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pn06a

sofars::pnp

Function pn06a 

Source 
pub fn pn06a(
    date1: f64,
    date2: f64,
) -> (f64, f64, f64, [[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3])
Expand description

Precession-nutation, IAU 2006/2000A models: a multi-purpose function, supporting classical (equinox-based) use directly and CIO-based use indirectly.

This function is part of the International Astronomical Union’s SOFA (Standards of Fundamental Astronomy) software collection.

Status: support function.

Given: date1,date2 double TT as a 2-part Julian Date (Note 1)

Returned (function value): (dpsi, deps, epsa, rb, rp, rbp, rn, rbpn) (f64, f64, f64, [[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3], [[f64; 3]; 3])

dpsi,deps nutation (Note 2) epsa mean obliquity (Note 3) rb frame bias matrix (Note 4) rp precession matrix (Note 5) rbp bias-precession matrix (Note 6) rn nutation matrix (Note 7) rbpn GCRS-to-true matrix (Notes 8,9)

Notes:

  1. The TT date date1+date2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TT)=2450123.7 could be expressed in any of these ways, among others:

       date1          date2

2450123.7           0.0       (JD method)
2451545.0       -1421.3       (J2000 method)
2400000.5       50123.2       (MJD method)
2450123.5           0.2       (date & time method)

    The JD method is the most natural and convenient to use in cases where the loss of several decimal digits of resolution is acceptable. The J2000 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience.

  2. The nutation components (luni-solar + planetary, IAU 2000A) in longitude and obliquity are in radians and with respect to the equinox and ecliptic of date. Free core nutation is omitted; for the utmost accuracy, use the iauPn06 function, where the nutation components are caller-specified.

  3. The mean obliquity is consistent with the IAU 2006 precession.

  4. The matrix rb transforms vectors from GCRS to mean J2000.0 by applying frame bias.

  5. The matrix rp transforms vectors from mean J2000.0 to mean of date by applying precession.

  6. The matrix rbp transforms vectors from GCRS to mean of date by applying frame bias then precession. It is the product rp x rb.

  7. The matrix rn transforms vectors from mean of date to true of date by applying the nutation (luni-solar + planetary).

  8. The matrix rbpn transforms vectors from GCRS to true of date (CIP/equinox). It is the product rn x rbp, applying frame bias, precession and nutation in that order.

  9. The X,Y,Z coordinates of the IAU 2006/2000A Celestial Intermediate Pole are elements (3,1-3) of the GCRS-to-true matrix, i.e. rbpn[2][0-2].

  10. It is permissible to re-use the same array in the returned arguments. The arrays are filled in the stated order.

Called: iauNut06a nutation, IAU 2006/2000A iauPn06 bias/precession/nutation results, IAU 2006

Reference:

Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855