SLA_EARTH

Approx Earth Pos/Vel

ACTION:
Approximate heliocentric position and velocity of the Earth (single precision).
CALL:
CALL sla_EARTH (IY, ID, FD, PV)
GIVEN:

IY

I

year

ID

I

day in year (1 = Jan 1st)

FD

R

fraction of day


RETURNED:

PV

R(6)

Earth [x, y, z, ẋ, ẏ, ż] (AU, AU s−1)


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)
The Earth heliocentric 6-vector is referred to the FK4 mean equator and equinox of date.
(3)
Maximum/RMS errors 1950-2050:
  • 13/5  × 10−5 AU = 19200/7600 km in position
  • 47/26  × 10−10 AU s−1 = 0.0070/0.0039 km s−1 in speed
(4)
More accurate results are obtainable with the routines sla_EVP and sla_EPV.