Compute the E-terms vector – the part of the annual aberration which arises from
the eccentricity of the Earth’s orbit.
CALL:
CALL sla_ETRMS (EP, EV)
GIVEN:
EP
D
Besselian epoch
RETURNED:
EV
D(3)
E-terms as
$\left[\Delta x,\Delta y,\Delta z\phantom{\rule{0.3em}{0ex}}\right]$
NOTE:
Note the use of the J2000 aberration constant (′′2049552). This is a reflection of the fact
that the E-terms embodied in existing star catalogues were computed from a variety of
aberration constants. Rather than adopting one of the old constants the latest value is
used here.