  We consider null mean curvature flow along the standard lightcone in the de
Sitter spacetime. This flow was first studied by Roesch--Scheuer along null
hypersurfaces for the detection of MOTS, and independently by the author in the
specific case of the standard Minkowski lightcone. Similar to the Minkowski
case, null mean curvature flow along the de Sitter lightcone can be related to
$2d$-Ricci flow for surfaces of genus $0$ by an appropriate rescaling. Building
on this rescaling procedure, we analyse singularity formation, asymptotic
behavior and ancient solutions to the flow.
