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2. ):SADLISG TF.CIISOLOGY PRo(;wAM\as
2.1 Subsystem9
A sigriificant purcion of the ASTP effort is clcvotrd to tho
dcvclopmcnt of satellite subsystem tcchnologics.
Suhs)stems such as pwer suppliks. attitude tlctcrminolion
and control devices. comm,unicotionq. computer
prcrcessing and memory storoge. propulsion units for
stnti:,nkccping rnd repositioning ore. of necessity.
prcscnt on virtually every satcllitc (whrtlirr "light" or
"heavy"). All of these items contriburc to tlic weight of
the snteilite nn-orhit; thus. niajtir reductions in wcigltt and
cost not only hcncfit the soteIIite. hut nIso aid in reducing
the sire nnd Coli of the booster vchicles that pul t h h in
orhit. The ultimate ohjcctive is to minimile the six and
maRioiire the efficiency of launcher vchiclcr and the
satellite bus so that the "business end" of the the space
systrm -. thc payload -- comprises o much morc significant
frat-tinn of the ovcroll satellite weight.
2. I, I LiRkrwcifihr Rcarrion U'hrzl
ne Lightweight Wrartion Whccl (LHW) is a magnclicdly
rusprnded reoction wheel with rrdundarit elcctronics that
will provide five timer the mnmcntum of erirting units at
the I me weight, with growth potenlid to ten limes the
momenturn. hy using rnognctic bcoringr in lieu of boll
bearings and fastcr rotational speed. The LRW requires
U percent lcrs power and can hc used nn all sntellite,: its
higher speed 4 rrduccd bearing vihration pntrntially CM
hcncfil oprraticin of onhoud scnsors (e.g.. lcss "bluning"
of a scnwr's imrgc). This cfron is aimal at ihr design and
delivery of a prototype LKW for testing a?d siihrcquent use
on a satellite. The prototype LKW will he flown on an
upcoming Air Force Space Test I'mgram llight.
2:l.Z Aliniaurc Global Positionin# Sy.strm Rtrtivrr
This effort ia a technology devclnpicnt project to design.
fabricate. develop. deliver and demonstrate. in an
apcrotional cnvirnnment. a spncc.qunlificd. niultic!innncl
Global Positioning System (GPS) rcceivcr lhan can bc uscd
to support autonom~us navigation onbnard spacecraft
(Figure I). The GPS receiver will enahle the simultaneous
reception of mulliple CPS navigation sipnals. therehy
providing p:ratrr psition accurory in cottiparison with
cunrntly ovailahlc rcccivers that sqricntially receive the
miiltiplc GI'S navi~atinn signals. The IIW cif gallium
arsenidc (GaAs) tc#:hnology has ennhlctl this morc
"pwcrful" rccciver to fit in a much more compact package
(one-tcnth the siic of previously space-qualified
receivers). The GI's rcccivcr is scheduled to "fly" on
several space rnissinns hr4;inning in 1993.
2.1.3 Artitndr Dricrminnlion. Control and Nuvigaiion
S y.5 tcm
A single. fully inrcgratcd guidance. navigation and control
system is hcing dcvclopcd under the Attitude
Dctcrminotion. Cnn:rol and Navigation Systcin (AWNS)
projcct. It will IIW low cost stu trackers. fihcr optic
gyro*. gencric VllSlC space-borne coniprrirrs nnd the
ASTP-dcvclopcd GPS rcccivcr (sec parogrnph 2. I.?). The
strap-down star tracker is designed to determine attitude by
recognizing stnr pntirriis via an acquisition search pattern
(a slow attitude chnnge maneuver) and mnintnin that
attitude dctcrmination in ony orientetion via ncorly
continuous star tracking. Low cost, high!y reliable fiber
optic gyros provide attitude determination during high
slew rate rnnncuvcrs. smoothing between aiai sighlings
wid rnte stabilin~tion. Spocccraft autonomy is maintained
by using L h GPS lor navigational updates. AdvPnlagCs of
this' project include a star pattern recognition algorithm
that r\iminkcr he nmd lor U\ initial altitude acquisition
scnsor (i.e.. no sun or wth scnsor is required) and generic
applicability to all three-axis. stabilited spacecraft.
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Figure 1. Miniature GPS Receiver
2.1.4 /nJ?atahkc 'Torut Solor Array 'ferhrvhgy
Solar arrays typicolly provide spocecraft power. At
present. as the omount of power required increases. the sire
and wcight of the solar arrays incrcaw _- n situation that
rieccssnrily constrains the capabilities of poyloads r ,
small satrllitcs. The ASTPs lnflatahlc Torus Solar Array
Tcclinology (ITSAT) prnjcct amis to ni:ike pssihlc spacc
missions that are othcrwisc imlwssiblc hy providing
incrcawd ovnilahlc pwcr while niaintnining vmall launch
vrilurrie and wright. An inflatnhle. srlf-rigidizing torus
striicturc ruplwris :he solnr ccll hlonkei. The inodulilr
design allows for cosy insertion of new solar cell
tcchnology including thin film arroyq. Thc current ITSAT
under dcwlopmcnt hog dcsign goals of 100 watts/lcg and
120 wai.s/m2.
2.15 Atiniaturizcd, Lav. Pavtr Parallel Processor
The basic goal of the Miniaturized, Low-Powcr Parsllrl
Processor technology dcvclopment prajrct is the
rcduction. hy an ortlcr of m:ignitutlc. of onhurd pror essnr
sire. weight and pnwcr consuml)tion for s~iarc..h:isc~l
scnsor systenis. Such proccn.cors must cmphiy niazsivcly
parallel architrcturcs with lorgc numhcrs or processing
elements in order to actiicvc thc high throughputs required
(up LO tens of billions of operations pcr sccond or more).
The appronch for achieving this goal is to use threc-
diinensional. hyhrid wafer scale intcrconnect aiid
pacia~iiig technology. In this conccpr. individual
modules with multiple. unpockaged seiniconductor chips
are compactly intcrccinncctcd intq a high dctisity packagc
with substantial weight and power saving5 over cxisting
packaging appoachcs (Figure 2).
2.1.6 hlugnetic Disk Macs Mrmnury
Hotuting disk mcmory subsystrrns have becn n leading
technology product for many years. Allhough not widcly
applied to space applications. they represent statc-of-thc-
art for high tlcnsity. mechonicrl mcniory suhsystcm~.
They arc less complex and hnve fcwcr potential mechanical
failure pints then troditionol spacchornc talx recorder
systems. Thc objcctive oi thc Magnetic Disk Mass
Memory project is LO dcvelop a magnetic rotating disk
mcmory suhsystem that will provide up to 1 Cigobyte of
high-speed data storage. The effort will rcvicw availohle
optical and rnibnetic disk equipment. detcrmine the