The Pioneers, 1973-1979, Page 2

Robert McMillan

I started here in July of ’79, and preparations were made for the encounter of Pioneer 11 with Saturn. By September, I was up there at NASA Ames, in the Mountain View, California area, to help run the instrument, the imaging photopolarimeter that Tom Gehrels had developed on the Pioneer spacecraft. Because I was single and unattached, they gave me the graveyard shift, midnight to 8am, because they needed people there 24 hours a day to help run the instrument—send the commands up to the instrument and watch the data coming back.

It was a long roundtrip time. I think it was about three hours roundtrip, a big travel time between the commands and response. That was one of the most exciting things I ever did in my career, actually being in that big control room and watching the data come down on the consoles.

The most exciting moment of that mission was the ring-plane crossing. You have to realize at that time there wasn’t that much knowledge about the Saturn system. Even though the Pioneer spacecraft was passing Saturn at a distance that was beyond the boundaries of the known rings, we didn’t know what sort of particles would still be in those rings that hadn’t been visible from Earth. The issue was whether the spacecraft would be destroyed at that instant, as it passed through the ring plane.

This was not only important for the survival of the spacecraft itself and the continuity of the mission, it was also important for the upcoming Voyager encounters with Saturn, because they wanted to know how close they could get. I think, in fact, it had to do with whether they would be able to deflect the spacecraft off to go to Uranus afterwards and so on.

So there was a lot at stake in this ring-plane crossing. We had this big electronic clock up in front of the room, showing the Earth-received time of the carrier wave signal from the spacecraft, and they were counting down on that to see if the spacecraft would survive. Of course, if the spacecraft had been destroyed there would have been just a complete loss of signal.

During that countdown, we—at least I—forgot that I was sitting at Ames and really felt more like we were there with the spacecraft. We were the ones going through the ring plane and trying to decide if we were going to survive or not. So this countdown, watching for this continuity of the signal, was really a pretty exciting moment.

Harold Larson

The first pictures of Jupiter and Saturn were better than what could be done from the ground, but not that better. It wasn’t like we were seeing pictures for the first time. What we were seeing for the first time were spectra that told us what things were made out of, not how things looked. To me more of the excitement was in the spectroscopy, which the public didn’t take to very well—that’s too long a word. But the awareness of what things were made out of, in a scientific sense, eclipsed how things just looked.

But NASA had to put a camera on every mission to take pictures, because the public likes pictures. To this day pictures are still revealing the newer worlds out there, the things that we never had a chance of studying in detail.

Martin Tomasko

The first image of Titan was actually made by Pioneer, not by Voyager. I remember staying up the night before, trying to plan the sequence, and trying to make sure that Titan was in the frame. Of course Titan’s atmosphere was filled with these photochemically-produced aerosols, and we couldn’t see anything on the surface. But it was clear that Titan was an interesting object.

Since then Voyager did great imaging. I was involved in Cassini-Huygens, so that was a thread in my career that was going to go on for a lot longer than I realized at the time. But it was an exciting time, to see these first pictures of objects that had only been specks of light in the sky. I came here with a degree in astronomy. These things were all space astronomy; they were little specks of light in the sky. You couldn’t resolve that Titan is one arc-second across, it’s just a speck of light, and the game was how much can you learn about the physical situation on this object from the light that you get back to the Earth.

But now of course we’ve been to most of these places, in orbit around them, or with entry probes going through them. They’re geophysical places now. We know what they look like; we know what the ground looks like; we know a fair amount about them. So there’s been an evolution over the last couple of decades from points of light in the sky to real places.