Hello. So thanks for having me. I want to tell you about the incredible work that the three teams you see on the screen here have done. We have the Voyager flight team, an Anomaly Team that helped us

resolve the anomaly that happened on the flight data subsystem, and the Deep Space Network, the

set of antennas we use to track our spacecraft. The biggest question you may have is, what is a

mission assurance manager? I have the best job in the whole world. Whenever anything goes wrong with

an instrument or spacecraft, I get to jump in and help solve the problem. In addition, I'm kind of

the independent reviewer. You can all imagine back when you were younger, you would get together with

your friends, you would have this great idea, and it goes terribly wrong. That happens to engineers

and professionals at all levels. So my job is to be the adult in the room and make sure we don't

have issues. So to get started, I want to tell you a little bit about the mission so you understand

why it's so important to us. And it is very important to us. The Voyager was launched in 1977.

They were designed to explore the outer planets, especially Jupiter and Saturn. They got to all

four of them. Voyager 2 reaching Uranus and Neptune. And it changed the way we thought about planetary

science. The heliosphere is a bubble that surrounds the sun. We're in the heliosphere. It's

far out, even beyond the planets' orbits. The idea was that Voyager would move beyond the planets,

sample the outer heliosphere and make it into outer space. Because nobody knew if there was a boundary or how far it was. That was our goal in 1990. Today we've crossed that boundary and we're in interstellar space.

And I think this might be our most important dataset we'll ever collect. Nobody is going to be here again for decades, perhaps longer. These two spacecraft are deep in interstellar space, giving us information that's critically important.

Why? Because, as you can see in the upper corner there, other stars have heliospheres as well. They're called astrospheres.

So an astronomer can collect those photons and make an interpretation of what they're seeing. But it's really valuable to have the actual understanding of what that interstellar space might be like, that those shock waves are interacting with. So it gives astronomers ground truth in terms of interpreting things like this.

The other thing you can see here is that... This is some data from one of our instruments. This is the plasma wave subsystem.

What it does is it collects electromagnetic information, frequencies, against time. Which we heard about earlier today. The PWS actually collects plasma waves. Plasmas are ions and electrons that are embedded in a magnetic field.

When that situation happens, those particles will exhibit wave-like characteristics. So this instrument is designed to find those. All those dark splotches are actually the... What happens when a coronal mass ejection, the things that cause errors on Earth -- those propagate

for years and when they hit the heliosphere, Voyager was hearing the eruptions from the sun outside the heliopause. Which is really cool. Nobody expected that.

And you can see this line. There's a thin line that goes out. That thin line represents the primary plasma frequency and

That gives us density. So this is just one example of the amazing science that these instruments are still providing. Excuse me. So this is a map of essentially where we were and where we are.

This is in astronomical units, on the x-axis, on the bottom. An astronomical unit is the distance between the Earth and the sun, or about eight light minutes. You can see we're well out there, out from the sun.

And this is the ecliptic latitude, how far north or south we are. If you look at the tiles, one of those is an AU. Voyager is about as far away as this patio is across.

The distance between Earth and Mars is about that far. So the Voyagers are extremely far away. Oh, actually, you'll see the blue boundary there is also where we crossed into interstellar space.

So it was much further out than most astronomers thought. So these are the instruments: we have a magnetometer, the plasma wave subsystem.

They use these antennas, on a boom, to keep them away from the spacecraft. The PWS is these whip antennas. This is a 13-meter boom. These are not little spacecraft.

This is a 3-meter across antenna, and we have particle instruments, the cosmic ray subsystem, looking at high-energy particles, and plasma instruments.

So those are the instruments that are still active on our spacecraft. Let's talk about our spacecraft status. We are 15 billion miles away for Voyager 1.

I'm going to talk mostly about Voyager 1. That's what we're here to talk about. Our light time...

is 22.5 hours away. That's how long it takes to get a command to our spacecraft. To get a round-trip response, it's 45 hours. Basically, we get contact with our spacecraft after we do something two days later.

This diagram in the upper corner shows you Voyager 1 and Voyager 2 crossing outside the heliopause. It's another graphic. I like it, because it shows that we're actually moving out through the nose of the heliopause.

In other words, just by dumb luck, we ended up leaving the solar system in the direction the sun was going. The Voyagers are no longer gravitationally bound to the sun.

They're actually orbiting the center of the galaxy, and have a 200-million-year period, 3 AU per year faster than the solar system. Imagine a candle.

You can see the light from it. You can feel the heat. So all that energy, if you collect it, take that and divide it by 6, so 1/6 of a candle, that's 13 watts of energy.

So a 70-meter station, the large dish over on the far right, that station, 70 meters across, can detect that signal and pull 160 bits per second out of it.

Three 34-meter stations arrayed together can also perform that feat. So that's essentially how we collect data. The spacecraft is always broadcasting.

We can track it as often as we can get these antennas. We can actually go up to 1.2 kilobits per second, and that's how we got the data I showed earlier.

And it still works great. That data comes down only when we can array all of the stations.

So this picture happened earlier this year. This is the first time we arrayed all six antennas. We

usually have only five in the array. So we're working to try and get more and more antennas,

because we're getting out towards the limit of this 1.2 kilobits per second. We don't have a safe

mode. Many spacecraft play it safe when something goes wrong. They shut things down and stop doing

things. Voyager just resets its processes, picks up the pieces and goes. It has very robust

aggressive fault protection. We have 94 years of experience with our flight systems between the two spacecraft; about 12 people working on the spacecraft now. Many of them are part-time. That's

a lot of spacecraft for a very small number of people. And then our big problem that we're dealing with

is power and thermal these days. We launched with enough plutonium to power the spacecraft. It has

a half-life of 88 years. This is a picture of the fuel cladding. When they're fresh, they glow red hot,

embedded in little cans that stick off Voyager, and there are thermocouples around them. They generate

electricity based on the heat difference between the interior and the exterior. We're down to about

as much power as a box fan or rice cooker at this point, for those big spacecraft, which is pretty

incredible. We also just started operating them with unregulated voltages. We realized we could go

off the voltage regulator and keep the instruments powered, which is the reason we're there. That was

kind of a scary moment for us, but it worked well.
So far, so good. Generally, we have to take action

within a year or less, all the time, because
of our power and thermal constraints. The less

power we have, of course we risk undervolting
our spacecraft, and power is also dissipated,

so we have thermal issues. We may freeze our
lines. We'll talk about that a little more. This

is a functional block diagram of our spacecraft.
You can see Voyager 1 looks good. Red are things

that failed and black are powered off because of
power. We have gold items that are just degraded

subsystems. We all wished our appliances
worked this well after 47 years. I'll point

out... This right here... This is the flight data
subsystem. We're going to be talking a lot about

that. You'll notice it's a very thin line going
down into the telemetry modulation unit. And

then down into the radio subsystem down there. So
this is the path we're going to talk about. The path

from the flight data computer to the telemetry
modulation unit to the radio. Just quickly,

speaking of things that are wrong, to keep our
spacecraft operating, we have to make changes all

the time. And it's getting more and more frequent.
Back in the early part of the last decade, it was

not a big deal. We had things happen occasionally
that we had to adjust to. More and more now,

we're having to take steps to either keep
from losing an instrument, avoid degradation, or actually prevent the loss of our spacecraft. So
it's getting tougher to fly these with our small

team. All right. This is what you guys came to hear. Computers and the anomaly. So we have three

very cool computers on the Voyager spacecraft. And there are two of each type, for redundancy. These

are humanity's oldest continuously operating computers. I think it's important to remember that. As you hear about them. These are the first reprogrammable deep-space flight computers. They

operate without microprocessors. And each has its own JPL-constructed assembly language. So the CCS

is basically responsible for issuing commands for the spacecraft. It's a Viking machine, essentially. The Viking landers and orbiters used a computer of this type. It's an 18-bit interrupt-

driven processor, constructed out of transistors. It's TTL logic. We actually use some RC logic on

some of our subsystems, but this is a fancy TTL machine. It has 4,000 words of plated-wire memory.

You can look that up on the internet. It reminds me of Rebecca's talk on weaving. You store data by

putting a small magnetic field into the wires. And it works great after all these years. Our

attitude control subsystem, used to control the attitude and pointing of our spacecraft. It's a

very similar machine. It has an extra board that they used to make sure there was enough speed

to manage the attitude of the spacecraft. These two are basically alike. Voyager -- the command

computer system, we actually use both processors, because we're short on memory. So finally, the one

that matters to us is over on the far side. That's the FDS. So this was added because

during the planning for the mission, they realized that when Voyager flew through a planetary system,

It was going to overwhelm the spacecraft data system. All this data coming in, in under a day, essentially.

They didn't think these computers could handle it. So they built a CMOS machine. And it has

8,000 words of memory. And this was put on board, basically to make sure that we could process all

that data. This is a very important computer for us, because it basically commands the instruments.

It collects and formats all of our science and engineering telemetry, and it provides all of our

timing information. So... What happened? And how did we figure it out? So back in November of last

year, we had a normal pass come up, but we had no telemetry. So telemetry is basically processed by

taking -- looking for a frame marker, saying this is a packet of data, and we're going to decode it,

and look at what it says. We were not getting those frame markers. And the only good thing was

we had a carrier signal. Otherwise, we would have been really scared. So we could see the carrier,

but it was not being modulated. The deep space tracking network, all the antennas were working,

but we were seeing a constant stream of ones and zeros. There were no telemetry frame markers. There was no visibility on our spacecraft. Voyager will drift back and forth

and we can see the variation over a few hours. We could see the radio frequencies -- in the

next few days we could see we could command the spacecraft, but that was it. This is kind of like

Saving Voyager 1! - Bruce Waggoner at !!Con 2024

!!Con

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