WWV Moves to Colorado - Part II
February 1967 QST Article
is the second of a two-part series on the move of the WWV transmitter
stations operated by the National Bureau of Standards (now called National
Institute of Standards and Technology) from Greenbelt, Maryland, to
WWV Part I
appeared in the January 1967 edition of the ARRL's QST magazine.
WWV began transmitting time / frequency standards in 1920 in order to
provide a means for remote stations and laboratories to calibrate local
standards that would prevent transmitting stations from interfering
with each other. Although most people don't realize it, the 60 kHz
signal that their 'atomic' clocks and watches use to self-adjust time
emanates from the WWVB antenna in Boulder. The first installment of
the article discusses the history and rationale for relocating the WWV
facility to a new location. This second part gets into the technical
aspects of the WWV facility's equipment and operation. As usual, I am
amazed at the pioneers who conceived of, designed, and implemented these
kinds of operations.
February 1967 QST
of Contents]These articles are scanned and OCRed from old editions of the
ARRL's QST magazine. Here is a list of the
QST articles I have already posted. All copyrights are hereby acknowledged.
Note: I wrote a short
a couple years ago.
See all available
vintage QST articles.
WWV Moves to Colorado
In Two Parts: Part II
By Yardley Beers, W0EXS
earliest function of WWV was to transmit standard carrier frequencies
to provide frequency calibrations so that radio stations could stay
on their assigned frequencies and avoid mutual interference, and to
allow persons having receiving sets and wavemeters or frequency meters
to calibrate them. Indeed, it is this feature of the broadcasts which
is of chief interest to amateurs today. However, in the course of history
the usefulness has been greatly increased by superimposing time markers
and other information by a suitable program of modulation. In addition,
mainly because of the needs of stations used for tracking of rockets
and space vehicles, the present accuracy is far in excess of that required
for the original purpose. However, for the moment, we shall confine
our remarks to this original function.
Quite clearly, if the
objective of avoiding interference between stations on adjacent channels
is to be accomplished, all frequency measurements must be coordinated:
that is, they must be referred to a single standard. Similar reasoning
holds for countless other physical quantities: length, force, speed,
voltage, current, resistance, power, to name a few. However, most of
these are not independent. They may be related by definition. For example,
if one measures the time necessary for an object to travel some previously-measured
distance, he can determine the speed. Or they may be related by physical
laws. For example, if a known current flows through a wire of known
resistance, the voltage drop between its ends, as measured by a voltmeter,
must agree with that computed by Ohm's Law.
Thus, to digress for a moment, we are led to the concept that all the
physical measurements within the U.S.A. form the National Measurement
System. This System is involved in essentially all activities of commercial
and private life. It makes it possible to assure a housewife that when
she pays for a pound of meat in a Denver supermarket she will receive
the same amount of meat as when she shopped at her former market in
Chicago. It makes it possible for the piston of an automobile motor
made in Detroit to give proper performance when used in a cylinder block
made in New Jersey. This System is something far greater than the National
Bureau of Standards, but the Congress has given the Bureau the responsibility
of providing "the basis for accurate and consistent measurements": that
is, for providing standards and for leading the coordination of measurements
within the System.
Sadami Katahara, KH6DK, engineer-in-charge, makes adjustment to
frequency control equipment at WWVH.
Richard F. Carle K0LYM, engineer-in-charge of WWVB-WWVL, with some
of the frequency control equipment of that station.
Fig. 1. Accuracy of WWV broadcasts as a function of time. Solid
curve gives accuracy of the transmitted signal. Dashed curve gives
accuracy of received signal at about 1,000 miles from transmitter.
Degradation of accuracy is due to propagation effects. See text
for information on present accuracy.
However, the coordination is not solely confined
to measurements within the U.S.A. Frequency measurements must be consistent
with those outside if international QRM is to be avoided, and manufactured
goods on the international market must have specifications given in
units which are internationally significant. Therefore, NBS is further
given the responsibility of making international comparisons. As part
of its coordinating role, NBS must participate in the standardizing
of the units and definitions of quantities. As the result of the recommendations
of international committees to which NBS is a party, NBS has adopted
for its own use the hertz as the unit of frequency, and it is encouraging
others to do the same. For this reason, this unit is used in this article.
In the hierarchy of measurements, "frequency" and the very closely-associated
quantity "time" collectively play a very important and unique role.
It has been stated above that the measurements of many quantities are
interrelated. In fact, the interrelations are so numerous that it can
be shown that the system of measurements of physical quantities is based
upon the units of just four quantities; frequency-time is one of these,
the others being length, mass, and temperature. Also, it is the only
unit for which the user can obtain instantaneously a virtually direct
calibration against the NBS Standard in his laboratory, factory, or
home. For this latter reason, there is an effort to convert measurements
of other quantities into measurements of frequency by the use of suitable
Fundamental Considerations of Time and
If the reader is to appreciate fully the significance
of the WWV broadcasts, it is necessary to review some fundamental concepts.
The measurements of both time interval and frequency are based upon
some physical phenomenon which ideally is perfectly repetitive - or
which, if not exactly repetitive, is accurately predictable, such as
the oscillations of a piano string, the motion of a pendulum, or the
electrical oscillations of a resonant circuit composed of an inductor
and capacitor. Until recently, the most accurately-predictable repetitive
phenomenon available was the revolution of the moon around the earth
(although the results are generally expressed in terms of the time-equivalent
motions of the earth about the sun). Until recently all measurements
of time and frequency have been referred to this. However, it is now
generally believed that the electromagnetic radiation emitted by atoms
and molecules is much more uniform, and that there is no physical reason
to suppose that there should be any variation provided the atoms are
either isolated or maintained under constant environmental conditions.
Therefore, the best present standards of time and frequency are based
upon these atomic radiations. Measurements of the motions of the earth
and moon referred to them reveal nonuniformities in these motions which
are quite trivial from the human point of view but which, scientifically
speaking, are very significant.
A standard frequency is determined
by the number of cycles of the reference phenomenon per second of time.
Conversely, if one counts the number of cycles of standard frequency
which occur between two events, he can ascertain the time interval between
those events. Thus, a clock consists of (a) a physical configuration
which gives rise to a repetitive phenomenon and (b) a device which counts
oscillations. When one is counting the intervals between large numbers
of events, it is convenient to refer measurements to one particular
event, which is said to define the "epoch" of a time scale. For example,
when we speak of the year 1966 A.D., we are speaking of a time scale
for which the epoch is defined by the birth of Christ, and we are referring
to some event occurring 1966 years later, approximately.
unit of time used by scientists is the second, and at present this has
two different definitions. One of these, called the "Ephemeris" second,
is based upon astronomical measurements, and we shall not give the details
here. The other, the "atomic" second, is the time interval required
for exactly, 9,192,631,770 cycles of the radiation absorbed or emitted
by a certain transition of isolated cesium atoms. This last statement
is equivalent to saying that, by definition, the frequency of this radiation
is exactly 9,192,631,770 hertz. These two definitions of the second
are consistent; that is, if one were to refer any given time-interval
measurement either to appropriate astronomical observations or to the
cesium atom, he would obtain essentially the same result for the first
several digits, but he would find the measurements relative to the cesium
atom to be more precise: that is, more of the digits in his answer would
be meaningful. Furthermore, if one has the proper apparatus, measurements
relative to the cesium atom can be carried out much more conveniently
than the astronomical ones. Mainly for the first of these two reasons,
atomic measurements are preferred for accurate scientific work.
Frequency and time are the primary business of WWV, and the physical
facilities described in Part I of this article exist solely for
the dissemination of highly accurate information about these two
quantities. The article concludes with a description of the basic
standards used for this purpose, how they are used to control the
transmitters, a brief history of WWV and a description of the NBS
organizational setup that is responsible.
At the present, two types of time scales have been established for people
who have need for accurate time measurements. One of these is Atomic
Time, which does progress uniformly, in principle. The other is Universal
Time, which progresses in synchronism with the slightly-irregular rotation
of the earth; this is required for earth navigation. To generate Universal
Time from Atomic Time, it is necessary to compensate for the irregularities
of rotation. The most widely-used type of compensation involves a combination
of (a) offsetting the frequency of the oscillator in the clock by an
amount determined by the International Time Bureau in Paris and (b)
by making occasional step adjustments of 0.1 second, as determined by
the International Time Bureau in consultation with astronomical observatories
all over the world. At present, the frequency offset is three parts
in a hundred million lower than specified by the definition of the second,
an amount much too small to be noticeable by radio amateurs and many
others, but large enough to be important to those who track satellites.
This offset is held constant within any calendar year, but frequently
it has been necessary to change it from year to year. Therefore, many
people feel it would be better to eliminate offsets completely and use
only step adjustments, even though there would be a few more of them.
This subject received considerable attention at the 1966 meeting of
the CCIR (International Consultative Committee on Radio) in Oslo, and
as a result of agreements made there, the use of offsets, which has
been mandatory in standard-frequency transmissions on certain frequencies,
is now optional. It is likely that in the near future many standard
frequency transmissions will eliminate them.
At the present time,
however, the frequencies of WWV, WWVH, and WWVL are offset, and their
time signals are on the so-called NBS-UA Time Scale, which is generated
by an atomic standard but which is compensated by the offset and by
step adjustments to agree with Universal Time within about 0.1 sec.
On the other hand, 60 kHz is not one of the frequencies covered by this
international agreement, and at the present time the frequency of WWVB
is not offset; the time is broadcast in accordance with the so-called
Stepped Atomic Time Scale (SAT), which uses 0.2 sec. step adjustments
only to keep within approximately 0.1 sec. of Universal Time. The offset
and step adjustments of the NBS-UA Scale are determined by the International
Time Bureau on the basis of data supplied from many sources. Step adjustments
of the SAT Scale are determined by NBS on the basis of data supplied
by the U.S. Naval Observatory. When a step adjustment is made on either
scale, it is made at the beginning of a month and announced in advance
in the Federal Register and in publications of the IEEE.
WWV, WWVH, and WWVL broadcast time on one scale and WWVB on another,
Universal Time on either scale can be obtained from any broadcast by
means of corrections partly coded in the broadcasts. The details of
how this can be done, and much other information concerning the broadcasts,
can be obtained from a booklet.1
Accuracy of NBS Broadcasts
The first broadcasting conducted
by NBS, in 1920, was on an experimental basis in order to gain technical
competence. For a brief time entertainment and market reports were transmitted
for the Department of Agriculture. Although speech and music were transmitted,
code was used for the reports. After a short time, this work was discontinued.
It should be noted, however, that these broadcasts preceded the much
more publicized pioneering broadcasts of KDKA.2
standard frequency broadcasts from WWV started on March 6, 1923, with
the station originally located upon the grounds of NBS in Washington.
(Some previous experimental tests had shown that wavemeters owned by
some of the listeners were off by as much as seven percent!) Originally
transmissions took place only a few hours a day, and spot frequencies
were transmitted in accordance with a previously announced schedule.
These frequencies ranged from below the a.m. broadcast band to considerably
After a brief interlude in College Park, Maryland, the
station was moved in 1932 to a site near the now-discontinued station
in Greenbelt, Maryland. In 1931 essentially continuous operation on
5 MHz was initiated and, while oscillators using quartz crystals had
been used for reference for some time previously, at that time the frequency
of the station became directly crystal controlled. Operation on various
spot frequencies continued as before for a time, but it tapered off
while continuous operation on 2.5 MHz and on integral multiples of 5
MHz were gradually added to the service. On November 6, 1940, the station
was demolished by fire. By ingenuity and hard work, a new station was
improvised and put on the air within a few days. On August 1, 1943,
the station went on the air with improved "permanent" facilities in
Greenbelt. In 1948, similar broadcasts were initiated from WWVH in Maui,
Hawaii on some of the same frequencies (at present 2.5, 5, 10, and 15
The accuracy of the carrier frequencies of these broadcasts,
as to be expected, increased with time by many orders of magnitude,
as indicated by the solid curve of Fig. 1, which gives the accuracy
of the ground-wave signal. This improvement was due to the innovation
of improved reference standards and control methods, as noted on the
figure. At present, the accuracy is of the order of a few parts in a
million million (1012), and the control system is so good
that this closely approaches the accuracy of the NBS Atomic Standard.
It is, of course, far in excess of that needed by radio amateurs and
other services for keeping their transmitters on assigned frequencies.
If an amateur can measure a 50-MHz signal with an accuracy to 50Hz,
he would probably consider that his accuracy is far greater than he
needs. Yet this would be only one part in a million (106).
Needs for other transmitting services are hardly any greater; only the
tracking of satellites and pure science require this extreme accuracy.
It is to be noted that a spectacular increase in accuracy resulted
from the introduction of the use of a cesium atomic standard. The cesium
atoms give a resonance which corresponds to a Q of about 100 to 1000
million, which exceeds that obtainable from quartz crystals and is far
in excess of that obtainable from inductors and capacitors. Also, the
cesium standard is far less vulnerable to environmental effects such
as changes in temperature. At present, NBS and many other laboratories
are continually improving atomic standards and investigating other types,
such as the hydrogen maser, which many people feel is superior to the
cesium standard. It is amusing to note that the quartz-controlled oscillator
has passed from something which was avante garde for a primary standard
to something which is a consumer item, as contained in walkie-talkies
that can be purchased at many corner drugstores.
Unfortunately, the accuracy of the signal from WWV as received at some
distant point, typically 1,000 miles away, is considerably poorer than
that of the transmitted signal. This is indicated by the dashed curve
in Fig. 1. This deterioration of accuracy is due to Doppler shifts resulting
from motion of the ionosphere. The horizontal slope of the latter portion
of this curve indicates that the accuracy of the received signals is
ultimately limited by this effect. For distant users the present frequency
control of the station is far better than it need be.
The NBS cesium beam atomic frequency standard NBS-with C. J. Snider
(left) and D.J. Glaze, W0YVZ
Howard E. Michel, Jr., K0BPY, checks the standing wave ratio
of the 15 MHz transmitter before turning on the power of the 10
kw. transmitter connected to the dummy load equipment shown here.
other hand, there are special users who require these high accuracies,
and many of them are located at large distances. To satisfy their needs,
other methods had to be sought. One method is to use radio stations
with much lower frequencies, where propagation errors are far less serious.
This approach led to the establishment of WWVB and WWVL. Another approach
is physically to carry high-quality quartz clocks and small atomic clocks
from NBS and other reference laboratories to field sites. NBS and other
organizations are presently engaged in such an activity on a limited
The establishment of WWVB and WWVL was indirectly assisted
by the move of the principal radio work and some of the low temperature
work of NBS from Washington to new laboratories at Boulder, Colorado,
the home of the University of Colorado, during 1951-1954. At about that
time the standards work and propagation work were separated organizationally
into the Radio Standards Laboratory (RSL) and the Central Radio Propagation
A principal purpose of the move
was to provide access to better sites for propagation studies, and in
due time experimental standard-frequency transmissions with low power
were commenced on 60 kHz from the Boulder site and on 20 kHz with an
antenna strung across Sunset Canyon, a few miles to the west. It was
shown that propagation errors at distances up to 2,000 miles were negligible
at 60 kHz. The 20-kHz transmission gives poorer accuracy at these distances,
but at distances above 2,000 miles its errors are less than those of
60 kHz. However, should the accuracy of the frequency standards improve
by another factor of 10 greater than they are today, it is almost certain
that propagation errors at these two frequencies will tend to limit
the accuracy of the received signals, and the carrying of clocks will
play an even more important role.
As the result of the success
of this experimental work, the present stations WWVB and WWVL were constructed
on a site approximately seven miles north of Fort Collins, Colorado,
which is known as the home of Colorado State University. NASA provided
the funds and sponsored the WWVL facility, and is the main potential
user of its signals for synchronizing distant satellite stations. This
site provided a large area of flat land of very high conductivity, which
aided in improving the antenna efficiencies at these lower frequencies.
Also, it was far enough away from Boulder (56 miles) to avoid serious
interference to propagation studies from the high-powered transmitters.
The question arises: Why was it necessary to rebuild WWV if these
lower frequency transmissions give greater accuracy? The answer is that
it is a matter of convenience. This article is concerned with WWV, and
it would be inappropriate to give a long discussion of the details of
the construction of WWVB and WWVL and the methods of using their signals.
It suffices to say that most commonly-available receivers cannot receive
them at all, and if their signals are to be fully utilized, special
and rather expensive receivers are required. The users who need the
full accuracy, such as NASA, are very important but are few in number,
and are of a type that usually can afford these special receivers. On
the other hand, WWV and WWVH can be received on sets which are generally
available either without modification or by the addition of a very simple
converter. The number of users whose needs can be met with the accuracy
of WWV, using simple receivers, is very large. Amateurs, of course,
are in this group. Therefore, it is considered justified to maintain
and improve the service offered to this larger group.
Modulation of WWV
Originally the WWV transmissions
provided only standard radio frequencies, with the principal purpose
of making it possible for radio stations to stay on their legally assigned
frequencies. In 1935, the service was augmented by modulation of the
carrier to provide time pulses at one second intervals and standard
musical pitch. Later, other information - such as time, time-scale corrections,
and propagation warnings - was added to the modulation program, as described
in detail in Reference 1. Incidentally, signals from WWV and WWVH may
be partially distinguished, even though they are on the same carrier
frequencies, because the station announcements are staggered and they
have different silent periods (15 to 19 minutes after the hour for WWVH
and 45 to 49 minutes after the hour for WWV). Propagation forecasts
(mainly relevant to North Atlantic paths) are given only by WWV, and
are given after each station announcement at five-minute intervals.
They consist of a letter ("N" for normal, "U" for unsettled, and "W"
for disturbed) and a number from one to nine to indicate the quality.
Audio tones of 440 and 600 Hz are transmitted on the schedule contained
in Reference 1, where one can also find explanations of other features
which are of less interest to most amateurs.
of Time and Frequency
The administration of WWV is
related to the manner in which the frequency of the station is controlled.
Administratively, the station comes under the jurisdiction of the Radio
Standards Physics Division, which, with a full-time staff of slightly
more than 100 people, is one of the two technical divisions of the Radio
Standards Laboratory. About one-half of the Division's staff, distributed
among three sections, is devoted to time and frequency matters (the
other three sections deal with radio materials, quantum electronics,
The Atomic Time and Frequency Section, headed by
Dr. James A. Barnes, has the responsibility of operating the NBS Atomic
Frequency Standards. The standard in use is a particular cesium atomic
beam built by NBS and referred to as "NBS III." However, the cesium
beam standard is a passive device, and the present one is not designed
to give automatic calibrations twenty-four hours a day. Therefore, the
Section also operates continuously five very stable oscillators, some
controlled by quartz crystals and the others stabilized by atomic resonances.
The frequencies of these oscillators are continuously compared with
each other, and the data are recorded automatically. Also, once each
working day they are compared to NBS III. The output of one of the five
oscillators is fed to a correction device consisting of a driven phase
shifter. The rate of drive of the phase shifter is adjusted to (a) make
output frequency correspond to the average of the five oscillators (or,
automatically, to the average of four of them if the fifth one is in
serious disagreement) and (b) to correct for the average drift through
aging of the oscillators. The output of this correcting device is referred
to as the Drift Controlled Oscillator (DCO), and this serves as the
basis for the NBS time scales and for the control of the radio stations.
Connected to the DCO is also a device for producing the frequency offset
required by the NBS-UA Time Scale. Connected to these oscillators and
other circuits are a number of devices which count cycles and thus become
clocks for telling time on both the NBS-UA and NBS-A Time Scales. Originally
the epoch of the NBS-A Scale, which, unlike the Stepped Atomic Time
Scale (SAT) broadcast by WWVB, has never had any step adjustments, coincided
with that of UT on approximately January 1, 1958. At the present time,
NBS-UA, which has been adjusted to keep within close synchronization
with the rotation of the earth, lags NBS-A by about five seconds due
to the irregular motion of the earth, which during the immediate past
has been slowing down.
Besides routine operation and maintenance
of these devices, the Atomic Time and Frequency Section also does fundamental
research and development of atomic frequency standards, and it possesses
several others of various types, partly for backup for NBS III and partly
for research purposes. An important part of this research is the study
of very-low-frequency noise. Additional important work on atomic frequency
standards is also carried out in the Quantum Electronics Section, headed
by Dr. Donald A. Jennings.
Control of the Radio Stations
The NBS radio stations administratively are part of the Frequency
and Time Broadcast Services Section, of which Mr. David H. Andrews is
Chief. The headquarters of the Section is in Boulder.
are controlled by a system which makes direct reference to the NBS standards
in Boulder, and at the same time provides each station with high-quality
oscillators so that it can preserve a high approximation of synchronization
with the NBS III in case the control link fails for a time. Furthermore,
each station (counting WWVB-WWVL as one station for this purpose) is
equipped with three oscillators. On the assumption that it is unlikely
that more than one oscillator will fail or be in serious error at one
time, it is assumed that should one disagree with the other two, those
two can be considered as being correct. The new Fort Collins WWV has
three new commercially-manufactured cesium-controlled oscillators.
The new WWV is located in a new building about one-quarter mile
away from the building housing the WWVB-WWVL transmitters, but the two
stations are integrally interconnected so that one person can monitor
all of the transmitters on the site and observe and correct any equipment
that malfunctions. Furthermore, although the WWV and WWVB-WWVL frequency-control
systems are nominally independent, in the event of failure of one of
them, switches can be thrown to allow the remaining operating system
to control all transmitters. Also contained in the Fort Collins complex
are spare devices for generating frequency offsets.
with the NBS standards in Boulder is accomplished by the use of some
monitoring receivers located in Boulder and operated continuously. The
received signals are compared to a signal supplied from the DCO in the
Atomic Time and Frequency Standards Section, as mentioned above. Electronic
circuits determine the sign and magnitude of any frequency error, and
these control the modulation of a 49.85-MHz transmitter which transmits
the corrections to receivers at Fort Collins. Demodulating circuits
connected to these receivers generate correction voltages which are
applied to the oscillators that control the transmitters. Thus, the
system forms a closed-loop electronic servo, which not only corrects
for drifts in the oscillator, but also for changes in phase resulting
from swaying of the antennas in the wind. Incidentally, local v.h.f.
amateurs regularly use the signal from the 49.85-MHz transmitter to
check their 50-MHz receivers. However, in the near future the 49.85-MHz
link may be replaced by a microwave system.
Control of WWVH is
accomplished primarily by monitoring the WWVB and WWVL signals and correcting
the oscillators. A check upon the time synchronization is made occasionally
by carrying portable clocks, partly by NBS personnel and partly by others.
It is the aim of Mr. Andrews to have at least four clock-carrying trips
made to WWVH each year.
The Frequency and Time Dissemination
Section, headed by Mr. A.H. Morgan, does research on new ways of transmitting
frequency and, especially, time calibrations - for example, by the use
of satellites and the use of VHF meteor-scatter propagation. It studies
propagation errors for correction of the WWVB and WWVL signals. It operates
a number of receivers for monitoring both NBS and some non-NBS standard
frequency broadcasts. Comparisons are continually made between the NBS
standards and those elsewhere, both in the U.S.A. and in foreign countries.
The theoretical group in the Division Office, headed by Dr. George
E. Hudson, also has made important contributions to the time and frequency
program through representing the Division on important committees such
as the CCIR, in analyzing data, and in aiding in the determination of
frequency offsets and step adjustments.
As stated previously, Mr. David H. Andrews is Chief
of the section which administers the new station, and Mr. Peter P. Viezbicke
is the engineer in charge of the design and construction of the new
station. Mr. R.S. Gray served as an assistant to Mr. Viezbicke during
early construction. Mr. John B. Milton is in charge of the design of
the frequency-control system of the new station.
The writer could
not have prepared this article without the help of many individuals,
especially many of those mentioned in the article, in supplying information
and checking the manuscript for correctness. He is also indebted to
Mr. Hugh J. Stewart for help in obtaining the photographs; to Mr. Eldred
C. Wolzien for correcting the historical portions; and to Mmes. Donna
Stolt and Eddyce Helfrich for typing and editing.
last few months of operation of the Greenbelt station, it was necessary
to have extra staff in order to man both the old and new stations. During
this period, much of the manpower at Greenbelt was supplied under contract
with the Philco Corporation by a staff headed by Mr. W.M. Swartz.
NBS Miscellaneous Publication 236, "NBS Standard Frequency and Time
Services" (1966 Edition). For sale by Superintendent of Documents, U.S.
Government Printing Office. Washington, D.C., 20402 - Price 15 cents.
2 "Measures for Progress - A History of the National
Bureau of Standards, U.S. Department of Commerce, 1966.
3 In October, 1965, the organizational separation was made much
more complete when CRPL, although not moved geographically, was removed
from the jurisdiction of the National Bureau of Standards completely
and joined to a new agency of the Department of Commerce called the
Environmental Science Services Administration (ESSA). At that time CRPL
was renamed the Institute for Telecommunication Sciences and Aeronomy
(ITSA). It was joined by other organizations, either removed to Boulder
from elsewhere or newly created, to form the Institutes of Environmental
Research (IER) which is a major unit of ESSA.
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