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use crate::rfam::*;
/// Frame bias components of IAU 2000 precession-nutation models; part
/// of the Mathews-Herring-Buffett (MHB2000) nutation series, with
/// additions.
///
/// Returned:
/// * dpsibi,depsbi longitude and obliquity corrections
/// * dra the ICRS RA of the J2000.0 mean equinox
///
/// # Notes:
///
/// 1) The frame bias corrections in longitude and obliquity (radians)
/// are required in order to correct for the offset between the GCRS
/// pole and the mean J2000.0 pole. They define, with respect to the
/// GCRS frame, a J2000.0 mean pole that is consistent with the rest
/// of the IAU 2000A precession-nutation model.
///
/// 2) In addition to the displacement of the pole, the complete
/// description of the frame bias requires also an offset in right
/// ascension. This is not part of the IAU 2000A model, and is from
/// Chapront et al. (2002). It is returned in radians.
///
/// 3) This is a supplemented implementation of one aspect of the IAU
/// 2000A nutation model, formally adopted by the IAU General
/// Assembly in 2000, namely MHB2000 (Mathews et al. 2002).
///
/// # References:
/// * Chapront, J., Chapront-Touze, M. & Francou, G., Astron.
/// Astrophys., 387, 700, 2002.
/// * Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
/// and precession: New nutation series for nonrigid Earth and
/// insights into the Earth's interior", J.Geophys.Res., 107, B4,
/// 2002. The MHB2000 code itself was obtained on 2002 September 9
/// from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
///
/// This revision: 2021 May 11
pub fn bi00(dpsibi: &mut f64, depsbi: &mut f64 , dra: &mut f64)
{
/* The frame bias corrections in longitude and obliquity */
const DPBIAS: f64 = -0.041775 * URSA_DAS2R;
const DEBIAS: f64 = -0.0068192 * URSA_DAS2R;
/* The ICRS RA of the J2000.0 equinox (Chapront et al., 2002) */
const DRA0: f64 = -0.0146 * URSA_DAS2R;
/* Return the results (which are fixed). */
*dpsibi = DPBIAS;
*depsbi = DEBIAS;
*dra = DRA0;
/* Finished. */
}