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use crateera00;
use ;
/// Update context for Earth rotation
///
/// In the star-independent astrometry parameters, update only the
/// Earth rotation angle. The caller provides UT1, (n.b. not UTC).
///
/// This function is part of the International Astronomical Union's
/// SOFA (Standards of Fundamental Astronomy) software collection.
///
/// Status: support function.
///
/// Given:
/// ```
/// ut11 double UT1 as a 2-part...
/// ut12 double ...Julian Date (Note 1)
/// astrom iauASTROM* star-independent astrometry parameters:
/// pmt double not used
/// eb double[3] not used
/// eh double[3] not used
/// em double not used
/// v double[3] not used
/// bm1 double not used
/// bpn double[3][3] not used
/// along double longitude + s' (radians)
/// xpl double not used
/// ypl double not used
/// sphi double not used
/// cphi double not used
/// diurab double not used
/// eral double not used
/// refa double not used
/// refb double not used
/// ```
/// Returned:
/// ```
/// astrom iauASTROM* star-independent astrometry parameters:
/// pmt double unchanged
/// eb double[3] unchanged
/// eh double[3] unchanged
/// em double unchanged
/// v double[3] unchanged
/// bm1 double unchanged
/// bpn double[3][3] unchanged
/// along double unchanged
/// xpl double unchanged
/// ypl double unchanged
/// sphi double unchanged
/// cphi double unchanged
/// diurab double unchanged
/// eral double "local" Earth rotation angle (radians)
/// refa double unchanged
/// refb double unchanged
/// ```
/// Notes:
///
/// 1) The UT1 date (n.b. not UTC) ut11+ut12 is a Julian Date,
/// apportioned in any convenient way between the arguments ut11 and
/// ut12. For example, JD(UT1)=2450123.7 could be expressed in any
/// of these ways, among others:
/// ```
/// ut11 ut12
///
/// 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 and MJD methods are good compromises
/// between resolution and convenience. The date & time method is
/// best matched to the algorithm used: maximum precision is
/// delivered when the ut11 argument is for 0hrs UT1 on the day in
/// question and the ut12 argument lies in the range 0 to 1, or vice
/// versa.
///
/// 2) If the caller wishes to provide the Earth rotation angle itself,
/// the function iauAper can be used instead. One use of this
/// technique is to substitute Greenwich apparent sidereal time and
/// thereby to support equinox based transformations directly.
///
/// 3) This is one of several functions that inserts into the astrom
/// structure star-independent parameters needed for the chain of
/// astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
///
/// The various functions support different classes of observer and
/// portions of the transformation chain:
/// ```
/// functions observer transformation
///
/// iauApcg iauApcg13 geocentric ICRS <-> GCRS
/// iauApci iauApci13 terrestrial ICRS <-> CIRS
/// iauApco iauApco13 terrestrial ICRS <-> observed
/// iauApcs iauApcs13 space ICRS <-> GCRS
/// iauAper iauAper13 terrestrial update Earth rotation
/// iauApio iauApio13 terrestrial CIRS <-> observed
/// ```
/// Those with names ending in "13" use contemporary SOFA models to
/// compute the various ephemerides. The others accept ephemerides
/// supplied by the caller.
///
/// The transformation from ICRS to GCRS covers space motion,
/// parallax, light deflection, and aberration. From GCRS to CIRS
/// comprises frame bias and precession-nutation. From CIRS to
/// observed takes account of Earth rotation, polar motion, diurnal
/// aberration and parallax (unless subsumed into the ICRS <-> GCRS
/// transformation), and atmospheric refraction.
///
/// Called:
/// ```
/// iauAper astrometry parameters: update ERA
/// iauEra00 Earth rotation angle, IAU 2000
/// ```