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SLA_ETRMS - E-terms of Aberration   

ACTION:
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 $[\Delta x, \Delta y, \Delta z\,]$

NOTE:
Note the use of the J2000 aberration constant ( $20\hspace{-0.05em}^{'\hspace{-0.1em}'}\hspace{-0.4em}.49552$ ). 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.

REFERENCES:
1.
Smith, C.A. et al., 1989. Astr.J. 97, 265.
2.
Yallop, B.D. et al., 1989. Astr.J. 97, 274.


next up previous
Next: SLA_EULER - Rotation Matrix from Euler Angles
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Previous: SLA_EQGAL - J2000 to Galactic

SLALIB --- Positional Astronomy Library
Starlink User Note 67
P. T. Wallace
12 October 1999
E-mail:ptw@star.rl.ac.uk