  The aim of this Letter is rather pedagogical. We considered the static
spherically symmetric ensemble of observers, having finite bare mass and trying
to measure geometrical and physical properties of the environmental static
(Schwarzschild) space-time. It is shown that, using the photon rockets (which
the mass together with the mass of their fuel is also taken into account) they
can managed to keep themselves on the fixed value of radius. The process of
diminishing the total bare mass up to zero lasts infinitely long time. It is
important that the problem is solved self-consistently, i.e., with full account
for the back reaction of both bare mass and radiation from rockets on the
space-time geometry.
