A-rj ST

NASA TECHNICAL TRANSLATION NASA TT F-14,660

DISCUSSION AND PLANNING OF A SYSTEM

FOR A TELEVISION TRANSMITTING SATELLITE

H. Billig

Translation of: "Systemauslegung und

Planung fuer einen Ferhsehrundfunksatelliten,"
Gesellschaft fuer Weltraumforschung mbH,
Porz-Wahn, West Germany, Report No. 72-051,
October 1972, 18 pages.

~'73-159~

)DIscSSIOV A'ND Unclas

'_F- 1660)ATLEVIsION .
ser~TITE21Sc ' l50aS 930
OF A SAT~~2 HL$3T2 CSC1.L OF~ --

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

WASHINGTON, D. C. 20546 JANUARY 1973
 STANDARD TITLE PAGE

1. Report No. 2. Government Accession No. -3. Recipient's Catalog No.

14,660 i
4. Title and Subtitle 5. 'R.eort Dote
DISCUSSION AND PLANNING OF A SYSTEM FOR A Jan. 19, 1973
TELEVISION TRANSMITTING SATELLITE 6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

H. Billig
..... H.. Billig10. Work Unit No.
. .,......
_._',.,.....

11. Contract or Grant No.

9. Performing Organization Name and Address NASw-2483
'..-,i SCITRAN - - 13. Type of Report and Period Covered
Box 5456 Translation
Santa Barbara, fA 9~1OR rnsato
12. Sponsoring Agency Name and Address
NationalAeronautics and Space Administration
Washington, D.C. 20546 14. Sponsoring Agency Code

15. Supplementary Notes

Translation of: "Systemauslegung und Planung fuer einen Ferhsehrund-
funksatelliten," Gesellschaft fuer Weltraumforschung mbH, Porz-Wahn, iY)
West Germany., Report No. 72-051, October 1972, 18 pages.

16. Abstract
The requirements_.of the _Federal Post Office for more television--
programs in the forseeable future can be met by a satellite
television system. This is particularly attractive in combination
with local cable systems. Although many problems are yet to be
solved, an operational satellite system could be completed by
about 1980.

17. Key Words (Selected by Author(s)) 18. Distribution Statement

Unclassified - Unlimited

19. Securin, Classif. (of this report) 20. Security Classif. (of this page) 21. No. oi Page 22. Pic
2.lassified Un.lassPage
Unclassified Unclassified
22.
5 Prle.3ff
f7
5.~~~~~~~~~~~~
.1

~ '
____ '
 DISCUSSION AND PLANNING OF A SYSTEM
FOR A TELEVISION TRANSMITTING SATELLITE

H. Billig

ABSTRACT. The requirements of the Federal

Post Office for more television programs in the
forseeable future can be met by a satellite
television system. This is particularly attractive
in combination with local cable systems.- Although
many problems are yet to be solved, an operational
satellite system could be completed by about 1980.

/1*
1. Introduction

The Society for Space Research, under contract from the

Federal Ministry-fY Education and Science, has had conceptual
studies made by the industry and intends to let short study
contracts for feasibility analyses of the recommended concepts.

The communications requirements established by the German

Federal Post'Office and the television transmission system are
explained, and important results of the first studies, as well
as problems in system design and project planning, are presented.

*Numbers in the margin indicate pagination in the original foreign text.

1
2. Requirements

In planning for the forseeable future, the authorities

responsible for television in the Federal Republic of Germany
proceed from the assumption that there will be an additional
requirement for television programs. They have worked out the
following planning model:

- Number of additional video channels: 3 - 5

- Audio channels: 2 per video channel
- Television standard G-Pal
- Area Covered: 1. Federal Republic
of Germany
2. German-language
areas of Europe
- Picture quality: 48 dB (Evaluation
factor 16.3 dB)
99% of the time
- Receivers: Standard commercial
equipment
- Programming time: To 1:00 AM
- Time of beginning operation: After 1980

Various transmission systems offer themselves for the solution

of such a problem:

- further development of the terrestrial television network

- cable system
- television transmitting satellite
- mixed systems
/2
Choice of a broadcasting system depends, on one hand, on its
reliability, flexibility and economy; and on the 6the hand, on the
availability of appropriate frequencies and on international agree-
ments in this respect.

2
 At this point we will not go more deeply into these consider-
ations about the possible broadcasting systems. The following
discussions, therefore, refer only to a television transmitting
satellite, for which the Post Office has established the following
limiting requirements:

- frequency upward: 11.7 - 12.5 GHz

- frequency downward: 14 - 14.5 GHz (10.95 - 11.2 or
12.5 - 12.75 GHz)
- video modulation FM
- audio modulation FM on a subcarrier, or PCM in the
video signal
- RF bandwidth ca. 30 MHz
- atmospheric attenuation 1 dB (99% of the time)
(gas, clouds, rain): 3 dB (99.9% of the time)
- receiverst: Individual receiver:
G/T = 4 dB/°K
Community reception:
C/N about 3_--81 dB higher than
for individual reception.

Figure 1 shows the corresponding receiving area as seen from the

satellite. The inner ellipse circumscribes the region of guaranteed
reception. Because of the expected attitude error of about 0.1 ° ,
there is an antenna diagram projected on the Earth corresponding to
the large ellipse with a drop of 4.3 dB with respect to the center
(maximum field efficiency).
/3
The image quality defined in the planning model for the television
receiver is plotted in Figure 2 as a function of the signal-to-noise separa-
tion] evaluated in the luminance channel. This presentation clearly
shows the extent to which the satellite power must be increased in
order to improve the picture quality.

Now, from the planning model and the limiting requirements for
the television transmitting satellite, there arise the following
particularly critical requirements for the over-all television

3
transmitting satellite:
- new frequency range (12 - 14 GHz)
- very high amplification and transmitting power (ca. 120 dB,
ca. 600 W per channel)
- high directional accuracy for the antenna radiation lobe
(roll and pitch axes 0.1 ° , position 0.1° )
- receiving systems with favorable costs.

These requirements determine the design of the total system.

They will now be investigated in relation to their effects on the
most important systems or subsystems involved.

3. Over-all television transmitting satellite system

The total system for the television transmitting satellite is

divided up as follows:
- Mission analysis
o Communications technology system
o Mi-sion profile
o Booster system and apogee motor
- Satellite and payload system
o Antennas
o Transponder
o HF wiring
o Orbit and attitude control
o Power supply
o TM/TC
o Heat balance
o Test planning
o Product assurance
o Home receiving systems
o Ground transmitter sites
o Ground operating system

The communications technology system is shown in Figure 3. The

attenuations of the television signal are indicated crudely and the
most-Eimportant system data are entered.

4
 As the antennas must be continuously directed toward the Earth
and the solar cells must be as nearly perpendicular to the solar
radiation as possible, these two subsystems must be arranged so that
they can be rotated with respect to each other. From this there
arise two basic satellite concepts which are sketched in Figure 4.

The first is characterized by an axis of rotation between the

solar generator and the satellite body. The specific technological
problems are in the transmission of the power across the axis of
rotation:

Power Transmission Components

Requirements:
- long lifetime
- low rate of rotation
- high power level

Possible solutions:
- slip rings
- rotary transformer
- liquid metal slip rings
- roll of cable (requires additional maneuvering)
- elastic contact rollers

Problems:
- insufficient space experience with the prescribed requirements.

In the second basic satellite concept the antennas are attached

to the satellite body so that they can be rotated. Here the problem
is represented by transmission of RF power in both directions through
a rotary antenna coupling.

5
Rotary antenna coupling

Requirement!:
- low-loss transmission of the transmitted signal between the
Earth-oriented antenna and the sun-oriented satellite body.
- decoupling of the transmitted and received signal and
signal transmission

Possible solution:
- integrated disk and waveguide rotary coupling

Problems:
- insufficient space experience

4. Satellite subsystems

Both the satellite concepts described above present idential

or similar problems to the other subsystems. These requirements, as
well as possible routes to solutions and major problems, are tabulated
below.

Transmitting antenna

Requirements:
- high antenna efficiency
- small minor lobe
- low thermal and dynamic deformation
- if necessary, equipment for fine direction of the beam

Possible solutions:
- parabolic antenna
(0.64° x 1.15° elliptical major lobe)
- mechanical or electrical control of the antenna patte-rn-

Problems:
- maintenance of the prescribed shape
- fine direction of the beam

6
 Transponder

Requirements:_-
- transmitter tube power of 500 - 800 W RF per video channel
- decoupling of the receiving and transmitting paths and of the
individual channels
- maintenance of requirements for electromagnetic interference

Possible solutions:
- single or double frequency conversion
- use of traveling wave tubes or klystrons

Problems:
- transmitter tube efficiency
- control of the high supply voltages at high power
- attainment of decoupling

Orbit and Attitude Control

Requirements:
- maneuver (transfer and acquisition phase)
- mission operation
o positional accuracy: ca. + 0.1'
o attitude accuracy: roll and pitch axis: ca. + 0.1 °
-- - reacquisition maneuver

Possible solutions:
- attitude measurement: rate gyro, solar sensor, infrared sensor,
star sensor, RF sensor
- attitude control
o with thrust system (hot gas, cold gas, electric drive)
o with supplementary flywheels
o with supplementary antenna fine control (electronic or
mechanical)
- orbit control
o separate system (hot gas, electric drive)
o combined with attitude control

7
Problems:
- high directional accuracy for the antenna lobe
- large satellite mass and dimensions
- low satellite rigidity
- long Ilifetime

Power supply

Requirements:
- production of the power necessary for the transfer and
acquisition phase
- production of about 5 KW until the end of the satellite lifetime
- production of the necessary power during the shadow phases /8
- power conditioning and distribution

Possible solutions:
- solar generator (which can be unrolled, unfolded, or spread out)
- control: shunt, input control, etc.
- type of power: AC or DC
- main bus or buses with different voltages

Problems:
- solar generator
- high-power components
- maintenance of electromagnetic interference requirements

Heat Balance

Requirements:
- maintenance of the thermal operating limits of the satellite
under the following conditions:
o change in power generation
o change in external heat stress
o fluctuating power consumption

8
Possible solutions:
-- A
- passive heat regulation (coatings, SSM, insulation, radiators, etc.)
- active heat regulation (shutters, heat pipes, cooling circuits,
etc.)

Problems:
- cooling of the power tube, the output multiplexer, the power
generation system, and the power distribution system
o power tube (very large amount of heat, possibly high temper-
atures)
o output multiplexer and power distribution system (large
amount of heat, low temperatures, smaller temperature range)
/9
The mass of the satellite is greatly affected by the technical
quality of the various components (e. g., the efficiency of the power
tube). But, quite separately, the mass depends on some yet undecided
planning data such as the number of channels, the picture quality,
?andthe reception area. These relations are shown in Figure 5.

5. Home receiving system

Of the remaining systems, only the home receiving system will

be considered here because of its particular importance.

Requirements:
- highest possible quality factor
- conversion of frequency-modulated 12 GHz received signal to the
existing television standard
- favorable cost for the system

Possible solutions (Figure 6):

- individual system, consisting of parabolic antenna (diameter
up to 0.8 m), converter, amplifier and modulation converter.
- cable system with the same components, but correspondingly
more expensive because of the higher demanddon them.

9
Problems:
- economy of the system
- direction accuracy of the antenna
- system degradation

6. Project planning

Planning and construction of an operational satellite system

for television broadcasting include technological, temporal, and
financial risks- which cannot yet be surveyed completely. In order
to make these risks calculable, phase-wise project planning is
applied for the system (Figure 7).

Here the course of the project is organized so that the knowledge

of all aspects of the project increases from phase to phase. Each
phase is in itself a complete plan with its own objectives and its
own program plan. This ensures that costly developments are started
only if their necessity and achievability have been sufficiently
demonstrated in the preceding phase; that is, when the financial
and technical risk for the customer has been reduced to a minimum._\

At the end of development phase C, when only 5 - 8% of the

total resources are spent, all aspects of the project will be known
well enough so that a decision can be made on the development and
construction of the equipment and on test operations, that is,
on application of the total resources.

The first satellite can be launched after about 7 years, with

the start of operation 15 months later.

In parallel with the phased project performance, preliminary

developments will be undertaken with the goal, on one hand, of
working out the technical bases for decisions on conclusion of
the individual phases, and, on the other hand, of solving critical
technical problem areas in good time.

10
 A further decrease in the risk and better optimization of the
operational system c6Uld-betachieved by use of a test satellite
(Figuie 8). This would be characterized by a decrease in the number
of channels and of the picture quality, lifetime, and reliability,
as well as by redundance of critical components. With use of a
test satellite, to be sure, the first operational satellite could
only be launched after some 10 years.
/11l
7. Costs

Determination of the costs for the operational system for tele-

vision broadcasting by satellites is an extraordinarily complex
problem. Its findings must still be very uncertain, particularly
because important requirements for the customer, such as the number
of programs to be transmitted, the area to be covered, video and
audio quality, and the system reliability required, are not yet
clearly established. Only after knowing these requirements can the
operational system be optimized with respect to its parameters, and
a detailed cost analysis performed (this work is being prepared
at present by the Society for Space Research).:

- number of channels per satellite

- reliability of the satellites
- satellite lifetime
- satellite development costs
- production costs of the satellites
- reliability of the booster system
- costs of the booster system
- investment in ground systems
- home receiver systems
- time of starting operation of the system
- annual operating costs

Here we shall undertake only a qualitative comparison of

costs between a cable system and a satellite system for television-I
transmission (Figure 9). This shows that the cable system is superior

11
to the satellite system for centers of population_(tpw percentage
number of viewers). On consideration of thinly settled areas and
high percentages of viewers, television transmission via satellites
becomes less expensive' than a pure cable system. It might be
possible to optimize the system by combining the television trans-
mitting satellites with cable systems and, if necessary, with
local ground transmitters.
/12
l8._)Summary - K

The German Federal Post Office requirements for an additional---

need for television programs in the forseeable future can be met by
a satellite system for television broadcasting. Particularly in
combination with local cable systems, this system is an attractive,
relatively economical solution for broadcasting, with which almost
every viewer in the coveredarea can be reached directly.

There is still a seriesjof technological and systems-technology

problems. For their solution, a directed pre-development program
and a test program with a preliminary test satellite are recommended.

Construction of an operational satellite system for television

broacasting could be completed by the beginning of the 1980's.

REFERENCES

1. "Konzeptstudie fur einen Fernsehrundfunksatelliten," [Conceptual

Study for a Television Transmitting Satellite (preliminary
phase A)]. Siemens AG., Standard Electrik Lorenz, Messer-
schmitt-B6lkow-Blohm GmbH. May 1972.

2. "Konzeptstudie Fernsehrundfunksatellit," [Conceptual Study for

a Television Transmitting Satellite (preliminary phase A)].
AEG-Telefunken, Dornier System, ERNO-Raumfahrttechnik GmbH.
May 1972.

12
3. TRW-Systems-Group, Television Broadcast Satellite Study.
October 1969.

4. NASA, Phased Project Planning Guidelines, 1968.

The author thanks Mr. Fromm, Dr. Mecke, and Mr. Schacks for
their kind assistance in production of the manuscript.

13
7,
 \

\1N-

\
----------

N~~ ;?f__
50

\ S!
-- Guararnteed
reception are ea/-
\
450

IO_

-. 0 _ 6w

.- -- -
' __..__~\
50
I0O

.
considering an attitude error of 0.1°
Figure 1. Coverage area,

14
 ]Qdua1Yt-y sc~aleJ
(Rosser, Ailnatt and Lewis)
A Outstanding'i, 100-i--

-yl--k _-
601
_ _8__
,C Fairly good- I
40-
D F1 1,--rt LL-4r- ---
S/N Evaluated signai
"
.11 44 46 43 50
4Z ,
t o-noise separation
'in the luminance channel (dB)\
-I -. .

Figure 2. Quality evaluation of a television picture disturbed by noise.

i '
F FIRP w 70dBV
+20dB
+120 dB
_ -
r
I
FIRP -70 dBW
.- 1 .I I .9 . . _.

0b1m GA w-45dBO,64°x1,150
Attitude and orbit errort-1,5

- 208dB

-0,5 +--3,5 dB

EIRP w 85 rlBW G/r z,4 dB/K

D < 8m 0 < ,89 rn
P > 500 W NF > 10 dB
Directional error- and
F.I -0 4r, n1i w -, S,,R

Figure 3. C ommunications technology system.

Figure 3. Communications technology system.

15
 I i
1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.
i~~~~~~~ ! --
Axis .of.r..~tation.wi-th.1 I .Axis. of...rotation withj_
p.we.r _t.ransmiassio.n4 Ii ' 'RF.power transmi.ssi'
I

Figure 4. Basic concepts for a television transmitting satellite.

- -I
I

IT . L _ _ . - - _ _--
ll l
'Satellite mass (kg)

1500

l umb
. !har
c

e -1000

500

l
Figure 5.
Figure 5. Dependence of satellite mass on the picture quality.

16
 I!

11
I ni-idual.. system-fi-

Figure 6. Home receiver system.

17
 i
i

*CConceptuall. studyt I
i

Feasbilty analysi.s #A i

i
'P'rcje.ct-..de f-ini.t ion :B
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( Cre.iminary. development i-- - - -~~~~~~~~~~~~~~
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I I I !t I I I . I
5 ._ _ 7 _ 8
sts
_ 2 - 3 9 Years-I
i, cost-s] ' -- 5-8 %/ --- d
- . - l... I0 00/ -

Figure 7. Television transmission satellite. Phasewise

project planning without a test device.

estt satelliteJ
".Feas ibilityanaly isV A
r------1
g~~~:'.-~cepe~~
- . _ .. _
Pr(oject definition1 1B
Design 4.
r-I D
and constructiori\
tart operation
D
,Operational satelli.tej
e
.. .;1,
atI Feasibility
_
........
analys~isI. ___

Project. definition|
.De s I
Deelo ment..
Sand ofnsetrauction\-
Start off operati-oi
'(Prelim-inary.._devel.opment)\ - - _ __ - - - LI
,LILiIt D r: Lc:i ri o
. _ _ _. .. _ . . . . .f
I I . ,I . : ' I1 . zt I
V 1 2 3 ' -. 6_ g 9 I') _
[Y~e ar ;
r--F
Figure 8. Television transmission satellite. Phasewise
project planning with a test device.

18
 !.
Totaal oost i

i
I I i
#'
I

the

Figure 9. Crude cost comparison between a cable system and

a television transmitting satellite.

19