SLA_ECOR - RV & Time Corrns to Sun   

ACTION:

Component of Earth orbit velocity and heliocentric light time in a given direction.

CALL:

CALL sla_ECOR (RM, DM, IY, ID, FD, RV, TL)

GIVEN:

$$[\,\alpha,\delta\,]$$ RM,DM

IY I year

ID I day in year (1 = Jan 1st)

FD R fraction of day

RETURNED:

RV component of Earth orbital velocity (km s^-1)

TL R component of heliocentric light time (s)

NOTES:

1.

The date and time is TDB (loosely ET) in a Julian calendar which has been aligned to the ordinary Gregorian calendar for the interval 1900 March 1 to 2100 February 28. The year and day can be obtained by calling sla_CALYD or sla_CLYD.

2.

Sign convention:

• The velocity component is +ve when the Earth is receding from the given point on the sky.
• The light time component is +ve when the Earth lies between the Sun and the given point on the sky.

3.

Accuracy:

• The velocity component is usually within 0.004 km s^-1 of the correct value and is never in error by more than 0.007 km s^-1.
• The error in light time correction is about $0^{\rm s}\hspace{-0.3em}.03$ at worst, but is usually better than $0^{\rm s}\hspace{-0.3em}.01$.

For applications requiring higher accuracy, see the sla_EVP routine.