national Bureau of Standards

-^ Library. N.W. Bldg

SEP 9 1963

^eckniccil riotc 92c. f26

MUTUAL INTERFERENCE BETWEEN

SURFACE AND SATELLITE COMMUNICATION SYSTEMS

WILLIAM I. HARTMAN AND MARTIN T. DECKER

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS

technical ^Ttote f26

August 1, 1963

MUTUAL INTERFERENCE BETWEEN

SURFACE AND SATELLITE COMMUNICATION SYSTEMS

(November, 1961]

by

William J. Hartman and Martin T. Decker

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington, D.C. 20402 Price 35 cents

TABLE OF CONTENTS

Page No.

1. INTRODUCTION 1

2. TRANSMISSION LOSS 2

3. VARIABILITY 7

4. RESULTS 11

5. EXAMPLES 12

5. 1 Example 1 13

5, 2 Example 2 . ,_ 15

6. CONCLUSIONS 16

7. REFERENCES 18

MUTUAL INTERFERENCE BETWEEN

SURFACE AND SATELLITE COMMUNICATION SYSTEMS

William J. Hartman and Martin T. Decker

Estimates of the mutual interference expected to

occur between the ground terminals of space communi - cations systems and surface point-to-point systems are

presented in a fashion suitable for engineering applications.

These estimates are obtained from recently developed

methods for predicting the transmission loss over

tropospheric paths in terms of parameters such as

geographic separation, elevation angle of the antenna,

antenna patterns, and frequency. It is concluded that

these systems can share the same frequency assignment under sioitable conditions.

1. INTRODUCTION

Many problems of mutual interference between proposed

satellite communication systems and surface communication systems

can be investigated in terms of available theories. The primary

purpose of this paper is to predict the conditions under which a service will be interference -free for a given percent of the time.

The prediction methods that are developed are intended to have a wide range of applicability. Examples are used to illustrate the

use of the method for specific systems.

In general, the effects of an interfering signal must be

determined for each system. Tolerable interference will depend

not only on the relative levels of the desired and unde sired signals,

but also on the type of modulation used in both signals. In most

* This work was sponsored by the Joint Technical Advisory

Committee of E.I, A. and I. R. E.
cases it must be determined experimentally, in some cases subjectively (for example, subjective rating of television pictures).

Further, neither desired nor interfering signals will be steady signals, but will be subject to fading; hence the ratio of desired to

interfering signal will be represented by a distribution of values.

Because of this, satisfactory operation should usually be specified

in terms of an hourly median desired signal to an hourly median

undesired signal ratio required to provide a given grade of service

or better for some percentage of the hours. A further discussion

of this problem is given by Norton [ 1959 ]

. However, in view of the

many unknowns, the problem has been somewhat simplified for the

purposes of this paper by simply relating the hourly median interfering signal to the noise power of the receiver under consideration.

Thus, the question answered here is: What separation distances and

antenna elevation angles are required so that the interfering hourly

median signals are equal to or less than the receiver noise power

for a given percent of the hours ? All of the calculations in this paper are presented with the

following assumptions: (1) The main beam of the ground terminal

antennas will not be pointed below about 5 above the horizon,

because of the increased atmospheric absorption and antenna noise

from ground reflections [Pierce and Kompfner, 1959 ]; and (2) the

frequency band most suitable for space communication systems is

the band from about 1 Gc/ s, (thousand million c/ s), to above 10 Gc/ s [Haydon, I960].

The use of a particular value or assumption will be justified

where necessary and possible. In cases where the state-of-the-art

limits the ability to predict with accuracy, values will be used that

will predict the larger interference.
2. TRANSMISSION LOSS

The usual concept of transmission loss [Norton, 1959;

Rice, Longley, and Norton, 1959 ] will be used here to predict the

mutual interference between surface systems and space communication systems. The median transmission loss in decibels,

L = 10 1og_. P /P , (I)

10 r a

is given in terms of the ratio of the power radiated from the transmitting antenna, P , to the available power at the receiving antenna,

P . No distinction will be made here between system loss and

a transmission loss. The method used to predict L is a modification

of the method published by Rice, et al.[ 1959 ]

, which makes use of

basic median transmission loss,

L =L + G , (2) b p

where G is the path antenna gain in decibels. The loss L that is

predicted here is the hourly median for typical winter afternoon

hours. Variation for other times of the year will be discussed in a later section.

As a point of reference, we first calculate the basic median

transmission loss for various frequencies and distances over a smooth

spherical earth. This gives the loss expected if nondirectional

isotropic radiators are used at both the transmitter and receiver.

If care is taken in locating the interfering systenas, the assumption

of a smooth earth will correspond to a lower path loss, and therefore to potentially more interference than would be encountered over

a rough earth. L is shown in figure 1 plotted versus distance

(or angle). The npiinimum distance shown here is 100 miles. At
distances of less than 100 nniles, diffraction beconnes mo-re important

and eventually becomes dominant. This can be calculated using the

methods given by Rice, et al, [ 1959 ]

For the purposes of calculation, it has been assumed that the

receiver antenna beam is being tilted upward through an angle i|j

(see figure 2) in the great-circle plane determined by the location of

the transmitting antenna, T, and receiving antenna, R. This

designation of T and R is not a restriction on the problem, however, because the reciprocity theorem holds for tropospheric propagation. In order to reduce the number of parameters, it has been

assumed that the antennas are 30 feet above a smooth spherical

earth. The results will not be essentially different for antenna

heights up to 60 feet when the antenna is tilted 5 or more above the

horizon. Varying this height will change a (see figure 2), the

angle between the line connecting transmitter and receiver, TR, and

the horizon ray from the transmitter in the great-circle plane; and

will change (3 , the angle between TR and the horizon ray from the

receiver, also in the great-circle plane. The change and, hence,

the total effect will be small. The main and side lobe of both transmitter and receiver beams will be centered about the great-circle

plane; for the miinimum values of a and (3 , the main beams of

o o the antennas will be centered on their respective horizons.

The path antenna gain, G , is given in terms of the freespace gains of the transnnitter and receiver,

where G is the loss in antenna gain [Hartman and Wilkerson, 1959]

Here, parabolic dishes are assumed for the calculation of G . HowP

ever, since the parameter used for predicting G is actually the

half-power beamwidth, and since the calculations are not done using

k
the entire antenna pattern, but only one part (such as the main lobe

or one side lobe), the calculations can be used for arbitrary patterns

that have the same half -power beamwidths. (The method actually

restricts the patterns to be symmetric although good approximations

can be made for asymmetric patterns. ) Figures 3 through 23 show the transmission loss for the combinations of antennas shown in table 1.

TABLE 1

Transmitter Receiver Transmitter Receiver

10' dish 60' dish 10' dish 6' dish

6' dish 60' dish 6' dish 6' dish

Isotropic 60' dish Isotropic 6' dish

Table 2 gives, for frequencies of 1, 2, 6. 5, and 10 Gc/ s, the gain

in decibels above an isotropic antenna; the half -power beamwidths;

and, for the 60-foot dish, the location of the first and second side

lobes relative to the main beam axis.

The antenna pattern assumed here will consist of the main

beam, one side lobe, and the remaining portion of the pattern

isotropic. However, this may be modified to conform to an actual

antenna pattern by adding the contributions from additional side

lobes. For the assumed pattern the total power available at the

receiver will be approximately

P; = P^(io-L'/ (4) '° + 10-L^ ^ 1% lo-'^'

/

'°)

or in terms of transmission loss,

L' = -10 log^^ (lO-^-^ '° + 10-^^ ' '° + 10-^'^ '") . (5)
o f^ -^

— .H O O L. vDO LT)

00

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+->

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•M Vl h4 f-t 0}o

•iH (U

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>-^

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CO C^ CO c> CO o cy^ CO c> CO t^ CO

CVJ 1 0)

4-i

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CO t—

^ ro f\a '^ CO (M in -* CO nO '^ ^ «

<:H

(-> * o

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>^ 00 c^ o CJN 00 c 1 ^ t^ o o o t . s o o o d o o CO 00 d (M* fvj d —-' fM 1—

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ffi CQ u

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no*
where Lj is the transmission loss for the main beam, L2 is the

transmission loss for the side lobe, and L3 is the transmission loss

for an isotropic antenna. (In a given antenna, L3 may be above or below an isotropic antenna by 10 or even 20 db. The exact amount

depends on the design and construction of the specific antenna. ) The

loss for a beam with several side lobes could be accounted for in

the same way. Considering only one side lobe, this loss could have

a variety of forms, two of which will be discussed here. Assuming

that the side lobe is 20 db down from the main beam^the side lobe

could be a broader beam, like that of a 6 -foot dish compared to a 60-foot dish with the same power, or it could have the same halfpower beamwidth with less power. The former case is covered by

the curves for the 6 -foot dish; the latter case is covered by adding

20 db to the transmission loss curves for the 60-foot dish.

It will become apparent later in the paper that the use in

these examples of a 60-foot dish at the receiver is not a critical

assumption, and that the conclusions reached concerning the interference will not be changed significantly if the 60-foot dish is replaced by a 30-foot dish or by a 120-foot dish. However, the use of

a 10-foot dish at the transmitter does place some limitations on the

types of systems that can be assumed.

The curves shown in figure 24 (transmission loss versus

frequency for 100 and 350 miles) have been prepared to show only

the effect of frequency by using a constant beamwidth of 5 mr at the

receiver end and an isotropic antenna at the transmitter end. This

corresponds approximately to a 240-foot dish at 1 Gc/ s and to a 24-foot dish at 10 Gc/ s.

3. VARIABILITY

The values of transmission loss described in section 2, and

shown in figures 3 through 23, are median values of hourly medians

7
for typical winter afternoons. In order to account for the variability

of the hourly medians frona this median value, empirically derived

curves from Rice, et al. [ 1959 ] are used. These curves, shown in

figure 25, are the best available estimates of the variability, although

most of the data from which these were derived are for frequencies

below 1 Gc/s and for broad-beamed antennas. However, the trend

in the data indicates that the largest variability occurs near 400 Mc/ s and decreases with frequency to 1 Gc/ s. In general, it is expected

that the variability will be less for the frequencies frona 1 Gc/ s to

10 Gc/ s than is indicated on these curves. The largest variability

in these curves occurs at about 10 mr, which is approximately where

the diffracted and scattered components are equal. The possibility

that the path antenna gain, G , varies with high fields might be the

cause for some concern. For the portion of the antenna pattern

directed at the horizon, the loss in antenna gain will be snaall and

therefore any variation of G will be small, and is included in the

ir total variation by use of the curves in figure 2 5. The loss in antenna

gain for the main beam can be large, but since in this report the very

narrow main beanas are directed above the horizon, all of the following

mechanisms normally responsible for the high fields are not very

effectual. High fields due to ducting of the main beam will not- occur,

since the maximum observed angle at which the radio waves can be

trapped is 5. 8 mr [Bean, 1959 ], while the antenna beam is elevated

above 50 mr. Superrefraction, causing bending of radio waves, can

cause only a very small percent of change in 9 when the original

main beam elevation angle is above 3*^ [Bean and Thayer, 1959 ].

Here 9 is the angle between the rays in the great circle plane at

the lower edges of the common volume of the antenna beams. Moreover, terrain effects that are emphasized by refraction when the

main beams are near the horizon would have little effect at the higher

8
elevation angles. Fields associated with reflection by elevated

layers will be smaller at the high angles and high frequencies for

two reasons: (1) The gradient required for reflection is directly

proportional to frequency; and (2) by examining Rayleigh's criterion

for the roughness of the reflecting surface we see that the reflecting

stratum must be increasingly smoother at the higher frequencies.

Thus we conclude that if any variations in G exist they must be

P

very small in the problem under consideration.

It would be desirable to obtain experimental variability curves

more directly applicable to the specific conditions of this problem.

Preliminary measurements over a 165-mile path from Table Mesa to

Haswell, Colorado, at 409.9 Mc/ s using a 14-foot dish for a transmitter and a 60-foot dish for the receiver, are shown plotted together

with the predicted median transmission loss in figure 26. These

experimental values are medians for five -minute periods during

which the receiving antenna is tilted above the horizon at the angle

indicated.

The value of hourly median transmission loss of concern here

is that value which will be exceeded p percent of the hours, and is

given by

L(p) = L - V(.100-p, 6). (6)

The actual transmission loss is less than the transmission

loss for only the *nain beam, or for only a side lobe, or for only an

isotropic antenna; furthermore, because of the nature of the approximation made in (5), it is greater than the transmission loss L'.

Thus, in the following sections, the smallest of the three values of

transmission loss (L. , L-, L ) will be assumed to be the pertinent

1. Li J

value of L'.
The following value of the parameters will be assumed:

Frequency = 1 Gc/s

d = 100 miles, d = 150 miles,

a = 6=8 mr

o o P = 99 o 9%

Receiver = 60-foot dish with one side lobe 20 db

below the main beam and located 33 mr

from the main beam axis, and isotropic

radiation otherwise.

Transmitter = 10-foot dish.

Figure 27 shows the transmission loss, L(99o9), plotted versus

the angle ^, the elevation angle for the main beam. This figure

shows values of transmission loss that will be exceeded by 99. 9 percent of the hourly medians for each of the following combinations:

T R

10' dish 60' dish--main beam only

10' dish 60' dish--first side lobe only

10' dish Isotropic

Isotropic Isotropic

Similar curves for different frequencies are shown in figures 28, 29,

and 30. Figure 31 shows the 1 Gc/ s curves at the 99 percent level.

All of the previous curves have been prepared using a value

for the surface refractivity, N , of 301. N varies with geographic

S o location and this will have a small effect on the values of L and L,(p).

Figure 32 shows a map of the United States with contours of N for

February [Bean, Horn, and Ozanich, I960]. For the largest value

N = 335, L will be decreased by approximately 5 db, and for the

smallest value, N = 245, L will be increased by approximately

5 db with a corresponding change in L/(p).

10
4. RESULTS

The following procedure is used to determine the separation

distances and antenna elevations necessary to make the interfering

hourly median signals less than or equal to the receiver noise power

for a given percent of hours.

1. Select the separation distance, the frequency, and the

antennas to be considered, together with the required

percent of the hours, p, for which the interfering

signal must be less than the receiver noise.

2. Plot curves of Ij(p) = L - V(100-p, 9) versus antenna

elevation angle where L is taken from the appropriate

curves of figures 3 through 23, and V(100 -p, 9) is

taken from figure 25. These curves are plotted for any

portion of the antenna patterns which may be of interest.

Here we plot curves for the main beam, lower side lobe,

and isotropic side lobes. Note that for isotropic side

lobes the value of L - V(100 -p, 9) will not be a function

of the antenna elevation angle since this portion of the

antenna pattern will always extend to the horizon.

3. Determine the noise power, P , in decibels, for the

receiver being considered. This may be either

P = NF + 10 log KTb = NF + 10 log b - 204 (7)

or P = 10 log KT b = 10 log T b - 228. 6, (8)

where NF is the effective noise figure [Norton, 1959 ] of the receiving system,

K is Boltzmann' s constant^

b is the noise bandwidth of the receiver in cps ^ T is a reference temperature, for a conventional

receiver 288. 48° K^

and

T is the effective noise temperature of the receiver

and antenna combination.

11
4. Compute the value of transmission loss required to make

the interfering signal equal to the noise power. This

value is

L =P-L-M-P (9) req t c n

where P^ is the power, in decibels, of the interfering

transmitter.

L represents coupling losses in the system and

may include transmission line losses, cross

polariation losses, etc.

M is a term to allow for the situation in which the

transmitted energy is spread over a frequency

band different from that which will be accepted

by the receiver. It will depend on the type of

modulation as well as the bandwidths, but an

estimate is made here by letting M = lOlogbVb

where b^ and b are the transmitter and

t r receiver bandwidths, respectively.

5. The value found in step 4 is then compared with the curves

of step 2 in order to determine if L ^ L', where L'

is the smallest of the values of the transmission losses

for the main beam or the side lobe or the isotropic part

of the antenna pattern. If this requirement is satisfied,

no interference will be encountered for the conditions

assumed in step 1.

5. EXAMPLES

As an example of the use of the transmission loss curves

consider systems operating on the same frequency assignment and

with the main beams centered in the great-circle plane connecting

the two terminals. At one end of the path a 10-foot dish is pointed

at the horizon and here represents one terminal of a surface pointto-point microwave relay system. At the other end of the path a 60- foot dish represents the earth terminal of a satellite communication system and may be elevated above the horizon by an angle ^.

12
It has characteristics as in table 2 with the first side lobe 20 db

below the main beam. The radiation pattern, for the purpose of this

example, is assumed to be isotropic outside the main beam and

first side lobe. It is assumed that the interfering signal must be

less than the receiver noise power for at least 99. 9 percent of the

hours. The curves of Li(p) in figures 28 through 31 are plotted for

the above conditions using the method given in section 4, step 2.

5.1. Example 1

Consider first the case of interference from the earth terminal transmitter to a point-to-point relay receiver. The receiver

noise power is determined as in step 3 assuming a bandwidth of

20 Mc/ s and a noise figure of 10 db. Then

P = NF + 10 log b - 204

n

= 10 + lOlogl 20 X 1 «') - 204

= -121 dbw.

The transmission loss required to make the interfering signal

equal to the noise power is found as in step 4. Assume a transmitter

power of 1 kw, coupling losses of 4 db, including line and polarization losses, and a transmitted bandwidth of 20 Mc/ s. Then

L =P^-L -M-P

req t c n

= 30 - 4 - - (-121)

= 147 db.

13
This transmission loss value is now used with figures 28

through 31 to determine whether the condition of step 5 can be met.

It is clear that for a separation distance of 100 miles and for all

four frequencies the transmission loss from the isotropic portion

of the transmitting antenna is less than the 147 db required loss.

For a separation of 150 miles the energy transmitted by way of the

main beam becomes significant and the required conditions can be

met at all frequencies if the main beam of the 60-foot antenna is

elevated above the horizon by approximately 5 . At 2, 6.5, and

10 Gc/s lower elevation angles could be tolerated.

A number of changes can be made in the system parameters

assumed for this case. The analysis assumes that the antenna of

the surface point-to-point system is directed toward the earth terminal. Rotating this antenna so that the main beam does not point

directly toward the earth terminal would increase the transmission

loss. When the pattern of the 10-foot dish is at the isotropic level

in the direction of the earth terminal, the "isotropic-isotropic"

curves of figures 28 through 31 will apply rather than the "10-foot

dish isotropic" curves. The transmission loss via main and side

lobes will, of course, increase by approximately the same amount.

Therefore, the 99. 9-percent tinne requirement could be met at

100 miles and at all frequencies by orienting the 10-foot dish to reduce

the interfering signal by 19 db at 1 Gc/s and by lesser amounts at the

other frequencies.

Other earth-termiinal-to-satellite systems might require more

or less transmitter power. Suggested systems [FCC, I960] range . from approximately 3 to 36 dbw. The effect of changing this parameter in the above example ^ would give a range of L from 120 to ^ & req

153 db at the 99.9-percent level.

Ik
If, instead of a 60-foot dish, a 120-foot or a 30-foot dish were

used for the transmitter, the only noticeable effect would be in the

calculations for L(p) for the main beam. In the former case, L((p)

for the main beann would be decreased by less than 6 db and in the

latter case, L(p) would be increased by approximately 6 db. This

can alter the conclusions only by increasing (or decreasing) the

required elevation angle of the transmitter by at most 2 . A reduction in the percentage of hours for which the interfering

signal must be less than the receiver noise is illustrated in figure 31,

The conditions are the same as in figure 28 except that the time requirement has been reduced from 99, 9 to 99 percent. Similar

curves can be drawn for any percent value using step 2.

5. 2. Example 2

Consider next the case of interference from a point-to-point

microwave relay transmitter to the earth-terminal receiver of a

satellite system. Figures 27 through 31 again apply. It is assumed

that a wide -deviation FM system is used in the satellite-to-earth

link, so that the earth terminal receiver has an RF bandwidth of

100 Mc/ s. With the use of a low-noise antenna and maser amplifier.

reduced to 30 K.

we assume that the effective noise temperature of the receiver is

I to 30°K.

By step 3,

P = 10 log T b - 228.6

n

= 10 log 30 + 10 log 100 X 10^ - 228. 6

= 14. 8 + 80 - 228.6

15
Compute the transmission loss, L , as in step 4, assuming

req

a transmitter power of 1 w, coupling losses of 4 db, and a transmitted

bandwidth of 20 Mc/ s. Then

L =P-L -M-P

req t c n

= - 4 - 10 log 20/100 - (-134)

= 137 db.

This value of L is compared with figures 27 through 31

req

to determine whether the requirement of step 5 can be met. It is

seen that under these assumptions the point-to-point antenna could

not be directed toward the earth terminaL at a distance of 100 miles.

As in the previous example, the curves indicate that the requirements could be nniet by not allowing the 10-foot dish to be directed

toward the earth terminal.

The effects of varying the transmitter antenna size and the

transmitted power were noted in example 1. Similar statements can

be naade about varying the receiver antenna size and transmitted

power in this example. Values of the power used for typical pointto-point microwave relays range from -3 dbw to +7 dbw.

6. CONCLUSIONS

Our theoretical analysis indicates that space communication

systems and surface systems of the conventional microwave relay

type can share the same frequencies if care is used in locating the

possible interfering sources. As seen in the exainples, separation

distances of from 100 to 150 miles will usually suffice, and under

ideal conditions, distances of less than 100 miles could give adequate protection. Estimates for other systems, such as radar using

16
large antennas and power outputs, can be found using the curves in

this paper. Some authors [Bond, Cahn, and Meyer, I960] have

concluded that these high-powered radar systenns will cause intolerable interference at the satellite, and this may be the limiting factor

rather than the interference to (or from) the earth terminals.

If the radar antenna is directed toward the earth terminal,

and away from the satellite, harmful interference should not be

experienced if the radar and earth terminal are separated by distances of 500 miles or more. In many systems shorter separations

may suffice.

It is important that some of the basic assumptions made in

this theoretical analysis be checked experimentally over long

periods of time. However, it is expected that such experiments

will only substantiate some of the estimated values and will not be

likely to contradict the broad general conclusions reached.

The authors wish to acknowledge the contribution of

A. F. Barghausen who supervised the measurements reported

here.

17
7. REFERENCES

Bean, B. R. , Climatology of ground-based radio ducts, J. Res.

NBS 63p, (Radio Prop. ), No. I, 29-34, ( July-Aug. , 1959).

Bean, B. R. , J. D. Horn, and A. M. Ozanich, Jr. , Climatic

charts and data of the radio refractive index for the United

States and the world, NBS Monograph 22, (November I960).

Bean, B. R. , and G. D. Thayer, CRPL exponential reference

atmosphere, NBS Monograph 4, (October 1959).

Bond, F. E. , C. R. Cahn, and H. F. Meyer, Interference and

channel allocation problems associated with orbiting satellite

communication relays, Proc. IRE 48, No. 4, 608-612,

(Apr., I960). •

Federal Communications Coinmission, Allocation of frequencies in

the bands above 890 mc, FCC Docket 11866, (I960).

Hartman, W, J. , and R. E. Wilkerson, Path antenna gain in an

exponential atmosphere, J. Res. NBS 63D, (Radio Prop. ), No. 3, 273-286, (Nov. -Dec, 1959).

Haydon, G. W. , Optimum frequencies for outer space communication, J. Res. NBS 64D, (Radio Prop. ), No. 2, 105-109,

(Mar. - Apr. , I960).

Norton, K. A. , System loss in radio wave propagation, J. Res . NBS 63D, (Radio Prop. ), No. 1, 53-73, ( July - Aug. , 1959).

Pierce, J. R. , and R . Kompfner, Transoceanic communication by

means of satellites, Proc. IRE 47, No. 3, 372-380, (Mar., 1959).

Rice, P. L. , A. G. Longley, and K. A. Norton, Prediction of the

cumulative distribution of ground wave and tropospheric wave

transmission loss (Part I), NBS Technical Note 15, PB 151374,

(July 19 59). Order by PB nunnber from the Office of Technical

Services, U. S. Department of Commerce, Washington 25, D. C.

Foreign remittances must be in U. S. exchange and must include

one-fourth of the publication price to cover mailing costs. $1. 50.

18
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TRANSMISSION LOSS EXCEEDED 99.9 % OF THE TIME

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TRANSMISSION LOSS EXCEEDED 99.9% OF THE TIME

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Figure 30

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48
TRANSMISSION LOSS EXCEEDED 99 % OF THE TIME

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49
50
U. S. DEPARTMENT OF COMMICRCE

Luther II. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

Boulder, Colorado, is suggested in the iollowing listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside ofthe

front cover. WASHINGTON, U. C.

Electricity. Resistance and Reactance. Electrochemistry. Electrical Instruments. Magnetic Measurement&

Dielectrics. High Voltage.

Metrology. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering Metrology.

Mass and Scale. Volumetry and Densimetry.

Heat. Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Piu-e Substances. Spectrochemistry. Solution Chemistry. Standard Refer- ence Materials. Applied Analytical Research. Crystal Chemistry.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls. Polymers. Macromolecules: Synthesis and Structure. Polymer Chemistry. Polymer Physics. Polymer Characterization. Pol>'mer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research.

Metallurgy. Engineering Metallurgy. Microscopy and Diffraction. Metal Reactions. Metal Physics. Electrolysis

and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Glass. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials. Codes and Safety Stand^ds. Heat Transfer. Inorganic Building Materials. Metallic Building Materials. Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics. Operations Research. Data EVocessing Systems. Components and Techniques. Computer Technology. Measurements Automation.

Engineering Applications. Systems Analysis.

Atomic Physics. Si)ectroscopy. Infrared Spectroscopy, l-'ar I'ltraviolet Physics. Solid State Physics. Electron

l^liysjcs. Atomic Physics. Plasma Spectroscopy.

Instrumentation. F,ngineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instru- ments. Basic Instrumentation. Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Ele- mentary Processes. Mass Spectrometry. Photochemistry and Radiation Chemistry.

Office of Weights and Measures. BOULDER, COLO.

Cryogenic Engineering Laboratory. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Cryogenic Technical Services. CENTRAL RADIO PROPAGATION LABORATORY

Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Research. Prediction Services. Sun-Earth Relationships. Field Engineering. Radio Warning Services. Vertical Soundings Research.

Radio Propagation Engineering. Data Reduction Instrumentation. Radio Noise. Tropospheric Measurements.

Tropospheric Analysis. Propagation-Terrain Effects. Radio-Meteorology. Lower Atmosphere Physics.

Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency Research. Fre- quency Utilization. Modulation Research. Antenna Research. Radiodetermination.

Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. High Latitude Ionosphere

Piiysics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Physics. Radio Broadcast Service. Radio and Microwave Materials. Atomic Frequency and Time-Interval Standards. Radio Plasma. Millimeter-Wave Research.

Circuit Standards. High Frequency Electrical Standards. High F'requency Calibration Services. High Frequency

Impedance Standards. Microwave Calibration Services. Microwave Circuit Standards. Low Frequency Calibration

Services.
NBS