João Gomes wrote:
Hey..

Does anyone knows what programs does NASA use to simulate and predict
the orbit of a spacecraft? and for simulate the reentry phase of the
shutle and from now on orion?


There's no one answer to the first question; every NASA center has its
own trajectory analysis software. NASA does use POST quite a bit but it
is not the only program used.

Regarding the second question, NASA/JSC uses the Descent Design System
(DDS) and Spacecraft Trajectory and Mission Planning Simulator (STAMPS)
to simulate space shuttle entries.