Figure 7 shows radiometric observations made at 13.6 GHz for 8, = 38,2°
at Palmetto, GA, during the period June 1973-June 1975. Radiometric obser-
vations inherently include clear air attenuation; therefore, it is presumed
to be included in the data of the following figures. The comparative attenua-
tion distribution predictions have been made for Atlanta, GA, a location
roughly 15 mi. from Palmetto.

Figure 8 shows radiometric observations made at 13.6 GHz for 8 = 27.3°
at Grant Park, IL, during the period July 1976 to Jume 1977. These data are
compared with predictions of attenuation distributions for Chicago, IL, which
is approximately 40 mi. north of Grant Park. Figure 9 shows radiometric
observations made at 13.6 GHz for 8 = 42.6° at Longmont, CO, during the two-
year period June 1973 to July 1975. These data are plotted on the figure
along with the attenuation distribution prediction curves for Denver, CO,
approximately 40 mi. to the south of Longmont.

In general, the comparison of data and predictions in Figures 2 through 9
appears to be relatively good. Of all the figures, however, probably the set
(Figs. 4, 5, and 6) that compare the Holmdel, NJ, CTS data with predictions
for 3 different locations is the most exemplary of the type of frustration
likely to result when using predictions. In Dutton (1977a), it was indicated
that, even in a small subzone of stations on the east coast with fundamentally
similar climatologies, sizable differences in earth-space attenuation predic-
tions to the same satellite were possible. Basically, this means that the
meteorological data for one station theoretically should not be used to predict
results for potential earth-terminal sites even a few miles away. Yet this
kind of situation is likely to arise, since terminals will probably be remote
from urban, interference-producing, areas, but U.S. Weather Service stations
are either downtown or at the local airport. Figures 5 and 6 illustrate the
problem clearly. The Newark, NJ, and New York City, Central Park, NY, stations
are both in urbanized locations, about 10 mi. apart. Yet the Newark predic-
tions compare rather poorly with the Holmdel CTS data, whereas the Central Park
predictions compare rather well with the Holmdel CTS data. Both stations are
about 30 mi. from Holmdel. More data in the southern, western, and midwestern
U.S.A. is clearly needed for comparison purposes-especially data observed

directly from geostationary satellites in the 12 to 14 GHz frequency band.

12


in the spherical triangle ABE to determine the angle ECB (=x/r) in Figure A-2.

Then, in Figure A-2, we can use the law of cosines,

Ro = 1? + (x + 2)? - 2x(r + z)cos (:) (A20)

to determine the slant path, R. Whence, using the law of sines in Figure A-2,

sia(®)
AL (A21)

R .

we can determine the elevation angle, 80> as

8, = cos + (x + 2)

For geostationary satellites,
z = 5.619r, (A22)

thus 8, is readily determined for elevation angles, 0 2 5°,
For a given percentage of a year, P, the predicted attenuation results

discussed in the main text are given by
[t,(5°,P) - T,(90°,P)] (1 - sind,) sin 5°

T, (05 5P) = 1, (90° ,P) + 3 (A23)
(1 - sin 5°) sin 8,

i.e., by a "cosecant law" (Dutton and Dougherty, 1973) applicable in the range

5° 50,5 90° . (A24)

In (A23), Tt is attenuation along the satellite-earth path at elevation angle
8» and f is frequency in CHz.

Thus we see that T,(8,P) can be determined from Aye A, and 6, or can
be determined from Ay alone for any particular earth-station location with

known co-ordinates A and ¢,

REFERENCES for Appendix A
Bean, B. R., and E. J. Dutton (1968), Radio Meteorology (Dover Publications
Inc., New York, NY), p. 337.

Brownlee, K. A. (1965), Statistical Theory and Methodology in Science and
Engineering, 2nd Ed. (John Wiley and Sons, Inc., New York, NY),
pp. 310-330.

33


It was thought that some other more representative statistical descriptor
of all variances within a zone could be found to replace the pooled-data vari-
ance. Indeed, another descriptor, called the "fixed effects model" variance
(Brownlee, 1965) was examined in detail, but was found to be little better
than the pooled-data variance, when applied on a per-station basis for stations
within a zone.

Therefore, we are left with little choice but to use the station variances
of M', D', and U', directly. It would have been expedient to use a single,
zone-wide descriptor to represent variance for stations within a zone, but this
descriptor must first and foremost have some meaning. Consequently, with
reluctance, the author has tentatively abandoned the zone-wide approach to
rainfall description, postulated in Dutton (1977b).

There are basically no major refinements to the SHF earth-space attenua-
tion prediction technique, the Dutton-Dougherty (DD) model (Dutton, 1977a).
However, as noted in that report, the use of the normal distribution to des-
cribe variability of R, (in terms of R, and 9) is not completely compatible
with the characteristic that Ro must be non-negative. The rain rate, Ry is
used to predict the rain attenuation, T, (04), on an earth-satellite link at
frequency, f, and earth-station antenna elevation angle, 8). Further,

T,(8,) must also be non-negative. Therefore, the same problem with the normal
distribution, as applied to Ry» also applies to T,(8,)- To maintain reasonable
compatibility with the Dutton (1977a) procedure, the truncated normal distribu-
tion was used to assess the variability of the annual distribution of T,(8,)-
The truncated-normal distribution was chosen because it a) is indistinguishable
from the normal distribution for many situations in the U.S.A., especially
when considering the upper confidence limit (i.e. 99.5%) of the distribution
of T,(8,)5 and b) it has a non-zero probability of T, (85) = 0, a clearly
feasible result that some other distributions (such as the gamma or Rayleigh)
do not have.

Another new feature for the purposes of earth-space geostationary
satellite attenuation modeling is the ability to produce a curve of attenua-
tion versus satellite suborbital longitude, Age that is expected for a parti-
cular percent of a year. This methodology is applicable for 8, > 5°. This
is because above 8, = 5°, ray bending due to atmospheric refraction (Bean

and Dutton, 1968) is essentially negligible, and rays can be treated as

29


11.7 GHz. In this case, the data are compared with predictions for Roanoke,
VA, a location approximately 25 mi from Blacksburg, VA. Furthermore, in (B8)
we have used x = 92 days and y = 365.25 days. The data were obtained from
an experimental setup at the Virginia Polytechnic Institute and State
University (VPI) at Blacksburg, VA.

It is readily apparent from figure B-1 that neither of the hypothesized
data distributions compares very well with predictions. This is true of even
the assumption (B8), which leads one to believe that even if a year's data
were available, they would also not compare well with the Roanoke predictions.
There is, however, a special extenuating circumstance with regard to these
data that once again shows the profound influence of microclimatology.
According to Bostian et al. (1978), the VPI path is located in a relatively
mountainous region in the Allegheny Mountain chain. The CTS path looks almost
directly down a valley along Stroubles Creek, which apparently is a location
known for strong summertime convective activity. This fact would tend to
bias any data results observed along the CTS path toward the high side (by the
authors' own admission). By the same token, the experiment, which also
observes 19 and 28 GHz results from the COMSTAR satellite, looks along the
COMSTAR path over Price Mountain through a much drier microclimatological
regime. Out of curiosity, this author made predictions at 19 GHz for the
COMSTAR path (elevation angle = 44 degrees), and compared with the VPI 19 GHz
COMSTAR data for the July-August-September 1977 period. These data were
adjusted by (B8) ("Adjusted data" on graph) and (B10) ("Attenuation data" on
graph), and the results are shown in Figure B-2.

The comparison of data and predictions in Figure B-2 are definitely
closer than in Figure B-1, but the comparison of data adjusted by (B10) is
still inadequate. This, however, only serves to reinforce the observation
that less than a year's worth of data should be compared with annual
predictions with considerable caution, especially in a mountainous area
such as that between the prediction location, Roanoke, VA, and the data
location, Blacksburg, VA.

Figure B-3 shows the comparison of CTS data adjusted by (B10) from the
University of Texas at Austin, TX (Vogel and Straiton, 1977), with annual pre-

dictions for Austin, TX. Thus, at least here, data and prediction locations

38


5 Eb
2 =

no}

o

B® | KE

8 [=

B£

205

9 |

3 |_
0.2

o

E

ri

€- 01 E-

o

8 [—

& [—
0.05}—
0.02 -—
0.01

{Litt

X = Attenuation Data

4

\-N\4
aN
LIS |_|

J

Curve
Curve
Curve
Curve
Curve

1

2
3
4
5

8 ~©= 0 2 14

Atmospheric Attenuation (dB)

Figure 2. Comparison of CTS data from Greenbelt, MD, and predictions
for Washington, DC, for 11.7 GHz at an elevation angle of
29 degrees, data period is June 1, 1976 to May 31, 1977.

represents
represents
represents
represents
represents

the
the
the
the
the

0.5 percent confidence limit;

5 percent confidence limit;
mean prediction;

95 percent confidence limit; and
99.5 percent confidence limit.




3. PREDICTION RESULTS

Attenuation expected on earth-geostationary satellite links has been
predicted for 75 geographically and climatically diverse locations throughout
the U.S.A. These results are shown in Tables 1 through 4. Results are shown
for four potential satellite suborbital longitudes, Ay» and are given for
three percents of a year (.01%, .1%, and 1%) at each Ay: Table 1 shows the
attenuation expected at 12.2 GHz during an average year, whereas Table 2 shows
the predicted 99.5% confidence limit on that attenuation, using the truncated-
normal distribution discussed in Appendix A. Table 3 shows the attenuation
expected at 14.5 GHz during an average year, and Table 4 shows the predicted
99.5% confidence limit on that attenuation.

Results in these tables are fairly much as expected, with the largest
values of attenuation on a given link occurring in the southeastern U.S.A and
the smallest values occurring in the desert southwest, particularly for 0.01
and 0.1 percent of a year. Largest values at 1 percent of a year on a given
link tend to occur in the northeast and the midwest, reflecting a greater
tendency toward polar airmass type precipitation. Although the values in the
0.1 and 1 percent columns of tables 1 to 4 appear "small" compared to those in
the 0.01 percent column, the user should keep in mind that these are values
expected 10 and 100 times more often, respectively, than at 0.01 percent, and
that an attenuation of 3 dB still represents 50 percent loss of signal power.

In Dutton (1977a), sample computations were made at some of the stations
of Tables 1 to 4 for a satellite at 110°W longitude. Some of these computa-
tions were made at 12 and 14 GHz, so seemingly they should be comparable to
the results in Tables 1 to 4, or just slightly less. However, one notes,
especially for 0.01 percent of the time, that there are occasionally some
apparent discrepencies between values at the same percent and same (nominal)
frequency. Some of these values are larger at 12 GHz than at 12.2 GHz.

The reason for these differences is that the rain rate values, from which
the attenuations are computed, were not obtained in exactly the same manner.
As noted in Section 1, rain-rate values used in this report are obtained from
the original RH model, whereas values in Dutton (1977a) were obtained from the
modified RH model. As noted in Dutton (1977b), it is for rain rates that occur

around 0.01% of the time in temperate climates that the greatest divergence

16


Dutton, E. J. (1977a), Earth-space attenuation prediction procedures at 4 to
16 GHz, Office of Telecomm. Report OTR 77-123, May (Access No. PB269228/AS,
NTIS, Springfield, VA).

Dutton, E. J. (1977b), Precipitation variability in the U.S.A. for microwave
terrestrial system design, OT Report OTR 77-134, November (Access No.
A049041, NTIS, Springfield, VA).

Dutton, E. J., and H. T. Dougherty (1973), Modeling the effects of clouds and
rain upon satellite-to-ground system performance, Office of Telecomm.
Report OTR 73-5, March (Access No. COM 75-10950/AS, NTIS, Springfield,
VA).

Dutton, E. J., H. T. Dougherty, and R. F. Martin, Jr. (1974), Prediction of
European rainfall and link performance coefficients at 8 to 30 GHz,
U.S.Army Communications Command Rept. No. ACC-ACO-16-74 (Access No.
A000804, NTIS, Springfield, VA).

34


TABLE OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

ABSTRACT -

1. INTRODUCTION AND BACKGROUND

2. COMPARISON OF OBSERVATIONS AND MODELING

3. PREDICTION RESULTS

4. CONCLUSION

5. ACKNOWLEDGEMENTS

6. REFERENCES

APPENDIX A: IMPROVEMENTS IN RAIN RATE AND EARTH-SPACE
ATTENUATION MODELING

REFERENCES

APPENDIX B: COMPARISON OF LESS THAN A YEAR'S ATTENUATION
DATA WITH PREDICTIONS

REFERENCES

Page
vi

vii

16
25
25

26

27

33

35

41


APPENDIX A
IMPROVEMENTS IN RAIN RATE AND EARTH-SPACE ATTENUATION MODELLING

For all practical purposes, the parameters other than R, in the expression
_ *
(1) for P(R,) can be simply expressed in terms of M, D, and 8. This is in

contrast to the original R-H model expressions, particularly for Ry and Tow?

as given in Appendix C of Dutton et al. (1974). The parameter Ry is very
nearly a constant, with a U.S.A.-wide mean of

< Rip >= 33-6642, (Al)
and the U.S.A.-wide standard deviation of

s = 0.8017 , (a2)

1
based on the 305-station sample used in Dutton (1977b). The remaining

parameters can be expressed as

T,, = BM/R, > (A3)
R,, = 3.96D , (A4)
and T), = GQ - B)M/R,, - (A5)

In Dutton (1977a), s? was obtained from the so called "modified" R-H
model. This modeling allowed us to express se algorithmically as

2 2 42

2
Sa = FM, B, Ds Sys Sgs Sp) (a6)

2 2
where F denotes the function given in detail in Dutton (1977a), Sue Se and

s? are the variances of M, 8 and D at a particular location, respectively.
The result (A6) was achieved by using the first term of a Taylor series

expansion, and therefore requires that a criterion on the order of
38 <M , (A7)

and 38) < D (A8)

*
See section 1 for definitions of M, D, U, and fp.

27


Ltt

X = Attenuation Data = _]

05

0.2

0.1

Percent Time Abscissa Is Exceeded

0.05

0,02

0.01
0

Atmospheric Attenuation (dB)

Figure 7. Comparison of radiometric data from Palmetto, GA, and
predictions for Atlanta, GA,for 13.6 GHz at an elevation
angle of 38.2 degrees. Data period is June, 1973 to
June 1975. See Figure 2 for definition of curves 1 to 5.

13


Table 2. 99.5 percent confidence limit attenuation predictions for .01, .1, and 1 percent of a year at

12.2 GHz on earth-geostationary satellite links for satellites located at the indicated suborbital longitudes, |.

Ay = 110°W 90° 130° 70°W

Location “Ole 1k sor 1 1 sol 1 1 sol 1 1

Worcester, MA 13.3 5.64 1.79 12.6 4.99128 15.9 8,02 3,66 12-4 4.84 117
Boston, MA 18.2 7.23. 1.88 «17.4 6,501.32 2119.94 = 3.971723 6.3318
Providence, RI 116 5610 1.75 10.8 4.46 1424 14137246360 10,67 43D
Concord, NH 11.7 5.19 1.89 160452134 14.4 7666 389 10.8 4.36 1.22
Portland, ME U5 513-1687 10.7, 4431630144 78L OL 10.54.26 117
Burlington, VI 15.5 6.06 1.85 «15.0 5.47 1634173 «8183.69 14.95.36 1.28
Newark, NJ 12.5 5.16 1.56 12,0 4.64 1.16 14.5 6.97 3,00 11.94.54 1.07
Hartford, CT 22.6 8.62 1.86 21.97.88 1629 24.8 10.7 3,43 21-8 7.78121
Trenton, NJ 16.4 6.21 1654 «15.9 5472-113 18,.0 7.91294 15.8 5.63 1.06
NY Central Park, NY 19.4 7.44 1,66 © 18.8 6.83. 1.20 21.79.56 3-29 18.7 672 LL
NY LaGuardia, NY 18.4 7.191676 17686571628 20,7 9.34 342176645119
Rochester, NY 10.3 419-1642 «9,90 3.791610 11.7 5453-250 9.86 3.76 1.07
Buffalo, NY 10.9 4.36 1.40 10.53.99 1610 12,2 5.60 2.40 10.53.98 1.08
Pittsburg, PA 10.4 412-1622 10,0 3.80966 11S 5418 2,07 10.03.80. 966
Philadelphia, PA 10.7 4.531638 «10,0460 :102 12.5 HAL 26110-1399. 960
Wilmington, DE 14.8 5.71 1.40 -14,3 5.261603 16,5 723220651443 517.978
Washington, DC 16.16.08 16411547 5.631606 17.6 7655-257 15.6 5591.02
Albany, NY 13.6 5.41 1.664 13,1 4,881.19 15.4 7,303.22 -13,0 4.78 1.10
Syracuse, NY 17.5 6.57 16217-1608 1.22 :19.0 8,233.02, :17.0 6011.16
Harrisburg, PA 21.8 7.96 1.56 21.4 7647 1S 23.29.58 269321 742A
Baltimore, MD 22.4 8.27 1.54 ° 21.8 7.74 1413 -24.2, 10.02.89 21.8 7.67 1.09
Richmond, VA 24.2 8.96 1.40 23.6 = 8.44 «= 1,03 26.2 10.7 2663 23,6 8139997
Charleston, WV 20.3. 7.13. 1.23 20.06.82 973. 21-1816 2,09 20,2 6.84 994
Greensboro, NC 18.0 6.46 Led. 1767, GD 853 191753197 17.7 68ST
Charlotte, NC 16.1 5.83 1,07 15.8 5.52, 831.1742 6,83 1684 15.8 5.53840
Columbia, SC 27.5 10.2 112 26.9 9472, 849-2966 116 2.0L 26.99.75. 62
Atlanta, GA 20.6 7.32 971 20.37.06 = «7822165819161 20.4 701331
Pensacola, FL 25.1 9,52 876 24.79.26 736-2666 10.4 = 1382419 9.40 BL
‘Tampa, FL 28.5 11 1,03 27.5 10.5 s71L 31.8 13,1 2,09 27.7 10.6 +755
Miami, FL 33.7 13.4 1633 32,2 «12.6 = L601 38.5 15.9 2.38 32.3 12.6 101
Birmingham, AL 22.5 8.19 956 22,2, 7.94 «790 -23.6 9,091.55 22,3 8.07. 874
Montgomery, AL 24.8 9.34 1.04 24.28.97 1816 26.6 «10.71.83 24.59.13 913
Memphis, TN 19.6 6.95  .908-19.4 679.793 20,3 7,601.37 19.6 6.95. 908
Nashville, TN 17.5 6.21 69741763601 820181692 14531764 GL. 897
Jackson, MS 20.9 7.34 848 -20.7 7218739 21.6 7696 1429 20,8 7.34 BSL

19


Littl

|] X = Attenuation Data

>
I
i

05

0.2

0.1

Percent Time Abscissa Is Exceeded

005

0.02

0,01

Atmospheric Attenuation (dB)

Figure 9, Comparison of radiometric data from Longmont, CO, and
predictions for Denver, CO, for 13.6 GHz at an elevation
angle of 42.6 degrees. Data period is June, 1973 to
July, 1975. See Figure 2 for definition of curves 1 to 5.

15


be imposed so that the higher order moments of M and D, and crossterms
involving sa and st will not influence (A6). A similar criterion applies to
Spe but since it can be expressed as a function of M, U, My si and s., by
using (2) and the first term of a Taylor series, the result (A7) and the

restriction

38, < 0 (A9)

must also be imposed. In the above, s° is the variance of U. A further
requirement for use of (A6) is that M, 8, D, and U have low correlation
between pairs. This is essentially no problem, except that, since 8 is
partially a function of M, it would not be unreasonable to expect some correla-
tion. Further, in Dutton (1977b), within the therein defined zones, M/S was
a constant -- implying perfect within-zone correlation. The M/® characteristic
was none too successful in defining these zones, however (Dutton, 1977b).
Further, the contour maps in Dutton (1977b) give no indication of much
correlation between M and 8. Since the zonal concept is not used in this
report, there is now no seeming contradiction in assuming M and B are not
highly correlated.

In Dutton (1977, 1977b), the variances si 8°, and Ss. were represented
on a zone-wide basis by pooling all of the M', D' and U' data within a zone,
where M' D' and U' represent annual values for a given year at a given location
rather than average annual values as represented by M, D, and U, respectively,
Sa s. and so then, were those for the
pooled data sample, and were assumed applicalbe at each location within that

at a given location. The variances,

zone. As mentioned earlier, the conditions (A7) to (A9) should be met as
frequently as possible to insure reasonable validity of the results obtained

from (A6). Unfortunately, results obtained from the pooled-data variance

approach for Sue s*, and st gave values that for many zones -- particularly
in the west and Alaska -- resulted in consistent violation of (A7) to (A9).

There is no a priori justification for the use of the pooled-data vari-

ances to represent the variances at a particular location in the zone. These

zone-wide variances are heavily influenced by extreme values of M', D', and U'.
If, for example, all the extreme values occur at one particular location in the
zone, then the resultant variance would not be expected to be very representa—

tive of the other locations in that zone.

28


Lt ttt

X = Attenuation Data

|

i Lil

|

5
2

ao)

®

3

S

wi

2 05

B

3

a

» v2

&

cE

5 Ol

5

a
0.05
0.02
0.01

Figure 5.

Atmospheric Attenuation (dB)

Comparison of CIS data from Holmdel, NJ,and predictions
for Newark, NJ,for 11.7 GHz at an elevation angle of 27
degrees. Data period is April 26, 1976 to April 26, 1977.
See Figure 2 for definition of curves 1 to 5.

10


significantly altered from the classic Ryde (1946) relationship, for use on
earth-space links. It has been found helpful to model (rather than measure)
the distribution of mean Ro» Ry (or "rain rate expected during an average
year") and the variance Sp of R, for a particular percentile on the distribu-
tion, in order to describe the distribution of rain rate at a given location.
This was achieved in Dutton (1977a) by use of a modification to the Rice-
Holmberg, RH, (Rice and Holmberg, 1973) model.

The RH model expresses the percent of time, PR), that the mean rain

rate, Ro is exceeded during a year. This is expressed mathematically as

P(RS) = KT, exp (-R,/R, 1) + +35kT 1 exp (-.453074R /Ry1)

+ .65 kT), exp(-2.857143 R/ op: a
A fast and accurate interative-recursive technique for large-scale computers
has made it desirable to solve (1) for Ry rather than use the less-accurate
modified RH model to estimate Ry» given P(R,) (Dutton, 1977b). The basic
meteorological parameters used in (1) are M, the average annual precipitation
at a location of interest; My the greatest monthly precipitation in 30
consecutive record years; D, the average annual number of days with pre-
cipitation 20.25 mm; and U, the average annual number of days with thunder-

storms. In (1), Up and T, are functions of Mi» M, D, and U; and

Riv Rov
k = 0.01141, a conversion from hours/year to percent of a year (see also
Appendix A). There are two types of rainstorms considered by Rice and
Holmberg (1973), whence the "1" and "2" subscripts on the various parameters

in (1). The second subscript (always a "1") refers to "one-minute rain rates".
Another important variable used in connection with the RH model is 8, the

ratio of precipitation associated with thunderstorms to the total precipitation

for an average year. The parameter 8 can be expressed in terms of M, My and

U as

3 = p, fo.2s 2 on, 0.5(340.12519 | . Q)
where

8, = 0.03 + 0.97 [-5 exp(-0.004",)] -. ©)


between the modified and original RH models is observed. Thus, Tables 1
through 4 should be interpreted as representing state-of-the-art earth-
satellite attenuation values, at least insofar as modeling at the Institute

for Telecommunication Sciences (ITS) is concerned.

4. CONCLUSION
In Dutton (1977a), it became evident, even in a small zone (subzone)

of generally similar rainfall characteristics, that station-to-station
meteorological data within that zone could still result in some substantial
prediction differences for identical 6, and P(R,)- This conclusion is rein-
forced, particularly based on the results seen in Figures 5 and 6. As des-
cribed in Section 2, here are two stations (Newark, NJ, and New York City,
Central Park, NY) about 10 mi. apart and surrounded by essentially the same
urban environment that result in completely different prediction-data
comparisons using their respective meteorological data as prediction input.
There may, of course, be a rational explanation (e.g., micro-climatological

effects), but the fact remains that large predicted or observed differences in

earth-space attenuation distributions are possible over relatively short

distances. These differences are not resolvable with the current data base.
Further these differences could well be important to a prospective user
wishing to place an earth-station several miles from the exact location of

the nearest first-order weather station from which data have been gleaned.

5. ACKNOWLEDGEMENTS
The author is particularly indebted to Dr. John Labrecque of the
National Bureau of Standards Statistical Engineering Laboratory for his help
in analyzing the rain rate variability problem. Other helpful advice and
contributions to the report have come from Dr. P. M. McManamon, Dr. E. L. Crow,
Dr. H. T. Dougherty of NTIA/ITS, Mr. E. C. Keppelmann of Potomac Research,
Incorporated, and Messrs. C. B. Brooks and D. C. Howard of the University of

Colorado.

25


Table 3 (Continued)

Mean attenuation predictions for .01, .1, and 1 percent of a year at 14,5 GHz on earth-geostationary

satellite links for satellites located at the indicated suborbital longitudes, A,

A, = 110°W 90°" 130°W 70°"

Location 01 kk ol 1 1 sl 1 1 solo 1

Louisville, KY 17-6 5.95 1423-174 547310051862 672.86) 17.S 50822
Columbus, OH 10.2 3.84 1631 9,91 3,58 1610 ALL 4.73203 9.953,62 1.13
Cleveland, OH 8.68 3.49 1.43 8.38 3.20 1618 9.69448 2.25840 3.22.20
Cincinnati, OH 16.6 5,631.27 16.4 54391081763 6.43192 16.55.45 113,
Indianapolis, IN 14.6 5.02 1625-144 4,81 «1.08 15.3 5.751.886 1445901
Detroit, MI 6.42 2.95 1.36 6.09 2,67 1615 7,533.88 = 2.10 6152.72.18
Des Noines, IA 16-1 5.28 1616 16.0 5419109 16,5 54751652 16.25.39 1428
Milwaukee, WI 8.62 3.38 1,36 8.43 3.19 1.20 9,32 4,061.92 8553.31.30
Minneapolis, MN 6.49 2.93 1,42 6,372.82 1.33 7143.49 «1.88 6633.06 1.52
Sioux Falls, sD 8.31 3.27 1,30 8,25 3.22 1.26 8.773.701.6555 3501.49
Fargo, ND 6.82 2.93 1.47 6,76 2.88 1.43 7634 -3,38 1.84 7610318 1.67
Billings, MT 4.58 2.53 1.63 4,76 2.69 1.76. 484-2675 1.8L 559337233
Chicago, TL 15.2 5.18 1,35 «15.0 5,00 1429 15.8 5.89 «1,92 15.15.12 1.29
St. Louis, MO 9.50 3.66 1.19 9,33 3.511.071.2427 1.68 9513.67 1.20
Kansas City, MO V2  4.81 1618 142473 LAL 1455275614349 1.30
Wichita, KS 12.20 4.24 1,10 12.2 4,22 10071266 4631412 B28
Omaha, NE 15.3 4,98 1,07 15.2 4,93 16031547 5.37137 15.5 5.16121
New Orleans, LA 24.9 8.93 1.01 24.78.70 848 26.0 98H 1.66 24.9 8,93 LOL
Shreveport, LA 15.9 5.32 901 «15.8 5.23830 16635478 = 1278543 98K,
Little Rock, AR 19.3 6.50 1,03 19.2 5,38 932 «19.77.05 1.50 19.4 6.57110
Oklahoma City, OK 12.34.18 944 -12.3 415 91812-7453 1222S OL
Tulsa, 0K 22.3 7.66 1.09 22.3 7,591.03 22.8 B17 -22.5 7.89 1.28,
Dallas, TX 17.2 5.646 969-1762, 5460933175 6.021628 17.4 5.8514
Ft. Worth, TX V4.2 4,68 = 876. 14.2463 84K 1465031514487 1.03,
Grand Rapids, MI 7.15 3.06 1.38 6,922.85 1.20 7,983.81 2.00 7.03 2.95 1.29
Amarillo, TX 10.6 3.64 1.05 10.6 3.67107 10.9 3,901.26 1.03.99 1.33,
Houston, TX 23.3 8.05 893. 23.27.96 = 829 -23.9 8.61 131 -23.5 8.27 1.06
San Antonio, TX 15.5 4,80 4735 «15.5 4.78 = 724. «15.8 5.05931 15.7 4.99 88S
Albuquerque, NM 2.57 1.86 1.43 2.691696 «1.51 2683 -2.06 = 1.6603.31 2.45 LOL.
Denver, CO 5.12 2.50 1.39 5,222.58 1645 5.42 24751659 5.79306 1.85
Cheyenne, WY 4.20 2.67 1.86 = 4.31 2,771.94 4582.99 2135.06 3.37245,
Boise, ID 2.45 1.75 1.32 2,76 2,001.52 2.51 1681 1636 3.68 2.85 2.21
Salt Lake City, UT 3.47 2.05 1.17 3,73 2623131365217 1.26 4.722.931 BL
Phoenix, AZ 3.57 1.75 6563.84 190 7323.74 «1485 7054822246 10.
Reno, NV 3.77 1.97 68754419 2,251.06 = 3.77 «1,98 8765460 3.18 1.66
las Vegas, NV 3.10 1.44 4233.44 161 4853.20 1649441 4.582018 700
Los Angeles, CA 3.03 1,60 764 3.34 1681 9103.06 1.62776 4.386 2511.39
San Francisco, CA 3.44 1,89 9453.91 2,221,618 = 3,401,686 9245.44 3.31 1.96
Portland, OR 4.65 2.51 1,26 5.23 2.96 1.60459 2.47 1622 7,.20 4.50 2.79
Seattle, WA 5.01 2.74 1.46 5,633.23 «1.83 4.952670 1417675492316

22


List of Figures (Continued)
Page

Figure B-1. Comparison of CTS data from Blacksburg, VA and 37
predictions for Roanoke, VA for 11.7 GHz at an
elevation angle of 33 degrees. Data period is
July through September, 1977.

Figure B-2. Comparison of COMSTAR data from Blacksburg, VA 39
and predictions for Roanoke, VA for 19.0 GHz at
an elevation angle of 44 degrees. Data period
is July through September, 1977.

Figure B-3. Comparisons of CTS data from Austin, TX and 40
predictions for Austin, TX for 11.7 GHz at an
elevation angle of 49 degrees. Data period is
June 12, 1976 to August 30, 1976.

LIST OF TABLES
Page

Table 1. Mean attenuation predictions for .01, .1, and 1 percent 17
of a year at 12.2 GHz on earth-geostationary satellite
links for satellites located at the indicated suborbital
longitudes, Ao

Table 2. 99.5 percent confidence limit attenuation predictions 19
for .01, .1, and 1 percent of a year at 12.2 GHz on
earth-geostationary satellite links for satellites
located at the indicated suborbital longitudes, Ay:

Table 3. Mean attenuation predictions for .01, .1, and 1 percent 21
of a year at 14.5 GHz on earth-geostationary satellite
links for satellites located at the indicated suborbital
longitudes, Ay:

Table 4. 99.5 percent confidence limit attenuation predictions 23
for .01, .1, and 1 percent of a year at 14.5 GHz on
earth-geostationary satellite links for satellites
located at the indicated suborbital longitudes, Ay:

vii


Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

1.

4.

5.

7.

A-l.

A-2.

LIST OF FIGURES

Mean atmospheric attenuation expected at a Washington,
DC earth terminal at 12.2 GHz as a function of geo-
stationary satellite position.

Comparison of CTS data from Greenbelt, MD and predictions
for Washington, DC for 11.7 GHz at an elevation angle of
29 degrees, data period is June 1, 1976 to May 31, 1977.

Comparison of CTS data from Rosman, NC and predictions
for Asheville, NC for 11.7 GHz at an elevation angle of
33 degrees. Data period is June 1, 1976 to June 30, 1977.

Comparison of CTS data from Holmdel, NJ and predictions
for Trenton, NJ for 11.7 GHz at an elevation angle of 27
degrees. Data period is April 26, 1976 to April 26, 1977.

Comparison of CTS data from Holmdel, NJ and predictions
for Newark, NJ for 11.7 GHz at an elevation angle of 27
degrees. Data period is April 26, 1976 to April 26, 1977.

Comparison of CTS data from Holmdel, NJ and predictions
for New York City, Central Park, NY for 11.7 GHz at an
elevation angle of 27 degrees. Data period is April 26,
1976 to April 26, 1977.

Comparison of radiometric data from Palmetto, GA and
predictions for Atlanta, GA for 13.6 GHz at an elevation
angle of 38.2 degrees. Data period is June, 1973 to
June 1975.

Comparison of radiometric data from Grant Park, IL and
predictions for Chicago, IL for 13.6 GHz at an elevation
angle of 27.3 degrees. Data period is July, 1976 to
June, 1977.

Comparison of radiometric data from Longmont, CO and
predictions for Denver, CO for 13.6 GHz at an elevation
angle of 42.6 degrees. Data period is June, 1973 to
July, 1975.

Earth-satellite geometry over a spherical earth.

Geometry in the plane of the earth-satellite link and
the earth's center.

vi

Page

10

11

13

14

15

31

32


05

0.2

0.1

mene

X = Attenuation Data

l Lil

Percent Time Abscissa Is Exceeded

0.05

0,02

0.01

Figure 6.

10

Atmospheric Attenuation (dB)

Comparison of CTS data from Holmdel, NJ, and predictions
for New York City, Central Park, NY, for 11.7 GHz at an
elevation angle of 27 degrees. Data period is April 26,
1976 to April 26, 1977. See Figure 2 for definition of
curves 1 to 5.

11


Earth-Space Attenuation Predictions for
Geostationary Satellite Links in the U.S.A.

E. J. Dutton

ABSTRACT

The previously developed Rice-Holmberg (RH) rain-
rate model and the Dutton-Dougherty (DD) attenuation
model for earth-space links, and their subsequent
modifications, are reviewed. Predictions are compared
with data observed both from the Communications Technology
Satellite (CTS) and from radiometric measurements. Then
predictions are made at 12.2 and 14.5 GHz for 75 possible
U.S.A.-based earth stations pointing to several potential
geostationary satellite locations.

Key words: attenuation distributions, earth-space
attenuation, microwave frequencies,
prediction confidence limits, rain-rate
distributions, satellite-earth
communication links.

1. INTRODUCTION AND BACKGROUND

An earlier report (Dutton, 1977a) discussed the development of a model
for the prediction of earth-space attenuation, principally due to rain, at
4 to 16 GHz. This model was applied to earth-space communications systems
for time-availabilities of 99% or more. As this report showed, the rain
attenuation problem was much more substantial for systems using the 12 to
14 GHz frequency band than for systems using the 4 to 6 GHz band. Hence,
this report will concentrate on the earth-satellite attenuation in the
12 to 14 GHz band.

As was discussed in Dutton (1977a), precipitation-caused attenuation has
been traditionally linked to a difficult-to-measure parameter, "one-minute
rain rate", R,> at the earth's surface. This tradition has been maintained

in Dutton (1977a), but the relationship between Rg and attenuation has been

*,

The author is with the Institute for Telecommunication Sciences, National
Telecommunications and Information Administration, U. S. Department of
Commerce, Boulder, CO 80303.

*K
or simply "rain rate".


Table 1.

Mean attenuation predictions for .01, .1, and 1 percent of a year at 12.2 GHz on

carth-geostationary satellite links for satellites located at the indicated suborbital longitudes, ‘\,.
AS = 110°W 90°W 130°W 70°W

Location OI 1k sl 1 1 “Ol 1 1 Ol 1 a

Worcester, MA 6.97 3.30 1,51 6.38 2.79 1410 9125.16 2.99 6.252068 1.0L
Boston, MA 8.44 3.63 1.50 7.91 3.12 1.08 10.4 5,503.04 7479 3.01998
Providence, RI 6.10 3.05 1.48 5.48 2.54 1,07 8344.92 2.96 5.342043 9B
Concord, NH 5.14 2,78 1,54 4,532.27 16137641464 3.03 439-2416 1.04
Portland, ME 5.71 2,96 1,54 5.05 2.42 111 8,215.04 3.19489 2.29 1.00
Burlington, VP 6.19 2.81 1,425.76 2641 1,08 7.70427 2.66 5.69 2.33 102
Newark, NJ 7.06 3.14 1,32 6,60 2.73 990 8,66 4.56 2.46 651265932.
Hartford, CT U1 4.29143 10,6 3.82104 12.3 5,592.51 10.63.7598
Trenton, NJ 9.55 3.68 1.25 9.20 3.32946 10.84.93 2.28 9.143.268. 895
NY Central Park, NY 8.33 3.41 «1630 7.92 3,02 .970 9.76 4,802.43 7684 2.94 909
NY LaGuardia, NY 9.33 3.81 1,42 8,90 3.37 1.07 10.8 5,302.67 8.82 3.29 :1.00
Rochester, NY 5.15 2.34 17 4.84 2605934617 3.29 1,984.82 2.03.92
Buffalo, NY 4.95 2.31 117 4.65 2,04 9425.95 3,221.93 4.64 2.03932
Pittsburg, PA 4.97 1.61 512,470 -2,00 8345.87 3.04 «1.67 4,702.00. 834
Philadelphia, PA 5.66 2.68 1.16 5.21 2.31 6879-7417 3.92 2135.12.26 83H
Wilmington, DE 7.78 3.22 117 7.39 2.86 88491443213 7233 2.8L B42
Washington, DC 9.06 3.49 1615 8.75 3.17888 10.1454 2.00 BTL 3.14 86
Albany, NY 4,91 2.446 1,28 4.46 2,06 9736.48 «3579 -2.38 4.38 1.99 916
Syracuse, NY 7.09 2.87 1,22 6,80 2.56 952, B11 «3,932.12 6.76 2.5297
Harrisburg, PA 12.1 4,33) 1413-118 4,03 884 13.25.33 1.93 1B 3.99857
Baltimore, MD W.1 4,06 117 10.7 3.74 = 902,«12.0 5.14 2.06 10.6 = 3,70
Richnond, VA 12.74.54 -1,05 12.4 4.240813 13,6 «5521.86 12.4) 4.22. 790
Charleston, KV 9.95 3.50 944 9,76 3,30 780 10,6 4417049 9.77 3.31793
Greensboro, NC 10.1 3.55 873 9,89 3,33 4696 10.8 4.28146 9,893.33 694
Charlotte, NC 9.23 3.36 890 9,013.14 7129.96 4081.47 9,023.15. 719
Columbia, Sc 13.6 4.78 879 13.4 455684 14,2554 1452134 4.56693
Atlanta, GA 12.4 4.3L 81S 12.2413 670 «12.9490 ASL 2.318.707
Pensacola, FL 15.2 5.42742 «15.0 5.25614 15.9 6.03 -1,2015.1 5.34 683
‘Tampa, FL 18.1 6,90 805 17.6 © 6.52579 20.0815 1.55 17.7657 610
Miami, FL 19.6 7.71 895 «18.8 = 7.18597 22.29.3986) 18.87.19 600
Birmingham, AL 14.7 5.23 6850-145 5.06 = 7075.3 5.86 1.36 14.6 515.780
Montgomery, AL 17,0 6.32882 «16.6 6,07 708 18.2 7.24 «5016.8 618.784
Memphis, TN 10.4 3.67768 «10.3 3,56 678 10.8 9412112 10.4367. 768
Nashville, TN 11.7 4,04 8171.6 3,90 700 12.2 455126 63.9758
Jackson, MS 10.6 3.65 «705. 10.53.55 624 11.04.06 = 1.03 10.6 3.66. 708

17


NTIA-REPORT-78-10

Earth-Space
Attenuation Predictions for

Geostationary Satellite Links
in the U.S.A.

E. J. Dutton

U.S. DEPARTMENT OF COMMERCE
Juanita M. Kreps, Secretary

Henry Geller, Assistant Secretary
for Communications and Information

October 1978


Percent Time Abscissa Is Exceeded

0.5

02

0

0.05

002

0.01

T

1

X = Attenuation Data

Figure B-3.

Atmospheric Attenuation (dB)

Comparisons of CTS data from Austin, TX, and
predictions for Austin, TX, for 11.7 GHz at an
elevation angle of 49 degrees. Data period is
June 12, 1976 to August 30, 1976. See Figure
2 for definition of curves 1 to 5.

40



‘uotqtsod eqTTTEIes
Areuotje1s0e3 Jo uopWoUNy e se ZHD Z*ZT 3 TeuTw1e] YyIIve

oq ‘uojZuTysem e Je poqoedxe uoT}enuejj}e oOTIJeydsomje UBER *T aan3ty
(‘buo) m Bap) Oy ‘apnyiBu07 joyiqsogns 9411/2}0S
0g! del oll 00! 06 . 08 ol
T T qT T T T if T qT T
r |
| ol |
=
[_ %oV'O
L 12
+p 3
a
Le
| de 3.
L 4 2
: 9 8
L | 8
S
_ 4) =
[ 72
L +8
[— %100=4 |
| 6
- —0!
H | {ot



Expressions (2) and (3) are empirical relationships. Based upon M and 8B for
305 first-order U.S. Weather Service locations, the United States of America
was divided into 19 telecommunication-oriented, rainfall zones in Dutton
(1977b). Each zone presumably represented a region in which rainfall patterns
are similar, and by pooling raw data within a given zone, zone-wide so values
were obtained for application at any particular location within that zone.
This approach, however proved less than optimum for many zones. For this and
other reasons discussed in Appendix A of this report, the zonal concept has
been discontinued so far as this report is concerned.

The variance of attenuation, s°, about a mean value, tT, predicted for a
given percent of a year, was handled in Dutton (1977a) by simply assuming all
the attenuation model's variability was due to s.. This gave a restricted
(upper and lower bounds) range of attenuation variability. In Section 2,
recent data from the CTS satellite observations at 11.7 GHz have been compared
with this approach, in a further effort to assess the model's meaningfulness.
This is in addition to the data-model comparisons made in Dutton (1977a). In
Section 3, results using this model are given at 12.2 and 14.5 GHz.

Figure 1 shows an example of geostationary satellite-earth attenuation
and a relationship between mean satellite suborbital longitude for Washington,
DC, at 12.2 GHz. Three separate curves are displayed that are parametric in
percent of a year that the attenuation is expected. Attenuation values are
those expected for an average year. This relationship is derived in detail
in Appendix A.

2. COMPARISON OF OBSERVATIONS AND MODELING
Recently, much attenuation data from the Communications Technology
Satellite (CTS) taken at 11.7 GHz have become available for various locations
throughout the U.S.A. Most of these data are presented in a cumulative dis—
tribution format, which facilitates their comparison with the Dutton-Dougherty
(DD) model (Dutton, 1977a). The DD model, however, is, at this stage, still a
model which predicts annual distributions of earth-space attenuation, only,
and does so only as low as 0.01 percent of a year. Much of the data examined
to date (Vogel and Straiton, 1977; Bostian et al., 1977, 1978) covers a period
of time much less than a year; e.g., a summer. There are various ways that

both this kind of data or the DD model can be manipulated to accommodate these


Second, consider the situation when the frequency of occurrence of T in the
interval y-x is identical with that in the interval x; i.e.,

PO = Py (TD - (39)
This clearly leads to

P(A >T = PLA >T). (B10)

When the data for what occurs in the interval y-x is unknown, as it is with
much of the rain attenuation data alluded to in section 2 of this report, we
can use the two hypothesized year-long data intevals, (B8) and (B10), to make
comparisons with predictions. Note that while (B8) is certainly one extreme
condition, (B10) is not the other. However, the other extreme is difficult
to postulate. For example, no rain attenuation is one extreme that is
realizable; i.e., dry and wet season climates. On the other hand, "infinite"
rain attenuation in the interval y-x is simply unrealizable anywhere, and to
postulate some other form than the straightforward linear extrapolation (B9)
will involve additional and perhaps unwarranted assumptions, based strictly
on conjecture. Furthermore, when (B10) is used to plot data as in Figures
B-1 and B-3, it represents the actual distribution of the data during its
observed interval x, as well as that hypothesized for an annual distribution.
As a matter of fact, (B10) may well represent an extreme situation in Figures
B-1 and B-3, because the data here is summertime data, and the frequency of
occurrence of high rain attenuation during the off-summer period rarely
exceeds the frequency of occurrence during the summer in practically all parts
of the northern hemisphere.

As mentioned at the start of Section 2 and above, there are data of about
a summer's length available from Blacksburg, VA (Bostian et al., 1978) and
Austin, TX (Vogel and Straiton, 1977). Figure B-1 shows the comparison of the
DD model annual distribution of earth-satellite attenuation with data for the
(nominal) months of July, August, and September, 1977, at Blacksburg, VA,
adjusted by (B8) ("Adjusted data" on graph) and by (B10) ("Attenuation data"
on graph). The comparison is made at an earth-station elevation angle of

8 = 33 degrees, the angle of data observation, and at the CTS frequency of

36


Table 4 (Continued)

99.5 percent confidence limit attenuation predictions for .01, .1 and 1 percent of a year at 14.5 GHz on
earth-geostationary satellite links for satellites located at the indicated suborbital longitudes, A,

A, = l0°H 90°W 130°W 70°w
Location 01% 1% Ol 1 1 -ol1 1 ol 1
Louisville, KY 30.0 10.6 1,56 29.7 10.2130 31.2 182.49 29.8 10.4 140.
Columbus, OH 18.4 6.63 1.58 18.16.28 1,28 -19.4 = 7812.57 18.16.3413
Cleveland, OW 23.0 8.43 1.88 22.6 «7.95 1.50 24,5 10.03.17 22.6 7.99153
Cincinnati, OH 31.6 11,0 1.693163 10.6 ©1437 32,7 12032477 BL 107146
Indianapolis, IN 26.3 9.11 1,59 26.1 8.811433 27.2 10,2, 2,51 26.2 8.941
Detroit, MI 16.8 6.36 1.70 16.4 5.97 1,39 18,0 7667 2.77 16.4 6,031
Des Moines, TA 32.4 12 1.67 32.3, 1101533382 12,0239 32.6 183
Milwaukee, WI 18.4 6.67 1.69 18.26.40 1.47 -19,3 7067253183 6.57161
Minneapolis, MN 20.6 7.57 1682 20.57.40 1.68 2164 8.42254 20.8 7.74 197
Sioux Falls, sD 19.4 6.93 1.61 19.4 6.86 «1455 20.0 7.552.119.7226 1.89
Fargo, ND 15.9 5.88 1.674 «15.9 5.811668 = 16.6 = 6502.26 16.36.22 201
Billings, MT 19.1 7,08 1.93 19.37.29 2412194 72382619 20.28.27 2.96
Chicago, IL 31.4 11.0 1.86 31.2 10.6 = 1659 32.4 12.22.88 31.3 10.8 1.76
St. Louis, NO 20.4 7.49 1.48 20.27.27 131214 839-2616 20.4 27,501.48
Kansas City, NO 28.2 9.76 1.51 28.19.63 1.40 28.9. 10.5212 28.5 10.01.70
Wichita, KS 28.6 9.89 1.43 28.6 ©9682-1437 29.3 10.6 = 1.96 = 29.0 10.31.75,
Omaha, NE 30.9 10.5 1.51 30,8 10.4 144 3165 11.2210 31.2 10.81.78
New Orleans, LA 36.5 13.5 111 36.0 13.1 935° 38.4 14.7 9 181 3645 13.5 LD
Shreveport, LA 31.0 10.7 1.09 30.9 10.6 +996 31.9 115 1.61 3163 10.91.22
Little Rock, AR 33.1 16 1,23 32.9 503442 12,5 10833342 BL
Oklahoma City, OK 22.37.63 1616 22.2 7658 1222.8 = 8181.59 22.6 7.98 1.43
Tulsa, 0K 47.4 175 1,59 47.2 174 1648 49.3 18.9 2.40 48.3 18.21.96
Dallas, TX 36.9 12.8 1.28 36.7 12.722 3768 13.6 1686 37.4 13.2159
Ft. Worth, TX 27.6 9.33 1dL 27.59.26 1.05 28.29.94 158 27.9 9.66 1.36
Grand Rapids, MI 15.8 6,011.68 «15.55.72 1,44 16.97.08 254 15.75.86 1.55
Amarillo, TX 19.5 6.67 1.24 19.5 6.7L 1.27 19.8 7.071.656 20.07.21 1.68
Houston, TX 37.3 13.4 1,09 37.1132 997 38.6 14.3169 37.8 13.8 1.33
San Antonio, TX 36.5 12.3 1.02 36.5 12.3 1992 37.2 13,0 1648 37-1 12.8 1.37
Albuquerque, NM 5.81 3.07 1.46 5.98 3.20155 6.16 3.33165 6.81 3.82 2.03
Denver, CO 15.6 5.90 1.59 15.7 6,011.68 «= 16.06.26 1.88 16.56.70 2.28
Cheyenne, WY 16.2 6,51 2,09 16.3 6.63 2.20 16.6 6.94 20451717045 2.88
Boise, ID 6.41 3.16 1.35 6,85 3.47 1.59 6,503.21 1.40 8.37 4,58 2.40
Salt Lake City, UT 11.9 4.82134 12.2 5.081452 12,1 4,991.46 13.46.06 2,23
Phoenix, AZ 8.38 3.66 9668.71 «3.86 1.1L 8.593478 = 1,606 = 9.92 4,691.65.
Reno, NV 5.47 2.80 1.17 6,06 3.19 1.642 5.47 2,80 1618 8024.47 2.25
Las Vegas, NV 4.50 2.40 1,12 4.91 2.66 1,28 «4.622648 «1.16 6.33 3551.82
Los Angeles, CA 6.77 2.92 852-7417 3.20 1,04 6.80 2.95 8688.47 4121.68
San Francisco, CA 9.55 4.04 1,02 10.2, 4.511435 9.49400 993 12.3 6,062.45
Portland, OR 17.1 6.78 1.60 17.9 7645 2421761672155 20,5973. BH
Seattle, WA 13-1 5.71 1677 13,9 6,392.30 13,2565 1473 16.7 B72 AD

24


are (nearly) coincident. These data were taken from the CTS satellite at a
frequency of 11.7 GHz and an elevation angle of 8, = 49 degrees. Comparison
of data adjusted by (B8) with predictions in figure B-3 was not possible,
because data results were all below the 0.01 percent ordinate value.
Comparison is "good" below the 0.01 percent ordinate between data and predic-
tions, but since the model presupposes a lower limit of 0.01 percent of a year
for prediction purposes (Dutton, 1977), such comparison is not meaningful in
the current context. Comparison of data adjusted by (B8) with predictions
in Figure B-3 is superior to the analogous situation in Figure B-1, but, of
course, if such adjustment is meaningful, considering the proximity of data
and prediction locations and the Texas terrain, one would expect a superior
comparison in Figure B-3 to that in Figure B-l.

The methodology presented in this appendix should be used with consider-
able caution, and should be carefully interpreted. It is, however, recognized
that occasions do arise when engineering estimates must be made based on less
than a full year of data. In these cases, the meaningfulness of the estimates
made must be properly assessed. It is still preferred that users have at least
a year's data available before comparing with the prediction model results.

As an example of concern in this regard, consider that one thunderstorm in an
entire year's data is capable of so influencing the resultant distribution
that the 0.01 percent of a year attenuation value can nearly double as a con-
sequence of this one event. This implies that a distribution based on
3-months' data can be rather different than the distribution with 1 or 2
months' worth of additional data. A distribution based on a (continuous)
year's worth of data, on the other hand, may not contain all the extreme
events either, but the likelihood that the "peaks" and "valleys" of the

climatological year are included is much greater.

REFERENCES for Appendix B

Bostian, C. W., W. L. Stutzman, E. A. Manus, P. H. Wiley, R. E. Marshall,
S. R. Kauffman, W. P. Overstreet, and R. R. Persinger (1978), Current
results of 11, 19, and 28 GHz satellite path attenuation measurements,
presented at the National Radio Science Meeting, U. of Colorado, 9-13
Jan. 1978, Boulder, CO.

41


Table 4. 99.5 percent confidence limit attenuation predictions for .01, .1 and 1 percent of a year at 14,5 GHz on
earth-geostationary satellite links for satellites located at the indicated suborbital longitudes, A ,.

Al = 110°W 90" 130° 70°W

Location Ole 61% -ol 1 1 sol 1 1 sl 1 1

Worcester, MA 20.4 8.38 2.47 19.4 7.46176 24.0 1167 = 5409 -19,1 7426 1.60
Boston, MA 27.9 10.8 2.60 26.8 «979-1681 3169147 5454 26.5 9551.63
Providence, RI 17.6 7.53 2.41 16.6 66314702164 10.95.00 16.4 6421.54
Concord, NH 17.8 7.65 2,60 16.8 6701.84 21.5 UL 5640 16,5 6.49167
Portland, ME 17.5 7.55 2.57 16.4 6.571.792.6113 5456 16.2 6331.60
Burlington, VT 23.4 8.95 2.56 22.7, 8121.84 25.8 11.9 ©5414 22.6 7.96 1.70
Newark, NJ 19.27.67 2.15 18-4 6,94 1,57 21-9 10.24.16 18.3 6BL 1.47
Hartford, CT 34.3 12.9 2.58 33,2, «118 ©1678 3764 15.8 4,80 33,271.67
Trenton, NJ 25.0 9.29 2.13 2h.4 8595S 27-2 ALT 1024.2 BT 1.46
NY Central Park, NY 30.0 11,2 2.31 -29.2. 10.4 1,65 33,2 14.34.60 28.9 10.21.53
NY LaGuardia, NY 28.3 10.8 2.43 27-4 9.92 1763S 13-9 477 27.2 9.76 1.63
Rochester, NY 15.7 6.16 «1.95 15.1. 5.61 1.501765 8023.46 IS.L 5456 1.46
Buffalo, NY 16.6 6.44 1,93 16.25.93 LSE 18.3816 3,33 16.15.90 1.49
Pittsburg, PA 15.8 6.10 1.68 15.4 5.66 1.32 17-4 7582.87 15.4 5.66 1432
Philadelphia, PA 16.3 6.71 1.90 15.5 6,051.39 18.8 = 8,95 3,621.4 5.95 1ST
Wilmington, DE 22.4 8.48 1.96 21.7 76811642 24.8 10.8 3.70206 7.7L 130
Washington, DC 24.5 9.09 1.95 23.9 8,46 1.45 26.6 «1.23.59 23.8 8.40 1.40
Albany, NY 20.7 8,022.26 © 20.07.27 1,63 23.2 10.74.48 19.9 7613 1ST
Syracuse, NY 26.8 9.84 2.24 «26.39.16 1,67 28.8 12.24.20 26.29.07 1.59
Harrisburg, PA 33.1 11.9 2.28 32.6 «10.2159 3540 14,2 4123245 ALL 153
Baltimore, MD 34.0 124 2.16 33.2 16 1657 36.6 15.0 4,07 33.2 11.51.50
Richmond, VA 37.1 13.6 1.96 36.2 12,8 1643 39,9 16.0371 3642 12-7 1.38
Charleston, WV 30.9 10.7 1.71 30.5 10.2134 32,0 121-2693 3065 10.31.37
Greensboro, NC 27.9 9.77155 27-4 9030 B- 29,3 132.76 27-4 9.380117
Charlotte, NC 24.78.78 148243834 LS 26,2 10,2258 24.38.36 1.16
Columbia, SC 42.3 15.5 1.57 414 16.9 118 45.4 «17.72.84 414.9 1.20
Atlanta, GA + 3146 1.01.35 31.0 1067108 32.7 12.32.26 3152 -10.8 115
Pensacola, FL 38.8 14.6 1.21 38,2 14.2 LOL 4160 15.9191 38,5 14.4 12
Tampa, FL 44.1 17.2 1.49 42.6 16.2 1,01 4961 20,2 3.08 42.8 16.31.08
Miami, FL 51.6 20.4 1.90 49.3 19.2142 58.9 24,2345 4963 19,2 1.43
Birmingham, AL 34.5 12.6 1.33 34.0 12.1 1,609 36.2 13,8 2-18 3443 12.3 LD
Montgomery, AL 38.1 14.3 1.48 37.3 13.7115 40.9 16.22.64 3766 14.01.29
Memphis, TN 30.2 10.6 1.25 29.9 10.3 16093163 MS LOL 3042 10.6 1.25
Nashville, TN 27.0 96431435 26.7 915113279 10.4213 26.8 9,291.28
Jackson, MS 31.9 11 117 31.6 10.8 1,02, 32-9 -12.0 1,80 3-9 D118

23




|
4
5 4
| X = Attenuation Data = _|
2 4
no}
o
ao]
o | —
oO t—| 4
ZF q
wi _ a
2 05 |
fo]
QD [— 4
2
3 t— +
a
5 02 4
&
i
5 ue —
° [— S|
@ — 4
a }— 4
0.05-- Z|
0.02;—- 4
0,01
0 30
Atmospheric Attenuation (dB)
Figure 8. Comparison of radiometric data from Grant Park, IL, and

predictions for Chicago, IL, for 13.6 GHz at an elevation
angle of 27.3 degrees. Data period is July, 1976 to
June 1977. See Figure 2 for definition of curves 1 to 5.

14


Figure A-1. Earth-satellite geometry over a spherical earth.

31


Figure A-2. Geometry in the plane of the earth-satellite
link and the earth's center.

32


Table 2 (Continued)

99.5 percent confidence limit attenuation predictions for .01, .1, and 1 percent of a year at 12.2 GHz on
earth-geostationary satellite links for

satellites located at the indicated suborbital longitudes, \,.

A, = la0ew 90°w 130°W 70°"

Location 01% 1% i sol 1 1 sl 1 1 sl 1 1

Louisville, KY 19.5 6.99 1,13 19.36.75 +944 20.37.83) «1.79 19.4 6.84 1,02
Columbus, OH 12.0 4.44 114 1.7 419 +936 12.8 5.29 1.85 11.8 4.23 +970
Cleveland, OH 15.2 5.67 1.36 14.95.33 1,09 16.36.79 2.28 14.95.35
Cincinnati, O8 20.9 7.331422 20.6 = 7,06 1995 21.6 8.24 1.98 = 20.77.13 1.05,
Indianapolis, IN 17.1 6.04 1.15 16.95.82 +965 17.7 6.81 1.80 17,0 5.91 1.04
Detroit, MI 11,0 4,28 1.23, 10.7401 1,0L11.9 5423 1,99 10.7 4051.04
Des Moines, IA 214 746 1622 2137.34 LAL 22.98.07 1,72 21.5 7660 1.33,
Milwaukee, WI 12.0 4.48 1,23 11.8 4,291,607 12.75.20 1,84 LL.
Minneapolis, MN 13.75.12 «1633136 5,011,283 14.3 5,73 1,84 13.8 5.251
Sioux Falls, sD 12,6 4.64 1417126 4,58 1513 :13.0 5,09 1,55 12,8 4.88 1.37
Fargo, ND 10,5 3.99 1.28 10.4 3.94 1623 10.9 4.45164 10.726 18.
Billings, MT 12.5 4.77 14k 126 4.92 15401267 4,98 159 13,3 5.632413
Chicago, IL 20.8 7.34 1.34 20.6 = 7-AL 1152165819 2,06 = 20,7725 1.27
St. Louis, MO 13.2 4.98 1.07 13.0 4,82 +952 13.9 5,62 1,56 13,2 4991.08
Kansas City, MO 18.2 6.43 1.09 18,2 6.34 «1,01 18.8 6.97 1.52 18.4 6,60 1,22
Wichita, KS 18.5 6,50 1,03 18.4 6.45 +991 19.0 6.98 1.40 18.8 6.79 1.26
Omaha, NE 20.3. 7,02 1,10 20,3 6.95 104 = 20.8 «97452 1,51 20.5725 1.29
New Orleans, LA 23.7 8.80 +794 23.3 8.58 +673 25.0 9.66 = -1.28 = 23.78.80. +795
Shreveport, LA 20.3. 7.10 +790 20.2 7,00 721 20.9 7,62 1419 .20.4 = 7.23 +880
Little Rock, AR 21.6 7.70 +889 21,5 7.57 +797 22.6 8.31 «13187278, 947
Oklahoma City, OK 14.6 5,09 +841 14.6 5.05 +81315.0 5.47 1.14 14.95.33 1,03
Tulsa, OK 30.9 114 112 30.7 11.3 1,04 32,1 12.3 1.67 31,4 11.8 1.37
Dallas, TX 2.1 8.43 1914 24.1 8.36 +869 24.8 8.98 1.31 24,5 8.73113.
Ft. Worth, TX 17.8 6,12 +797 17.8 6,07 +759 18.2, 6.54 112 18.0 6.35, 2974
Grand Rapids, MI 10.4 4,06 1,22 -10.2, 3.85 160511624683 1684 10.33.95 1..13
Amarillo, TX 12.6 4.43 1903 12.6 4.45 19240012.8 4.710113 12.9 48112
Houston, TX 24.3 8.75 773 %.1 8.65 -7TML 25.1 9.40118 24.6 9.01. +937
San Antonio, TX 23.9 8.12 +734 23.9 8,09 s715 24.4 8.57 1,06 24.38.46 +980
Albuquerque, NM 3.98 2.16 1,08 = 4.09 2,251.15, 4.22 2.34 1,22 4.69 2.70 1.49
Denver, CO 10.2 3.98 1.16 © 10.3 4,06 122 10.5 4424 137 10.84.56 162.
Cheyenne, WY 10.6 4.42 «1,52 10.7451 1601104273 1,678 1 5102.09
Boise, ID 4.37 2.20 1995 4.69 2.46 1174442426 1603578324 176
Salt Lake City, UT 7.87 3.29 1976 8.103.470 Lad 8.02 3.41 1.07 8.99 4.16 1.62
Phoenix, AZ 5.65 2.52 +709 5.88 2.68 +815 5.80 2.62 777 6.75 3.27 120
Reno, NV 2.67 1.68 1.03 3,11 1.97 1.23 2,68 «1.68 = 1.03 4,552.94 1.89
Las Vegas, NV 3.16 171 1829 3.44 1.90 +946 3.23 1.77 1864 4452.54 1.35
Los Angeles, CA 4.54 2.02 1629 4,83 2,22 769 4,572.03 1641-5475 2,88 1.23
San Francisco, CA 6.35 2.76 752, 6,803.09 +989 6.31 2.72 +730 8.304.200 -1.77
Portland, OR 11.2 4551616675602, 2453 L450 14131366 = 6462 2.77
Seattle, WA 8.70 3.89 1,29 9.28 4.37 1.66 = 8.65 3.84 1625 11.36.04 =~ 2.96

20




Percent Time Abscissa Is Exceeded

TTTT

on
T

T

+

05

02

al

0.05}

02

00!

LiL

X = Attenuation Data
O =Adjusted Data

|

Figure B-2.

Atmospheric Attenuation (dB)

Comparison of COMSTAR data from Blacksburg, VA,
and predictions for Roanoke, VA,for 19.0 GHz at
an elevation angle of 44 degrees. Data period
is July through September, 1977. See Figure 2
for definition of curves 1 to 5.

39


Percent Time Abscissa Is Exceeded

05

0.2

a

0.05

0,02

001

|

X = Attenuation Data

O = Adjusted Data

Figure B-1.

Atmospheric Attenuation (dB)

Comparison of CTS data from Blacksburg, VA, and
predictions for Roanoke, VA, for 11.7 GHz at an
elevation angle of 33 degrees. Data period is
July through September 1977. See Figure 2

for definition of curves 1 to 5.

37


Ltt

X = Attenuation Data

Lil |

5
2

mo]

a

mo]

o |

g

x

uJ

2 05

12}

8

rs)

3

< 02

o

£

=

5 0.1

&
0.05
0.02
0.015

Figure 3.

Atmospheric Attenuation (dB)

Comparison of CTS data from Rosman, NC, and predictions
for Asheville, NC, for 11.7 GHz at an elevation angle of

33 degrees. Data period is June 1, 1976 to June 30, 1977.
See Figure 2 for definition of curves 1 to 5.


Percent Time Abscissa Is Exceeded

0.05

0.02

0.01

L111

X = Attenuation Data

|

|_| Lol

Figure 4.

10 2 16

Atmospheric Attenuation (dB)

Comparison of CTS data from Holmdel, NJ, and predictions
for Trenton, NJ, for 11.7 GHz at an elevation angle of 27
degrees. Data period is April 26, 1976 to April 26, 1977.
See Figure 2 for definition of curves 1 to 5.


PREFACE

The study presented in this report was partially supported by the
Advanced Mail Systems Directorate of the U.S. Postal Service, Rockville, MD
20852, under Agreement Number 104230-78-T-0681. The U.S.P.S. technical
monitor for the program was Mr. Ralph Marcotte of the Systems Division.

The program director at the Institute for Telecommunication Sciences was
Dr. Peter McManamon.
The opinions expressed herein are those of the author and are not

to be construed as representing policies or doctrines of the U.S.P.S.


straight lines over the earth's surface. This, in turn, means the value of
8, can be determined from elementary spherical and plane trigonometry; thus,
a straightforward relationship between oO» Aye and the latitude, ®%, and
longitude, A, of the earth station can be determined. Then, because at a
specific frequency, T, (84) is an algorithmic function of A> it can be
represented as a function of Ay graphically for any given earth-station
location.

Consider the octant of a spherical earth shown in Figure A-l. Assume
that on this model earth, an earth-station terminal of an earth-geostationary
satellite link ES is located at point E. The point S represents the satellite
terminal so that the path length is Es, which we shall call R; i.e.

R=ES . (A10)

Further, let C be the earth's center; A be the suborbital longitude of
the satellite, measured at point B on the equator; A be the longitude of E,
measured at point A on the equator; and © be the latitude of E, measured on the
meridian intercepting the equator at A. If we are dealing with ray trajec-
tories of earth-satellite paths in the conterminous U.S.A., then the ray path
is essentially equal to the slant path R, and the elevation angle of the earth
station antenna is equal to 8 o> the angle between the tangent plane to the
earth at E and R. This is also shown in Figure A-2, which indicates the geo-
metry in the plane ECS. In addition, let

r = CB = CE, the earth's radius, (All)
x = the great circle arc BE, (A12)
z= BS. (A13)
Since
Angle BAE = 90°, (A14)
Angle BCA = Ay - Ay (A15)
Arc BA = r(A, - A), (A16)
Angle ACE = 4, (A17)
and Arc AE = ro, (A18)

we can use the spherical trigonometric relation

xX . -
cos = = cos ® cos(A, - A) (A19)

30


Table 1 (Continued)

Mean attenuation predictions for .01, .1, and 1 percent of a year at 12.2 Giz on earth-geostationary satellite
links for satellites located at the indicated suborbital longitudes, Ny.

9 7 Hotw 90°W 130°W 70°"

Location Ole 1k -ol 1 1 sol 1 1 solo 1
Louisville, KY 11.4 3.98 904: 11,3 3682773119454 1363388. 8NH
Columbus, OH 6.75 2.65 970 6,552.46 812746433430 150 6.592449. 838
Cleveland, OH 5.81 2.43 1,06 5.59 2.22 8786.56 3415 1.66 5.61 2,23 892
Cincinnati, OH 10.8 3.78 = 934 -10.7 3.60794 L437 L107 3,65. 832
Indianapolis, IN 9.56 3.39 924 9413.24 = 79910. 3.93137 9.47 3430. 85T
Detroit, MI 4.36 2.08 1.01 4.121688 = 85254172676 1456 416191. 878
Des Moines, IA 10.5 3.55 862, 10.43.49 8120.83.90 113 :10.6 3.64 924
Milwaukee, WI 5.77 2.35 1.0L 5.63 2.22 8976.29 2,685 16435472 2.30. 968
Minneapolis, MN 4.42 2.07 1.06 4.32 -1,99 993 4892.48 16404451 216 1613
Sioux Falls, SD 5.57 2.28 9695.53 2.24 9395.91 2,59 1623575 2645 LLL
Fargo, ND 4.64 2.08 1.10 4.59 -2,04 1,06 = 5,02 2.421437 4.85 2.26 1.26
Billings, MT 3.19 1,82 1,21 3.321693 1,30 3,371,698 134 3.92 24431472
Chicago, IL 9.94 3.51 9989.80 3.37 8851064403142 9.88 3.45954
St. Louis, MO 6.31 2.52 878 6192.41 «792680 2.96 16236312052. 883
Kansas City, MO 9.23 3.24 8699.18 3.19821 9,563.58 LIS 93K 335.956
Wichita, KS 8.01 2.88 808 7.99 2.85 786 8.30 3.16 «1603819 3.05 946
Omaha, NE 9.97 3.35 798 «9.93 3,31 768 10,3364 10210. 3.48899
New Orleans, LA 16.2 5.88 «727 «16.0 5472614 17.0 652118 16,2 5.88728
Shreveport, LA 10.3 3.54 658. «10.23.48 = 608. 10.63.87 925 10.4 = 3.62 724
Little Rock, AR 12.5 4.30 6752-1264 4226811268470 1081245435797
Oklahoma City, OK 8.06 2.82 696 8.03 2.80 6778.32 3,08 8978.23 2.98 823
Tulsa, OK 14.6 5.08 «798-1415 5.03756 14.9 5645110147 5425934
Dallas, TX U1 3.75709 L372 6844039321390 BL
Ft. Worth, TX 9.27 3.13 644 9.24 3.10 6219453 3.38 84594 3.27. 753
Grand Rapids, MI 4.83 2.15 1.02 4,66 2,00 8955443 2,70 148 4.74 2,07. 955
Amarillo, TX 6.99 2.48 7717.01 2,50 78576182467 92474252474. 979
Houston, TX 15.2 5.31 64615415425 6011566 STL 942 «15.4 547.764
San Antonio, TX 10.13.18 541 :10.0 3.17533. 10,2337 684 10.2333 650
Albuquerque, NM 1,839 1.35 1.05 1,92 1.42 LL 2,02 249 172,36 177 14D
Denver, CO 3.51 1.78 1,02 3.58 1683 1.07 3.731696 1174.00 2,181,386
Cheyenne, WY 2.95 1.93 1.37 3.03 1.99 1.43 3.23 2,16 1573.56 2643 1.80
Boise, ID 1.75 1.28 9791.98 1.46 14131680 1.32 L0L 2.77 2,081.64
Salt Lake City, UT 2.44 1.47 6873. 2.63 1661972257 1656 9383.34 2.11.34
Phoenix, AZ 2.51 1.25 49524701636 55226631432 S3L 34177. 762.
Reno, NV 1.91 1,22 .768 2.231643 9151921622 77034272474 1.40
Las Vegas, NV 2.20 1.06 3312644 173792427 1,08 3453.27 1,59 4
Los Angeles, CA 2.10 1.14 6575-2633 1306832412116 584 3,06 1,801.04
San Francisco, CA 2.38 1.34 «709 2,72 1.58 = 8832435132694 3.81" 2.37 1.46
Portland, OR 3.20 1.79 932-3462 21219316 1475907 503-3422 2.06
Seattle, WA 3.45 1.95. 1.07 3.89 2.301.353.4191 1.04 «5642 3,53 2.33

18




Dutton, E. J. (1977), Earth-space attenuation prediction procedures at 4 to
16 GHz, Office of Telecomm. Report OTR 77-123, May (Access No. PB269228/AS,
NTIS, Springfield, VA).

Vogel, W. J., and A. W. Straiton (1977), CTS attenuation and cross-polarization

measurements at 11.7 GHz, U. of Texas, Elec. Eng. Report under NASA
contract NAS5-22576, Austin, TX 78758, April.

42


6. REFERENCES

Bergmann, H. J. (1977), Satellite site diversity: results of a radiometer
experiment at 13 and 18 GHz, IEEE Trans. Ant. Prop. AP-25, No. 4, July,
pp. 483-489.

Bostian, C. W., S. B. Holt, Jr., S. R. Kauffman, E. A. Manus, R. E. Marshall,
W. L. Stutzman, and P. H. Wiley (1977), A depolarization and attenuation
experiment using the CTS satellite, Quarterly Technical Progress Report I
(Second Year), Elec. Eng. Dept., Virginia Polytech. Inst. and State U.,
under Contract NAS5-22577, Blacksburg, VA 24061.

Bostian, C. W., W. L. Stutzman, E. A. Manus, P. H. Wiley, R. E. Marshall,
S. R. Kauffman, W. P. Overstreet, and R. R. Persinger (1978), Current
results of 11, 19, and 28 GHz satellite path attenuation measurements,
presented at the National Radio Science Meeting, U. of Colorado, 9-13
Jan. 1978, Boulder, CO.

Dutton, E. J. (1977a), Earth-space attenuation prediction procedures at 4 to
16 GHz, Office of Telecomm. Report OTR 77-123, May (Access No. PB269228/AS,
NTIS, Springfield, VA).

Dutton, E. J. (1977b), Precipitation variability in the U.S.A. for microwave
terrestrial system design, OT Report OTR 77-134, November (Access No.
A049041, NTIS, Springfield, VA).

Ippolito, L. J. (1978), Rain attenuation and communications link characteriza-
tion measurements with HERMES (the Communications Technology Satellite),
presented at a Symposium on HERMES (The Communications Technology
Satellite), held by The Royal Society of Canada, 29-30 November 1977,
Ottawa, Canada.

Rice, P. L., and N. R. Holmberg (1973), Cumulative time statistics of
surface point-rainfall rates, IEEE Trans. Commun. COM-21, No. 10,
October, pp. 1131-1136.

Rustako, A. J., Jr. (1978), An earth-space propagation measurement at
Crawford Hill using the 12-GHz CTS satellite beacon, BSTJ 57, No. 5,
May-June, pp. 1431-1448.

Ryde, J. W. (1946), The attenuation and radar echoes produced at centimetre
wavelengths by various meteorological phenomena, in Meteorological
Factors in Radio Wave Propagation (The Physical Society, London, U.K.),
pp. 169-188.

Vogel, W. J., and A. W. Straiton (1977), CTS attenuation and cross-—
polarization measurements at 11.7 GHz, U. of Texas, Elec. Eng.
Report under NASA Contract NAS5-22576, Austin, TX 78758, April.

26


APPENDIX B
COMPARISON OF LESS THAN A YEAR'S ATTENUATION DATA WITH PREDICTIONS

Let ty@ be the time during a year, y, that the attenuation T will be
observed, and let t (1) be the time during a time interval, x, less than a

year in duration, that the attenuation T will be observed. Then clearly
tyr) = t,.() + tO , (B1)

where ty) is the time that the attenuation Tt will be observed in the
time interval y-x. Let the frequencies of occurrence of t during y, x, and

y-x be Py (t)» P(t), and Pyig(T) > respectively. Clearly, then

Py (t) = toy ’ (B2)

P(t) = tC) /x , (B3)

and Py ig = ty_4(D/G-») > (B4)
or, substituting in (Bl),

yp, (7) = xp, (t) + (y-x) Py_(T) . (B5)

Upon integrating (B5) from tT to TM, we obtain a relationship between the

probabilities PY > T); PL > T), and Pyax A > T) that a (random) attenua-

tion, A, exceeds t during the intervals y, x, and y-x, respectively; viz
P(A >T) =
y )

PL(A> 1) + (1 - (A>). (B6)

x X)
y y yrx

There are two possibilities in (B6) that are worthwhile considering.
First, consider the situation when there is no attenuation Tt observed in the

interval y-x; i.e.,
t(D =0 (B7)
for any value of t. Then (B6) becomes

P(A > DTP AD. (B8)

x
y

35


Table 3, Mean attenuation predictions for .01, .1, and 1 percent of a year at 14.5 GHz on earth-geostationary

satellite links for satellites located at the indicated suborbital longitudes, A,

A= 0%w 90°% 130° row
Location Ol kt ol 1 lL 1 solo 1
Worcester, MA 10.64.75 2.06 9.55 4.041650 1.37032 9383.88 1.37
Boston, MA 12.7 5.26 2,05 12.04.56 147 15.37.86 416. 11.8 4.40 1.38
Providence, RI 9.00 4.37 2.01 8.15 3.66 1.46 12.16.96 4,057.96 3.50 1.33
Concord, NH 7.50 3.92 2.08 6.653.231.5306 6.491246 3,071.40
Portland, ME 8.36 4.20 2.09 7.46 3.45 1.50 187.06 4.34 7.24 3.27 1.35
Burlington, VI 9.17 4,00 1.92 8.61 3.45 «1645259835989 3.34 1,38,
Newark, NJ 10.6 4.54 2.46 9.93 «3.97 -1,35 «12,7 650337 9,813.86 1.27
Hartford, CT 16.8 6.30 1.96 16.35.67 1.40184 8.08343 16.2557 133
Trenton, NJ 5 5.40 1.70 149128162 TL 324.0822
NY Central Park, NY 12.6 4.97 1.77 12,0 4.42132 145687332432 123
NY LaGuardia, NY Wel 5.56 1.95 13.54.97 «1.456762 3.66 «13.4 4,861.36
Rochester, NY 7.62 3.32 1.58 7.21 2.96 1,26 9,00 4.632.677.7290 1,23
Buffalo, NY 7.30 3:28 1.58 © 6,902.91 -1.27-8.67 4.53 2.61 6.88 2.89 1.25
Pittsburg, PA 7.37 3.200 1.39 7,00 2.87 1413860 4.29 2.27, 7,002.87
Philadelphia, PA 8.39 3.85 1.58 7.78 3.34 «1.1910. 5.57 2.90 7.68 3.26 1.13
Wilmington, DE 17 4.691.591.2420 1.20135 6.36 2.92 L421
Washington, DC 13.8 5.12 1,56 13,3 4.69 L2k 15.26.56 2.74 13,3 4064 LAT
Albany, NY 7.20 3:46 1.73 6.58 2.93 1.319.386 5.30-3.22 6.47 2831.23
syracuse, NY 10.6 4.14 1,66 10,3. 3.72 1628 12,0 5.58287 10.23.67 1.23
Harrisburg, PA 18.6 6.43 1.52 :18.2 6,03. 1,20 19.87.79 2.63182 5.9816
Baltimore, MD 16.8 6,011.59 16.45.57 1.23 BL 7649 2.82 16.4 55218
Richmond, VA 19.5 6.80 1.45 19.2 6.401411 -20.6 8132.56 19.26.36 1.08
Charleston, W 15.2 5.19 1,28 15.0 4.91106 16.06.09 2.03. 15.0 4.94 1.07
Greensboro, NC 15.5 5.29 119 15.24.99 994164 6.28 1.99 15.2 4.98942
Charlotte, NC Wel 4,98 1,22 13.8 4.67970 «15.15.98 2.0213.8 4.69980
Colunbia, sc 20.97.21 1,22 20.7 6.89 9402.7 8.25212 20,7691 953
Atlanta, GA 19.2 6.49 1,22 19,0 6.25916 «19.97.3181 19.0632 969
Pensacola, FL 23.3 8.20 1,03 23,0 7.95 846. 24.29.0869 23,2 8.08945,
Tampa, FL 28.1 10.6 1413 27.3 10.0 805 30.8 12.4 2.20 27.4 10.1 850
Miami, FL 30-5 1.8 1.27 -29.3 1836 34.4 14.32.67 29.3 LL. 840
Birmingham, AL 22.5 7,90 1.18 22,3 7.65974 23.4 8.79191 22.47.78 1,08
Montgomery, AL 26.1 9.62 1.23 25.79.96 = 9762768 10.9210 25.9» 9.41 1,08
Memphis, TN 16.0 5,50 1.05 15.8 5.35 927 16.6 6.131455 16.05.50 1.05
Nashville, TN 18.0 6.07 1.12179 5.87953. :18.6 6.781.708.0597 1,03
Jackson, MS 16.3 5.49 970 16.2 5.35856 16.96.06 1.43 16.4 5.50974

21


intervals of less than a year. However, in view of the facts that there are
sufficient other data, both radiometric and CTS, available for at least a
year in duration, and that manipulation of the data and/or model lends
considerably less credence to the results, no data of less than one year

in extent has been used for comparison with DD model predictions herein.
Nonetheless some accommodations for this kind of data are considered in
Appendix B. Data presented in Dutton (1977a) will not be repeated here.
Thus the comparisons are essentially new.

Figures 2 and 3 show the comparison of the DD model with the CTS data
presented by Ippolito (1978). The data used in figure 2 were taken at the
NASA Goddard Space Flight Center, Greenbelt, MD, for the year from June 1, 1976
to May 31, 1977. The data results were observed at 11.7 GHz for an elevation
angle 8 = 29°. The data included 96.7% of the rain events for that period.
The data as presented by Ippolito (1978) did not include clear-air attenuation,
so that attenuation (approximately 1 dB) was added to the data presented in
Figure 2. In all cases that follow (except Figure 4, where there are several
"nearby" stations), the nearest first-order U.S. Weather Service station was
used for prediction comparison with the data. In some cases these "nearby"
stations are 30 or 40 miles away, which can introduce some skepticism as to
the validity of any such comparisons. However, no meteorological data with
which to make predictions were available (to this author) closer, and, addi-
tionally, such comparisons are in keeping with similar comparisons (Dutton,
1977a, Rustako, 1978) elsewhere. In Figure 2, however, the prediction compari-
son site, Washington, DC, is relatively close (about 15 mi) to Greenbelt, MD.

The predicted attenuation distributions are for the same frequency and
8, as the data, and there are five prediction curves in Figure 2, and subse-
quent figures. Proceeding from left to right on the figure as it faces the
reader, these curves correspond to the predicted 0.5 and 5 percent confidence
limits, the mean prediction, and the 95 and 99.5 percent confidence limits
respectively.

Figure 3 shows a comparison of CTS data also reported by Ippolito (1978).
These data, however, were observed by NASA at Rosman, NC at 11.7 GHz and
8, = 33° for the period from June 1, 1976 to June 30, 1977. The predicted
attenuation distributions were determined from data at Asheville, NC, which

is located roughly 35 mi from Rosman. Again, as in Figure 2, the predicted


FoRM OT-29
(73)

BIBLIOGRAPHIC DATA SHEET

U.S. DEPARTMENT OF COMMERCE
OFFICE OF TELECOMMUNICATIONS

T. PUBLICATION OR REPORT NO] 2. Gov't Accession No.

NTIA Report 78-10

3, Recipient's Accession No.

4, TITLE AND SUBTITLE

Earth-Space Attenuation Predictions for Geostationary
Satellite Links in the U.S.A.

5, Publication Date

October 1978

6. Performing Organization Code

7. AUTHOR(S)
E, J. Dutton

8. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Department of Commerce
NTIA/ITS-3
325 Broadway
Boulder, CO 80303

9. Project/Task/Work Unit No.

10, Contract /Grant No.

11, Sponsoring Organization Name and Address

U.S. Postal Service
Rockville, MD 20852

12. Type of Report and Period Covered

14, SUPPLEMENTARY NOTES

15. ABSTRACT (A 200-word or less factual summary of most significant information.
bibliography ot literature survey, mention it here.)

Tf document includes a significant

The previously-developed Rice-Holmberg (RH) rain rate modeling and the

Dutton-Dougherty (DD) attenuation modeling for earth-space links, and their
subsequent modifications, are reviewed. Predictions are compared with data
observed both from the Communications Technology Satellite (CTS) and from
radiometric measurements. Then predictions are made at 12.2 and 14.5 GHz
for 75 possible U.S.A.-based earth stations pointing to several potential
geostationary satellite locations.

16. Key Words (Alphabetical order, separated by semicolons)

Attenuation distributions, earth-space attenuation, microwave frequencies,
prediction confidence limits, rain rate distributions, satellite-earth
communication links.

17. AVAILABILITY STAT

20, Number of pages

48

18. Security Class (This report)

[a unemaren Unclassified

19. Security Class (This page) 21, Price:
(7) FOR OFFICIAL DISTRIBUTION.

Unclassified

U.S. GOVERNMENT PRINTING OFFICE: 1978-0-677-448/226

USCOMM-DC 29716-P73


clear-air attenuation at Asheville was added to the Rosman data for more
accurate comparability with the predictions.

Figures 4, 5, and 6 involve attenuation data from CTS at 11.7 GHz and
8, = 27°, taken at Holmdel, NJ, by Bell Laboratories during the period April
26, 1976 to April 26, 1977. These data are presented by Rustako (1978). The
data plus 0.3 dB clear-air attenuation (Rustako's value) are presented in
figures 4, 5, and 6 for comparison with attenuation distribution predictions
made at 3 locations: Trenton, NJ (Figure 4), Newark, NJ (Figure 5), and
New York City, Central Park, NY (Figure 6). The reason that three locations
were compared is that all 3 are approximately equidistant (30 to 35 mi. away)
from Holmdel, NJ. Climatologically speaking, however, Trenton, NJ, would
seem the least likely station to be comparable to Holmdel, since it is much
farther inland than Newark or New York City. However, since Rustako (1978)
uses his Trenton prediction methodology for comparison purposes, this author
feels obliged to do the same, for consistency.

CTS data are being observed at the Ohio State University in Columbus, OH,
at the University of Texas in Austin, TX, and at the Virginia Polytechnic
Institute in Blacksburg, VA. Unfortunately, as of this writing, only data
for short segments of a year were available to this author from the latter two
of these locations (see Appendix B). No full-year data were available to his
knowledge. It would have been helpful to have a year's worth of data from
locations such as Austin, TX, because it would have given a comparison with
an entirely different area of the country than was contained in Figures 2
through 6. Since attenuation predictions have been made for the entire con—
terminous U.S.A. in the next section (Section 3), such a direct-observation
data distribution as the Texas data would have been highly desirable for com—
parison with prediction. There are, however, some indirect observations of
satellite-to-ground attenuation, made by radiometer, for locations more geo-
graphically diverse throughout the U.S.A. than those for the CTS. These
radiometric observations are also of at least a year's length, and are shown
in figures 7, 8, and 9. They were taken by Bell Labs and presented by
Bergmann (1977). As discussed in Dutton (1977a), most radiometric data, when
interpreted as attenuation, cannot be trusted above about 10 dB. For values
below 10 dB, however, radiometric data should be nearly as reliable as direct

observations.