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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:

 D EP Besselian epoch

RETURNED:

 D(3) EV E-terms as

NOTE:
Note the use of the J2000 aberration constant ( ). 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.

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SLALIB --- Positional Astronomy Library