and we also have to process data -- there's auxiliary data besides the science associated with these missions which tells us the temperature on the rover, it tells us how far the rover thinks it went, it tells us the status, is the camera -- does the camera think it's working okay? Or does the camera think there's a problem with it? And so all of that information is lumped into a category we call telemetry, and that telemetry is what's transmitted back and that's what's received in that -- early in the direct to Earth communication that's received, and that data is processed in that black category called telemetry processing.
So if we just kind of look at this chart as it was designed -- again, chart number 7 -- we'll see that from about 13 hours to, oh, 15 and a half hours, so, you know, normal times in the U.S., that would be like one o'clock till 3:30 -- somebody can actually 3:30, we're processing that data.
Just above that you'll see a category called "sleep." It actually turns out that when the main part of this chart takes place, it's middle of the night or late afternoon and early morning and night on Mars. So at 1500 hours, it's 15 on the category, the third column, there's a little blue triangle that says "sleep." At that point the rover goes to sleep. And it stays asleep until it wakes up at ten o'clock the next morning.
So the rover is asleep during most of this process. In other words, it's in a very low energy state and which is not doing a lot of activities. It may do some scientific investigations bullet for the most part it's not very active. The category below that on this time line, below the telemetry processing is image processing so the images come back and what do we do with them? Well, often the images need to be processed in order to make them usable or even make them make sense.
Let me just give you one example of that. In the case of the MER rover, as was the case in Pathfinder and is often the case in planetary missions, we don't do color by -- color images don't a priori come back as part of the data. In order to do color, we have the capability for putting a different filter in front of the lens. So we have a camera that has a number of pixels in it, and if we want a different spectral response, if we want to understand what that image looks like in a different part of the spectra, what we do is we rotate and filter in front of the camera, and that allows us to perceive it in that.
Now, MER has about a dozen filters of various kinds to look at various kinds of mineralogy, and it looks like sort of your typical VCR camera or Polaroid, out of that red, blue, and green we can actually build an amage that looks pretty-like, pretty human perceptively realistic like. So one of the things we want to do is take those images, to make them back -- is to put them back together, if we want a color image. So if we've taken those red, blue, and green filters, then we need to also -- we need to parse that, we need to take those three separate images -- red, blue, and green images -- put them back into a single image that can be displayed and looks like a color image.
So that's one of the things we do, but there's a whole suite of image processing that takes place, but it takes some period of time. And in this case we've allocated, you know, a couple hours, two and a half hours of initial processing of that so we can really understand what the images are, what the data is. And again, imaging is our primary window into the world. There are a lot of other things that we do, a lot of other scientific information that comes in, but we really get grounded by the image data so that's one of the crucial things to really knowing where we are, what's gone on, and what there is interesting around us.
In addition to that, let's see, what else could I tell you about? Just at the end of that cycle, at the end of that, you know, 15:30 hours, so at the end of that 3:30, we have done with our initial image processing, we've done with our initial telemetry assessment. We have what's called a science downlink assessment. Now, a science downlink assessment means that the science team now can be given the data, and we have to assess whether it worked or didn't work. You know, did this taking of these images, did we take what we wanted? I mean very often we'll point to a particular rock and we'll say, "Go to that rock and take that image, take an image of that, and then give me spectral information on that same rock." Or we might say, "Eye like to you place the arm on this piece of soil or on this rock, and then give me back the spectral -- the alpha x-ray proton spectrometer data on that," or "Give me back the minitest data on that, or the Moss-Bauer data on that." In order for me to know I was really on the rock that imented to go to I need an image as well to make sure. So at the end of this process the science team actually sits down and starts ongoing as the data comes in, but there is an assessment, did we really do what we're trying to do, is there anything unusual, is there anything exciting, what's going on? And that is a process that continues throughout that day and continues throughout many days as you review the data by your local team and distributed teams.
But in particular, in the process of the time line of the activity we've allocated in this case, you know, three and a half hours for that process to be assessed well enough that the science team can come back to the overall -- can regather and have a discussion and really say in detail what we believe occurred.
Did occur what we planned to happen? Is there anything interesting about it? Were there any problems associated with it? And we do that at what's called a science assessment meeting, which is also, you know, it's a half an hour or 45-minute meeting in the middle of that process where we actually get back together and say, oh, here's what we think, because -- the thing I -- when we're doing the science assessment, that tends to be a distributed process in which you'll have a set of scientists going out and looking at the mineralogy, so we wanted to put the -- we wanted to put the Moss-Bauer spectrometer on this piece of rock and we'll get a Moss-Bauer specter back, did it work, and is it an interesting Moss-Bauer spectra? The class of people or the set of people that know about Moss-Bauer spectrometer and are interested in that particular instrument sit around the table together or they send I would have but they as a team are responsible for figuring out whether that worked or not. At the same time, there's somebody looking at microscopic images. We took a microscopic image of that same place that we did the Moss-Bauer spectra. Did it work? Do we get a good image, can we say anything from the grain size, what's going on? So that little team is running around trying to understand the results of that microscopic imaging. So you have this whole suite of science teams trying to understand all these pieces so that we can -- and this is all -- let me back up a moment. What we're trying to do is figure out what to do tomorrow. So this whole daily schedule can be thought of as, did it work today, and what are we going to do tomorrow?
So -- and here's the point I wanted to make. We are operating on this roughly 24-hour, 24-hour, 40-minute, cycle. And we're really basically in the schedule of let's up-link a set of commands, and let's look at them when they come back and figure out what to do for tomorrow. So we're basically on a one-day schedule. And there's something funny about that.
When I first started looking at how you design rover missions, you know, 15 years ago and how you actually do operations of rovers in these kind of designs, the predominant belief was that we were going to operate these missions in a way that we would send up a command every 30 minutes, every 40 minutes, and that we'd get something back in there, and the next 40 minutes we'd send up another one. So we'd send up a dozen commands during the day. That was the belief of how we were going to do our operation. And that comes from the fact that if you look at how long it takes to send a signal from Earth to Mars, it takes anywhere from a few minutes, four minutes, something like that to 20 minutes to go one direction. And to to get a signal there and to get it back, you send a signal which says "drive forward three feet," and you send that signal "drive forward three feet" and it drives forward three feet and you get it back "okay, I did that, here's what I see," in order for that to take place, it's going to take that light time, the travel of the radio signal, which travels the speed of light, from Earth to Mars, you know, four minutes to 20 minutes, one way, you're going to do your operation and send it back. So, you know, you think about, in terms of a turnaround, of a command, to data return, on the order of half an hour to an hour. That was the way that people thought about how to plan these missions.
We don't do it that way. We haven't done it that way on any of the missions, and I think we don't do it that way for a good reason. And the reason has really to do with the fact that it takes a while to figure out what you accomplished. It's a coupling of two things actually. It's a coupling of the fact that it takes a while to figure out what you accomplished, and the second part that's interesting about it is that we also have the level of commanding that we can basically command for a day's worth of activity.
You know, we can command a set of movements, we can tell the rover to travel, you know, 20 meters. And that may be a very reasonable thing for it to accomplish in a day, so it's not as if there necessarily is a great decrease in the scientific return from having only one up-link and one -- effectively. Sometimes we do have more, but the general rule is, you know, that we're aiming toward one up-link, one downlink a day. And it doesn't appear that that drastically decreases the scientific return, both because the awe ton mee that we've added to the vehicles and the capability of the vehicles, and part of that autonomy actually resides on Earth where you're really clever in figuring out how to send it up, and that autonomy is part of what occurred, and the other element that makes sense is it just really takes quite a while to figure out what really did happen. It's not a priori obvious. So we have a one-day cycle, and it's all about doing -- it's all about understanding what occurred, having a consensus amongst a team as to what you do next and then, given that consensus from the team, designing a set of commands, checking those commands and making sure they're accurate and don't kill the rover, and then up-linking or what we call radiating those commands to the planet.
So that's why you have roughly a day cycle.
Let's see, is there anything else I want to tell you about that? Yeah, in the middle -- in the middle of the chart there's a blue line that goes across called SOWD chair. SOWG, and a few lines above that, there's a little green box that says "science operations working group meeting." And that's actually the one I wanted to point to. So the science operation working group meeting is a two-hour in this schedule, it's a two-hour meeting of where the whole science team gets together and people say what they think occurred the last time, and people pro podes what they would like to do in the next mission, and there's a discussion of that. And the primary operation of that in the '03 mission is by consensus, and so the team will have a consensus as to what is the best thing to do next, and that will go forward as a set of recommended uplinks and then we will try to see if we can actually accomplish that within the resources we have available during that day.
. The only other thing I wanted to say about that is let me back up one slide. And again, on the rover image on the left, there was one -- I pointed a couple of minutes ago to high gain antenna. The other thing I wanted to point to was something called a UHF antenna. What that antenna does is communicates with an orbital satellites. There are a number of satellites in the orbit of Mars and what they're doing is they're taking scientific data about Mars. They're taking all the wonderful images that we've seen for years from the Mars Global Surveyor, you know, these great, beautiful images, of the Mars surface. And incredible scientific value from those. That satellite, that spacecraft, is capable of communicating -- listening to the rover on the surface of Mars, taking that signal, and if you go to it on tape, effectively, putting it in its memory, and then later communicatedding that back to Earth at a high bandwidth. So actually most of the data that comes back actually will come back through these orbital satellites. And the way we talk to those orbital satellites is using this low-gain -- is using this UHF antenna. So we are going to effectively talk to these orbital items as they come by and ship a lot of data back through them, which will come back. And this data arrives -- and I wasn't very clear about it in the schedule, but, you know, these can arrive at various times during the time day. It's not a fixed time. It depends on the whole geometry of Earth and Mars, where the satellites are, and competition, resource competition for those facilities.
That's probably more than you ever wanted to know about a schedule for a planetary mission. But I thought it was valuable to give you a sense of how we do operations and sort of what the constraints are of doing those operations.
Let me say a word about what missions are chosen and why we do those missions. There's a whole class of NASA missions that take place, planetary missions, and I really want to only -- I'd like to restrict myself to only one class of those missions, and that class is -- that class of missions is rovers -- or surface missions on Mars. So let me just look at that class of missions. That class of missions is part of a program inside of NASA called the Mars Exploration Program, and the Mars exploration program is run out of Jet Propulsion Laboratory, JPL, in Pasadena, and the Mars Exploration Program is a very successful, long-term whose initial goal was to send a and a lander every two years. Turns out about every 26 months the geometry of the orbits of Earth and Mars align in such a way that it's very convenient to -- by that I mean very low energy to get an object from Earth to Mars. So we think of these 26-month windows of opportunity to send a mission to Mars, and we have done that very regularly. We haven't kept every possible opportunity but we've certainly done that very, very regular and will there's been tremendous support for that both inside of NASA and inside the federal government.
So that's the Mars Exploration Program. It's an ongoing program. Pathfinder was part of that. The Mars Global Surveyor and the Odyssy mission is also a part of that, and the MER 2003 mission is part of that. As part of that there's also a new proposal cycle coming up where proposals have already been submitted which see called Mars Scout Missions, and the idea is that a set of independent investigators -- anybody, effectively -- can propose a mission to go to Mars, and there's a pot of money that NASA set aside to fly those missions and teams get together to propose to go ahead and do that and fly those missions. And the particular set of those that were currently under consideration are called the Mars Scout Missions, and those will launch in 2007. Now, 2007 may seem like a few years away -- five, even. But 2007 is very close in terms of doing the whole suite of things you have to do to propose to get a mission to fly. You have all of the details of the engineering and logistics and all the components of that fit together in order to make the mission occur. So it's a difficult challenge, but [TPHO-PBLGS] that's what the next set of challenges are. In addition to that there are proposals -- let me back up a little bit before I go to human missions. So the Mars Exploration Program currently exists, and the way that the decisions are made about the Mars Exploration Program is that fundamentally the program office, in other words, the JPL program office, will do studies, it will ask a lot of people for advice, and then it will propose particular missions to occur, so the Mars 2007 is one of those, and they propose that mission to occur, and then they go to NASA headquarters in Washington, D.C., and they present it, and they say this is what we'd like to do. And NASA headquarters either supports that or does not support that or they say we'd like you to do this other thing.
But most of the time they will say, "Okay, this makes sense," because ahead of time people had a discussion about what the constraints are, you know, how much money we have, when we expect you to do this. So most of the time you would expect that process to get agreement at NASA headquarters. In order for us to fly these missions, a Mars mission now costs several hundred thousand dollars -- million dollars, sorry -- several hundred million dollars. That's very cheap relatively to what missions used to cost. Steve Spielberg in a given year might be able to afford one of those missions from his income. I don't know what Bill Gates or Warren Buffet make in a given year but I'm sure this is less than 10% one half they make in a year. So individuals can -- few, but some individuals could afford this.
But nonetheless, it's also much, much cheaper than missions used to be.
So these are expensive missions, but not incredibly expensive, and -- but missions in that category do not occur without congress agreeing and the budget office, which is called the office of budget and management, OMB, or management and budget, buying in and saying, "This makes sense," so that we need agreement for those for any of these missions to occur.
And then as part of that these missions are decided based on input from the science community and the science community says, "Yeah, this is a good thing to do," or "it's not." Here's our first priority for the next mission. Here's our second priority. And they're very explicit about that. And often it's not a unified perspective. Different scientists have different parochial interests and different reasons they would like missions to occur, and different evaluations of the priorities of the science. So it's a difficult process to sort of ferret that into a clean set of objectives as to why we hold a mission.
But that's part of the process. That's how it occurred. And given that, we get teams together and teams to design the mission, at a very high level, and then you get engineering teams which look at the specific details, really at a design level to begin with, to decide can we really build these components, can we build the rover the size of the MER rover? Can we communicate from Mars during that period of time? You know, is there some problem with it, do we have enough power? Do we have enough power to do the kind of things you want to do during a given day?
And that process iterates throughout the entire development process, so all the way until launch almost those teams are continually looking at their plans, looking at the details, and re-deciding what is appropriate and what is best.
Once the vehicle is launched, there is operations teams take over and then you have teams that operate the vehicle on the way to a planet, and then once you've landed on a planet like Mars with a rover you have an operations team which decides how you're going to do that operation. And that operations is determined by a coupling between a science team and a set of engineers who are responsible for the welfare and the operations of that vehicle.
So as a team, together, they collaborate to make the mission occur.
And finally there's an outreach team, which is really the objective of that is that it's -- you know, is to educate, to communicate what we do.
Those of us that work at NASA, many of us, feel incredibly privileged to, you know, have a chance to play this game. And it's really -- you know, we're keepers of a dream, in a sense, and it's part of our -- part of our job to share that dream and to let the world know, and especially children, in my view, young people, to let them know what it is that we're doing, and the excitement that there is about it.
That's part of our game.
So that's more or less how we choose missions.
Now, what I'm going to do is I'm actually not going to say anything more about the next slide, since that is pretty consistent.
What I'm going to do is I'm going to very briefly, in about ten minutes, maybe less, talk about a specific mission, and this is a particular proposal that I was part of the team that proposed and it was part of one of those Scout proposal missions. So it's not -- it hasn't been accepted. It's one of about 30 proposals submitted, and if -- you know, if you just rolled the dice, the chances are not very good that it is going to go to Mars in 2007. Nonetheless, it will -- I think it will give you a good example of the interplay that occurs between the science and the engineering and the operations.
So it's called Long Day's Drive because the intention is to go to the polar region of Mars. Now, the angle of spin, the spin angle of Mars is roughly equivalent to the tilt of the spin angle of Earth. And on Earth you know if you're in the northern polar region or the southern polar region you have 24 hours of daylight during a certain time of the year.
Same thing occurs on Mars for exactly the same reason. So it's a consequence of that if we land a rover in this northern polar region above the arctic circle, effectively, of Mars, then we get 24 hours of sunlight, and that translates into a lot of power over a day, and it has a number of advantages. It means that the thermal -- we don't get -- the thermal cycles, we don't get as cold and as hot. The variation in the thermal cycle is not as great as it is equatorial, so that makes the thermal design of the rover easier. It means that we can do continuous operation, so even though we're doing operations for, you know, two or three months, that's somewhat misleading because, if you remember, if we -- the operations schedule that I showed you a few moments ago for the rover, for MER, we were only operating, you know, six hours a day or something. Here we're talking about 24 hours a day of operation. So that, you know, is a sizable multiple of the amount of activity we can accomplish over a given period. Again, we have to solve the same issues we had to solve in the MER case, which was we have to be able to get the information to the people that need it in a forum that's usable quickly enough so there's a big information technology issue that drives us to certain kinds of automated pipelines of information through that process. But we're going to try.
So that's the goal.
And what you see on slide 11 is just a drawing of that, of that rover on a particular area of Mars where we're intended to investigate called the polar layer deposits. The intention was to go to the northern polar region during the summer, to use a robot to do the exploration. And let me skip ahead to slide number 13. So slide number 13, what you see is a -- which you may see -- is a long image, and this is a MOC image, it says image from the Mars observer camera. And this is a region called a polar layer terrain. Mars orbital camera, MOC, "mock," is the high resolution camera that is on the Mars Global Surveyor, and it's operated by Maelin -- Mike Mailen's aerospace camera company. So, nonetheless, that image, you can't see it in detail right now, but what you see -- but there are actually a number of stripes across it, stratigraphy. There are some kinds of patterns. I'm very interested in the very white band across the middle. These are called polar layer deposits. Now, you can now or later, if you download the PDF you should be able to see this in detail on the next slide, 14, but you'll see a number of stripes across this white region. What these are, we believe, are the remnants from a process which has taken place on Mars over the last, you know, maybe ten million years, relatively recent in geological history, but we're talking fairly long periods of time, you know, maybe ten million years. And what you're looking at is a sequence of layers, what we believe are a sequence of layers, and it's as if you see the stratigraphy on the side of the road, only these are sliced very thin across the top. This is a pretty flat region, okay, it's a pretty benign place. We believe rovers can go across it pretty easily. It's a pretty flat region, the white part is a pretty flat region, the whitish part in the middle. And what we believe we're looking at are in the annual cycle, you get the polar cap, and you get freezing of ices, both water ice and CO2 ice being deposited on this northern region, and you occasionally have dust storms which deposit grains of dust throughout this. And what we believe as we're looking at the annual or multiple annual patterns of that deposition at this spot, and what we are proposing in this mission to do is actually go to those places and look at that stratigraphy and get a clue into what's happened overall in Mars long-term. These polar layer deposits exist on the Mars surface, and if I can look at my slide for a second, if we look at this slide number 15, what we'll see is the blue dots on that represent places of images that we've seen have polar layer deposits. So what we'd like to do is go to one of those blue dots, and you see they're quite diverse, quite spread out in the northern polar region. I'm not going to go through this in detail, but I just want to say that part of justification for doing such a mission is you really need to argue why you want to try to do this, what's the science you're trying to do, and that really sort of is part of the starting point. And one of the ways to get the science, one of the ways to have agreement among the community on the science is to have some of the official -- some official committee, effectively, that blesses certain kinds of science, they say this is an important thing to do and this is less important. And that committee for the Mars science is MEPAG, Mars Exploration Program advisory group, and MEPAG is a scientific group that decides here's the good science to do next. So in choosing a mission we do things like take MEPAG reports and we do a determination as to what class of science we want to do. What we do here is listed a number of goals, determine whether life ever arose on Mars, say something about the climate, the geology, and then say something about preparation for human exploration.
Great. Yep. Thanks. And say something about human exploration. So what we have is -- what I've listed on this chart is really just for the Long Day's Drive, if we look at the MEPAG recommendations for scientific investigations what I've done is just listed some of those and how they're relevant. And then eve taken each of those in the next few slides so the next one is slide number 17 is the MEPAG goal number 1, life, and determine whether life ever arose on Mars, and then what are we going to do that's relevant to that. We're not actually -- we don't expect to actually, you know, grab a hold of an amoeba and shake it around and say here's an amoeba, and we don't expect to pick up a dinosaur bone, but we do expect to do things that are very relevant to whether life ever did exist, so we're going to look for organic molecules, and that's our primary search there, is are there organics there, and what might be going on on those, and are they biotic organics, or not? Did they arise from biological sources?
We're going to look at the climate because, remember, the stratigraphy is talking about climate. I'm going to skip a whole bunch. There are issues about geology, issues about preparation for human missions, which I won't mention as well, and then there's a specific slide, 21, where I go into detail in a font you probably can't read as to the particular MEPAG goals and particular activities on a mission. So really the point I'm trying to get to is that we ask a set of scientific questions -- I'm at slide 22 -- we ask a set of scientific questions associated with interacting with doing these missions, so -- and then we relate that to what are the overall scientific objectives, and that's what I've done so far, and there's another part to that puzzle I'm going to tell you in just a minute, but that's what I've done so far, and so slide 22 is really, well, what are the questions we're going to ask scientifically in this mission? So Long Day's Drive, a proposal to go to Mars, go to the northern polar region with a rover, going to travel a fairly long-distance, 100 kilometers on the Mars surface. What is the nature and the record of those polar deposits? What's the nature and distribution of the ground ice? Is there ground ice there, like there might be in a permafrost or something. What's the nature of these polar terrains in general? Are there organics there? So those are the kind of questions we're asking and we're looking for, and, so I can be clear, most of the acceptance or rejection of missions is going to be based on a belief of the quality -- the importance of those questions and how well we're answering them, you know, do we have the right tools for answering these important questions, and are we doing it with tools that we believe you can actually do a good job.
So that's really how the primary first filter of a mission of this category is decided, and so those are the kind of questions we have and those are the kind of questions we decide on.
And then we propose -- so given that sort of scientific questions, what we want to do is we actually want to measure things, right, because we -- send a rover, and we want to be able to say if we can make anything -- say anything specifically about those questions.
So we're going to measure a bunch of things, and let me just give you one of those.
Slide 23 is a list of some of those. One is we want to measure the ice-to-dust ratio. In other words, how much ice versus how much dust is in the polar layer deposits. And does that -- does that vary over time? What is the mineralogy of that dust over time? What elements are coming in? Was there a volcanic event that influenced the composition of that dust? Really what is it that is taking place? And we want to measure organic content, for example, at a sensitivity of one part per million.
So those are the kind of things -- okay, so we've taken a set of scientific goals that the community agrees on. We get a set of scientific questions that we're trying to answer. We've now proposed a set of measurements which measure quantities relevant to those measurements, and then we're going to try to do a couple things. One is we're going to map the science to the instrument. So I would like to be able to tell you, "Okay, I'm carrying this instrument because this is the science I'm trying to accomplish." And the other thing we want to do is -- okay, I don't have it there. Maybe it occurs later. The one thing we want to do is measure that, and we would really like to verify that the level of detail at which we can do the scientific measurements is sufficient to answer the scientific questions we asked. And that may seem obvious, but it's not always done. I mean you have to be really careful about that, because it's easy to sort of be boasting in your arguments as to what you can do scientifically, so it's important to have that traceability of those measurements all the way from an instrument going down and we built this instrument with this calibration and this capability, all the way back to the fundamental scientific goals, and we try to paint that as a logical set of steps that are related to each other.
So, finally, on the -- what slide is this? I can't read the number -- slide 25, for a mission like this, I've just sort of -- you see a cartoon picture of some of the details of coming into orbit and what it looks like, and in this kind of mission, the Long Day's Drive was based on the 2003 mission in terms of what we do, so you see a bouncing of the air bags as the rover gets to the surface.
Oh, this is the one that I thought was earlier. And in chart number 27 is really that trace -- sorry -- there was a -- that was not true. We talked about traceability earlier.
Chart 27 is something different. Chart 27 says, once we've landed on the planetary surface, what are we going to do? And 27 has -- I'm sure you can't read it, if you're doing this online, but what it does is on the left-hand column, or the rows across, it divides it into four classes of things. The first one is, we land, and we want to do contingency science. We want to do that just in case we die quickly, and we want to get -- gather up some science right around the lander. So that's what the first stage is. The second stage is, lets go to this polar layer deposits, because we're not assuming we landed on them, we're assuming we have to travel to them. Second level stage is, let's travel to the polar layer deposits, let's go from where we are to the polar layer deposits, and what do we do during that process? Well, what we do is, this table tells you. This table says here's the science we do, you do it this frequently, and that's what we do and then the next thing is, okay, we've got the polar layer deposit, what are we going to do when we get there? And then there's a whole set of measurements that we do, and that's really what occurs in the rest of the chart.
So that's the end of the charts, and maybe it's a good time to open up for questions. Actually, before I do that, let me actually make sure I said a couple things. Sorry. The first thing, I had a list of things I wanted to make sure I said, so in particular people could properly answer the multiple-choice questions, and I haven't answered all those. One is, Pathfinder was the second rover to actually land on Mars. The first rover was landed by the Russians, and it did not live very long. Ten seconds, 20 seconds. In any case, the Russians landed a rover about the size of a toaster, which had sort of ski-like elements on each side that rotated up and down. It didn't operate for any period of time.
There were also two additional rovers that went to the moon. There was a Lunicod 1 and a Lunicod 2 sent by the Russians, and they traveled about 30 kilometers together, they lasted several solar days so they were quite substantial.
Second point I wanted to make is that when we're landing on Mars, we're landing with two rovers. We're not going to put -- we don't want them to be right next to each other, and the reason is it's hard to pull apart the communication that they're doing. It's difficult to understand which one is talking at what point and communicate directly so we're going to actually separate them by about 30 degrees so that it will also shift the human Earth cycles so that some people will be working a few hours later than other people. But regardless, we're all going to be on this crazy cycle where your day is a little longer.
And that was it. That was actually all the questions I wanted -- So now questions.
NASA Moderator: Okay, great. We have a lot of good questions in here. Let's start out with back to when you were talking about the day cycle on Mars, Daniel asked, "Relating to the length of a Martian day, when the combing through potential astronauts that would go to Mars, could you study their day cycle, looking for someone whose biological clock is longer than normal?" And anecdotally Dr. Cummings suggests I could definitely volunteer to sleep 40 minutes later every day.
Michael Sims: Yeah, that sounds nice, doesn't it? I always keep pushing that alarm off. I don't know whether there's ever been any actual work on people planning that, but I suspect it's not a very big issue, it's not a very hard problem for the following reason. Historically there's been work in caves on Earth where you actually take people where they have absolutely no clues as to the day-night cycle. And it turns out they don't stay on 24-hour cycles. People have different personal periods, and people adjust fairly comfortably, apparently, to the slightly longer day. What I think --
And, in fact, there's a large number of people that fall into slightly longer days.
What I think is really difficult about it is that -- and, by the way, all of this speaking is outside my particular personal expertise, so this is -- take that as a lay comment. What I believe creates the difficulty has to do with the fact that our day cycles get reset by the sun, so exposure to sunlight is one of the triggers to setting your internal biological clock, and as a consequence of that, when you're sort of in this world where, you know, you're operating like it's night, I mean you go outside and it looks like it's night all the time, and yet you're inside operating, it's difficult to keep those compatible. That's kind of a lousy answer, but -- I'm not too worried, personally, and I'd certainly volunteer in a moment as well.
NASA Moderator: Okay. All right, Nick is asking again, "The rotation of Earth and Mars plays an important role in communication windows, but how much does the orbit of the planets play a role? How long is that communication window?"
Michael Sims: Great. So -- that's a wonderful question. So let me talk about the rotation first. When Earth -- it becomes pretty obvious to you the first time you're in a planetary landing on Mars that Mars is in the daytime when we're at night, during close encounters. So if you think of Earth and then Mars the next planet out, you can think of the sun shining behind you, and the sun is shining on Mars, and you're in night. So what that means is you're up at night during these early missions a lot. As the planets rotate further around in their orbit, as they get further around their orbit that's not necessarily true, and certainly that effect lessens as they get further apart.
In terms of communication, the amount of data that we can transmit at a given power -- in other words, we transmit -- we have a radio transmitter, and we have a certain power that transmits at, and given that power, and given some constraints as to how narrowly we're focusing that power, but for a given power we get a decrease in communication as you would expect as we get further and further apart. There's a 1-over-R-squared law of radiation decrease over distance.
So as -- so it turns out that we can communicate with Mars almost the entire orbits of both, and particularly through the satellites, except for a very short period when Earth and Mars on the other side of the sun. So we're on opposite sides of the sun. There's a period where it's kind of hard to communicate for a couple of weeks, and it's really, really tough to talk for a few days, okay? And except for that, we can communicate during most of the time but the amount of data we get back is very depended on how close or how far apart we are. So in particular, in 2003, we're much better shape for the data we get back than we are in 2007. In 2007 the data that we're going to receive is going to be much lower, just because of that effect.
Other questions?
NASA Moderator: Okay, Brad wants to know, would you be able to have a longer mission in the polar regions of Mars because of the 24-hour sunlight?
Michael Sims: Yes. So it's maybe useful to spend a moment and say what restricts the period of a mission. Rovers -- a lander mission can die for a number of reasons. In the case of Pathfinder, the rover itself had nonchargeable batteries. And so the batteries died, I don't know, a couple of weeks into the mission, we lost the batteries. What that meant was, the rover could not operate at nighttime, but it could operate when it had sunlight. It knew how to operate with sunlight, only, with no batteries.
The lander was not able to operate without batteries. The lander was not designed to be able to operate without batteries. So when the batteries died on the lander, that's when we lost the mission, because the lander was the communication back to Earth.
So in that case, the limitation on the lifetime of that mission was really based on the survival of the batteries on the lander, and that was -- effectively, that was a design issue. That was how it was designed.
In the case of the 2003 mission, the restriction is going to be the ability to have enough power to move around and then later to have enough power to communicate. So it takes quite a bit of power on the rover to communicate. And it takes quite a bit of power to move around. And then at some point we're going to have insufficient power to do -- to both keep our instruments warm and to at the same time communicate back to Earth. And at which point the mission will probably die. In the case of the polar region, the design -- it's really a design issue, partially how you manage this. So our design of our polar mission was by design, it was to die, effectively, the first time it became dark. So we designed the mission to die the first time it became dark. And all that really means is that we didn't build it sufficiently robust that we knew it could survive a night, or long darkness.
We could have made the mission longer by doing two things. One way to make the mission longer would be to land earlierier in the year because we actually land in the Long Day's Drive mission, the plan is to land midsummer. If we land late spring, we'd have another few months of survivability, so that would make the mission longer.
The other way to make any of these missions longer is to have a power source which is not so dependent on the particular cycle of the planet. And so radioactive power sources, nuclear power sources as, for example, were on the Viking missions, would have the capability of having these missions last long, you know, many years.
That's what the Russians used on the Lunicods that allowed them to live on very, very cold nights and very, very hot days on the moon. But all of the U.S.-proposed missions to date have been solar-based, and as a consequence of that they have shorter lifetimes.
Next question?
NASA Moderator: Okay, I think these are related, too, but maybe have a little bit of a different slant. Frankie wants to know, will the MER be able to run in more time the Sojourner Pathfinder did? And Daniel asks in connection with that, "Why do missions only last a few months, and what goes bad on the robots that limits its life span?"
Michael Sims: The MER missions, each of the rovers is designed to live about three months. That's a design which is intended to be pretty much a commitment to live three months. It could be -- there's a little flexibility in that process, but you're really building it to live three months.
Now, that means under normal circumstances, it might live quite a bit longer, okay? So we may get more power, for example, than we -- we might have been too conservative in how much power we consumed, which might have it to last longer.
But there are a few things which could kill a rover. One of which it could sort of benignly manage getting cold in the night.
It's interesting that the Sojourner Rover was designed not to need its batteries, and when Sojourner Rover did not receive a signal from Earth, so after the lander died, it had a routine which said, "Well, assume, assume the best possible thing, and the best possible thing is that your receiver is bad, but everything else is working." So what would you do if your receiver was bad and everything else was working? Well, you might run around, take awe few measurements, take some images, and then ship them back -- keep sending them back. So the Sojourner Rover had a strategy which was, "Let's start effectively a circle around the lander and send back images whenever I can." Now, it wasn't very good at localizing where it was, so that circle around lander could have wandered into spiraled, long distances away. And so I mean it's within the realm of conceivable that the Sojourner Rover is still running around in circles, or spirals, or helixes or something and, you know, sending back images to nobody listening.
So one of the things that kills it and one of the things that would probably kill the Sojourner one is thermal cycles.
In other words, when it goes from very cold to very hot and back again, it is very -- it's difficult on the -- especially the electronics, okay? A whole bunch of things could fail, but especially electronics. And the reason is that when you -- you have electronics, you normally have a metal attached to a silicon or a plastic. And the difference is that metal expands -- this particular metal might expand at a different rate as it's heated up from the plastic, or contract at a different rate, so if you have a connection which attaches a electronic component on a silicon to a piece of metal and one expands and the other doesn't, they have ath a tendency to sort of break. And so if you have large thermal cycling on any set of components, you have a high probability of getting breakage of those components, and that's the most likely failure mode for these components.
NASA Moderator: Okay. I do have one that came in that looks an awful lot like a follow-up on that. Dr. Cummings wants to know if the rover collects data while we're out of contact, is there any way to retrieve the data later?
Michael Sims: Yes. All of these vehicles have what's called nonvolatile memory, memory that stays permanent. And how much you have of that varies from mission to mission, but in modern-day missions to the surface, you have a lot of it. We take a lot of data. To take a full panorama of that, fold the old resolution in, you know, three colors or several spectras is a huge amount of data, and it takes a long time to ship that back to Earth. But nonetheless, we still have pretty substantial storage, effectively hard disk data storage on these vehicles. So as long as the vehicles are still alive and the electronic components are still working, we can store data when they're out of communication. And, in fact, you do that every day in the day-to-day cycle, and one of the other things you do is you often take consingsy data early in a mission, and it's occasionally true that that contingency data will stay there for months on the vehicle just in case, you know, you need it. Other questions?
NASA Moderator: Okay, the inevitable question: How much did MER cost to build, and a follow-up from Eric -- I'm sorry. The first question was from Christian, the second from Eric. "Why do the missions cost less than they used to? Aren't they more technical and more complex?"
Michael Sims: MER is a fairly expensive mission. MER. I don't know the real numbers but I'll give you ballpark numbers. Ballpark is three-quarters of a billion dollars, 700 million, 800 million, something like that. So that's a pretty expensive mission of this class. There are two rovers, and there are two launch vehicles, and there are also very substantial science teams. I don't know if I convinced you that there was a lot to do in the science, but there are no -- there's 70 of us on the science team or so. Fifty, 50 to 70, depending on who you count.
So there are a lot of people working on it. So that's roughly the class of what MER cost. Pathfinder was, I don't know, 200, 300 million, I don't know. I'm sure you can find it on the web site, but in that range. Most -- there's a class of missions like the Scout mission that are designed to be in the 200ish in the 300, a little more, million-dollar class.
Missions cost less -- I think missions cost less for a few reasons, one of which is they cost less because people require them to cost less. In other words, someone walked in the door, and initially it was a NASA administrator, and he said this will cost less money or you're not going to do it. And so people said, "That's not possible," to begin with. And then eventually they said, "Well, okay, we'll try this." And it's always a little occasion there's always a little difficulty in that game as to what is the right amount of money to spend, but not too late. I mean these are games that if you spend too little you're likely to have it blow up or make some big mistake. So it's often difficult to find out what is the right amount of money that one should spend in order to really get the best return on the dollar that you want, plus the science return. So it's kind of difficult to price those. There's also -- there's also been a difference in the design philosophy of missions. So -- and let me do that, let me describe that with respect to a particular mission called Mars Observer. Mars Observer was a multi-billion-dollar mission, and it was a wonderful mission, great mission, and as it came in to do its last set of orbital adjustments or near last set near Mars, it blew up. And we think we know why it blew up, you know, it had to do with some procedures not followed in terms of transferring fluids late in the game or something like that but nonetheless it blew up.
As a consequence of Mars Observer, one of the -- but Mars Observer had a huge suite of scientific instruments on it. One of the things we did post-Mars Observer is we took that suite of instruments and we divided it into parts. So if you look at the Mars Global Surveyor, it has maybe, I don't know, half or a third of the instruments that were on Mars Observer. And then if you look at Odyssey, it's got some other set of those than were on Mars Observer, and then you may need another mission to actually complete what was on Mars Observer. So one of the things we've done is actually try this partition, instead of doing this huge mission, have smaller missions that are focused on a particular set of objectives.
NASA Moderator: Okay. Jenny is asking, "Will the two MER each have specific functions, and will they be deployed to the same area of Mars?"
Michael Sims: So, to answer the first -- the second part first. There are going to be -- well, let me answer it in a general case first. Where do we decide to go? I mean where is it we go? It's conceivable that we could have the NASA administrator, or the president say, "Fly there. That's a good place." Or, we could have someone propose a mission which flies to a very specific place, and people can do that, as part of Mars Scout program, you could propose to fly to this place, and that would be exactly where you decided to fly.
In the case of MER, Steve Squires and the Mars exploration team decided on a different -- Steve Squires is the principal investigator. He's the -- he's good night in charge of the mission, effectively. Squires and the Mars exploration team decided a different strategy, and the strategy was, "Let's try to get -- Let's look at places on the planet that are interesting to land. We have a set of instruments, and where could we use those instruments best? And let's open up that discussion to the Mars community, so let's have broad workshops where anyone -- effectively anyone -- in the Mars community who has ideas of where they would like to go, and wants to argue that case, can show up and argue this is a place we'd like to land. So in the case of the Mars -- in the case of the MER missions, each of the rovers will land -- there's going to be a set of recommendations out of that community. The ultimate decision will actually be made by a project manager for the MER mission, in agreement with Steve Squires, the science lead, and agreement with NASA headquarters. So the three of those will get together eventually and say we'll land here or we'll land here.
Now, the reason the project manager is part of that decision process is because not all sites are equally safe. Some sites are more dangerous than others, and if the Mars -- it's the project manager's job to make the mission successfully land, successfully accomplish what it set out to do. Okay, that's his job. He's got to get it there, he's got to get it launched, he's got to get it landed, and he's got to make it work. And we as a science team might say, "Okay, let's land on this boulder field," and he'll look at us and say, "No way. I'm not going to send a rover to a place I think it's going to die with a 50% chance -- just not going to do it." So there's a discussion going on, what are the dangers of a landing site, what is the specific merit of a landing site, and there's even a little, not much, but a little discussion about what's the public appeal of a sight. Can I see Vallu" Marinarus, the little hills in the distance. There's a little consideration of that, but it's not big in the process. That's sort of where the decisions arise. In the case of MER we have a constraint that we're working with which is we want to land about 30o of longitude apart, and the reason for that is a communication issue. It's really about if an orbiter is passing over, and we don't want -- there's orbiters are not designed to talk to multiple landers at the same time. So we don't want sort of a confusion about that, we want to decrease -- we don't want to decrease the volume of data that we transmit back, which is which would happen. If we had two sitting on top of each other we'd only get half the data from each that we would if they were further part. So we're going to land them somewhat apart, and then the question is, where do we land?
And then the decision is on the quality of the science, really, and sort of the first pass is these are scientifically interesting sites. So we're looking at places, I think there's still categories in Vallus Marinaris that may be possible. There's a hematite site where there's a particular chemical exposure on the surface that has relevance to -- believed to be relevance to hydrothermal processes. There's another site of interesting, Yusef Crater which he believe was a -- is a large impact crater, and we believe, or some people believe there was once a lake there, and there's a drainage flow out of that. So this might have exobiological or astrobiological implications. Conceivable there might have been, you know, microbial life there or something like that. So we don't know.
There's a whole suite of scientifically interesting sites are being juggled with this thing, "Can I land there? Are the winds too strong? If I land, am I going to get thrown against all the rocks as I'm coming down and just smash it to pieces?"
So that process is how we decide where to land.
NASA Moderator: Okay, we've got about one minute left so I'm going to ask a combined question here. Brat Gates says, "How many more missions to Mars have been planned, and Chris wants to know how far off from human missions are we?"
Michael Sims: Okay, the first one is the ones that are planned is there is expected to be a mission in 2007. Surface missions, I'll tell you. Expected to be a mission in 2007. That's the Mars Scout program, and there is planned a 2009 Mars smart lander, which is a large landing, large rover, very large rover. How far we're off from human -- human -- I didn't talk about human missions, I just didn't have time. Human mission process is very different. My personal bias is it could be anywhere from ten years to 30 years before humans get to Mars. Some people would say that's too optimistic, but that's my bias. And -- but the decision on humans is much more political than it is technical. There were some technical issues that need to be managed, but they're minor relatively to the technical issues we managed in the Apollo era, I say. They're significant, but they're not as big as they were in the Apollo era. But the real issue is it's political; you know, is congress and is the president willing to say, "This is something we want to do"?
NASA Moderator: Okay, that pretty well covers a couple of other questions on the politics of it all. So that's great, and we want to thank you an awful lot, Dr. Sims, for joining us today on this webcast, and we want to thank all the students who have sent in their excellent questions. I'm sorry we didn't get to more of them than we did. But it was just a lot to cover in one day. Thank you very much, and till next time.
Michael Sims: My pleasure.
(End of broadcast.)