determined byanalysisarebetterthan0.04degreeofwhichlessthan0.02degreeiscontributed bythe SAAstructure.Elevationandazimuthpointingcalibrationuncertainties oflessthan0.10degreeandless than0.16degree,respectively, wereachievedfortheSAS,whichexceedtherequirements. ThebearingsystemconsistsofapreloadedDFduplexbearingpairattheupperendoftheshaft,andan angularcontactsimplexbearinglocatedatthebottomoftheshaft.Theduplexbearingsarepreloaded againsteachothertoprovideaxialandradialstiffness.Thesimplexbearingispreloadedagainstthe duplexpairwithanaxiallycomPliantdiaphragmtoprovideadditionalangularstiffness.Theduplex bearingisbasicallyasetofconventional thinsectionbearingsmachineddirectlyintoabearingcartridge, eliminatingseveralpartsandthehightolerancefitsusuallyrequiredbetweenthem.Thedesignfeatures aone-pieceinnerraceandseparate outerracesthatarefastened together. Boththeduplexandsimplex bearings are440-Csteelwithsegmented phenolic cagesandaremanufactured toABEC-7 equivalent tolerances. Preload sensitivities tofitsandtemperatures areminimized bymounting thebearing ina titanium sleevethatisstructurally isolated fromthesurrounding aluminum structure byslotsthatare electrodischarge machined intothetitanium. Thisalmostcompletely eliminates preload changes dueto fitsandthermal expansion differences between thealuminum structure andthebearing. Theduplex bearing islocated several inchesfromtheSAA/AA interface, whichallowstheuseofathin-walled hollow titanium shafttoprovide thermal isolation. Thehighdeflection diaphragm thatprovides preload tothe simplex bearing keepsthebearing preload almostconstant overtheentiretemperature range.The bearing lubrication system usesNYE179Aoilwithsacrificial oilreservoirs andlabyrinth sealstoprovide reliable lubrication overmission life. TheV-Band launchretention mechanism prevents antenna rotation andoffloads thebearings from dynamic loadsduringlaunch(Figure 5).Amarmon clamparrangement thatconsists ofasetofV-blocks onatitanium strappullstheantenna mountdownintocontact withthestructure oftheSAAandagainst a springforceprovided bytwodiaphragms. Whendualpyrotechnic initiators arefired,aseparation nut releases andtension isreleased intheband.Thetwodiaphragms pushtheantenna mountapartfrom themainhousing, forcingtheV-blocks outward andallowing anaxialgapof1.5millimeters (0.06inch) between therotating andnon-rotating features. TheV-Blocks arepulledoutofcontact withthestructure byasetofcoilsprings andcaptured inasetof"catcher" mechanisms thatpositively locktheminplace untiltheyaremanually released. Whenthebandseparates, abreakwireopenssending arelease telemetry signal. Theinterfaces between theV-blocks andstructure arelubricated withamolydisulflde lubricant thatisburnished intothesurface ofthestructures. TheEAconsists ofacompact arrangement ofelectronics modules housed withinanaluminum chassis. Allelectrical interfaces tothespacecraft, exceptthoseforthepyrotechnic actuators, aremadethrough thecircular bulkhead connectors ontheEA.TheEAcontains allfunctions required forcommand, control, andtelemetry oftheSAS.Twoisolated andredundant channels ofpowerconversion, power conditioning, andspeedcontrol/telemetry modules areprovided. Thepowerconditioner/converter module receives anominal primary 40VDCbusvoltage andgenerates the15and5VDCrequired internally bytheEAaswellasconditioned 28VDCrequired fortheSAA.Ratecontrolelectronics receive encoder pulsesfromtheSAAandderiverateasananalogvoltage. Thesignalisfedbackand differenced withareference voltage representative of18or20rpm,asselected byground controllers. Thechoiceoftwoslightly different operational speeds isprovided asacontingency against the coincidence ofrotational speedtoadynamic modeofthespacecraft. Therateerrorsignalis compensated andoutputtotheSAAasananalogtorquecommand. Theanalogratesignalisalso conditioned andoutputasactiveanalogtelemetry. Encoder pulsesareaccumulated ina16-bitcounter, whichisresetbyazeroindexpulse.Thisdataisrepresentative ofantenna azimuth angleandis conditioned andoutputasRS422telemetry. Thespeedcontrolloopcircuitry rampsuptherotational speedoftheantenna duringstartupatanartificially slowrateinordertominimize torques induced tothe spacecraft. Thecircuitcardmodules oftheEArepresent alloftheelectronics thatare"new"tothe SeaWinds program. Allelectronics retained fromtheGGSheritage unitarecontained withintheSAA itself. 279