MARS PROBE TO LAND
As fireworks go up in the sky, the U.S. spacecraft Pathfinder will be landing on Mars, ending a seven month voyage. As a preview, Jeffrey Kaye takes us on a virtual tour of the red planet.
A RealAudio version of this NewsHour segment is available.
An Online Forum on the possibilities of life on other planets
March 10, 1997:
Report on the Galileo probe and the moons of Jupiter.
December 4, 1996:
The Pathfinder Mars probe takes off.
August 7, 1996
Kwame Holman reports on a Martian meteorite that has the scientific community buzzing.
July 10, 1996
Jeffrey Kaye looks at the moons of Jupiter
May 28, 1997:
The space shuttle Atlantis lands after a rendezvous with the Mir.
February 18, 1997:
NewsHour historians discuss the successes and future of the space program
September 26, 1996:
Astronaut Shannon Lucid returns to Earth after 188 days on the Mir.
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JEFFREY KAYE: In the flight control room at the Jet Propulsion Laboratory--JPL--in Pasadena, engineers have been sending 11th hour commands to the "Pathfinder" spacecraft.
STOLPER: Here we go, celestial track in transition.
JEFFREY KAYE: After a journey that began seven months ago on July 4th, there'll be fireworks as Pathfinder descends through the atmosphere of Mars to land on the red planet.
DONNA SHIRLEY, Mars Exploration Program: On Independence Day 1997, Earth is invading Mars.
JEFFREY KAYE: Donna Shirley is manager of the Mars exploration program at JPL.
DONNA SHIRLEY: Every twenty-six months we're going to fly to Mars, with either one or two--with either one or two spacecraft, we'll fly to Mars every twenty-six months.
JEFFREY KAYE: Pathfinder is part of a 10-year-long NASA program to explore Mars. As it dives into the Martian atmosphere, the spacecraft's heat shield will keep it from burning up. A parachute will pop out to slow it down. For the landing, engineers devised an unconventional technique, designed to cut costs and to allow Pathfinder to survive a 60 mile-an-hour collision with the Martian surface. Flight software engineer Steven Stolper described the solution.
STEVEN STOLPER, Software Engineer: The engineers were up late one night, thinking about it. And they were watching TV, and on TV, they saw a car commercial. And what would save someone from a crash in a car commercial? An air bag. Right before we land and hit the surface, we inflate four giant air bags, one on each side of the lander. So we're not only gonna hit, we're gonna bounce, and our first bounce should take us over an eight story building. So we're gonna bounce, and we're gonna roll. We're gonna tumble. And eventually we're gonna come to rest on the surface of Mars.
JEFFREY KAYE: The air bags survived rigorous testing prior to launch. Their operation is central to a mission whose prime focus is an engineering demonstration. According to Brian Muirhead, the spacecraft's flight system manager, the scientific experiments on Mars are a secondary objective.
BRIAN MUIRHEAD, Flight System Manager: The basic mission objectives were first to demonstrate a low-cost way of delivering a science payload to the surface of Mars. That was our first or highest objective. After that, it was to demonstrate NASA's commitment to doing missions in this faster, better, cheaper approach. And then finally it's to perform the science on the surface, which is to understand the geology of the planet, the evolution of the planet, from what we can learn at this specific site we're landing at.
JEFFREY KAYE: After the landing, the air bags will deflate to reveal the pyramid-shaped lander. The lander must open properly to release a remote-controlled rover designed to wheel around and explore the Martian surface. Stolper built a model of the lander to study another potential problem. What if the thing lands the wrong way?
STEVEN STOLPER: But if we land on the wrong side, what we do is the computer selects the down most petal, and it chooses to open the down most petal, and once we reach our base petal, we open up like a flower.
DONNA SHIRLEY: And the rover is sitting on one petal, and there's a camera in the middle, and so the camera goes up on a stalk and takes pictures, in stereo and twelve different colors. Those pictures are sent by the lander back to the Earth, the rover stands up and roams around, and that's how we do the mission. Brian Cooper, who's the operator, puts on three-dimensional goggles, looks into the scene, and can see, you know, how far away the rocks are, for example.
JEFFREY KAYE: He has a driver's seat view of what the lander is seeing?
DONNA SHIRLEY: He has a driver's seat view. Exactly. And the scientists do too, because that same data is there for the scientists. So the scientists will all be crowded around the screen, arguing with each other about what rock to send the rover to, and once they decide, they say, "okay, Brian, we want that rock," and then Brian takes a mouse and with an icon of the rover, a little picture of the rover, and he puts it on that rock, and he goes "click" with the mouse, and she goes off in the direction of--she knows where she is--and she goes off in the direction from where she is to where the rock is.
JEFFREY KAYE: The 22-pound rover is powered by solar energy and batteries. It is a science lab on six wheels, equipped with a camera and an unit called an "alpha proton x-ray spectrometer." That's a sort of high tech nose, designed to analyze the composition of Martian rocks. JPL engineers have been test driving a twin version of the rover. It has been programmed to move cautiously and to climb rocks. When it gets to Mars, engineers will program the rover once a day. Because of an 11 minute delay in getting a signal to Mars, the rover has to have a mind of its own.
DONNA SHIRLEY: The rover is about as smart as a bug and, in fact, uses a control scheme based on insect behavior. But if the--if the operator were to watch the rover in real time, and the rover were heading for a cliff, the operator would say, don't fall over the cliff," because it would be ten minutes before it could say, "No, no, don't do that." So that's why the rover has to be able to take care of itself, understand that those are obstacles, go around the obstacles, and if she can't get around the obstacles, she stops and calls home. "Help, I can't get around this obstacle."
JEFFREY KAYE: The rover will also be sending back data on its own performance.
BRIAN MUIRHEAD: On mobility, on the traction, on the mechanics of the soil, to understand that future rovers can work in this environment, because that's, you know, another main reason, engineering demonstration.
JEFFREY KAYE: So again, the main mission for the rover is an engineering one.
BRIAN MUIRHEAD: Primarily, yes. The first reason the rover was put on was to do the demonstration of mobility on the surface of Mars.
JEFFREY KAYE: At another JPL test site, engineers set up a "Mars Room"-- a large sand box with a mockup of the lander and rover. Rob Manning is Pathfinder chief flight engineer.
JEFFREY KAYE: And what's the role of the lander here?
ROB MANNING, Pathfinder Chief Flight Engineer: The lander is our eyes and our main communications mechanism for--between Pasadena and Mars. All commands that we send to Mars go to the lander. The lander then communicates directly with the rover with a small antenna.
JEFFREY KAYE: The lander also has a set of instruments designed to send Martian weather reports back to earth. The Pathfinder and other Mars missions are designed to pick up where previous projects left off. In the mid 1970's, the Viking missions sent back images of volcanoes, dust storms, polar regions, canyons and valleys the size of the United States, as well as evidence of lake beds and streams. But with all that is known about Mars, the mystery remains.
DONNA SHIRLEY: Did life ever start on Mars? Because it's the only other place in the solar system that we think had a good chance of life starting. Now, we know that life is not running around easy to find because the Viking missions did not find any and they were looking very hard. And we know there are no little a green people running around. But we don't know whether there are bacteria inside the rocks.
JEFFREY KAYE: Speculation about life on Mars has been fanned by discoveries last year of organic traces in meteorites that apparently fell to Earth from Mars.
BRIAN MANNING: By knowing the composition of the rocks, we can infer their origins. And I--in fact, we're landing in an area where there's rocks from all different areas from the highlands of Mars, because we're landing in the outflow channel of a large flood. With all these varieties of rocks, we can infer a bit about the history of Mars, and in particular answer the key question, how long water was on the surface of Mars. Of course that addresses the more key question of was there life on Mars early on, and, if so, how long did it last?
JEFFREY KAYE: And that's what the big mystery is, right? What happened to the water?
BRIAN MANNING: Exactly. Exactly.
JEFFREY KAYE: If things go as planned, Pathfinder should land Friday morning at 10 Pacific Time, four hours before sunrise on Mars. Pictures should start coming back to Earth by late afternoon.
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