Thenextstepwasanattempt todetermine theactualstateoftheshutter. Sincetheimpedance ofthe magnetic circuitchanges, resistance, inductance, andcapacitance measurements weremadeonthetwo shutter coilsandthesensor coilstodetermine thestate.Theshutter wasverified tobeopen.However, theshuttercoilswereinadvertently measured, including changing scalesontheresistance meter,before thoseofthesensor. Inlaterinvestigations, itwasdetermined thecurrent spikeproduced bychanging the scaleonthemulti-meter hadtheabilitytoopentheshutterifitdidremainclosed. Itwasneverdetermined whether theshutter opened attheendofthetesting, duringthemoveofthedewar, orduringthe impedance measurements, buttestingthesensorcoilprovedtobeavalidmeanstoverifyposition when theinstrument waspowered off. Asetoftests,runon6/3/01,instrumented thevoltage andcurrent waveforms toverifythefunctionality of theelectronics andtocapture thedifferences inbehavior usingthevarious software versions. These waveforms suggested thattheelectronics werehealthy andappropriately responding toallcommands sent.Theyalsoverified thedifferences between thecommand software versions andgaveinsighttothe behavior oftheshutter undervarious conditions. Duringtheattempt tocapture fullopening andclosing waveforms, itwasdiscovered thatusingashortpull-inandholdcyclewouldreproduce thefailure somewhat consistently. Figure6showsthecurrent andvoltage profiles ofanactuator thatfailstoopenat zerocurrent andonethatopens properly. Thiscommand sequence proved invaluable infurther [].i •_ : _ '.'" !....!....i_'Voltage Spike " (_fii''5.'00_' ...._ iO.OmV_' M_f.OOs' Ctii"k.''5.'0'9t ,.!,...!....)....ii,:..,Yoltage.Spike :. :1 i!i!_romRel_.,Open_ :tN 1iCurrent ii{!_X_ iiBackEM:_ ....:....i\.._.i.....-i-:_'__i['FromShuRet 1 ._?0ltage!_:if'N: i'-[\_"_ "t ......... _A---,.60_ PUilqn•.. Chl 5.OOV' _ tO.O'rnV(2 M1.OOs Chl"k.'-5.0"VJSpike Opening Figure6.Current andvoltage profiles foranactuator thatfailstoopenatzerocurrent (left)andonethatopensproperly (right) investigating theanomaly. Thefirstroundoftestsincluded capturing thewaveforms, sending individual commands toprovetheclosedshutter couldbeopened bysending current oftheopposite polarity, measuring thepull-inandrelease currents ontheshutter, andsending various staticcurrent levelsto properly calibrate thecurrent outputandtelemetry testpointsforupdating theground datasystem. Figure 7summarizes therelease current datafortheflightshutter. Theresultsofthetestson6/3/01showed that theholdcurrents onSideBwerelowerthanexpected, butdidnotrequire opposite polarity current to open.Thiswassupported bythefactthatSideBoperations NEVER ledtotheshutterremaining closed. SideAcurrent measurements showed thataslightcurrent intheopposite polarity opened theshutter reliably. Theresultsalsoshowed thatthepull-incurrents werevirtually unchanged fromprevious data. Thissuggested thatthespringandshuttercoilswerehealthy. Finally, thecalibration testsrevealed a+50 gASideAoffsetanda+360laASideBoffsetwhenzerocurrent wascommanded. Thecurrent output responded linearly tocommands andthetelemetry feedback equations wereupdated fromageneric approximation equation toside-specific equations whichfitthedata. Oncethesetestswerecompleted, anewandfinalversion ofthesoftware waswritten. Thenew command sequence addedacommandable current pulseintheopposite polarity tocounteract residual magnetism, moretimeforcurrent commands tosettle,andmoreflexibility incommand parameters. The Version 3.21opening sequence isasfollows: Turnontheposition sensor NASA/CP--2002-211506 18