sun_direction_eci
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Defined in: ephemeris.rs:121
fn sun_direction_eci(epoch: &[Epoch<Tdb>](../../structs/epoch/)) -> [Vec3<frame::Gcrs>](../../structs/vec3/)
Approximate sun direction (unit vector) in ECI (J2000) frame.
Uses a low-precision analytical model based on mean orbital elements. Accuracy is ~1 arcminute, sufficient for visualization purposes.
The Meeus series is referred to the mean equinox of date, so the result is rotated back to J2000 by the IAU 1976 precession (see the module docs).
Reference: Meeus, “Astronomical Algorithms”, Chapter 25.