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14-2
xiv)physical attack and protective measures against dirocted
energy beams (laser, particle. RF) and ASAT etc..
w)sensitive. light, long-life materials. Component9 nnd
devices for sensing, power generation. amplilicaticn and
control.
&The speed of progress made in the above arras will be
determined mainly by the urgency of the need for. and the
amount of resources allocated to, them. These technologies
and new production methods coupled with basically
software-controlled processing transponders with a capability
to continuously adapt to changing requirements are expected
to lead to more flexible and reliable, lighter and less-power
consuming and altogether more cost-effective satellites than
the present ones. Moreover these satellites can be launched by
a number of different launch vehicles. Further reduction in cost
may be obtained by sharing the satellites (single an/or cluster)
between NATO and the Member Countries.
9.h can be stated generally and with confidence that in the time
period in question it will be possible to design and build any
satillite to meet almost any requirement. Technology exists or
will be available for whatever communications perfcrmance
and level 01 hardening is required as well as launch vehicles
with capability to place the resulting satellite of whatever
weight and power into any required orbit. The constraints will
be the availability of orbital slots, frequency spectrum and, of
course, funds.
1O.The cost considare: ,IS have therefore been the driving loctor
for the systems reported here. When assesslng different
concepts for sate!lite designs and system architecture what is
importanat is not so much their absolute but rather their
relatlve costs. Accordingly a cost model of the satellite system
has been established which takes into account:
band used (SHF. EHF).
- number of transponders,
- spacecraft reliability,
- RBDmSt.
- power required.
- weight.
- launch cost,
- recurring cost.
- system availability.
I - frequency
11.Several SATCOM system architectures with the potentlal of
meeting possible future NATO requirements Implied in the
paragraphs above have been defined using different orbits
(geostationary, polar, 12-2dhr Inclined at 63'.4 and Low Earth
Orblt LEO) and a number of satellites with single and/or dual
frequency transponders (SHF and EHF) whlch rad be
configurod to meet any operational requirement. Table .l lists
the architectures considered in the report and gives the
number of active spacecrafl for full continuous coverage of tho
NATO area includino the polar reglon as well as the total
number of spacecraft needed for 7-years and 21-year periods
for a certain given Gpacecraft reliabllity. Archltectures based on
the use of LEO and a combination of geostationary and
pola:-orbit satellites were eliminated from further considerhtion
on cost grounds and the others were subjected to more
detalled cost-padormance analysis using the cost model
mentioned In paragraph 10 above.
12.Table . -2 lists some twenty different promising architectures
(Caseo) for a future NATO SATCOM and gives the associated
RBD. recurring and total msts for differont spacecraft reliability
and Wntinuous service availability for 7 yearr.The mmmon
attrlbutes of these architectures are the fol!owing(see Fig. .lI :
(a) I) The transponders have adapUvs receive (with
steerable nulls) and multl-beam trsnsmll nntennas (1
earth cover. 1 Europe m r . 1 polar spot and 2
steerable spots).
ii) A flexible channelization technique is used on board
tho satellites at both SHF and EliF. At EHF. this is
exploited in an omboard processing concept that
prevents the satellite downlink transmitter from being
loaded by the jammer and also to prevent
unauthorized access to the satellite. For flexible AJ
processing and ease of interoperability a full
bandwidth (2 Giiz at EHF. 500 MHz at SHF) filter band
is provided using perhaps different filter technologies
to obtain different selectivities required (see Fig. E-\)
where the channelization can be conlrolled by
telecommand to avoid interference, to alter the
satellite capacity allocated to various geographical
areas and to adapt the specilic requirements due to
restrictions in the tunability of the NATO cr national
ground segment. At EHF. where the flexhie
channelization technique is coupled with on-board
protessing for AI purposes then switchi;lg between
high-selectivity filter bank outputs (element filter
output) will be performed at a high rate and controlled
by an on-board transec equipment which can be
programm3ble (in orbit) to support several
simultuneous uplinks.
The ground segment would consist 01 both SHF and
EHF terminals. The SHF terminals would be those
existing at the end of the NATO IV era and would be
usod mainly to support common-user trunks. General
transition rom SHF to EHF is foreseen to take place
over the period covered In the study to support mainly
mobile/transportable users many of which may have
demanding AJ andjor LPI requirement.
The EHF ground segment:
i) has preferably non-synchronized frequency-
hopped (because of its better performance in
disturbed and time-variant propaoation
conditions and betler suitability to small
terminals than the direct sequence modulation
system) terminals operating in FOMA with
flexible data rates and redefinable codes,
ii) consists of the simultaneous accesses (for
system comparison purposes) given in Table
-3.
. #,
The systems . :
\) have the virtue of allowing easy transition from
exlsting to future architectures,
ii) Have minimum development. recurring and
launch costs.
. iii) are upgradable and expandabla on a scale to
meet operational requirements.
iv) defective and life-expired elements 01 the
system are replaceable without man
intervention,
v) spacecrafl are capable 01 being refuelled
without man intervention,
vi) have virtually zero down-time at low cost,
vii) make maximum use of orbital slot allocations,
vlii) allow spatial dlstribv(kn of spaceuaft to reduca
Uwir vulnscability to jamming and physical attack.