Narrator: A countdown to a touchdown on Mars. I'm Jane
Platt with JPL -- NASA's Jet Propulsion Laboratory in Pasadena,
California. It's really hard to successfully land a spacecraft
on Mars. But if all goes as planned, that's exactly what will
happen on May 25. Joining us is Barry Goldstein of JPL, project
manager for Mars Phoenix Lander. Barry, first off, why don't you
tell me where exactly Phoenix is headed and why it's going there?
Goldstein: Well, Phoenix is going to be the first mission
to hopefully successfully land north of the arctic circle on Mars.
And the reason we're going there is consistent with the Mars program
theme of following the water. We're actually going to dig and
anaylze the recently discovered near-surface water, ice water
in the northern plains of Mars.
Narrator: And how does this mission fit in with the science
goals of NASA's Mars program overall?
Goldstein: One of the obvious themes of the Mars program
has been to follow the water, and the reason the theme was to
follow the water is we know on Earth that wherever there is water,
regardless of other environmental extremes, whether it's at the
volcanic trenches in the ocean or even up in the Arctic, no matter
how cold or hot, where there's water there's always been various
signs of life. And while Phoenix is not a life detection mission,
what we are trying to do is determine the biological potential,
the potential for life being in a region on Mars and where better
to go than where the water is.
Narrator: OK, and the Phoenix lander is going there, and
has actually inherited some old technology. Tell me about that
Goldstein: Yes, what we've done on Phoenix, and its name
is somewhat apropos, is we've taken the concepts and designs of
the payload from the Mars Polar Lander, and we've taken the hardware
that was actually in development for the Mars '01 lander, which
was postponed after the MPL, Mars Polar Lander failure. And we've
basically resurrected them in a mission, and we've spent an enormous
time over the past five years testing, analyzing and simulating
all the capabilities of the '01 lander to make sure it's a success.
Narrator: Can you explain a little bit about how you took
the existing technology and you tested it and tested it and tested
Goldstein: Absolutely. What we had proposed when we first
put together our mission concept was that we would spend the first
portion of the mission actually going through the analysis that
was done and looking at the pedigree of the hardware and making
sure that it would be compatible with the mission we've designed.
So the first part of the mission, what we call Phase B, we went
and we re-did and re-looked at all the analyses and re-verified
the capabilities of the system performing the way we wanted it
to. We made several changes based on that, and then we went into
the next phase, which is looking at the system design and seeing
how it performed analytically. There is where the focus on EDL
really took hold, and we found several issues that we've corrected
relative to the architecture it was designed or defined, I should
say. And entry, descent and landing, which is our most difficult
phase. And we did a significant amount of testing, and we identified
several problems that were not known before with the architecture,
and we've mitigated all of them.
Narrator: So your comfort level is?
Goldstein: (chuckles) My comfort level -- apprehensive,
I'm very optimistic and very confident that we've done the best
job that can be done. I'm apprehensive because we're at the whim
of lots of things. The environment is one of the things we're
susceptible to. We've done everything we could in the design to
put margins in based on anything we could possibly think of in
this environment, as well as all the data that we've collected
in terms of our landing site, to be very confident that we won't
be at the whim of rocks. But the bottom line is we have a lot
of things going on in the span of the last 14 minutes before touchdown,
we have 26 events, pyrotechnic events, separations and deployments
that have to go right. And for all those things to happen autonomously
in that quick period of time outside of our control, we can't
react to those problems from Earth, obviously. There's a lot that
has to go right in a short period of time, so it makes people
Narrator: And that's the scary entry descent and landing,
Goldstein: Yes, entry descent and landing, no matter what
system you used, no matter how often it's worked in the past,
by its very nature, because its happening autonomously, its happening
outside of your control, and all the hardware, all the long hours,
all the sleepless nights of worrying about problems, all comes
down to that final period of time.
Narrator: A lot of people are familiar, especially our
younger listeners, with the two rovers that have been on Mars
for four years working great, Mars Spirit and Opportunity. Those
landed with airbags, as did Pathfinder back in '97. But this one,
Phoenix, is landing a different way. Explain briefly about that.
Goldstein: That's correct, we're using what we call pulsed
thrusters, for what we call terminal descent phase, the last phase
of slowing down the vehicle before it touches down on the Mars
surface. And the reason we went away from airbags is airbags have
a limitation, or I should say a shortfall, in that it's very mass
inefficient. By that what I mean is the amount of mass that you
have to put into an airbag system to deliver another amount of
mass that actually does the science on the surface is very high.
With thrusters, we actually have a much greater ratio of the amount
of mass that we can deliver to do the science relative to the
amount of mass we use for the terminal descent phase of entry,
descent and landing.
Narrator: OK, so basically a smaller rover, lander you
can use airbags, but Phoenix is bigger and you can't.
Goldstein: Phoenix is bigger and it becomes very mass expensive
to do so. Saying can't is probably a little bit too extreme, but
we believe and we know, I should say, that the amount of mass
we'd have to put into a lander of this size down on the surface
would be prohibitive.
Narrator: The reality is that Mars has not been a very
kind place to spacecraft coming to visit it.
Goldstein: Well that's absolutely right, and more to the
point, for landers its been particularly harsh. Fifty-five percent
of all the landers that have been attempted to Mars have been
failures. Obviously not a good statistic. U.S.-built landers have
done a little better than that. We've landed five out of six successfully
-- the two Viking missions, the two MER missions and Pathfinder
have all been successful. However, its been a while since we've
used thruster descent as our terminal descent phase, and hopefully
we can get that track record rolling in the right direction on
Narrator: As we count down the days and hours to landing,
how do you control your stress factor?
Goldstein: You're under the misconception that I' m controlling
it. (laughter) No, the best thing you can do is just realize,
and I do this all the time, I've been doing it for five years,
that I've got the best team in the world working on this. And
so I know I've got the, there is no better organization to work
on Mars landers than the teams that are working out of the various
organizations on Phoenix, between the team here at JPL, the Lockheed
Martin team, the U of A team, all of our partners at Langley and
Narrator: And landing time on May 25 is a very civilized
time actually, some of ours land in the middle of the night.
Goldstein: Well, it wasn't very civilized when we launched,
since we launched a little bit before 5:30 in the morning East
Coast time on August 4th. We actually land Pacific time at 4:53
p.m. on May 25th. That is when I should say we have detection
of landing, because the landing actually occurs a little bit more
than 15 minutes earlier than that, but it takes light that amount
of time to travel, and I should say in this case it's the radio
signal, that amount of time to travel to Earth for us to detect
Narrator: Well, let's hope we have a good day and everybody
will be excited and happy and we'll have some good science coming
Goldstein: That is what we're hoping for.
Narrator: Thank you very much for your time, I appreciate
Goldstein: Thank you very much.
Narrator: For a lot more information on Phoenix, including
animations, you can check out www.nasa.gov/phoenix.
And you can watch the landing live on Sunday, May 25th, from a
link on that Web site and also on NASA TV. Thanks for joining
us for this podcast from NASA's Jet Propulsion Laboratory.
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