Module marlu::pos::pal

Useful Starlink PAL functions re-written in Rust.

PAL depends on ERFA and (luckily) all the PAL functions we need just use ERFA. Code is derived from https://github.com/Starlink/pal commit 7af65f0 and is licensed under the LGPL-3.0.

Why not just depend on PAL? It’s a huge pain. (1) The C library is either named libstarlink-pal or libpal, (2) it depends on ERFA so statically compiling it in a -sys crate is much harder than it should be, (3) this code changes so slowly that we’re unlikely to be out-of-date.

Functions

palDcc2s^⚠

Cartesian to spherical coordinates

palDcs2c^⚠

Spherical coordinates to direction cosines

palDmxv^⚠

Performs the 3-D forward unitary transformation

palDranrm

Normalize angle into range 0-2 pi

palDvdv^⚠

Scalar product of two 3-vectors Arguments: va = double[3] (Given) First vector vb = double[3] (Given) Second vector Returned Value: Scalar product va.vb Notes:

palDvn^⚠

Normalizes a 3-vector also giving the modulus

palEvp^⚠

Barycentric and heliocentric velocity and position of the Earth.

palGmst

Greenwich mean sidereal time (consistent with IAU 2006 precession)

palMappa^⚠

Compute parameters needed by palAmpqk and palMapqk.

palPrenut^⚠

Form the matrix of bias-precession-nutation (IAU 2006/2000A)