Design Evolution Thevalueofadapting previously developed hardware forquickmissions canhardlybeunderstated. Risk isminimized, especially iftheheritage hardware hasflownorisflying,andthedesignisopento adaptability. Suchwasthecasebetween theGGS/Polar mission, theSeaWinds onADEOS IImission, andtheSeaWinds onQuikScat mission. Lessons learned fromonemission canbeapplied directly tothe designasitisadapted foritsnewmission. TheSAAportionoftheSASevolved directly fromtheGGSPolarspacecraft's Despun Platform Mechanism Assembly (DPMA). Inthatapplication, thespeedloopisclosedbyspacecraft electronics in ordertomaintain aninstrument platform stationary ininertialspacewhilethecylindrical spacecraft rotates at10rpmtoprovide stability. IntheDPMA,a69-channel slipringmodule inhabits thevolume now occupied bytheheaters intheSeaWinds SAS.Theslipringsarerequired toprovide arotaryelectrical interface totheinstruments ontheplatform. TheGGSDPMAlaunchlockdesignutilized customer-furnished separation nutsforactuation ofthe release mechanism. Thecustomer onthatprogram soughttominimize costsbyusingthesame configuration separation nutforeverypyrotechnically activated release mechanism onthespacecraft. Unfortunately, thisconfiguration wasnotoptimal fortheV-band release mechanism ontheDPMA. The noseoftheseparation nutcontained agrooveforaretaining c-clip.Theforcesinvolved inrelease and retraction oftheV-Band assembly wereoccasionally greater thanwouldbecontained bytheclip.This resulted inejection ofthec-clip,leavingtheseparation nutconnected tothemechanism onlybyits groundstrap.Thesolution atthetimewastosafetywirethenutandc-clipinplace.FortheSeaWinds device, thenoseoftheseparation nutwasredesigned byelimination ofthegroove andaddition ofa threaded feature. Thus,theseparation nutwaspositively heldinplacebyaspanner nuttooneoftheVBandtrunnions. Thismodification totheseparation nutwasmadeinsuchawaythattheoriginal qualification testingofthenutdesignwasstillvalid,eliminating thecostofrequalification. Thepowerbudget available foroperation oftheGGSDPMAwasverylimited, precluding theuseof heaters inthethermal design. Inordertominimize viscous dragandassureadequate torquemargin at coldtemperaturesl thebearing system wasdesigned tooperate withverylittlelubricant. 100mgofNye 179Aoilwasapplied toeachrow.Sacrificial oilreservoirs supplied supplemental quantities ofoiloverthe lifeofthemission. At10rpm,thebearing system operates inthemarginareabetween EHDandnonEHDregimes. Alifetestwasperformed inordertogainconfidence inthebearing andslipringdesigns. TheSeaWinds application hasamuchgreater powerbudget, butoperates atafasterspeedandmission lifeislonger. Analysis oftheGGSbearing intheSeaWinds environment indicated thatthesystem would meetHoneywell SSO'sinternal designpractice requirements forlubelossoverlife.Nevertheless, oil quantity wasincreased to1.25gramperrowtoaddmargin. Thisisclosetothemaximum quantity offree oilthatthebearing wouldhold.Thepresence ofheaters, theabsence ofdragfromsliprings,andamore benigncoldenvironment enabled thisincrease infreelubricant quantity yetstillensures significant torque marginatcoldtemperatures (aboutafactorof2at-20°Casdetermined duringthermal vacuum testing). Theincrease inspeedmovesthebearing operation furtherintotheEHDregime. This,coupled witha reduction inpreload, yielded abetterprobability ofsuccess valueinthefatigueanalysis. TheGGS instrument platform isapproximately 118kg(260Ib).TheSeaWinds AAisapproximately 6.8kg(15Ib). Thisdifference inpayload massresultsinasignificant decrease inbearing loadsandallowed the reduction innominal unmounted preload from980N(220Ib)to556N(125Ib).Confidence inthe successful heritage lifetestresultsandon-orbit performance data,extensive analysis, andthefactthatall ofthechanges movedthebearing designinafavorable direction resulted inadecision toforego additional lifetesting. SeaWinds successfully useda"redline"methodology fordesignchanges. Flexibility ofdesignallowed forinclusion ofheatercircuitry inthevolume madeavailable byremoval ofthesliprings.Thelarge opening through thecenteroftheshaftthatwasnecessary toaccommodate alargeboomantenna onthe Polarspacecraft provided thenecessary spacetoallowinstallation ofthewaveguidesanddualchannel 281