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`plan94(`

`jdtdb`, `planet`)

[SOFA] Returns the approximate heliocentric position and velocity at
TDB Julian Date

of major planet `jdtdb`

(1 = Mercury, 2 = Venus, 3 = emb, 4 = Mars, ..., 8 = Neptune).
`planet`

must be a `planet``scalar`

or an `array`

with
exactly 1 element. The result has the same dimensions as

except that two dimensions equal to 3 and 2 are
prefixed. If the result is `jdtdb``pv`

, then `pv(*,0,/all)`

are
the heliocentric equatorial J2000.0 (mean equator & epoch) cartesian
coordinates in AU, and `pv(*,1,/all)`

are the corresponding
heliocentric J2000.0 cartesian velocities (AU/d).

The algorithm is due to Simon, Bretagnon et al. (1994). Comparison with jpl ephemeris de102 says that during the years 1800 - 2050 the maximum errors in longitude l (arcsec), in the numerical order of the planets given above: 4, 5, 6, 17, 71, 81, 86, 11. The maximum errors in latitude b (arcsec) are: 1, 1, 1, 1, 5, 13, 7, 1. The maximum errors in radial distance r (Mm) are: 0.3, 0.8, 1, 7.7, 76, 267, 712, 253.

During the years 1000 - 3000 the accuracy is no worse than 1.5 times that over the years 1800 - 2050.

Comparison with the jpl de200 ephemeris give the following rms errors during the years 1960 - 2025: for position (Mm) 0.334, 1.06, 2.01, 7.69, 71.7, 199, 564, 158; for velocity (m/s) 0.437, 0.855, 0.815, 1.98, 7.7, 19.4, 16.4, 14.4.

Comparison against de200 during the years 1800 - 2100 gave the following maximum absolute differencs (and essentially the same using de406): longitude l (arcsec): 7, 7, 9, 26, 78, 87, 86, 11; latitude b (arcsec): 1, 1, 1, 1, 6, 14, 7, 2; radial distance r (Mm): 0.5, 1.1, 1.3, 9, 82, 263, 661, 248; radial speed (m/s): 0.7, 0.9, 1.0, 2.5, 8.2, 24.6, 27.4, 21.4.

See also: Astronomical Coordinate Calculations

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