Past exam of the physics 1 paper of the University of Oxford / 2016 / 10 / iii / Solution

At the outer tangent point, the vis-viva equation gives $v_a=\sqrt{\mu /r_1}\sqrt{2r_0/(r_0+r_1)}$. This is below the outer circular Kepler orbit's speed $v_1=\sqrt{\mu /r_1}$. The second impulse is therefore also prograde:It raises the pericentre to the outer radius, completing the circularization.