Destination Mars (13 page)

Sojourner was traveling moderate distances unassisted now, as had been planned. Much of the Pathfinder mission was a test bed for future missions, so it was important to learn as much as possible while the rover was operational and within view of the lander's cameras. There were glitches of course—false stops, occasional digital confusion, and misaimed trajectories. But overall, Sojourner was proving to be a tough, smart, and plucky little rover.
¹

By the end of August, ice clouds were seen in the surrounding skies, and the sunsets were picking up color. Blue sky was observed around the sun at some of these times; this is due to the Martian dust scattering the blue wavelengths. Temperatures were consistent—the low was -103°F, the high 14°F. Pathfinder recorded this, but cared not. The mission was always rocks, rocks, and more rocks. Sojourner, after spending the better part of a week getting there, explored the area called Rock Garden, which was replete with interesting samples. Things went well until the rover got stuck on a rock, Half Dome, and again shut off automatically. It was too steep. But each time Sojourner did this in automatic mode, and had to be driven off of the obstacle, the teams back on Earth were learning. What this would mean for future missions was not yet quite clear, but gaining experience was the key, and it would bode well for future rovers.

Scientists continued to observe the smallest of details from the images returned: ongoing looks at the dirt under Sojourner's wheels—the soil-mechanics experiments—saw many layers of material, almost certainly deposited by water, and created an ever-expanding database of soil types. Farther out, the ground was covered by a layer of fine sand and drift, bright in color, indicating some differentiation of local soil conditions. This was in keeping with the idea of landing in a river-delta area.

In early October, communications problems returned. While signals returned from the errant lander computer indicated that the spacecraft was still functional, getting a meaningful conversation going was tough. Pathfinder was in trouble. The onboard battery seemed to be the culprit. It was losing capacity and was not only allowing the transmitter to get entirely too cold in the long Martian nights, but also failing to track time and date measurements. Low voltage and continuing resets of the computer were bedeviling JPL's plans.

If communications disappeared for more than five days, the rover was programmed to go into a contingency mode and, like a
loyal dog, return to the base station (lander) and begin to circle it. This was designed to keep it from wandering too far afield or getting irretrievably hung up on a rock.

By mid-October it was becoming clear that the mission's days were numbered. On Earth, JPL engineers were testing identical hardware at a range of increasingly low temperatures in an effort to try to predict behaviors for the radio, but the results were not as useful as hoped. Still, the Pathfinder lander had outlived its planned primary mission of thirty days, and the rover had outlived its mission design of just seven days, but the ongoing sporadic failure of the radio was still a disappointment.

In three months of operations, Mars Pathfinder continued to refine the image of Mars as a planet awash in water during ancient times 3-4.5 billion years previous. However, the area surrounding Pathfinder appeared to have been dry and untouched by flooding for at least two billion years.

Sojourner's “nose,” the Alpha Proton X-Ray Spectrometer, found some of the rocks confusing. There was far more silica in them than expected from studying Martian meteorites that had fallen to Earth. They appeared to be volcanic in origin, which argued for a highly active geological period in Mars's past. This rock type, called
andesite
, is typical of rocks formed by magma cooling in subterranean pockets, as opposed to the types of rocks found on some parts of Earth and on the moon. This latter type, called
basalts
, results from lava flowing onto the surface and cooling there in large sheets. But andesites are also indicative of active plate tectonics, which Mars did not appear to have, and are usually found at plate boundaries. Later observations from Mars Global Surveyor and other spacecraft indicated that Mars may indeed have experienced plate tectonics early on, with that activity ending far long ago (Earth's are still active).

By the end of its three months, Pathfinder had returned 2.3 gigabytes of data (by far the most accomplished in such a short period), over seventeen thousand images from the lander and the
rover, performed sixteen detailed examinations of rocks, and sent back almost nine million bits of weather information. The team on Earth had gained valuable experience landing in an unorthodox fashion and driving a rover on Mars, which would prove invaluable for the next surface foray, the Mars Exploration Rovers. The understanding of the landing area had increased manifold, and modern electronics had been tested on the harsh and unforgiving surface of Mars.

Not a bad haul for a faster, better, and cheaper experiment called Pathfinder.

R
ob Manning is a congenial and soft-spoken, if unintentional, folk hero. If you were a fan of the Mars Pathfinder website during that heady mission, you saw his bearded likeness all over the webcasts—calling out the numbers during the descent, announcing a successful touchdown, and throwing his head back with a fist pump when Pathfinder bounced to a stop. He was what might be termed the “principal cheerleader” as well as the chief engineer for the project, and has since taken these talents on to the Mars Exploration Rovers and the upcoming Mars Science Laboratory. When not busy with his projects at JPL, he pursues his varied hobbies, including jazz trumpet, in his Southern California home (just minutes from JPL) with his wife and daughter.

His introduction to the Pathfinder mission was a bit of institutional serendipity: “We have a paper here at JPL called the
Universe
, and it had an artist's rendering of this funny little mission, a rover, a very odd painting. I thought, ‘JPL has no skill in this, it's been so many years since we've actually had to do something where we had to
land
on the planet.’…We hadn't really done a lander at JPL for many years. And while Viking was done at JPL, the lander was built at NASA Langley Research Center, who [
sic
] had since gotten out of the business of planetary exploration.”
¹

Rob was puzzled that the lab would take on a Mars landing after all these years, yet at the same time, it was intriguing: “So I thought about this for some time. Soon I got a phone call from
one of the people involved with this mission [spacecraft manager Brian Muirhead] who said ‘I need an electronic whiz to work for me, someone who knows about computers and software.’ I was an electronics- and software-systems engineer, so then we spent time in the JPL cafeteria and we hit it off, so he hired me as the chief engineer. I think he liked the fact that I wasn't super aggressive or controlling, and also that we really understood each other. That was around 1993. He taught me how to stuff a lot of electronics and complexity into a small little vehicle, and that was my charter: to work with the electronics team and the software team and the systems team. Over time it all grew together.”

Mars Pathfinder and the Sojourner rover were built at JPL, giving folks like Rob a chance to have a very hands-on involvement with the project from planning to nuts-and-bolts to execution. This was a great way to have a personal stake in the mission, as well as save a lot of development money.

“You see, Galileo and Voyager, in fact nearly all of the flagship missions were built right here [at the lab], so JPL had a long history of hands-on work. I guess they just hadn't done one where they went through the atmosphere and actually landed, so that was going to be unique. The Sojourner rover was part of the Mars Pathfinder project, and that team was within JPL. So at the time I was actually responsible for Pathfinder. Now I didn't design Sojourner, but I was very involved with the design of Mars Pathfinder. Later I was also put in charge of the entry and landing [for the mission], as the main guy behind that. It was actually a trio of us, and we were the three legs that held the entry-and-landing part of it together.

“Now, for a long time Tony Spear, who was the project manager, was very concerned that we didn't have an entity to pull all those complicated systems together, and so he was looking to outsource it to another company. But it's a very complicated thing to outsource, and we didn't have much time before we launched. Launch was in late 1996 and [by this time it was] 1993, and I
couldn't imagine writing a [specification] to tell people how to interface all those complicated things. How do you interface an airbag [landing system], for instance? So we finally talked Tony into letting us continue the process and building it here. Of course, we had lots of contractors working with us, so, for example, we designed the airbag architecture, but we didn't fabricate the airbag itself.”

Outside contractors were brought in for key components—the airbags, the aeroshell, and the rocket motor. But the overall design and assembly of these components were to be in-house, and the people working on it worked hard—and enjoyed it.

“There was a lot of concern at NASA headquarters that connections for all those things that you need to build a vehicle like that might not exist here. JPL had the chops to build spacecraft, but nobody had all the chops to put the whole system together. So [in a leap of faith], Wesley Huntress, NASA's associate administrator for space science, called Tony Spear and said ‘Tony, we would actually like you to implement this,’ and so we did.

“So we started our own testing once the job came to us, [we] tried out different airbag concepts. We had to [figure out how] to [deflate] these airbags upon landing. On Mars the atmosphere is so thin that the air coming out of the holes vents supersonically, really fast. It doesn't do that on Earth, so the ability to test it on Earth, at least outdoors, was really lousy. Nonetheless we continued to try and get the venting to work.

“Now earlier on, JPL had proposed working with other vendors to do a nonairbag system, thinking that would be perceived as a more reliable and safer way to land. But the price tag for that was much higher. Viking had landed with throttleable engines, and the throttle is the coolest part. But coming up with a throttle that actually has the precision that you want, the dynamic range, was a very difficult and expensive proposition back in early seventies when it was developed for Viking.”

One might think that this would be child's play by now, in the
twenty-first century. But not so. As with the Apollo program, much of the brain trust and technical expertise of the 1960s and 1970s have been lost, as has the manufacturing capability. It was a problem for the Pathfinder team.

“The trouble is, there isn't a big call for these kinds of [rocket motors] in the space industry, and that throttling mechanism simply no longer existed by the time the 1990s rolled around. To make matters worse, all the people [who worked on it] were gone, and there was the sense that it would be very expensive to restore that technology. So [NASA] headquarters said, ‘Keep it simple.’ Remember that we're talking about a $150,000,000 spacecraft, all together, including the launch vehicle. That's actually really cheap, cheaper than a big movie at the time.”

Amazing, but true. The motion picture
Titanic
cost $200 million to produce. Pathfinder was in line with the largest movie budgets of the time, and a bargain at that.

“So to keep it on budget, we thought the airbags would be the cheaper way to go. But it was also considered higher risk because we had never done it before. It had all these complexities that no one had ever dealt with; for example, how the hell to get out of it once we landed, how do you undress yourself on the surface of Mars without getting yourself wrapped up in knots and in tons of fabric? We had about two hundred pounds worth of fabric, and that's a lot.”

The worries and the testing went on, seemingly ad nauseum. But eventually the kinks were worked out, sometimes by trial and error. It was all so delightfully ad hoc and low-tech, but it worked, and soon they were ready to go. One huge advantage of such a low-budget mission was that NASA's expectations were minimal.

“The great thing about Mars Pathfinder was that [it was predicated on] a single page of level 1 requirements. These were: head to Mars in the 1996 launch opportunity, land in 1997, deliver a rover, send back some pictures, good luck, and here was some money to do some science if you have some time. So the mission
was to show that NASA could do things cheaply, efficiently, and effectively, and of course demonstrate that there are efficiencies in a faster, cheaper approach. Of course, this hadn't really been defined yet, because nobody ever agreed on what that meant.”

This was the dictate of the then NASA administrator Daniel Goldin: faster, better, cheaper. It was not a bad idea in principle, but it had unfortunate consequences in many cases. However, Mars Pathfinder was one shining example of how it could work. One efficiency they achieved was to move the Pathfinder team, and the associated technical base, as close together as possible; it was almost reminiscent of the Mariner 4 days.

“We wanted to put all the team in one spot; we thought that was important. Now we couldn't quite achieve that, because of space availability issues at the lab at the time. But we got a majority of the core team members all in one spot. Communication was considered very important, teamwork was considered important, close management between the team was important, tight bandwidth between the team was very important; so we set it up to accommodate this. Also, don't overspecify things, it's okay to rely on oral communication as opposed to doing everything with legal documents, and above all keep it simple. That was our mantra.

“We didn't skimp on testing, though sometimes the test articles were low budget. But we didn't skimp on the tests themselves, so that was the overall model. The airbag was the perfect example of test-test-test. But there never seems to be enough people and resources to get the job done…. [T]here's never a sense of a forty-hour work week, it's almost a foreign concept. You can't predict scope with accuracy, yet you have to predict scope in advance to get the money, and there's a balance to what you can ask for and what you can get. You're expected to live within your means, so what happens is you get this variable called
homelife
, where you have to spend your time away from home all hours of night and on weekends.”

But if their domestic routines were scrambled, most of the participants in the Pathfinder project seemed to replace that (temporarily at least) with an almost religious fervor in the mission…and they enjoyed it: “At Pathfinder I think we had a lot of fun because there was more team spirit, more sense that the team members in all levels of the project, even if they were a cog in the bigger wheel, could participate in a whole function of the thing by watching it. Part of it was the smallness [of the team] and part of it was the fact that there wasn't a lot of institutional pressure. It was a fantastic experience, everyone [who] worked at Pathfinder [whom] I know think of it as nothing but a fun experience.”

Although the metaphor may be inaccurate, it is tempting to equate some of their fun with the toys at hand. Manning insisted, early on, that there be a way to test Pathfinder and the Sojourner rover in something remotely like a Mars-like environment close to the control room. This would help to avoid mistakes.

“Right above JPL's master control center was one giant room, and that room was for Mars Pathfinder. We had a sandbox in there, right above us. I had to do a lot of arm-twisting to convince people to bring in thousands of pounds of sandbox sand from down the highway in Monrovia. I wanted [the sandbox] right there so it could be the hub of our project.”

We know the story of Pathfinder…the revolutionary bouncing landing, the deployment and travels of the plucky rover. But for Rob Manning, it was not just the spacecraft, but the people—and their interactions—that were fascinating.

“Mars Pathfinder had a very interesting attribute. Because it was a small project, representing a small number of people, each doing a large number of things, there's a lot of diversity in what people did for a living; if you were an electronics guy, you might find yourself doing airbags one day, or doing retracting tests, or software. There were a lot of unusual relationships, and I did all sorts of goofy things, mixing people up based on their skills, attributes, and interests. In a major business this is unusual
because normally you would have people who have an agreement to deliver certain products, and when they're done with the delivery they're off the job. I didn't believe in that, because it's not the most effective use of people. It was always a pleasure working with the capability of people, and to me one of the continuing returns of Pathfinder was to see all these people do things that they didn't think they could do.”

That said, it ultimately came down to the mission itself. It was a high-risk endeavor, trying lots of new techniques on the cheap. When it worked, the atmosphere at the lab was almost giddy: “I was the flight director during landing even, which really means that I knew when everything was supposed to happen, based on what the spacecraft was saying to us, which wasn't very much. We had a transmission delay of about eleven minutes at that time, so when we heard about it, it had either worked or it hadn't. During the landing, actually all the way down, I was giving a play-by-play on the net, with my headphones, and people were watching me as I was trying to interpret what I was hearing from [the tracking stations]…so it was really a lot of fun, and I was able to announce that it had landed, we had gotten a signal from Mars. It was really cool.”

Of course, this had been simulated over and over. When dealing with long delays and highly complex automated systems, simulation is the engineer's best friend. “We practiced through our simulation setup, which was right next to our operation area. We would put an eleven-minute light-time delay between what was going on [in]our test area and [in] our control room. So even though we could walk between one room and the other in about ten seconds, it was like adding two hundred million kilometers of distance. We had practiced it so much that when we actually landed it felt fake! It didn't really click, just how real this was, until we got our first photo back, and the we realized that this was
Mars.
So we got to the surface of Mars and went through the whole process of getting the vehicle deployed, and then the rover's
standing up, all within twenty-four hours. This was on the fourth of July. The first pictures came back in the evening, at about five o'clock Pacific time; that was our first view of Mars, including the picture of the rover. It was pretty darned exciting. There were also a lot of interesting stories about what had gone wrong, and surprises we saw. We had interesting anomalies after we landed; for example, our inability to talk to the rover. Because the antennae were crossed over, we found out that the signals weren't getting back and forth [between rover and lander] like walkie-talkies as well as they should have.”