The comparison of the backward dynamical evolution of the VC swarms of C/2002 T7 and C/2001 Q4. For each comet, two different swarms are shown: a green (light grey) based on all astrometric data and a red (dark grey) representing our preferred data model for a particular comet (PRE for C/2002 T7 and DIST2 for C/2001 Q4). In each case, the nominal orbit is drawn in black. We show also in black, the histograms of the swarm density at the moment of a previous perihelion passage. The horizontal dashed line depicts the “escape limit” of 120 000 AU used in our investigations.