Planetary Radio: Space Exploration, Astronomy and Science - Saving Voyager

Episode Date: May 30, 2005

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Will Voyager be saved? This week on Planetary Radio. Hi everyone. Welcome back to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. A lot of people were shocked to learn that the next NASA budget had no funds to continue the missions of Voyagers 1 and 2. One of those people was former JPL director Ed Stone.

We'll talk to the chief scientist for the Voyager interstellar mission on today's show. Yet another JPL director drops by during What's Up just to make Bruce Betts nervous, but our boy still manages to give away a couple of solar sail posters. Speaking of the solar sail, it leads our modest but wholesome review of space news this week. Cosmos 1 has successfully reached the Russian Navy base at Severomorsk, where it will soon be put in place atop a Volna submarine-launched rocket. Liftoff is still scheduled for mid to late June, with regular updates and background information available at planetary.org.

While you're there, you can check out Emily Lakdawalla's update on Cassini. While the spacecraft's cameras can't quite make out the individual particles making up Saturn's rings, scientists have now used its radio transmissions to determine the ring's fine structure. Not surprisingly, there are some surprises. Shuttle Discovery has been rolled back into the Vehicle Assembly Building for the switch out of external fuel tanks. This precautionary move will delay NASA's return to flight plans. And while it may not exactly require a correction, we do want to add something to last week's discussion of the solar sail. As a couple of listeners pointed out, there is a private,

non-profit organization that has been putting satellites in orbit since 1961. Lots of satellites. since 1961. Lots of satellites. It's the Radio Amateur Satellite Association, or AMSAT, along with an earlier group of, uh, hams. We call ourselves a travel show. Emily picks up on that theme as she helps us decide which world is the best vacation value, Venus or Mars. Start packing. I'll be right back with Ed Stone. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, Which is more like Earth, Venus or Mars? There are various geological and physical reasons why you might make the argument that Venus is more Earth-like, but for the casual tourist, Mars would be most like the Earth.

There are some problems with traveling to Mars. You'd have to protect yourself against the cold temperatures, but during the day, near the equator, the temperature does rise above zero and and we can deal with that weather. And, of course, the air on Mars is not breathable, so spacesuits are in order. Probably the scariest environmental hazard on Mars is the lack of protection from the sun's ultraviolet and higher energy rays. Long-term human presence on Mars will have to wait until we develop a way to protect our DNA from damage by the sun. But a tourist could take a short trip to Mars and see largely familiar types of terrain. Spectacular canyons, mountain ranges, polar

glaciers, and dry deserts lit by a sun that rises and sets on an Earth-like schedule. What about taking a trip to Venus? Stay tuned to Planetary Radio to find out more. We still look in awe at the magnificent images returned by Voyagers 1 and 2 as they made their grand tours of the outer solar system. Their achievements at Jupiter and Saturn were not equaled until the Galileo and Cassini orbiters, and no other spacecraft have visited Uranus and Neptune. Now, just as they reach another unprecedented achievement, there may not be enough money to keep the lights on. Dr. Ed Stone is chief scientist for the Voyager Interstellar Mission, as it is now called. The former director of the Jet Propulsion Lab is a Caltech professor of physics

and vice provost for special projects at the campus that operates JPL for NASA. He has been with the mission for an incredible 33 years and is now leading the effort to restore a few million dollars that will keep these spacecraft operating at the edge of our solar system and beyond. Stone has found reason for hope with the arrival of new NASA Administrator Michael Griffin, but the fight isn't over yet. We talked in a Caltech conference room a few days ago. Ed, for years now, you've been looking forward to your spacecraft meeting this thing called the termination shock,

and suddenly it seems to have taken on an entire new meaning. Well, I guess you're talking about the possibility that funding would not continue for Voyager, and that would certainly be the termination of the mission. But I'm hoping that that will not actually happen, that we will, in fact, continue our journey to interstellar space. that we will, in fact, continue our journey to interstellar space. I guess it was in December, mid-December, that you were able to determine that Voyager 1, at least, had reached a tremendous milestone. Yes. On December 16th, Voyager 1 crossed from the supersonic solar wind, which is where it's been and where all the planets are,

into a new region of the heliosphere, the bubble around the sun, a region where the solar wind is piling up as it presses outward against the interstellar wind. This is where sort of forces are balanced between the wind coming from other stars and our own solar wind? The termination shock is because the wind from the sun, which creates the bubble, is supersonic, it doesn't know that anything is out there until it goes through a sonic shock and slows down. And so we're now in the region where the wind can feel and react to what is outside, and that's called the heliosheath. It's a region where the wind is slower, thicker, and hotter than it has been for the last 27 years of our journey.

And when we talk about hot, you mean really hot. Yes, it's very hot there. It's about a million degrees now. But on the other hand, the number of atoms or ions in a cubic meter, a cubic yard, is only hundreds. So, in fact, it's a better vacuum than anything here on Earth. And the spacecraft is totally unaware that anything has happened. It's always fascinating to me when you can talk about vacuum that is that hard, having material in it that is zooming along at hundreds of thousands of miles per hour and at hundreds of thousands of degrees.

It certainly is a fascinating place to be gathering data. It is, and we are really exploring now the final frontier of the solar system. It's Voyager's last lap now on its journey, its race, basically, to interstellar space. And Voyager 1 is headed toward something called the bow shock, which I guess could almost be thought of as if the solar system were a boat forcing its way through the interstellar medium. Yes, this bubble, which we call the heliosphere that the sun creates, is, in fact, moving through the interstellar medium. As a result, there's a wind, and it turns out we're

very fortunate the two spacecraft are headed upwind the shortest way out of the bubble. And in front of the bubble, there will be a bow shock, just as there is in a stream when there's a rock in a stream, you'll see a small bow shock in front of the rock. Well, we are in fact, in a sense, a rock in the interstellar wind stream. And we haven't been there before. This is a first in our solar system. How do we know so much about the structure? And actually, we don't know that much, I guess.

That's why we want to continue receiving data from Voyager. The idea of a sphere around an astrosphere around a star was really first proposed many years ago when the solar wind was first hypothesized by a theorist called Gene Parker. And he realized that this wind, this supersonic wind, million-mile-per-hour wind, would create a bubble around the sun, and also similar bubbles would be created around other stars. And the Hubble telescope, in fact, has given us images of astrospheres and the bow shock in front of astrospheres around stars in the Orion Nebula.

Where all those beautiful pictures come back from Hubble, another mission that...