Retelling the Story:

"Architecting the Deep Space Network (DSN): Why We Set It up the Way We
Did"

by Eberhardt Rechtin

Thursday, August 25, 2000

Retold by Claire Marie-Peterson with Teresa Bailey and Eberhardt Rechtin

This was not my first experience with JPL Stories, so I knew to arrive
at the library early for the 4 p.m. start of the fifth installment in
the series: "Architecting the Deep Space Network (DSN): Why We Set It up
the Way We Did," presented by Eberhardt Recthin, identified on the
announcement flyer as "the 'father' of the Deep Space Network." When I
arrived with my cup of spearmint tea at 3:50, the room was already half
full and buzzing with conversation. This was the place to be that
Thursday afternoon for what turned out to be 100 to 120 JPLers grey,
green, and everything in between. "Is that Tom Vrebolovich?" someone
asked, as a lanky grey-haired fellow with an enormous agate tie clasp
took a seat near the front. "He must have retired twenty years ago."

On a display board behind the storyteller's chair a series of vintage
black-and-white photographs portrayed an earnest young man in tweed and
bow tie---drawing on a blackboard, conferring with colleagues, and
otherwise looking every inch the aspiring engineer of the post-World War
II era. Just to the right, leaning against the circulation desk, was a
monumental, framed watercolor of a scene recognizable to the untrained
eye as the Goldstone, California station of the DSN. Soon enough, the
storyteller himself stood at the front of the room---a bespectacled, tan
gentleman with fine, wavy, white hair, his mouth still turned down
earnestly at the corners. He was dressed, it occurred to me afterwards,
like a live oak---his shirt the familiar dark, brownish green that
dominates many a Pasadena vista, his slacks a tree-trunk tan.

Teresa Bailey, head of the storytelling team at the library, introduced
the speaker. The watercolor, we heard, was a gift to JPL from Dr.
Rechtin, who had received it from the Caltech Management Association
with their Excellence in Management Award---one of many professional
honors conferred upon him in the course of his illustrious career---or
rather, careers.

Most recently, he was Professor of Engineering at the University of
Southern California, where he established a graduate program in system
architecture that gave him occasion to teach many current JPLers who had
been enrolled in the program over the years---a group well-represented
in present company, I sensed, from grunts of recognition throughout the
talk. Before that, Dr. Rechtin was CEO of Aerospace Corporation from
1977 to 1987, Chief Engineer at Hewlett-Packard from 1973 to 1977, and a
high-ranking member of the Department of Defense from 1967 to 1973. But
his story today would center on his first career, the one that began at
JPL in 1948, while he was still working on his Ph.D. at Caltech, and
extended to 1967, by which time he had become an Assistant Lab Director.
In the years in between, Teresa told us, "he had invented much of the
early technology for deep space communications and developed the Deep
Space Network architecture. This is why we know him today as the father
of the DSN. In an oral history interview, Dr. Rechtin acknowledged his
most influential Caltech professor and mentor---and later his boss---was
Dr. William Pickering, JPL Laboratory Director from 1954-1976. He is,"
Teresa said, "certainly one of the major branches---if not roots---of
our JPL family tree."

When Dr. Rechtin took the floor, he played down the remarkable breadth
of his professional experience. His many careers, he said, showed that
there was indeed life after JPL---though it wasn't nearly as good. He
delivered such lines with perfect deadpan seriousness---his earnest
mouth erupting into brilliant white with the audience's response. He was
at ease in the role of storyteller, immediately contradicting what we
may have read in books about the Deep Space Network. It began in 1952,
he calmly stated, not 1958, as the history books would have it. And as
the chief (though not the only) architect of the DSN, he should know. In
1948, he was hired as a regular JPL employee, a Caltech Ph.D. under his
belt, one of "Pickering's boys." By 1952, the Korean War was on, and the
task of the moment was to design a jam-resistant radio guidance system
for communicating with Army/JPL missiles. It was this task that led to
the development of "Phase-Locked Loops," which in turn led to Microlock,
the Space Ground Link Subsystem (SGLS), the first Coded Doppler Radar
and Command system (CODORAC), the Unified S-Band system (USB), the World
Wide Network, the Deep Space Instrumentation Facility, and ultimately
the system of interplanetary radio guidance that we now know as the Deep
Space Network.

No, I did not get all of those systems and their respective acronyms
down in my notes. Although I did take copious notes throughout the
story, I did so knowing that I would have access to Dr. Rechtin's own
notes for the retelling of it. Although greying, I am rather green as a
JPLer, after all, and my own Ph.D. is in English, not Engineering. What
follows, then, is primarily in Dr. Rechtin's own voice, from his own
notes, with some elaboration and emphasis added from the live event.

Techniques available for radio guidance in the early 50s were all based
on AM or FM---both highly jammable---or on narrow-band channels with a
"low Q" ("Has anyone here even heard of Q?" Rechtin asked, getting some
nods). We needed something different, something not so wide open to
jamming, particularly for Doppler-producing high-velocity missiles. Then
it occurred to us: how much information is there in a missile trajectory
after all---100 bits? Why, then, would we want to use then-current
multikilocycle AM or FM bandwidths? The bandwidths we would need would
be a thousand times smaller than what AM or FM typically used. On the
basis of some information theory and thermodynamics, we concluded that
what we needed was to build closed-loop feedback systems based on
tracking the rapidly changing carrier signal---hence the term "phase
lock."

With only a smidgen of understanding of thermodynamics, we leaped to the
later validated conclusion that "noise," our greatest barrier to
success, was thermodynamic in nature and that trying to find a signal in
noise was chasing the wrong objective. Why not try to drive the noise
level down, first, say, by using very cool receivers and looking outward
into space instead of across or down into a 300-degree earth?

Better yet, why not *use* noise as a signal, Claude Shannon style (as we
learned through a Frank Lehan visit there. Indeed, MIT Lincoln Lab was
doing just that in a much different application)? Hence
"pseudonoise"---a digitally created, absolutely determinate,
near-statistical signal using "pseudo"-noise that we produced for both
the transmitter and receiver ourselves. With that we had all the
essential technology necessary not only for anti-jamming of radio-guided
missiles, but for what, about six years later, became the DSN.

Without really trying to, we had completely redefined radio guidance and
telecommunications. For these purposes, we had made obsolete such
concepts as AM, FM, PM, "Q," noise figure, "hum," and even fixed
bandwidths. We added "coded" signals to the vocabulary, the underlying
trick to Coded Division Multiple Access (CDMA), the Global Positioning
System (GPS), and multiple use of one channel for many signals. We
communicated "beneath" the noise. We converted "static" to processed
interference. In the process, we converted the infamous "Yellow
Peril"---a mathematical treatise hundreds of pages long, authored by
Norbert Wiener and published with a yellow cover---into a three-line
proof useable for the average Caltech Electrical Engineer.

In 1955, years before JPL was transferred to NASA (without funds,
incidentally), we in Walt Victor\'s CODORAC had nailed down all the
essential signal processing techniques needed for interplanetary
communications nailed.

But deep space would require still more. It would also need a different
kind of ground antenna than had ever been built before --- larger, much
more precise, much more robust, and much higher frequency. Walt Higa,
Bob Stevens, and Bill Merrick not only built the unprecedented DSN
antennas, they built them better, under cost, and on time against the
unforgiving schedules of the planets. They rewrote the antenna design
book to include aerodynamics (not just aerodynamic statics).

The other remaining obstacle, potentially a showstopper for precision
orbit determination and guidance technology, was the inherent
(uncalibrated) velocity of light in space. Without knowing the velocity
of light to better than one part in a million---as Nobel prize winners
(in other fields) cheerily pointed out---we could never get close enough
to the planets to be any more useful than a ground-based radio
telescope. "You guys are just plain nuts," they would say. We would need
at least a factor of a million or more

So, in a move that became characteristic of the DSN research, we
inverted the problem. Instead of finding out how far away a planet was
in meters by using light from the planet and angle measurements, we
would measure *time* instead and then guide our spacecraft there by
measuring time *differences* between the time it took for a radar to
measure the distance to an object and to a spacecraft approaching that
object. It is an inherent property of guidance radars that they measure
time differences very accurately, regardless of the absolute distance to
the target. As we responded to our critics, we didn\'t care if space
were molasses, we could still guide our spacecraft to the planets, once
we had measured \"radar time\" to Venus. In the process of doing
research, we dispensed with angle measurements entirely, and we very
precisely (one part in 10 to the 15^th^) calibrated the Astronomical
Unit (the average distance between the Earth and the Sun). All this well
before MIT, the Russians and the British agreed that their claims to
have detected Venus were shown to be untrue.

The special, errorless, technique we had used to send infinitely long
pseudonoise signals that could be \"cracked\" at any time needed. Our
critics had said, "You'd have to be geniuses to make that work." But of
course we were (the audience concurred, perhaps counting themselves in).
So what was the big deal? This concept of using pseudonoise and time
differences was critical to GPS. An important recognition in due course
came from the National Academy of Engineering when it at different time
elected seven of us to membership based on this work from that time at
JPL and what followed from it.

One would think that with all this obviously brilliant thinking, all we
would need from here on out was a bit of "engineering" and, lo and
behold, there would be a Deep Space Network.

The first wake-up call was that the many technologies needed to build,
operate, and analyze the performance of spacecraft were yet to be
developed. And that would take decades, literally. But the general
public wasn't about to wait decades for a response to SPUTNIK. Results
*now. Beat the Russians now!* was the order of the day. And the DSN
couldn't just perform once; it had to keep working. We could not fail.
"We will not fail first" became our motto, because if we did, nobody
would know what happened thereafter. We could only fail last. In
practical terms, the name of *this* game was steady, planable, and
*enormous* improvements with time. Unlike many networks, we were not
trying to take a single snapshot success. We were about to start (from
behind) a race into space that would take at least thirty to forty years
before anyone could claim to have "won." The DSN would have to design
for continually expanding needs for decades to come. And this is exactly
what happened. But it was no happenstance by lucky, if admittedly
brilliant people, many of whom are here today.

As part of the original plan (or architecture as we might call it today)
we asked NASA for 10% of the annual DSN budget from there on out to fund
the DSN research and development. Our model, I am the first to agree,
was the Bell Labs. We adapted it because it worked. The DSN was (and is)
not one more project, but an evolving, living thing. That's why
contracting out the management of the DSN and its research is a flat-out
mistake. Contractors are at their best in doing fixed work to a fixed
time for a pre-negotiated profit. No contract can capture all the
requirements needed for evolving continuously at a predictable rate for
decades into the future.

The process of contracting forces both parties to lock in performance
cost and schedule that need to change and keep changing far into the
future. From the first, we understood that we would need to be able to
predict, ten to twelve years ahead, with an uncertainty of plus-or-minus
less than one decibel (ten percent, roughly), exactly how well the DSN
would deliver the goods to as-yet-undefined projects ten to twelve years
in their futures---and keep doing it day after day, month after months
indefinitely. I think you can see the direct analogy with the now
defunct Bell Labs when they had to do exactly the same think for the
now-fractured At&T.

Why for us, in particular? To deliver either more or less than promised
would have been equally damaging. The difference, in each direction,
would have to be compensated for by basic design changes in the
spacecraft. Three decibels meant doubling the affected parts of the
design: power, weight, solar panel size, data rates, and so on. Further,
not only would it take years for the spacecraft to reach the planets
once launched, the basic design parameters would have had to been frozen
a decade before that! Hence the justly-famous "Mathison charts" designed
and built 40 years ago by the then recently-retired Dick Mathison.

But all this was in the future back in 1958 when the basic
structure---what I like to call the "architecture"---of the DSN was
being established. This statement begs the question of how to define
"architecture."

At this point, Dr. Rechtin pointed to an overhead transparency
(reproduced below) listing the features of that architecture. Every item
on that list was essential, he began. It's an "architecture" because it
all fits together in an interdependent way. You can't just start
crossing things off without changing the rest of the
tightly-interconnected parts---and hence the overall performance.

**The Architecture of the Deep Space Network (and Why)**

*UNIQUE PURPOSES*

[Communicate and Command]{.smallcaps} to the edge of the solar system

[Navigate]{.smallcaps} to the edge of the solar system

[Serve]{.smallcaps} all comers: NASA and other countries

[Supply]{.smallcaps} centralized flight operations facility for all
projects

*DESIGN*

Continuous reception and transmission

Plan for the decades

Very low-temperature receivers

Very quiet signal frequencies

Phase modulation of signals

Pseudonoise coding and reception

210-ft diameter, all conditions, antennas

Plan for \<10\' diameter spacecraft antennas

Plan for low-power (10-W) transmissions only

*MANAGEMENT*

By JPL DSN and NASA Office of Tracking and Data Acquisition (OTDA) for
all comers

Stable R&D by JPL DSN for decades

Continuing prototypes using operational facilities

Interplanetary radar and radio science

20-yr amortization of all facilities

4-year amortization of all electronics

Technical journal with signed reports therein

We recognized early that the only way to accomplish all this would be
with remarkable, extraordinarily dedicated people. You didn't come to
JPL for the pay (he said, to knowing smiles from the audience). Since we
couldn't pay people enough for what we were demanding of them, we
acknowledged them by publishing their work in a technical journal (the
last item on the slide), *The DSN Report*. Unlike most standard practice
in large, "team" organizations, the practice in the DSM had to be that
the person who actually did the work should be the one who signs its
reports---not the overseeing manage, professor or supervisor.

To accomplish the "Unique Purposes" listed at the top of the
slide---communicate and command to the edge of the solar system;
navigate to the edge of the solar system; serve all comers, NASA and
other countries; and supply a centralized flight operations facility for
all projects---we set up a series of 210-foot antenna stations around
the globe, each station completely staffed by the hosting country. We
wanted people worldwide to know that *they* had built the DSN. Here our
model was a typical international airline, the early TWA in particular.

Speaking of the Management issues on the slide, Dr. Rechtin said he was
a firm believer in ten-year plans. The predictions for 1958-1968, which
he wrote, proved to be good, he said, except where management was
concerned.

The DSN has sometimes been faulted for not doing space radar research.
(Yet we did and for very good reason---it was and is essential for our
mission.) But, how could we do what needed to be done while contending
against a specific law that NASA was not allowed to do ground-based
research? (As I understand it, the law was demanded by those with an
interest in protecting their own interests against the newcomer, NASA.)
When you broke you could get thrown in the clink. But to measure
planetary atmospheres and so forth, we needed to do just that! The
solution? We used operational gear designed for intensive future use,
modifying it as needed for our present research purposes (and, of course
vice versa but only at very low cost).

And then there was costing. "Costing," Dr. Rechtin pronounced, "means
absolutely nothing." (Here he is at least consistent. The same idea
appears in his published literature.) He related an anecdote about a
congressional staffer who came to his office wanting to know the exact
cost of the DSN for the Explorer Project. "Pick a number between zero
and infinity" was his reply. There are so many variables involved---how
many years the DSN will be in operation, how many missions will use
which equipment, how *much* each mission will use it, and over how many
years---that it is impossible to put a price tag on it. Evidently the
response was satisfactory, it never happened again. Even so, Dr. Rechtin
said, "I soon had a reputation for always having money." Part of that
comes from his belief that there is no such thing as cutting reasonable
costs, only redistributing them.

Back to the slide which never left the screen throughout the story
telling.

That slide, he said, of the slide he was just then removing from the
projector, is what we hoped and architected for the DSN into the
indefinite future. This, he said, as he put up the slide reproduced
below, is what seems to have happened in the 40+ years since.

**The Architecture of the Deep Space Network (Now)**

*~~UNIQUE~~ PURPOSES*

[Communicate]{.smallcaps} to the edge of the solar system

[Navigate]{.smallcaps} to the edge of the solar system

~~[Serve]{.smallcaps} all comers: NASA and other countries~~

~~[Supply]{.smallcaps} centralized flight operations facility for all
projects~~

*DESIGN*

~~Continuous reception and transmission~~

~~Plan for the decades~~

Very low-temperature receivers

Very quiet signal frequencies

Phase modulation of signals

Pseudonoise coding and reception

210-ft diameter, full coverage, ground antennas

Plan for \<10\' diameter spacecraft antennas

Plan for low-power (10-W) transmissions only

*MANAGEMENT*

~~By JPL DSN for all comers~~

~~Stable R&D by JPL DSN for decades~~

Continuing prototypes using operational facilities

~~Interplanetary radar and radio science~~

~~20-yr amortization of all facilities~~

~~4 year amortization of all electronics~~

Technical journal with signed reports therein

Pointing to the losses represented by the strikethrough type above, Dr.
Rechtin first and intensely regretted that the DSN's purposes are no
longer unique. The French and Italians now have their own systems for
exploring Mars. A big cost associated with recent "faster, better,
cheaper" policies, he said, is that we no longer serve the whole
world--- we have lost the monopoly over deep space communications that
we had held for over forty years. Low-orbit satellite relays around Mars
cannot provide continuous reception and transmission. They can't listen
continuously, so you very seldom know what's happening on the far side
of a planet. And because of the loss of monopoly, we can no longer plan
reliably for the decades. Reluctantly climbing onto what he admitted to
be his "hobby horse", Dr. Rechtin openly lamented that JPL no longer
managed, much less architected the DSN.

On a more positive note, however, he put up a third transparency
(below), listing all of the unplanned and unexpected accomplishments of
the DSN over the years---calibrating the Astronomical Unit, for
instance, as mentioned above, and rescuing legally dead spacecraft by
reprogramming them in space---essentially teaching them to "change their
minds" mid-mission! These and other such bonuses have been as welcome as
unexpected.

**Unplanned and Unexpected Accomplishments**

Calibration of the Astronomical Unit

Emergency spacecraft operations

Near-simultaneous US/Soviet service

Very close timing of Block IV implementation

In-flight network upgrades

Multiple (and higher) operating frequencies

Addition of special purpose ground antennas

Arrays of antennas for signal enhancement

Use of extremely stable clocks for new spacecraft capabilities

Determination of characteristics and composition of planetary
atmospheres

Precision determination of intraplanetary system orbits

Color pictures of planets and their moons

Finally, Dr. Rechtin wrapped up with the slide below, detailing the
glowing assessment of the DSN by highly honored Caltech scientist Lee
Dubridge (Caltech President during the development of the DSN, and
subsequently Science Advisor to President Nixon). In Dubridge's
assessment, the DSN is "the sole development that made the in situ
exploration of the solar system possible."

**Lee Dubridge's Assessment of the Role of the DSN**

The DSN is the sole development that made the in situ exploration of the

solar system possible.

Sensitivity: a factor of a million

Reliability: never failed a mission in 30 years

Precision: a factor of a million

Timeliness: never late

Cost: on budget every year to within l%; met every target cost for
antennas, operations

Predictability: within l dB ten years or more in advance; l0-year plans

Research and development: maser, antenna design, communications
parameters, uncrackable codes; quick cracking of "infinitely long"
pseudonoise strings

Deliberately dropped certain lines of research: angle measurements,
laser transmission through space, ionospheric transmission

Encouraged and funded other critical lines of research:

Higa and Townes, Golomb, Welch, etc.

50 years of technical journal signed research

The audience was invited to ask questions, many of which centered on
strategic thinking for the exploration of the planets. One heady
discussion concerned the prospect of sending geosynchronous relay
satellites to Mars (maybe funded by Hughes, Direct TV, or---why
not?---Mars Bars) so that spacecraft exploring the planet wouldn't have
to turn to Earth every time they wanted to communicate. They would only
have to communicate with these satellites.

It was a discussion that no one wanted to end. Indeed, it continued for
some time well after Teresa officially closed this session of the JPL
Stories by presenting Dr. Rechtin with a small, crystal globe that has
become the customary gift for recognizing the jewels of insight brought
to us by our storytellers.

**A postscript**

In his notes, Dr. Rechtin concludes with a meditation---implicit in his
story, though mostly unspoken---on insight, architecture, and the
relationship between them. It seems fitting to end this story *about*
the story by giving him the last word.

"Architecture" (he begins) is a strange and wonderful thing, and has
been since its initiation by the Egyptians 5000 years ago. Architects
are less interested in what's elegant than in what works. Architecting
is driven by purpose; that is, answers to the questions of why you want
to build this thing at all and with what. Such questions are not easy to
answer. The answers change with time, circumstance, and stakeholders.
Engineers might attempt to create a systems architecture by the classic
paradigm: generate options and optimize to get the best. In many cases,
this works. But where did the options come from, and what does "best"
mean to a diverse group of stakeholders? The answer may surprise some of
you: By insight.

As one such insight goes, "A picture may be worth a thousand words, but
an insight is worth a thousand analyses."

**Resources for Further Exploration:**

Deep Space Network Home Page:

<http://eis-fil-www03.jpl.nasa.gov/deepspace/dsn/index.html>

Deep Space Network Brochure:

<http://deepspace.jpl.nasa.gov/dsn/brochure/index.html>

IEEE Oral History Interview of Eberhardt Rechtin by Frederick Nebeker:

<http://swww2.ieee.org/organizations/history_center/oral_histories/transcripts/rechtin.html>