Thisstrategywasimplemented witha100%successrateon-orbit.Withtheexceptionofthefive pinpullersdamagedduringgroundoperations (tobediscussedinthenextsection)allcross-linkand gatewayantennadeployedasplanned. "HumanFactors" inGround Operations Anadvantage tousingHOPactuators istheirabilitytobeusedandresetmultiple timesforground operations. Thedrivetoreduce thepartcountandthecomplexity ofthosepartsledtoadesignwhichwas vulnerable toprocedural errorsbyoperators. Asaresult,5pinpullers onthefirstspacecraft were inadvertently damaged priortoflight,andwereunabletodeploy. Desi.qnChoices Afteroperation, anHOPpinpuller mustbereset.Resetconsists ofheating theunittomelttheparaffin, andtheninstalling aspecially designed resettool,whichscrews intothefrontendoftheretracted pin.The toolexertsaspringforceontheshaft,whichslowlyre-extends thepinasthewaxcools.Oncetheactuator iscooledtobelowthemelting pointoftheparaffin, thetoolcanberemoved, andtheactuator isreadyfor thenextoperation. Thefirstprototype unitsofthepinpuller weredesigned withastepfeaturethatwouldactasastopagainst over-extending thepin.Thissteponthepincametorestagainst thefrontsealsastheactuator wasreset. However, thestepcaused problems duringtheresetprocess. Theactuator wasrequired toresetwith68N (15Ibf)orless,andittookmoreforcethanthistopushthepinthrough thesolidifying paraffin. Whenthe stepdidcometorestagainst theseals,itwouldforcesmallbitsofsolidparaffin through theseals.In addition, therewasthepossibility thatthestopfeature mightdamage thefrontseals.Theexisting stop feature couldnotbeused. Anyotherdesign optionforthestopfeature meantadding parts,complexity inassembly, andcost.It wouldalsoaddtotheenvelope, whichwaslimited. However, without astopfeature fortheextended position itwouldbepossible topullthepinoutfartherthanthezero-position, whichcouldun-seat therear sealsfromthesmall(rear)bore.Ifleftinthatposition andpowered, theactuator wiltfailtopressurize, and liquidparaffin willflowaround therearsealandoutoftheactuator. Still,thefeasibility ofremoving thestop featurealtogether wasconsidered. Thereweredesign precedents forthelackofafronthardstopinthepuller.Several models ofparaffin actuator donothaveazero-stop andrelyontheinterface tolimitpinmotion. Forexample, theIH-5055 actuator rodisvirtually unrestricted initsmotion(inbothdirections) exceptbyitsinterface. Theissuewas explored withourcustomer, andthedecision wearrived atwastoeliminate thefronthard-stop feature. Thezero-position ofthepinwouldbeestablished bytheresettoolratherthanastopfeature. Tominimize theriskofover-extension, processes wouldbecarefully controlled. Onlyproperly trained technicians wouldusethequalified Starsys toolpertheestablished procedures. Properpinextension wouldalsobe verified following eachresettoinsurethepinhadnotbeenover-extended. Results -Ground Operation Errors Thelackofahardstopforthenominal shaftposition madetheactuator vulnerable tooperator error.The confidence inprocess controls ontheground wasunfounded forseveral reasons. First,though thereset process waseasyattheantenna level,itwasmuchmorecomplicated atthespacecraft level.Physical access tothepinpullers wassomewhat restricted. Theantenna hadtobepowered ingroups, andthat meantresetting several actuators simultaneously. Moreover, thepinpullers wereonesmallcomponent out ofmanyonthespacecraft, andprobably received lessattention thantheydidattheantenna level.These difficulties, combined withthevariability ofgreater numbers ofpeopleworking withtheactuators atthe integration facility, ledtoimproper resetting ofseveral actuators onthefirstspacecraft produced. Starsys firstlearned ofthisthrough atelephone callreceived immediately afterthelaunch ofthefirst groupofspacecraft. Fiveantenna ononeofthespacecraft werenotmoving afterallthepinpullers hadall beenoperated. Thepinpullers wereoperated asecond time,withalongerpowerduration. Still,the stepper motors couldnotmovetheantenna. Itwasclearthatthepinshadnotpulled,andthatadditional 282