Measurements of the atmospherically induced phase perturbations can be
made on a bright star (
in
Equations 12 and
14) and then the optical path length from the
both stars can be physically adjusted (typically using movable
mirrors) to remove the term
from the phase
perturbations from both stars. For star (SeS) we get:
In this mode of operation,
can be calculated in the
same way as in Section 2.2.3, providing
information about the angular separation of the stars. Note that the
phase of
(the astrometric phase) is only a
useful parameter when the S/N ratio of
is greater than unity, so that for faint (SeS) stars
must be integrated as a complex number until the
S/N ratio is greater than one before the
astrometric phase is calculated. This has important implications for
the software running the PRIMA FSUs.
Robert Tubbs 平成16年11月18日