Abstract: Animpulsecontrolmethodwasproposedforthepositionkeepingofaspacecraftnearasteroid.ConsideringthegravityoftheSunandasteroid,therelativeequationofmotionofthespacecraftwithrespecttotheasteroidwasderived.Thestatetransitionmatrixwasusedtodescribethemotioninthevicinityoftheasteroid.Athresholdcontrolmethodwasusedtoachievethepositionkeeping.Theimpulsecontrollerwastriggeredwhenthepositionerrorwaslargerthanaspecifiedvalue.Theresultsshowthatthismethodperformswellforthepositionkeeping,andthecontrolperiodislongandpropellantconsumptionislow.

Key words: Thresholdcontrol, Impulse control, Accompanyingflight, Asteroid, Probe