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- erfa Package

# erfa Package

## Functions

`a2af`(ndp, angle) | Decompose radians into degrees, arcminutes, arcseconds, fraction.
`a2tf`(ndp, angle) | Decompose radians into hours, minutes, seconds, fraction.
`ab`(pnat, v, s, bm1) | Apply aberration to transform natural direction into proper direction.
`ae2hd`(az, el, phi) | Horizon to equatorial coordinates: transform azimuth and altitude to hour angle and declination.
`af2a`(s, ideg, iamin, asec) | Convert degrees, arcminutes, arcseconds to radians.
`anp`(a) | Normalize angle into the range 0 <= a < 2pi.
`anpm`(a) | Normalize angle into the range -pi <= a < +pi.
`apcg`(date1, date2, ebpv, ehp) | For a geocentric observer, prepare star-independent astrometry parameters for transformations between ICRS and GCRS coordinates.
`apcg13`(date1, date2) | For a geocentric observer, prepare star-independent astrometry parameters for transformations between ICRS and GCRS coordinates.
`apci`(date1, date2, ebpv, ehp, x, y, s) | For a terrestrial observer, prepare star-independent astrometry parameters for transformations between ICRS and geocentric CIRS coordinates.
`apci13`(date1, date2) | For a terrestrial observer, prepare star-independent astrometry parameters for transformations between ICRS and geocentric CIRS coordinates.
`apco`(date1, date2, ebpv, ehp, x, y, s, ...) | For a terrestrial observer, prepare star-independent astrometry parameters for transformations between ICRS and observed coordinates.
`apco13`(utc1, utc2, dut1, elong, phi, hm, xp, ...) | For a terrestrial observer, prepare star-independent astrometry parameters for transformations between ICRS and observed coordinates.
`apcs`(date1, date2, pv, ebpv, ehp) | For an observer whose geocentric position and velocity are known, prepare star-independent astrometry parameters for transformations between ICRS and GCRS.
`apcs13`(date1, date2, pv) | For an observer whose geocentric position and velocity are known, prepare star-independent astrometry parameters for transformations between ICRS and GCRS.
`aper`(theta, astrom) | In the star-independent astrometry parameters, update only the Earth rotation angle, supplied by the caller explicitly.
`aper13`(ut11, ut12, astrom) | In the star-independent astrometry parameters, update only the Earth rotation angle.
`apio`(sp, theta, elong, phi, hm, xp, yp, ...) | For a terrestrial observer, prepare star-independent astrometry parameters for transformations between CIRS and observed coordinates.
`apio13`(utc1, utc2, dut1, elong, phi, hm, xp, ...) | For a terrestrial observer, prepare star-independent astrometry parameters for transformations between CIRS and observed coordinates.
`atcc13`(rc, dc, pr, pd, px, rv, date1, date2) | Transform a star's ICRS catalog entry (epoch J2000.0) into ICRS astrometric place.
`atccq`(rc, dc, pr, pd, px, rv, astrom) | Quick transformation of a star's ICRS catalog entry (epoch J2000.0) into ICRS astrometric place, given precomputed star-independent astrometry parameters.
`atci13`(rc, dc, pr, pd, px, rv, date1, date2) | Transform ICRS star data, epoch J2000.0, to CIRS.
`atciq`(rc, dc, pr, pd, px, rv, astrom) | Quick ICRS, epoch J2000.0, to CIRS transformation, given precomputed star-independent astrometry parameters.
`atciqn`(rc, dc, pr, pd, px, rv, astrom, b) | Quick ICRS, epoch J2000.0, to CIRS transformation, given precomputed star-independent astrometry parameters plus a list of light- deflecting bodies.
`atciqz`(rc, dc, astrom) | Quick ICRS to CIRS transformation, given precomputed star- independent astrometry parameters, and assuming zero parallax and proper motion.
`atco13`(rc, dc, pr, pd, px, rv, utc1, utc2, ...) | ICRS RA,Dec to observed place.
`atic13`(ri, di, date1, date2) | Transform star RA,Dec from geocentric CIRS to ICRS astrometric.
`aticq`(ri, di, astrom) | Quick CIRS RA,Dec to ICRS astrometric place, given the star- independent astrometry parameters.
`aticqn`(ri, di, astrom, b) | Quick CIRS to ICRS astrometric place transformation, given the star- independent astrometry parameters plus a list of light-deflecting bodies.
`atio13`(ri, di, utc1, utc2, dut1, elong, phi, ...) | CIRS RA,Dec to observed place.
`atioq`(ri, di, astrom) | Quick CIRS to observed place transformation.
`atoc13`(type, ob1, ob2, utc1, utc2, dut1, ...) | Observed place at a groundbased site to to ICRS astrometric RA,Dec.
`atoi13`(type, ob1, ob2, utc1, utc2, dut1, ...) | Observed place to CIRS.
`atoiq`(type, ob1, ob2, astrom) | Quick observed place to CIRS, given the star-independent astrometry parameters.
`bi00`() | Frame bias components of IAU 2000 precession-nutation models; part of the Mathews-Herring-Buffett (MHB2000) nutation series, with additions.
`bp00`(date1, date2) | Frame bias and precession, IAU 2000.
`bp06`(date1, date2) | Frame bias and precession, IAU 2006.
`bpn2xy`(rbpn) | Extract from the bias-precession-nutation matrix the X,Y coordinates of the Celestial Intermediate Pole.
`c2i00a`(date1, date2) | Form the celestial-to-intermediate matrix for a given date using the IAU 2000A precession-nutation model.
`c2i00b`(date1, date2) | Form the celestial-to-intermediate matrix for a given date using the IAU 2000B precession-nutation model.
`c2i06a`(date1, date2) | Form the celestial-to-intermediate matrix for a given date using the IAU 2006 precession and IAU 2000A nutation models.
`c2ibpn`(date1, date2, rbpn) | Form the celestial-to-intermediate matrix for a given date given the bias-precession-nutation matrix.
`c2ixy`(date1, date2, x, y) | Form the celestial to intermediate-frame-of-date matrix for a given date when the CIP X,Y coordinates are known.
`c2ixys`(x, y, s) | Form the celestial to intermediate-frame-of-date matrix given the CIP X,Y and the CIO locator s.
`c2s`(p) | P-vector to spherical coordinates.
`c2t00a`(tta, ttb, uta, utb, xp, yp) | Form the celestial to terrestrial matrix given the date, the UT1 and the polar motion, using the IAU 2000A precession-nutation model.
`c2t00b`(tta, ttb, uta, utb, xp, yp) | Form the celestial to terrestrial matrix given the date, the UT1 and the polar motion, using the IAU 2000B precession-nutation model.
`c2t06a`(tta, ttb, uta, utb, xp, yp) | Form the celestial to terrestrial matrix given the date, the UT1 and the polar motion, using the IAU 2006/2000A precession-nutation model.
`c2tcio`(rc2i, era, rpom) | Assemble the celestial to terrestrial matrix from CIO-based components (the celestial-to-intermediate matrix, the Earth Rotation Angle and the polar motion matrix).
`c2teqx`(rbpn, gst, rpom) | Assemble the celestial to terrestrial matrix from equinox-based components (the celestial-to-true matrix, the Greenwich Apparent Sidereal Time and the polar motion matrix).
`c2tpe`(tta, ttb, uta, utb, dpsi, deps, xp, yp) | Form the celestial to terrestrial matrix given the date, the UT1, the nutation and the polar motion.
`c2txy`(tta, ttb, uta, utb, x, y, xp, yp) | Form the celestial to terrestrial matrix given the date, the UT1, the CIP coordinates and the polar motion.
`cal2jd`(iy, im, id) | Gregorian Calendar to Julian Date.
`cp`(p) | Copy a p-vector.
`cpv`(pv) | Copy a position/velocity vector.
`cr`(r) | Copy an r-matrix.
`d2dtf`(scale, ndp, d1, d2) | Format for output a 2-part Julian Date (or in the case of UTC a quasi-JD form that includes special provision for leap seconds).
`d2tf`(ndp, days) | Decompose days to hours, minutes, seconds, fraction.
`dat`(iy, im, id, fd) | For a given UTC date, calculate Delta(AT) = TAI-UTC.
`dtdb`(date1, date2, ut, elong, u, v) | An approximation to TDB-TT, the difference between barycentric dynamical time and terrestrial time, for an observer on the Earth.
`dtf2d`(scale, iy, im, id, ihr, imn, sec) | Encode date and time fields into 2-part Julian Date (or in the case of UTC a quasi-JD form that includes special provision for leap seconds).
`eceq06`(date1, date2, dl, db) | Transformation from ecliptic coordinates (mean equinox and ecliptic of date) to ICRS RA,Dec, using the IAU 2006 precession model.
`ecm06`(date1, date2) | ICRS equatorial to ecliptic rotation matrix, IAU 2006.
`ee00`(date1, date2, epsa, dpsi) | The equation of the equinoxes, compatible with IAU 2000 resolutions, given the nutation in longitude and the mean obliquity.
`ee00a`(date1, date2) | Equation of the equinoxes, compatible with IAU 2000 resolutions.
`ee00b`(date1, date2) | Equation of the equinoxes, compatible with IAU 2000 resolutions but using the truncated nutation model IAU 2000B.
`ee06a`(date1, date2) | Equation of the equinoxes, compatible with IAU 2000 resolutions and IAU 2006/2000A precession-nutation.
`eect00`(date1, date2) | Equation of the equinoxes complementary terms, consistent with IAU 2000 resolutions.
`eform`(n) | Earth reference ellipsoids.
`eo06a`(date1, date2) | Equation of the origins, IAU 2006 precession and IAU 2000A nutation.
`eors`(rnpb, s) | Equation of the origins, given the classical NPB matrix and the quantity s.
`epb`(dj1, dj2) | Julian Date to Besselian Epoch.
`epb2jd`(epb) | Besselian Epoch to Julian Date.
`epj`(dj1, dj2) | Julian Date to Julian Epoch.
`epj2jd`(epj) | Julian Epoch to Julian Date.
`epv00`(date1, date2) | Earth position and velocity, heliocentric and barycentric, with respect to the Barycentric Celestial Reference System.
`eqec06`(date1, date2, dr, dd) | Transformation from ICRS equatorial coordinates to ecliptic coordinates (mean equinox and ecliptic of date) using IAU 2006 precession model.
`eqeq94`(date1, date2) | Equation of the equinoxes, IAU 1994 model.
`era00`(dj1, dj2) | Earth rotation angle (IAU 2000 model).
`fad03`(t) | Fundamental argument, IERS Conventions (2003): mean elongation of the Moon from the Sun.
`fae03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Earth.
`faf03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of the Moon minus mean longitude of the ascending node.
`faju03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Jupiter.
`fal03`(t) | Fundamental argument, IERS Conventions (2003): mean anomaly of the Moon.
`falp03`(t) | Fundamental argument, IERS Conventions (2003): mean anomaly of the Sun.
`fama03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Mars.
`fame03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Mercury.
`fane03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Neptune.
`faom03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of the Moon's ascending node.
`fapa03`(t) | Fundamental argument, IERS Conventions (2003): general accumulated precession in longitude.
`fasa03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Saturn.
`faur03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Uranus.
`fave03`(t) | Fundamental argument, IERS Conventions (2003): mean longitude of Venus.
`fk425`(r1950, d1950, dr1950, dd1950, p1950, v1950) | Convert B1950.0 FK4 star catalog data to J2000.0 FK5.
`fk45z`(r1950, d1950, bepoch) | Convert a B1950.0 FK4 star position to J2000.0 FK5, assuming zero proper motion in the FK5 system.
`fk524`(r2000, d2000, dr2000, dd2000, p2000, v2000) | Convert J2000.0 FK5 star catalog data to B1950.0 FK4.
`fk52h`(r5, d5, dr5, dd5, px5, rv5) | Transform FK5 (J2000.0) star data into the Hipparcos system.
`fk54z`(r2000, d2000, bepoch) | Convert a J2000.0 FK5 star position to B1950.0 FK4, assuming zero proper motion in FK5 and parallax.
`fk5hip`() | FK5 to Hipparcos rotation and spin.
`fk5hz`(r5, d5, date1, date2) | Transform an FK5 (J2000.0) star position into the system of the Hipparcos catalog, assuming zero Hipparcos proper motion.
`fw2m`(gamb, phib, psi, eps) | Form rotation matrix given the Fukushima-Williams angles.
`fw2xy`(gamb, phib, psi, eps) | CIP X,Y given Fukushima-Williams bias-precession-nutation angles.
`g2icrs`(dl, db) | Transformation from Galactic coordinates to ICRS.
`gc2gd`(n, xyz) | Transform geocentric coordinates to geodetic using the specified reference ellipsoid.
`gc2gde`(a, f, xyz) | Transform geocentric coordinates to geodetic for a reference ellipsoid of specified form.
`gd2gc`(n, elong, phi, height) | Transform geodetic coordinates to geocentric using the specified reference ellipsoid.
`gd2gce`(a, f, elong, phi, height) | Transform geodetic coordinates to geocentric for a reference ellipsoid of specified form.
`gmst00`(uta, utb, tta, ttb) | Greenwich mean sidereal time (model consistent with IAU 2000 resolutions).
`gmst06`(uta, utb, tta, ttb) | Greenwich mean sidereal time (consistent with IAU 2006 precession).
`gmst82`(dj1, dj2) | Universal Time to Greenwich mean sidereal time (IAU 1982 model).
`gst00a`(uta, utb, tta, ttb) | Greenwich apparent sidereal time (consistent with IAU 2000 resolutions).
`gst00b`(uta, utb) | Greenwich apparent sidereal time (consistent with IAU 2000 resolutions but using the truncated nutation model IAU 2000B).
`gst06`(uta, utb, tta, ttb, rnpb) | Greenwich apparent sidereal time, IAU 2006, given the NPB matrix.
`gst06a`(uta, utb, tta, ttb) | Greenwich apparent sidereal time (consistent with IAU 2000 and 2006 resolutions).
`gst94`(uta, utb) | Greenwich apparent sidereal time (consistent with IAU 1982/94 resolutions).
`h2fk5`(rh, dh, drh, ddh, pxh, rvh) | Transform Hipparcos star data into the FK5 (J2000.0) system.
`hd2ae`(ha, dec, phi) | Equatorial to horizon coordinates: transform hour angle and declination to azimuth and altitude.
`hd2pa`(ha, dec, phi) | Parallactic angle for a given hour angle and declination.
`hfk5z`(rh, dh, date1, date2) | Transform a Hipparcos star position into FK5 J2000.0, assuming zero Hipparcos proper motion.
`icrs2g`(dr, dd) | Transformation from ICRS to Galactic coordinates.
`ir`() | Initialize an r-matrix to the identity matrix.
`jd2cal`(dj1, dj2) | Julian Date to Gregorian year, month, day, and fraction of a day.
`jdcalf`(ndp, dj1, dj2) | Julian Date to Gregorian Calendar, expressed in a form convenient for formatting messages: rounded to a specified precision.
`ld`(bm, p, q, e, em, dlim) | Apply light deflection by a solar-system body, as part of transforming coordinate direction into natural direction.
`ldn`(b, ob, sc) | For a star, apply light deflection by multiple solar-system bodies, as part of transforming coordinate direction into natural direction.
`ldsun`(p, e, em) | Deflection of starlight by the Sun.
`lteceq`(epj, dl, db) | Transformation from ecliptic coordinates (mean equinox and ecliptic of date) to ICRS RA,Dec, using a long-term precession model.
`ltecm`(epj) | ICRS equatorial to ecliptic rotation matrix, long-term.
`lteqec`(epj, dr, dd) | Transformation from ICRS RA,Dec to ecliptic coordinates (mean equinox and ecliptic of date), using a long-term precession model.
`ltp`(epj) | Long-term precession matrix.
`ltpb`(epj) | Long-term precession matrix, including ICRS frame bias.
`ltpecl`(epj) | Long-term precession of the ecliptic.
`ltpequ`(epj) | Long-term precession of the equator.
`moon98`(date1, date2) | Approximate geocentric position and velocity of the Moon.
`num00a`(date1, date2) | Form the matrix of nutation for a given date, IAU 2000A model.
`num00b`(date1, date2) | Form the matrix of nutation for a given date, IAU 2000B model.
`num06a`(date1, date2) | Form the matrix of nutation for a given date, IAU 2006/2000A model.
`numat`(epsa, dpsi, deps) | Form the matrix of nutation.
`nut00a`(date1, date2) | Nutation, IAU 2000A model (MHB2000 luni-solar and planetary nutation with free core nutation omitted).
`nut00b`(date1, date2) | Nutation, IAU 2000B model.
`nut06a`(date1, date2) | IAU 2000A nutation with adjustments to match the IAU 2006 precession.
`nut80`(date1, date2) | Nutation, IAU 1980 model.
`nutm80`(date1, date2) | Form the matrix of nutation for a given date, IAU 1980 model.
`obl06`(date1, date2) | Mean obliquity of the ecliptic, IAU 2006 precession model.
`obl80`(date1, date2) | Mean obliquity of the ecliptic, IAU 1980 model.
`p06e`(date1, date2) | Precession angles, IAU 2006, equinox based.
`p2pv`(p) | Extend a p-vector to a pv-vector by appending a zero velocity.
`p2s`(p) | P-vector to spherical polar coordinates.
`pap`(a, b) | Position-angle from two p-vectors.
`pas`(al, ap, bl, bp) | Position-angle from spherical coordinates.
`pb06`(date1, date2) | This function forms three Euler angles which implement general precession from epoch J2000.0, using the IAU 2006 model.
`pdp`(a, b) | p-vector inner (=scalar=dot) product.
`pfw06`(date1, date2) | Precession angles, IAU 2006 (Fukushima-Williams 4-angle formulation).
`plan94`(date1, date2, np) | Approximate heliocentric position and velocity of a nominated planet: Mercury, Venus, EMB, Mars, Jupiter, Saturn, Uranus or Neptune (but not the Earth itself).
`pm`(p) | Modulus of p-vector.
`pmat00`(date1, date2) | Precession matrix (including frame bias) from GCRS to a specified date, IAU 2000 model.
`pmat06`(date1, date2) | Precession matrix (including frame bias) from GCRS to a specified date, IAU 2006 model.
`pmat76`(date1, date2) | Precession matrix from J2000.0 to a specified date, IAU 1976 model.
`pmp`(a, b) | P-vector subtraction.
`pmpx`(rc, dc, pr, pd, px, rv, pmt, pob) | Proper motion and parallax.
`pmsafe`(ra1, dec1, pmr1, pmd1, px1, rv1, ...) | Star proper motion: update star catalog data for space motion, with special handling to handle the zero parallax case.
`pn`(p) | Convert a p-vector into modulus and unit vector.
`pn00`(date1, date2, dpsi, deps) | Precession-nutation, IAU 2000 model: a multi-purpose function, supporting classical (equinox-based) use directly and CIO-based use indirectly.
`pn00a`(date1, date2) | Precession-nutation, IAU 2000A model: a multi-purpose function, supporting classical (equinox-based) use directly and CIO-based use indirectly.
`pn00b`(date1, date2) | Precession-nutation, IAU 2000B model: a multi-purpose function, supporting classical (equinox-based) use directly and CIO-based use indirectly.
`pn06`(date1, date2, dpsi, deps) | Precession-nutation, IAU 2006 model: a multi-purpose function, supporting classical (equinox-based) use directly and CIO-based use indirectly.
`pn06a`(date1, date2) | Precession-nutation, IAU 2006/2000A models: a multi-purpose function, supporting classical (equinox-based) use directly and CIO-based use indirectly.
`pnm00a`(date1, date2) | Form the matrix of precession-nutation for a given date (including frame bias), equinox based, IAU 2000A model.
`pnm00b`(date1, date2) | Form the matrix of precession-nutation for a given date (including frame bias), equinox-based, IAU 2000B model.
`pnm06a`(date1, date2) | Form the matrix of precession-nutation for a given date (including frame bias), equinox based, IAU 2006 precession and IAU 2000A nutation models.
`pnm80`(date1, date2) | Form the matrix of precession/nutation for a given date, IAU 1976 precession model, IAU 1980 nutation model.
`pom00`(xp, yp, sp) | Form the matrix of polar motion for a given date, IAU 2000.
`ppp`(a, b) | P-vector addition.
`ppsp`(a, s, b) | P-vector plus scaled p-vector.
`pr00`(date1, date2) | Precession-rate part of the IAU 2000 precession-nutation models (part of MHB2000).
`prec76`(date01, date02, date11, date12) | IAU 1976 precession model.
`pv2p`(pv) | Discard velocity component of a pv-vector.
`pv2s`(pv) | Convert position/velocity from Cartesian to spherical coordinates.
`pvdpv`(a, b) | Inner (=scalar=dot) product of two pv-vectors.
`pvm`(pv) | Modulus of pv-vector.
`pvmpv`(a, b) | Subtract one pv-vector from another.
`pvppv`(a, b) | Add one pv-vector to another.
`pvstar`(pv) | Convert star position+velocity vector to catalog coordinates.
`pvtob`(elong, phi, hm, xp, yp, sp, theta) | Position and velocity of a terrestrial observing station.
`pvu`(dt, pv) | Update a pv-vector.
`pvup`(dt, pv) | Update a pv-vector, discarding the velocity component.
`pvxpv`(a, b) | Outer (=vector=cross) product of two pv-vectors.
`pxp`(a, b) | p-vector outer (=vector=cross) product.
`refco`(phpa, tc, rh, wl) | Determine the constants A and B in the atmospheric refraction model dZ = A tan Z + B tan^3 Z.
`rm2v`(r) | Express an r-matrix as an r-vector.
`rv2m`(w) | Form the r-matrix corresponding to a given r-vector.
`rx`(phi, r) | Rotate an r-matrix about the x-axis.
`rxp`(r, p) | Multiply a p-vector by an r-matrix.
`rxpv`(r, pv) | Multiply a pv-vector by an r-matrix.
`rxr`(a, b) | Multiply two r-matrices.
`ry`(theta, r) | Rotate an r-matrix about the y-axis.
`rz`(psi, r) | Rotate an r-matrix about the z-axis.
`s00`(date1, date2, x, y) | The CIO locator s, positioning the Celestial Intermediate Origin on the equator of the Celestial Intermediate Pole, given the CIP's X,Y coordinates.
`s00a`(date1, date2) | The CIO locator s, positioning the Celestial Intermediate Origin on the equator of the Celestial Intermediate Pole, using the IAU 2000A precession-nutation model.
`s00b`(date1, date2) | The CIO locator s, positioning the Celestial Intermediate Origin on the equator of the Celestial Intermediate Pole, using the IAU 2000B precession-nutation model.
`s06`(date1, date2, x, y) | The CIO locator s, positioning the Celestial Intermediate Origin on the equator of the Celestial Intermediate Pole, given the CIP's X,Y coordinates.
`s06a`(date1, date2) | The CIO locator s, positioning the Celestial Intermediate Origin on the equator of the Celestial Intermediate Pole, using the IAU 2006 precession and IAU 2000A nutation models.
`s2c`(theta, phi) | Convert spherical coordinates to Cartesian.
`s2p`(theta, phi, r) | Convert spherical polar coordinates to p-vector.
`s2pv`(theta, phi, r, td, pd, rd) | Convert position/velocity from spherical to Cartesian coordinates.
`s2xpv`(s1, s2, pv) | Multiply a pv-vector by two scalars.
`sepp`(a, b) | Angular separation between two p-vectors.
`seps`(al, ap, bl, bp) | Angular separation between two sets of spherical coordinates.
`sp00`(date1, date2) | The TIO locator s', positioning the Terrestrial Intermediate Origin on the equator of the Celestial Intermediate Pole.
`starpm`(ra1, dec1, pmr1, pmd1, px1, rv1, ...) | Star proper motion: update star catalog data for space motion.
`starpv`(ra, dec, pmr, pmd, px, rv) | Convert star catalog coordinates to position+velocity vector.
`sxp`(s, p) | Multiply a p-vector by a scalar.
`sxpv`(s, pv) | Multiply a pv-vector by a scalar.
`taitt`(tai1, tai2) | Time scale transformation: International Atomic Time, TAI, to Terrestrial Time, TT.
`taiut1`(tai1, tai2, dta) | Time scale transformation: International Atomic Time, TAI, to Universal Time, UT1.
`taiutc`(tai1, tai2) | Time scale transformation: International Atomic Time, TAI, to Coordinated Universal Time, UTC.
`tcbtdb`(tcb1, tcb2) | Time scale transformation: Barycentric Coordinate Time, TCB, to Barycentric Dynamical Time, TDB.
`tcgtt`(tcg1, tcg2) | Time scale transformation: Geocentric Coordinate Time, TCG, to Terrestrial Time, TT.
`tdbtcb`(tdb1, tdb2) | Time scale transformation: Barycentric Dynamical Time, TDB, to Barycentric Coordinate Time, TCB.
`tdbtt`(tdb1, tdb2, dtr) | Time scale transformation: Barycentric Dynamical Time, TDB, to Terrestrial Time, TT.
`tf2a`(s, ihour, imin, sec) | Convert hours, minutes, seconds to radians.
`tf2d`(s, ihour, imin, sec) | Convert hours, minutes, seconds to days.
`tpors`(xi, eta, a, b) | In the tangent plane projection, given the rectangular coordinates of a star and its spherical coordinates, determine the spherical coordinates of the tangent point.
`tporv`(xi, eta, v) | In the tangent plane projection, given the rectangular coordinates of a star and its direction cosines, determine the direction cosines of the tangent point.
`tpsts`(xi, eta, a0, b0) | In the tangent plane projection, given the star's rectangular coordinates and the spherical coordinates of the tangent point, solve for the spherical coordinates of the star.
`tpstv`(xi, eta, v0) | In the tangent plane projection, given the star's rectangular coordinates and the direction cosines of the tangent point, solve for the direction cosines of the star.
`tpxes`(a, b, a0, b0) | In the tangent plane projection, given celestial spherical coordinates for a star and the tangent point, solve for the star's rectangular coordinates in the tangent plane.
`tpxev`(v, v0) | In the tangent plane projection, given celestial direction cosines for a star and the tangent point, solve for the star's rectangular coordinates in the tangent plane.
`tr`(r) | Transpose an r-matrix.
`trxp`(r, p) | Multiply a p-vector by the transpose of an r-matrix.
`trxpv`(r, pv) | Multiply a pv-vector by the transpose of an r-matrix.
`tttai`(tt1, tt2) | Time scale transformation: Terrestrial Time, TT, to International Atomic Time, TAI.
`tttcg`(tt1, tt2) | Time scale transformation: Terrestrial Time, TT, to Geocentric Coordinate Time, TCG.
`tttdb`(tt1, tt2, dtr) | Time scale transformation: Terrestrial Time, TT, to Barycentric Dynamical Time, TDB.
`ttut1`(tt1, tt2, dt) | Time scale transformation: Terrestrial Time, TT, to Universal Time, UT1.
`ut1tai`(ut11, ut12, dta) | Time scale transformation: Universal Time, UT1, to International Atomic Time, TAI.
`ut1tt`(ut11, ut12, dt) | Time scale transformation: Universal Time, UT1, to Terrestrial Time, TT.
`ut1utc`(ut11, ut12, dut1) | Time scale transformation: Universal Time, UT1, to Coordinated Universal Time, UTC.
`utctai`(utc1, utc2) | Time scale transformation: Coordinated Universal Time, UTC, to International Atomic Time, TAI.
`utcut1`(utc1, utc2, dut1) | Time scale transformation: Coordinated Universal Time, UTC, to Universal Time, UT1.
`xy06`(date1, date2) | X,Y coordinates of celestial intermediate pole from series based on IAU 2006 precession and IAU 2000A nutation.
`xys00a`(date1, date2) | For a given TT date, compute the X,Y coordinates of the Celestial Intermediate Pole and the CIO locator s, using the IAU 2000A precession-nutation model.
`xys00b`(date1, date2) | For a given TT date, compute the X,Y coordinates of the Celestial Intermediate Pole and the CIO locator s, using the IAU 2000B precession-nutation model.
`xys06a`(date1, date2) | For a given TT date, compute the X,Y coordinates of the Celestial Intermediate Pole and the CIO locator s, using the IAU 2006 precession and IAU 2000A nutation models.
`zp`() | Zero a p-vector.
`zpv`() | Zero a pv-vector.
`zr`() | Initialize an r-matrix to the null matrix.

## Classes

`ErfaError` | A class for errors triggered by ERFA functions (status codes < 0)
`ErfaWarning` | A class for warnings triggered by ERFA functions (status codes > 0)
`leap_seconds`() | Leap second management.

## Class Inheritance Diagram

# erfa.version Module

Wrapper, ERFA and SOFA version information.

## Variables

`erfa_version` | Version of the C ERFA library that is wrapped.
`sofa_version` | Version of the SOFA library the ERFA library is based on.
`version` | Version of the python wrappers.