Design of the EO-1 pulsed plasma thruster attitude control experiment

Charles ZakrzwskiGuidance. Navigation. and Control CenterNASA-Goddard Space Flight CenterGreenbelt. MD 20771Paul Sanneman and Teresa HuntSwales AerospaceBeltsville, MD 20705Kathie Blackmanthe Hammers CompanyGreenbelt, MD 20770AbstractThe Pulsed Plasma Thruster (PPT) Experiment on theEarth Observing 1 (EO-1) spacecraft has been designedto demonstrate the capability of a new generation PPTto perform spacecraft attitude control. The PPT is asmall, self-contained pulsed electromagnetic propulsionsystem capable of delivering high specific impulse(900-1200 s), very small impulse bits (10-1000 gN-s) atlow average power (<1 to 100 W). EO-1 has a singlePPT that can produce torque in either the positive ornegative pitch direction. For the PPT in-flightexperiment, the pitch reaction wheel will be replaced bythe PPT during nominal EO-I nadir pointing. A PPTspecific proportional-integral-derivative (PID) controlalgorithm was developed for the experiment. Highfidelity simulations of the spacecraft attitude controlcapability using the PPT were conducted. Thesimulations, which showed PPT control performancewithin acceptable mission limits, will be used as thebenchmark for on-orbit performance. The flightvalidation will demonstrate the ability of the PPT toprovide precision pointing resolution, response andstability as an attitude control actuator.IntroductionA Pulsed Plasma Thruster (PPT) is being flown as atechnology demonstration experiment on GoddardSpace Flight Center's (GSFC) Earth Observing 1 (EO-1) mission. PPTs can offer significant mass savingbenefits to spacecraft by replacing the combinations of