We present new [ SII ] images of the HH 30 jet and counterjet observed in 2006 , 2007 , and 2010 that , combined with previous data , allowed us to measure with improved accuracy the positions and proper motions of the jet and counterjet knots . Our results show that the motion of the knots is essentially ballistic , with the exception of the farthest knots , which trace the large scale “ C ” -shape bending of the jet . The observed bending of the jet can be produced by a relative motion of the HH 30 star with respect to its surrounding environment , caused either by a possible proper motion of the HH 30 star , or by the entrainment of environment gas by the red lobe of the nearby L1551-IRS 5 outflow . Alternatively , the bending can be produced by the stellar wind from a nearby CTTS , identified in the 2MASS catalog as J04314418+181047 . The proper motion velocities of the knots of the counterjet show more variations than those of the jet . In particular , we identify two knots of the counterjet that have the same kinematic age but whose velocities differ by almost a factor of two . Thus , it appears from our observations that counterjet knots launched simultaneously can be ejected with very different velocities . We confirm that the observed wiggling of the jet and counterjet arises from the orbital motion of the jet source in a binary system . Precession , if present at all , is of secondary importance in shaping the jet . We derive an orbital period \tau _ { o } = 114 \pm 2 yr and a mass function m \mu _ { c } ^ { 3 } = 0.014 \pm 0.006 M _ { \odot } . For a mass of the system of m = 0.45 \pm 0.04 M _ { \odot } ( the value inferred from observations of the CO kinematics of the disk ) we obtain a mass m _ { j } = 0.31 \pm 0.04 M _ { \odot } for the jet source , a mass m _ { c } = 0.14 \pm 0.03 M _ { \odot } for the companion , and a binary separation of a = 18.0 \pm 0.6 AU . This binary separation coincides with the value required to account for the size of the inner hole observed in the disk , which has been attributed to tidal truncation in a binary system .