Portion of MESSENGER’s trajectory around Mercury during the M1 flyby (red line) and two nominal orbits of MESSENGER on 23 April 2011, D113 (green line), and on 01 July 2011, D182 (blue line) in a cylindrical MSO coordinate system. The arrows show the direction of MESSENGER’s motion along each orbit. Superimposed are the approximate locations of the magnetopause (thick dashed line) and bow shock (thin dashed line) obtained from Winslow et al. (2013).