  An inverse obstacle problem governed by the Stokes system in the time domain
is considered. Two types of extraction formulae about the geometry of an
unknown obstacle are given by using the most recent version of the time domain
enclosure method in a unified style. Each of the formulae employs only a single
set of velocity and the Cauchy stress fields over a finite time interval on the
surface of the region where a viscous incompressible fluid occupies.
