One or more fixed-orientation fanned laser beams and one or more
displacement measurement devices to precisely measure the orientation of
a payload platform are disclosed in a metrology system and method. The
measurement devices may be distributed at locations across a payload
platform such that displacement changes of these devices can be used to
accurately determine platform pointing. Laser beam transmitters may be
fixed in the same reference block to which a spacecraft attitude sensor
is mounted. Fanned laser beams are transmitted from these sources to the
measurement devices so that their displacements can be determined with
respect to the plane of the fanned beams and thereby with respect to the
spacecraft attitude sensor. Only a small number of fixed laser beams are
needed to achieve precision measurements at a reduced cost, weight and
power, and with increased system reliability and simplified system
integration.