The True Story Behind the Mars Pathfinder Success

by Rob Manning, Brian Muirhead, and Richard Cook

retold by Barbara Amago

Who has the most fun working at JPL? Well, in spite of the stress and
fatigue caused by the long hours, short budget, and numerous snafus
encountered before, during, and after the mission, "The True Story
Behind the Mars Pathfinder Success," proved beyond a doubt that project
staff have more fun. Rob Manning, Pathfinder Project Flight System
Engineer, convinced Project Manager, Brian Muirhead, and Project Mission
Manager, Richard Cook to join him on September 26 in the JPL Library to
present a lively series of anecdotes and personal reminiscences about
their adventures working on the Mars Pathfinder Mission. Before they
began their presentation, Rob asked the assembled audience how many
ex-Pathfinder people were present, "Guilty! Guilty!" he laughingly
intoned as he pointed an accusatory finger at each one.

Then Rob kicked off the session by saying the three of them planned on
telling a few "random stories" in chronological order.

# The Genesis of Pathfinder

"The genesis of Pathfinder goes back to the Ames Research Center," Brian
began. Ames had come up with a concept for a fleet of droidal donut-type
vehicles that could sort of flop around on Mars. They hadn't really
progressed very far with the idea before NASA Headquarters decided that
such a mission really didn't belong at Ames and sent the concept to JPL.
At first, the mission was going to consist of 16 "hockey pucks" that
would be scattered over the surface to make a seismic and weather
network. It was Ames' idea to send one of these to practice with.

"But what was really interesting was how the mission actually ended up
at JPL," interrupted Rich. There was a lot of interest at the time in
the NEAR (Near Earth Asteroid Rendezvous) mission for which we were in
competition with the Applied Physics Laboratory (APL). That JPL did not
get the NEAR mission may have influenced NASA's decision to award the
Pathfinder project to JPL. As part of the Discovery series of missions,
JPL was given \$150M and three years to do this mission to Mars. Wes
Huntress deserves a lot of the credit for NASA's "better, faster,
cheaper" mantra, because, before Discovery no one had ever tried to do a
mission for that -- none even came close!

"Tell the story of Tony Spear's phone call from Wes!" said Rich. But,
since none of the three speakers had been there, Randy Taylor stood up
from the audience and described how he'd been in a meeting in Tony's
office and had been kicked out so Tony could take a call from Wes
Huntress. About five minutes later Tony came out of his office and said,
"That was Wes Huntress." \["We knew that," Randy said, drily.\] "He
asked if we could do one of those MESR things for a Discovery-class
mission ... I said 'Yes'. Now we're going to have to figure out how to
do it!"

"Which just tells you what a bunch of idiots we were!" laughed Rob.

Rich interposed with a comment about how random the process of selecting
a project can be. He spent several years doing advanced projects, where
they come up with lots of great ideas that never get funded, and then
one, like Pathfinder, just comes out of left field, "And it sticks!"
It's a complicated and not always predictable process that includes
politics, money, JPL culture, and cosmic convergence.

"What always impressed me about Pathfinder is the gall," exclaimed Rob,
"That we were going to be able to do a mission for \$150M! We just
decided to give it a shot!" A lot of it was due to Wes Huntress and his
willingness to let JPL take a chance and, for some reason, he had a lot
of courage and he really trusted Tony Spear. Rich surmised that the
creation of Code X at Headquarters, with Mike Griffen ending up leading
it, and the competition that was created between Code S and Code X may
have made Wes more willing to take a chance.

Brian said there had been different classes of missions, A, B, C, etc.,
and, up to this point, we had never done anything but class A (Galileo,
Voyager). But we decided to try a class C, which no one had ever done
before. "So we got to invent it!" And to do that, we needed to break
through the prevailing culture. "The reason we were invited onto this
project," said Brian, looking at his companions, "was that we were kind
of counter-culture." As an example of this difference, Brian offered his
recollection of a photograph showing a stack of paper that was the
Galileo Functional Requirements Documents (FRDs). He held up his finger
and thumb, "The Pathfinder equivalent was about this thick!" Guy
Beutelschies wrote the FRDs, validated them, and then went on to fly it.
A lot of people like Guy were there from concept to delivery. "That's
why we didn't need a lot of paper -- there was always damn little
paper!" he said. And Rob deadpanned, "And still to this day, we can't
even find that paper!" The audience laughed appreciatively.

**What They Didn't Know**

Rich then added, "We keep going back and forth between what was the
really great thing and what was really stupid. I'll just go back to what
was really stupid ...." And he launched into an explanation of
everything they didn't know about entry, descent, and landing (EDL) --
"five minutes of terror." Early on they had made the decision to just
come "screaming in" from the approach, since they really couldn't afford
to go into orbit first. Other than that, "we know nothing about EDL,
and, in fact, there really isn't a lot of knowledge about it at JPL," he
said. The concept started out with the hockey puck with airbags on
either side. They thought that wouldn't work and tried to make it look
more like Viking -- something with legs, active control, fun sensors --
and they took it back to show Wes. His comment was, "That looks like
Viking. And it can't look like Viking!" So, they had to go back and
start again. Then the question was, "What's 'different from Viking'?"
And Tom Rivellini, a "wild-eyed type" from Div. 35, went off and started
looking into airbags. If you take multiple inflated garbage bags and put
a bunch of them together, the shape that's inside is a tetrahedron.
Another of the "wild-eyed Div. 35 types," Mike O'Neill, came up with the
idea of making the Lander tetrahedron-shaped, so it would open up like a
flower. "We got even with Mike, though," laughed Rob, "We made him
configuration manager -- so he had the job of trying to fit the
electronics into this weird shape. I've never seen a guy so angry!" This
was the birth of a new type of EDL, a Viking entry capsule with
parachutes and airbags.

The team didn't have expertise on parachutes, but they had an avid
parachutist on the team who somehow convinced Brian to let him put
together a half-scal model entry capsule with a parachute on the back
that he was going to deploy with the static line. In fact, he tried to
convince Brian to let him jump out of the plane with the capsule, but
Brian had to direct him in writing not to jump. The shape he chose works
well at very high speeds, but when it goes more slowly (at subsonic
speeds), it has a tendency to flip.

At that point the team decided they couldn't do this themselves -- they
had to find somebody that knew something about aeroshells. "We learned a
new word," Rob interjected, "AERODYNAMIC."

# The Rover

So, how did the rover get on this mission? "That little 6-wheeled
parasite," they recalled.

JPL had worked rover concepts since the mid-80s, trying to solve the
mobility problem -- how do you get something little to go over something
big? Brian pointed out Don Bickler, inventor of the rocker bogey
suspension system used on the Pathfinder rover, who was sitting in the
audience. The rover we developed has become the hallmark of all the
rovers we use. Anyway, Donna Shirley and her "pack of technologists" saw
an opportunity with Pathfinder to finally fly one of their rovers --
which Tony Spear vigorously opposed. At first, there was a big culture
problem between the lander team and the rover team, which was
exacerbated by the teams' locations. The lander team was located in
building 230, and the rover team was way out by the east lot. But, after
a certain amount of resistance the teams began to work well together,
largely due to the efforts of Bill Layman.

# Budget Constraints

Pathfinder was a \$171M fixed-price mission. Because the budget was so
tight, Brian was very gratified that team members were treating it like
it was their own money -- that cost consciousness just became part of
the culture. "Without that we couldn't have done it," he said. "Yeah!
You wouldn't even let me buy a color monitor!" accused Rob as the
audience laughed.

Brian said there was always a lot of "horse trading" going on between
the subsystems -- when they needed money one place, they had to take it
out somewhere else. They had a 30% contingency fund built into the
budget, but, even then there was lots of give and take. Al Sacks, in
charge of the ground data system, was able to give up \$300K for gallium
arsenide solar cells on the lander, partly because he felt it would save
his team at least that much by not having to optimize the thing.

When all the bookkeeping was done, Pathfinder came in about \$10K under
plan. John Casani made a bet with Dave Layman, which he later had to pay
off, that Pathfinder would exceed its budget by at least \$30M. (The
audience learned during the Q & A at the end of the story that the bet
was for 2 cases of "expensive" wine that the team enjoyed at a party at
Dave Layman's house after the project was over.)

The "big spender" on the project was the software. Glenn Reeves, "a guy
who had never written flight code and that didn't know 'jack' about
managing anything," laughed Brian, "we put him in charge!" (Glenn was in
the audience and laughed good-naturedly.) Seven people did all the
coding, "and it even worked!" Brian joked.

Rob then told a story of how they had to modify their requirements for
flight computers in order to get ones that were small enough to fit in
the space they had. "Brian didn't even want a computer," he laughed.
"That's right," said Brian, "because then I wouldn't need software! I'm
a mechanical guy." Rob then sardonically described Brian's idea for
using a plumb bob to somehow detect the ground. As he did, he began to
swing his arms in a wide arc, and the audience (and Brian) laughed
appreciatively.

# Mass

Brian then introduced the topic of spacecraft mass. Since the project
was originally scheduled to launch on Delta 7925, launch mass was never
the problem. The problem was entry mass. With the addition of the rover,
among other things, Pathfinder's mass grew by 67%.

Rich said, "Rob used to have a saying, 'Every project needs a certain
number of miracles that it has to accomplish in order to get done and a
series of constraints it has to live with,' like performance, schedule,
money, mass. Pathfinder's three miracles were: 1) getting it launched;
2) entry, descent, and landing; and 3) getting the rover off. The
constraints were the short time, less than 5 years; money; performance
(they had a lot of flexibility here, because it was a 'proof of concept'
mission); and mass, which they used as a safety valve, which is why it
grew so much.

After 36 months, in June 1995, Pathfinder started ATLO (Assembly, Test,
and Launch Operations). This basically meant, Rich wryly pointed out,
that "we took some stuff down there and started ATLO, and then we took
it back and fixed it." The only problem they encountered was with the
Heat Rejection System (HRS). They had a problem because they had to
insulate everything really well on the surface of Mars, but when you do
that you overheat on the way to Mars. To try to finesse the problem,
Brian introduced the HRS that was essentially a refrigeration system
that pumped freon around. When they tested the spacecraft in the thermal
vacuum chamber, they turned on the system and heard a terrible noise.
When they investigated the source of the noise, they realized that they
had neglected to connect the freon to the pump, and burned up the pump.
This was a very embarrassing failure, and difficult to fix. The second
problem was that the solar array was running to hot and there was a
great risk of the voltage running too low. They needed a really good
thermal blanket guy, and the only one they knew of, Hugh Van Delden, had
retired from JPL. Brian had to convince him to come back, which he did,
and, in a few days we was able to re-do the blanketing and fix the
problem.

# Launch

Well, according the Rich, all that culminated in shipping the spacecraft
to the Cape late in August 1996. They learned that the Lab always ships
spacecraft by truck, never by air. The night that Pathfinder left the
Lab, the team congregated at the gate to see it off with "The Saints Go
Marching In" played by Rob on his trumpet. Brian had brought a bottle of
champagne to "christen" the truck before its voyage, but thought better
of it and broke it against the fence, instead.

Once it arrived at the Cape, they had to put the whole thing back
together and do one more system check, which went smoothly.

The launch itself took place at night and was "the thing to do" because
it was absolutely beautiful. However, few of the operations people got
to see it in person, because, of course, they were back at JPL running
the systems.

# Public Outreach

According to Rob, Matt Golombeck, Project Scientist, had been trying to
convert all the engineers at JPL into scientists. He wanted us to see
what Mars was really like, so he organized a field trip to eastern
Washington's scabland region, which he said was very similar to Mars'
Ares Mares. So, Matt, Rich, Thomas Rivilinni, Howard Eisen, and Rob went
off the Washington with a group of school teachers. A big public meeting
had been arranged for them in Spokane at a local high school. They were
absolutely stunned at the number of people that showed up at the high
school in the pouring rain to see them. They had no vu-graphs, very
little beyond a model of the rover to show and tell, but 800 people had
come to see them. Rob had an epiphany, "It's not just us working on this
-- the whole world is watching us!"

# Post Launch

After launch, as they were monitoring all the systems, everything looked
fine. Except when they came to Miguel San Martin, who was monitoring the
sun sensor. "Big silence." That the sun sensor wasn't working correctly,
was a big surprise, because they thought it was "rock solid." It was the
navigation guys that were able to give better information about the
spacecraft position. One of Miguel's quotes from that time was, "The
janitor knows the spin rate better than I do." Since the sun sensors
were next to the pyro hardware, the team thinks that an explosive fuse
might have ruptured and sprayed the sensors heads. "We had built in
redundancy -- two sensors, right next to each other," Rob deadpanned. As
it turned out, the sensors were working, but they couldn't use them the
way they'd planned; they needed a software patch. When they were ready
to send the patch, they came in one Saturday, ready to spend a couple of
hours. It turned out they were there for hour upon exhausting hour,
sending file after file that were being rejected by the spacecraft. They
grew increasingly desperate as the hours wore on. Meanwhile, one of the
JPL "old timers" who has since retired, Gordon Wood, was at another
station working on something else. Gordon was a great telecommunications
engineers whose "mission in life was to annoy as many upper-level
managers as possible," Rob laughingly explained. But he began to pay
attention to what we were doing and was eventually able to figure out
that there was an anomaly with the DSN antenna that, combined with the
rotation of the spacecraft was causing a blip. Gordon suggested lowering
the data rate (counter-intuitive for the non-telecomm engineer!) and,
sure enough, it worked. (They dubbed this technique, used again later in
the project, "woodulation.") From this the team learned a humbling
lesion about the consequences of a double failure.

# Entry, Descent, and Landing

When the spacecraft was about one and a half hours from arriving at
Mars, the launch valves didn't close. To solve the problem they needed
to verify the version of the software that was running, and someone got
the idea of looking in the fill frame, where they typically include
unique words that identify the version. They had included the name,
"Jordan Kaplan," a team member who had been killed in a place crash, in
the fill frame as a sort of memorial, and, when they found it, they were
sure that Jordan was still looking over them. They finally figured out
the problem and were lucky to finally see the signal.

Another coincidence that proved that they were "just plain lucky" (JPL)
was that the landing was on July 4 and drew such enormous public
attention. When asked if they had planned it that way, Brian noted
wryly, "I wish we were that smart!"

The last lucky break came with a piece of Kevlar cloth from the air bags
that very nearly got caught up in the rovers wheels. "We came this
close," Rob held up his thumb and forefinger, "to having a tethered
rover after all!"

Rich described how the rover got off the next day. It had been designed
to last 7 days, but lasted the whole time, 85 days. The lander also
lasted much longer than the 30 days expected. So, for three months, the
team members worked every day for the duration of the Mars day. People
scheduled their personal lives around it -- including taking vacations
and having babies. Rich finally got to take a vacation and went to Italy
with his wife for a conference. He made the mistake of calling in one
day and learned that the team hadn't heard from Pathfinder for two days.
"I went on vacation and they killed my spacecraft!" he lamented. He
surmised that what finally "killed" it was trying to wake the spacecraft
up at night to take at least one nighttime picture. Since the battery
was so low, the lander finally failed. It was assumed that the rover
probably outlived the lander -- and a favorite image at the time was of
the little rover circling its "mother" but getting no response.

In response from a question from the audience, Rob, Brian, and Rich
closed the program by saying that they took on the Pathfinder project
originally because they didn't know what it would take, and they've
since learned that there's a lot more to doing a mission than they
though. Some of people probably wouldn't do it again, but the bad
experiences fade and the good moments and the excitement remains. The
audience was left with the feeling that the three of them relished their
experiences on the Pathfinder project and, above all, that they relished
the opportunity to share their many stories with their fellow JPL
employees.