The JPL Open House

Every year, JPL turns into Disneyland for the weekend, at its annual JPL Open House. I volunteer every year. Sure, I'm spending my weekend standing around for hours on end, answering the same questions about the rovers over and over. But our visitors are excited, just thrilled to be there, to be seeing cool space technology and robots and the people who work with them, to be learning about the universe. It reminds me of how I was when I was one of those people -- when I was on the outside, when working at a place like JPL seemed so far away, when it was something other people did. It reconnects me with that feeling of excitement, pumps me up. Fixes my perspective.

(Usually. But not this year. This year, the crowds were nice, the questions were good, people were pleasant and interested and positive. They weren't the problem. I am the problem. I'm burned out. Intellectually, I see that as stupid. I have my dream job: I have a robot on another planet, and I get to drive it around and make it do stuff. And they pay me. But it's just not working for me any more.)

(But I digress.)

For the record, here are the answers to about 90% of the questions I get:

1. Is this as big as the real rovers? Yes, the demo rover you're seeing is the same size and general overall appearance as the real rovers.
• Extended answer: we built this model to practice getting off of our lander, the spaceship we rode to Mars, onto the Martian surface. You don't want to go three hundred million miles ... and then trip. Now that she's done that job, we retired her and just bring her out once a year to say hi to all you nice people. Hi, nice people! (If there are enough kids in the crowd at this point, I wiggle the high-gain antenna so it's like the rover's waving. They practically always laugh and wave back.)
  
2. Why does it move so slowly? It moves so slowly because it weighs as much as a motorcycle (another common question is, How much do the rovers weigh?), but only about enough energy to run two ordinary light bulbs. If you imagine trying to drive a Harley with just enough juice to run a couple of light bulbs, you can see that it won't go very fast. But even though they're not very fast, they are very strong. (I put a rock in front of the rover and show how the rover just pulls herself right over, hardly slowing down at all.)
   
• Extended answer involves joking that they are the fastest cars on the planet, that there aren't any cops around to pull us over for speeding, etc. Sometimes that takes the form of mock outrage: why do the rovers go so slowly? You mean, why do the rovers go so fast?
  
• The question is sometimes phrased as, How fast do the real rovers go? And I point at the model and answer: that fast! And then I do the above spiel.
• This is also often a good time to talk about Earth vs. Mars gravity. I usually phrase this as "The Martian Diet," and discuss how well it compares to the Atkins Diet.
  
3. Are the rovers still going? Yes, both Spirit and Opportunity are still working and still doing science every day -- four years into our three-month mission.
4. How long will the rovers last? Ninety days. We're now four years past our 90-day warranty, and they're still going.
• Other useful lines: everyone who's bet against the rovers so far has lost, so I don't recommend it. Never bet against the rovers!
  
5. How long does it take a signal to get from here to Mars? That depends. When Earth and Mars are on the same side of the sun, as close as they get (I hold my fingers close together), it's about four minutes each way. But when we're on opposite sides of the sun (I move my fingers farther apart), it can be up to about 20 minutes.
• Extended answer: That light-time delay drives everything we do. We'd like to drive the rovers with a joystick -- push forward on the joystick, and the rover goes forward; pull back and it stops. But the light-time delays make that impossible. Imagine trying to back your car out of your driveway like that. You look over your shoulder, hit the gas ... and nothing happens for four minutes. And when it does happen, you don't know about it for another four minutes, because your back windshield hasn't gotten the return signal yet. If we tried to drive the rovers like that, then by the time we saw the cliff coming and pulled back on the joystick to stop (I mime all of this as I'm talking, and pretend panic when I'm talking about seeing the cliff and needing an emergency stop) -- we'd be too late, the rovers would already have gone over the cliff.
  
  So we don't do that. Instead, we just command the rovers once a day. As the sun goes down in the Martian sky, and our solar-powered rover has to go to sleep for the night, it sends us pictures and other data telling us where it is now. Then the rover goes to sleep, and we go to work. We look at all the data, use a simulation to figure out what to make the rover do next, and build up a list of commands to script out the rover's whole next day. Then, as the sun comes back up in the Martian sky and the rovers are waking up, we send them those new commands. Then the rovers go to work, and we go home and go to sleep.
6. Is dust a problem? Oh, my, yes. Indeed, that's why we originally thought the rovers would last only 90 days, because we thought that's how long it would take for dust to build up on the solar panels and choke the rovers. But then the wind came along and blew the dust back off the solar panels.
1. Extended answer: this year, we had a huge dust storm that blocked out about 99% of the direct sunlight. Fortunately, the rovers survived that storm, but when the dust settled out of the atmosphere, it settled onto our solar panels. On Spirit, especially, the solar panels are dustier than they've ever been -- about 70% of the light coming from the sun is blocked by dust on the solar panels, and that's going to make it a tough winter for Spirit.
   
2. Extended answer: yes, we could have added something that would blow the dust back off the solar panels, but if we added that, we'd have had to take off a science instrument. Given that we're more than four years past our warranty, it's hard to argue with that judgment, no matter how nice it would be to have now.
   
7. What's that stuff on top of the rover? This is usually either "solar panels," or an explanation of the three antennae:
1. This big antenna is called our "low-gain" antenna. It communicates at only 10 bits per second, but it works even if the rover has lost track of time, doesn't know where the Earth is, or whatever. So it's the one the rover uses if it panics.
2. This lollipop-like antenna is called the "high-gain" antenna. It swivels back and forth like this, and rotates like this, and that lets us point it at the Earth no matter where the Earth is in the Martian sky. This one's a lot faster, about as fast as a slow modem -- up to about 28 kilobits per second. And this is the one we normally send commands to.
   
3. But this little, unimpressive-looking antenna, this one has sent back more than 90% of the data that the rovers have sent to Earth. That's because it talks to an orbiter in the sky over Mars, called Mars Odyssey, and Odyssey then sends the data back to Earth from there. It doesn't have to send a signal all the way back to Earth, so it can transmit a lot faster. This one's about as fast as a DSL connection, up to 256 kilobits per second.
   
8. What are those holes in the wheels? (Actually, what people notice is usually the broken-up pattern surrounding the holes, but I pretend they noticed the holes because it makes the answer better.) Those holes in the wheels (I demonstrate by sticking my finger through) serve three purposes:
1. They're where we tied the rover to the spaceship she rode to Mars, so she wouldn't bounce around inside too much.
   
2. You can see how the wheels are open on the inside, to save mass. (I demonstrate by sticking my whole fist in there.) That means the rovers can pick up rocks and dirt as they drive around. The holes give the rocks and dirt a chance to fall back out as we drive. Otherwise, too much stuff would build up in the wheels and clog 'em.
   
3. When we look back at pictures we take of our tracks, we can look at the pattern the holes make. If they're crisp and well spaced, that means we're on good driving soil; if they're mushy and too close together, that means we're bogged down.
• (Note: we don't really do the analysis that way so much any more, but we used to do that a lot and sometimes still do.)
  
That's a lot of value we get out of something that's really nothing at all, wouldn't you say? (I'd have said that it's a "hole" lot of value, except I don't want people throwing things at me.)

9. Are those real Martian rocks? Nope, but they look like real Martian rocks. They were made the same way as a lot of the rocks we've found on Mars: by volcanoes. Those rocks are just here to show you what the rovers look like when they're going about their daily routines.
   
• Extended answer: Although these aren't real Martian rocks, there are some real Martian rocks here on Earth. They probably got kicked here by an asteroid: a big rock falls on Mars, makes a huge explosion, and a few of the rocks that get kicked up by that explosion end up here on Earth. Doesn't happen often, but we have billions of years to play with. We know they're from Mars because we've carefully analyzed gases trapped in the rocks; they don't look like what we know about the early Earth atmosphere, and they do look like what we know about the early Martian atmosphere, so it seems reasonable to conclude that they must be from Mars.
10. How many cameras are there on the rovers? Nine. There are two up here on the top that can take color pictures. These two next to them only take black-and-white pictures, but they have a wider field of view, so they're better for driving. And then there are two down here in front, and another pair just like them in back; those are how the rover gets a good view of what's right in front of it and right behind it. So that's eight cameras. The ninth one is right here, on the end of the rover's arm, and that one has a microscope lens on it, so that the rover can take really close-up pictures of the rocks to help us see what they're made of.
    
• Extended answer: you notice that the rover's cameras come in pairs. That's so that the rovers can do what you and I do, build up a 3-D picture of the world. The rovers can then reason about what they see in that picture -- they can tell if a rock is too big, or if there's a cliff, and steer away from it.
11. Also, there's rarely an explicit question about this, but it's clear that a lot of people think that the particular rover they're looking at has been to Mars and back, and/or that we're going to bring the real rovers back. When I detect that mistake, I try to politely correct it. Spirit and Opportunity are on Mars to stay; that's their home; this is just a demo rover.
    

(Incidentally, don't misconstrue any of this to mean I think the questions are stupid or annoying. Quite the contrary! I think a lot of those questions are pretty perceptive, especially if you're just seeing the rovers for the first time.)

Those are the most common ones, by far. I got some questions about the drive and steer actuators, but just two or three. One thing I noticed was that some questions that were routine in past years, weren't asked at all this year. In particular, nobody asked me how far the rovers have driven. (Nearly 8km for Spirit, over 11km for Opportunity.)

You have to scale these answers up or down to fit the questioner and the crowd. If it's a kid who's asking, I usually kneel so I'm about their height and try to couch the answers in terms I think are age-appropriate.

Let's see ... another thing that came up repeatedly was the whole bit about how the rovers were all folded up for their trip to Mars, and had to unfold themselves once they got there. About halfway through the day I got the idea of calling the rover a Transformer; the kids dug that. And another thing was, every time Mike just dragged the rover where he wanted it, I made a rueful face and observed aloud that there were many times we've wished we could do that with the real ones.

Mars is normally down by the 303 cafeteria, but this year, we were set up by the front entrance for the first time. So as fresh batches of people came in, I would say this: "Howdy, folks, welcome to JPL, welcome to Mars. If you're just arriving, I'd like to make a recommendation. Go ahead and pick up your goody bag at the entrance, then stand right about where you're standing ... for eight hours. And then go home. Because nothing else you're gonna see today is as cool as these rovers." And that would get a laugh, and then I'd go on and talk about the model and solicit questions.

There are also several types of questioners. Among them:

• The Boy/Girl Scout. No, I mean literally. They come in with a list of questions they're supposed to ask as some sort of troop activity. Didn't happen this year (or not that I saw, though I saw some scouts there), but it's been a fixture of previous years.
• The super-bright kid. They talk with a kid's diction but an adult's understanding, or something a lot closer to it than you'd expect from their ages. These are my absolute favorites, because they mix an adult's intelligence with a kid's enthusiasm. And they're always, always jazzed about being there. I had two of them this year.
• One was an Asian kid named Max, who was incredibly excited to be there. Max told me he was five years old; he said this, and everything else, with an enthusiasm kids normally reserve for new Harry Potter releases. Max is going to be an astronaut, and his sister likes robots more than he does; he's really into airplanes. And did I mention he's going to be an ASTRONAUT! Max was awesome. Max is, he really is, going to be an astronaut.
  
• The other was a white kid, I'd say about eight or 10 years old. I didn't talk to him for very long, but he had an astute observation. "You said this is a rover just like the real rovers," he said, looking at me narrowly. And he's right, that's how I'd phrased it that time. "But the real rovers have explosive pyros for cutting the cables [he gestured to show me how the pyros work], and that rover has something on it that looks like Velcro." So I explained that this was a demo rover and we made it cheap because it just had to look and act like the real thing, but he was right that a lot of the parts weren't like the real parts. He nodded in understanding, satisfied, and moved on.

An important technique to use when working the crowds: know when to walk away. You're there for everyone. If someone starts to monopolize your time, don't make them feel bad about it -- it's just a product of their enthusiasm, after all -- but find a reason to walk toward the rover while you answer their latest question, maybe to gesture at something on the rover to illustrate a point. Then notice a question from someone else in the crowd.

There. Having said all that ... maybe I can feel okay about not volunteering next year. I'll just drop off a sign with the URL for my blog, so people can read this if they want to know anything. I'm sure that'll be fine.