“Challenging But Fun”: General Dynamics C4 Systems’ Larry Brown Shares his Unique Voyager Experience

When did General Dynamics win the Voyager contract?
We won the contract back in the early 70s, when we were part of Motorola’s Government Electronics Division (GED). The Jet Propulsion Lab (JPL) in Pasadena, Calif., selected us to design and produce the MJS-77 communication subsystems. MJS stands for Mariner, Jupiter/Saturn, which was the program name until six-months prior to launch, when it was renamed Voyager. To increase the chances of a successful mission and to provide more flight options, the Voyager program required twin spacecraft — we created the communications subsystems for both Voyager 1 and Voyager 2.

What technology did General Dynamics provide and what was its primary purpose?
We provided the onboard radio equipment which was the only link between the spacecraft and Earth. If our subsystem didn’t work, then the spacecraft would be lost, so it was a very vital link.

Specifically, we designed and built the Radio Frequency Subsystem (RFS), which enables two-way communications between Earth and the spacecraft. The RFS is often referred to as the “radio assembly.” The radio assembly has transmitted still pictures of all the planets Voyager has visited, and continues to send engineering and scientific data. The radio assembly also receives commands from Earth and forwards the signals to other onboard equipment. The radio assembly transmits in both S-band and X-band frequencies, which allows mission controllers to pinpoint Voyager's location. Incidentally, Voyager was the first deep space spacecraft to use X-band as the primary telemetry link frequency. This higher frequency was needed so Voyager could send pictures from great distances.

General Dynamics C4 Systems’ MJS77 (Voyager) radio assembly.

We also provided the Modulation/Demodulation Subsystem which includes the Command Detector Unit and the Telemetry Modulation Unit. The Command Detector Unit decodes signals coming from the onboard radio assembly and sends the message to other parts of the spacecraft. The Telemetry Modulation Unit receives data from equipment on the spacecraft and puts it into the proper format to send to the on-board radio assembly, which then transmits the data back to Earth.

As the engineering project manager, what were your main responsibilities?
I was responsible for directing the design of the radio assembly during both the development and the test phases, and I was the primary interface with the customer. My job was to make sure we met the program requirements, and of course that meant meeting all budget, schedule and technical requirements. The job took approximately three years, and we met every requirement.

What were the biggest engineering challenges of this project?
Size was one of the biggest challenges — the Voyager radio assembly consists of several subsystems and each one had to be relatively small; for example the S-Band Transponder weighed about eight pounds.

Another major challenge was getting signals across millions — let alone billions — of miles without consuming great amounts of power. The radio assembly receiver can pick up a signal from Earth that’s infinitesimal — just .0000000000000000001 of a watt — that’s 10 to the minus 18th power, or a decimal point with 18 zeros after it. So you make the receiver very sensitive and the ground transmitter very powerful.

Longevity was another concern — these radio assemblies had to operate reliably in very harsh conditions for at least 12 years. There’s not much you can do to fix a radio that’s millions of miles away, and without these radios, there would be no data, no science.

In this 1970s photo, located in General Dynamics C4 Systems’ Hayden facility, employees test the Voyager radio assembly in a lab.

Another challenge, in hindsight, was the technology and tools we had to work with in the mid to early 70s — they were very primitive by today’s standards. Most engineers today have two computers at their desks. We didn’t have any computers at our desks. And our test equipment was archaic by today’s standards — today’s computerized test equipment can look at things 1,000 times more closely.

Given the tools we had to work with then, and the limitations of the relatively primitive technology, the performance of Voyager has been phenomenal and the spacecraft continues to communicate with Earth every day, sending and receiving signals through the Deep Space Network. I think it just goes to show you the reliability and durability of our designs. And I believe that’s why JPL keeps coming back to General Dynamics -- the radio assembly is the only link from the spacecraft to Earth, and they cannot afford to have it fail.

When Voyager was launched, what was your expectation in terms of how far it could go and still function?
We built the equipment to withstand the planned 12-year cruise and operate farther from Earth than any previous radio equipment. Since we had built radio assemblies for other deep space missions, I don’t think we had any doubt that it would meet the specifications of this particular mission. But to believe it would be working 30 years later? I knew our equipment could continue to function as long as there was power, but I think this has far exceeded everyone’s expectations.

Scientists predict that there’s enough nuclear power left for both Voyagers to operate up to at least 2020. And what’s amazing is that once these spacecraft get into interstellar space, that’s such a benign environment that they’ll be almost the same a billion years from now. Of course they won’t be operating in a billion years, but if a future interstellar space traveller comes upon one of them, the spacecraft will serve in another capacity — as planetary ambassadors. They each carry a 12-inch gold-plated copper disk containing sounds and images selected to portray the culture and diversity of Earth. Plus, each craft holds six aluminum plates that contain the signatures of most of the people who worked on the program, including mine.

What are some of your best memories about this program?
I recall that Voyager was a tough program — very challenging. But we had the right team, and we developed the right relationships with JPL, so at the end of the day, it was also a fun program. We had a very young team, but it was a great team. Everyone was very close. I think what made our job go so well was our team developed an excellent relationship with JPL. We were able to jointly identify problems and correct them in a timely manner. It was a true partnership, and that was very rewarding.

The signatures of all Voyager personnel were photo printed onto six aluminum plates and placed aboard both Voyager spacecraft.

What was amazing about this program is that not only did we have the right team on it, but the timing was right, too. By taking advantage of a planetary alignment that occurs about every 175 years, the Voyager was able to make this grand tour of the planets. Originally Voyager was only going to go to Jupiter and Saturn. But the alignment of the planets gave NASA the option of also going to Uranus and Nepture, and sure enough Voyager 2 did go by all of those planets. The reason it could do that was because the alignment of the planets allowed a “gravity slingshot” effect, so they didn’t need a huge engine or a huge amount of fuel. As Voyager 2 went by Jupiter, it got a big gravitational assist that sent it on to Saturn, as it passed Saturn it got a big gravity boost that sent it on Neptune, and so forth. The trajectory of Voyager 1 was such that it couldn’t get that slingshot affect, so it headed out into interstellar space.

Voyager turned out to be a very special program — definitely one of my career highlights. Generally, when you finish a program, the only thing you’re focused on is your next project. But every few years, Voyager manages to achieve another major milestone, so it’s been like winning the lottery every couple of years — and the lottery just keeps getting bigger. Voyager doesn’t let you forget about all the great things that it’s doing.

“We've landed on, orbited or flown by every planet in our solar system,” added Ron Taylor, General Dynamics C4 Systems vice president and general manager. “We delivered the first words from the moon, the first breathtaking images of Jupiter and Saturn, and the first signs of water on Mars. And today we're the first to explore the edge of interstellar space.”

Two-way communications will be maintained until the Voyagers’ nuclear power sources can no longer supply enough electrical energy to power critical subsystems. According to NASA, Voyager I and II boast enough power and communications capability to keep radioing back to Earth until 2020.

How significant was General Dynamics work on the Voyager program, from a strategic perspective?
Up to that point in time, we had provided all of the deep space transponders, or deep space radio assemblies, for JPL. If Voyager had not done well, we could have let a competitor gain a foothold.

Fortunately, Voyager was a big success and we basically have built the two-way radio assemblies for every JPL deep space mission since. Today we’re building what we now call the Small Deep Space Transponder. We’re also working with JPL to develop the next-generation radio assembly. These radio assemblies have been a core product of ours for decades, so from a strategic perspective we certainly want to keep that heritage and partnership going strong.

Voyager I radio communications equipment designed and built by General Dynamics C4 Systems enabled this first ever “family portrait” of our solar system, a mosaic consisting of 60 frames, to be transmitted back to Earth on Feb. 14, 1990. After this final look back, the cameras were turned off. (Credit: NASA)

Voyager was also strategic in that it stimulated interest to continue deep space exploration. So not only did we further establish ourselves as a leader in space communications, but we also increased the global appetite for current and future deep space missions of discovery, including the Cassini mission and others which we're supporting in a similar fashion today.

How do you feel today knowing Voyager has far exceeded mission expectations?
Voyager is probably the most scientifically productive mission ever. When the spacecraft were launched in 1977, their ambitious mission was to undertake a 12-year tour of the outer solar system. No one had an inkling that, 27 years later, Voyager 1 and Voyager 2 would remain pioneers in outer space, or that Voyager 1 would become the first man-made object to reach and explore interstellar space.

It really feels great knowing that our equipment has done its job — if it hadn’t, nobody would know much about our outer planets, much less interstellar space. Really, I guess I feel fortunate to have been a part of that team.

What other programs have you worked on over the years and how do you compare them overall with your work on Voyager?
I guess there are probably a couple of programs that fit in the same category as the Voyager program. I was one of the engineers that helped design the S-band radio assembly for the lunar rover. To know that you were a part of designing the first moon radio was pretty great. The lunar rover vehicle had our S-band radio on it, so that was the only link the astronauts had to Earth.

A medallion commemorates Larry Brown’s induction into the Space Technology Hall of Fame for his work on NASA’s Advanced Telecommunications Satellite (ACTS) program.

Another program was NASA’s Advanced Telecommunications Satellite program, (ACTS). This was a technology satellite program and we built one of the key enabling technologies — the baseband processor, which provided throughput data at something like 200 megabits per second. In the late 1990s, ACTS was selected for the Space Technology Hall of Fame. I happened to be the program manager on our part of that program, so I was also inducted.

Today I’m still working on space-related programs and ground equipment for commanding and controlling the satellites.

How different is the technology General Dynamics created from Voyager from the technology we created for recent missions of discovery?
The radios we developed for Voyager were state-of-the-art at the time, but no longer. Technology evolves quickly. With all of the advances in large scale integration, and of course the digital revolution, you can just put orders of magnitude more functions and capabilities in the same 10 pound box today.

What’s it like knowing something you touched is now the first manmade object to touch interstellar space?
It’s remarkable to know that, as part of the Voyager team, we’ve accomplished something nobody else on Earth has ever done. I’m very proud of what the Voyager program has accomplished and expect there’s much more to come. It’s just a great feeling.

To learn more, go to http://www.nasa.gov/vision/universe/solarsystem/voyager_agu.html.

For more information on the Voyager missions, go to: http://voyager.jpl.nasa.gov/.