void eraC2t00a(double tta, double ttb, double uta, double utb, double xp, double yp, double rc2t[3][3]) /* ** - - - - - - - - - - ** e r a C 2 t 0 0 a ** - - - - - - - - - - ** ** Form the celestial to terrestrial matrix given the date, the UT1 and ** the polar motion, using the IAU 2000A nutation model. ** ** Given: ** tta,ttb double TT as a 2-part Julian Date (Note 1) ** uta,utb double UT1 as a 2-part Julian Date (Note 1) ** xp,yp double coordinates of the pole (radians, Note 2) ** ** Returned: ** rc2t double[3][3] celestial-to-terrestrial matrix (Note 3) ** ** Notes: ** ** 1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates, ** apportioned in any convenient way between the arguments uta and ** utb. For example, JD(UT1)=2450123.7 could be expressed in any of ** these ways, among others: ** ** uta utb ** ** 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. In the case of uta,utb, the ** date & time method is best matched to the Earth rotation angle ** algorithm used: maximum precision is delivered when the uta ** argument is for 0hrs UT1 on the day in question and the utb ** argument lies in the range 0 to 1, or vice versa. ** ** 2) The arguments xp and yp are the coordinates (in radians) of the ** Celestial Intermediate Pole with respect to the International ** Terrestrial Reference System (see IERS Conventions 2003), ** measured along the meridians to 0 and 90 deg west respectively. ** ** 3) The matrix rc2t transforms from celestial to terrestrial ** coordinates: ** ** [TRS] = RPOM * R_3(ERA) * RC2I * [CRS] ** ** = rc2t * [CRS] ** ** where [CRS] is a vector in the Geocentric Celestial Reference ** System and [TRS] is a vector in the International Terrestrial ** Reference System (see IERS Conventions 2003), RC2I is the ** celestial-to-intermediate matrix, ERA is the Earth rotation ** angle and RPOM is the polar motion matrix. ** ** 4) A faster, but slightly less accurate result (about 1 mas), can ** be obtained by using instead the eraC2t00b function. ** ** Called: ** eraC2i00a celestial-to-intermediate matrix, IAU 2000A ** eraEra00 Earth rotation angle, IAU 2000 ** eraSp00 the TIO locator s', IERS 2000 ** eraPom00 polar motion matrix ** eraC2tcio form CIO-based celestial-to-terrestrial matrix ** ** Reference: ** ** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), ** IERS Technical Note No. 32, BKG (2004) ** ** Copyright (C) 2013-2014, NumFOCUS Foundation. ** Derived, with permission, from the SOFA library. See notes at end of file. */ { double rc2i[3][3], era, sp, rpom[3][3]; /* Form the celestial-to-intermediate matrix for this TT (IAU 2000A). */ eraC2i00a(tta, ttb, rc2i ); /* Predict the Earth rotation angle for this UT1. */ era = eraEra00(uta, utb); /* Estimate s'. */ sp = eraSp00(tta, ttb); /* Form the polar motion matrix. */ eraPom00(xp, yp, sp, rpom); /* Combine to form the celestial-to-terrestrial matrix. */ eraC2tcio(rc2i, era, rpom, rc2t); return; }
int eraApco13(double utc1, double utc2, double dut1, double elong, double phi, double hm, double xp, double yp, double phpa, double tc, double rh, double wl, eraASTROM *astrom, double *eo) /* ** - - - - - - - - - - ** e r a A p c o 1 3 ** - - - - - - - - - - ** ** For a terrestrial observer, prepare star-independent astrometry ** parameters for transformations between ICRS and observed ** coordinates. The caller supplies UTC, site coordinates, ambient air ** conditions and observing wavelength, and ERFA models are used to ** obtain the Earth ephemeris, CIP/CIO and refraction constants. ** ** The parameters produced by this function are required in the ** parallax, light deflection, aberration, and bias-precession-nutation ** parts of the ICRS/CIRS transformations. ** ** Given: ** utc1 double UTC as a 2-part... ** utc2 double ...quasi Julian Date (Notes 1,2) ** dut1 double UT1-UTC (seconds, Note 3) ** elong double longitude (radians, east +ve, Note 4) ** phi double latitude (geodetic, radians, Note 4) ** hm double height above ellipsoid (m, geodetic, Notes 4,6) ** xp,yp double polar motion coordinates (radians, Note 5) ** phpa double pressure at the observer (hPa = mB, Note 6) ** tc double ambient temperature at the observer (deg C) ** rh double relative humidity at the observer (range 0-1) ** wl double wavelength (micrometers, Note 7) ** ** Returned: ** astrom eraASTROM* star-independent astrometry parameters: ** pmt double PM time interval (SSB, Julian years) ** eb double[3] SSB to observer (vector, au) ** eh double[3] Sun to observer (unit vector) ** em double distance from Sun to observer (au) ** v double[3] barycentric observer velocity (vector, c) ** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor ** bpn double[3][3] bias-precession-nutation matrix ** along double longitude + s' (radians) ** xpl double polar motion xp wrt local meridian (radians) ** ypl double polar motion yp wrt local meridian (radians) ** sphi double sine of geodetic latitude ** cphi double cosine of geodetic latitude ** diurab double magnitude of diurnal aberration vector ** eral double "local" Earth rotation angle (radians) ** refa double refraction constant A (radians) ** refb double refraction constant B (radians) ** eo double* equation of the origins (ERA-GST) ** ** Returned (function value): ** int status: +1 = dubious year (Note 2) ** 0 = OK ** -1 = unacceptable date ** ** Notes: ** ** 1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any ** convenient way between the two arguments, for example where utc1 ** is the Julian Day Number and utc2 is the fraction of a day. ** ** However, JD cannot unambiguously represent UTC during a leap ** second unless special measures are taken. The convention in the ** present function is that the JD day represents UTC days whether ** the length is 86399, 86400 or 86401 SI seconds. ** ** Applications should use the function eraDtf2d to convert from ** calendar date and time of day into 2-part quasi Julian Date, as ** it implements the leap-second-ambiguity convention just ** described. ** ** 2) The warning status "dubious year" flags UTCs that predate the ** introduction of the time scale or that are too far in the ** future to be trusted. See eraDat for further details. ** ** 3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly ** one second at the end of each positive UTC leap second, ** introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This ** practice is under review, and in the future UT1-UTC may grow ** essentially without limit. ** ** 4) The geographical coordinates are with respect to the ERFA_WGS84 ** reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the ** longitude required by the present function is east-positive ** (i.e. right-handed), in accordance with geographical convention. ** ** 5) The polar motion xp,yp can be obtained from IERS bulletins. The ** values are the coordinates (in radians) of the Celestial ** Intermediate Pole with respect to the International Terrestrial ** Reference System (see IERS Conventions 2003), measured along the ** meridians 0 and 90 deg west respectively. For many ** applications, xp and yp can be set to zero. ** ** Internally, the polar motion is stored in a form rotated onto ** the local meridian. ** ** 6) If hm, the height above the ellipsoid of the observing station ** in meters, is not known but phpa, the pressure in hPa (=mB), is ** available, an adequate estimate of hm can be obtained from the ** expression ** ** hm = -29.3 * tsl * log ( phpa / 1013.25 ); ** ** where tsl is the approximate sea-level air temperature in K ** (See Astrophysical Quantities, C.W.Allen, 3rd edition, section ** 52). Similarly, if the pressure phpa is not known, it can be ** estimated from the height of the observing station, hm, as ** follows: ** ** phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) ); ** ** Note, however, that the refraction is nearly proportional to ** the pressure and that an accurate phpa value is important for ** precise work. ** ** 7) The argument wl specifies the observing wavelength in ** micrometers. The transition from optical to radio is assumed to ** occur at 100 micrometers (about 3000 GHz). ** ** 8) It is advisable to take great care with units, as even unlikely ** values of the input parameters are accepted and processed in ** accordance with the models used. ** ** 9) In cases where the caller wishes to supply his own Earth ** ephemeris, Earth rotation information and refraction constants, ** the function eraApco can be used instead of the present function. ** ** 10) 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 ** ** eraApcg eraApcg13 geocentric ICRS <-> GCRS ** eraApci eraApci13 terrestrial ICRS <-> CIRS ** eraApco eraApco13 terrestrial ICRS <-> observed ** eraApcs eraApcs13 space ICRS <-> GCRS ** eraAper eraAper13 terrestrial update Earth rotation ** eraApio eraApio13 terrestrial CIRS <-> observed ** ** Those with names ending in "13" use contemporary ERFA 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. ** ** 11) The context structure astrom produced by this function is used ** by eraAtioq, eraAtoiq, eraAtciq* and eraAticq*. ** ** Called: ** eraUtctai UTC to TAI ** eraTaitt TAI to TT ** eraUtcut1 UTC to UT1 ** eraEpv00 Earth position and velocity ** eraPnm06a classical NPB matrix, IAU 2006/2000A ** eraBpn2xy extract CIP X,Y coordinates from NPB matrix ** eraS06 the CIO locator s, given X,Y, IAU 2006 ** eraEra00 Earth rotation angle, IAU 2000 ** eraSp00 the TIO locator s', IERS 2000 ** eraRefco refraction constants for given ambient conditions ** eraApco astrometry parameters, ICRS-observed ** eraEors equation of the origins, given NPB matrix and s ** ** Copyright (C) 2013-2015, NumFOCUS Foundation. ** Derived, with permission, from the SOFA library. See notes at end of file. */ { int j; double tai1, tai2, tt1, tt2, ut11, ut12, ehpv[2][3], ebpv[2][3], r[3][3], x, y, s, theta, sp, refa, refb; /* UTC to other time scales. */ j = eraUtctai(utc1, utc2, &tai1, &tai2); if ( j < 0 ) return -1; j = eraTaitt(tai1, tai2, &tt1, &tt2); j = eraUtcut1(utc1, utc2, dut1, &ut11, &ut12); if ( j < 0 ) return -1; /* Earth barycentric & heliocentric position/velocity (au, au/d). */ (void) eraEpv00(tt1, tt2, ehpv, ebpv); /* Form the equinox based BPN matrix, IAU 2006/2000A. */ eraPnm06a(tt1, tt2, r); /* Extract CIP X,Y. */ eraBpn2xy(r, &x, &y); /* Obtain CIO locator s. */ s = eraS06(tt1, tt2, x, y); /* Earth rotation angle. */ theta = eraEra00(ut11, ut12); /* TIO locator s'. */ sp = eraSp00(tt1, tt2); /* Refraction constants A and B. */ eraRefco(phpa, tc, rh, wl, &refa, &refb); /* Compute the star-independent astrometry parameters. */ eraApco(tt1, tt2, ebpv, ehpv[0], x, y, s, theta, elong, phi, hm, xp, yp, sp, refa, refb, astrom); /* Equation of the origins. */ *eo = eraEors(r, s); /* Return any warning status. */ return j; /* Finished. */ }
void eraC2tpe(double tta, double ttb, double uta, double utb, double dpsi, double deps, double xp, double yp, double rc2t[3][3]) /* ** - - - - - - - - - ** e r a C 2 t p e ** - - - - - - - - - ** ** Form the celestial to terrestrial matrix given the date, the UT1, ** the nutation and the polar motion. IAU 2000. ** ** Given: ** tta,ttb double TT as a 2-part Julian Date (Note 1) ** uta,utb double UT1 as a 2-part Julian Date (Note 1) ** dpsi,deps double nutation (Note 2) ** xp,yp double coordinates of the pole (radians, Note 3) ** ** Returned: ** rc2t double[3][3] celestial-to-terrestrial matrix (Note 4) ** ** Notes: ** ** 1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates, ** apportioned in any convenient way between the arguments uta and ** utb. For example, JD(UT1)=2450123.7 could be expressed in any of ** these ways, among others: ** ** uta utb ** ** 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. In the case of uta,utb, the ** date & time method is best matched to the Earth rotation angle ** algorithm used: maximum precision is delivered when the uta ** argument is for 0hrs UT1 on the day in question and the utb ** argument lies in the range 0 to 1, or vice versa. ** ** 2) The caller is responsible for providing the nutation components; ** they are in longitude and obliquity, in radians and are with ** respect to the equinox and ecliptic of date. For high-accuracy ** applications, free core nutation should be included as well as ** any other relevant corrections to the position of the CIP. ** ** 3) The arguments xp and yp are the coordinates (in radians) of the ** Celestial Intermediate Pole with respect to the International ** Terrestrial Reference System (see IERS Conventions 2003), ** measured along the meridians to 0 and 90 deg west respectively. ** ** 4) The matrix rc2t transforms from celestial to terrestrial ** coordinates: ** ** [TRS] = RPOM * R_3(GST) * RBPN * [CRS] ** ** = rc2t * [CRS] ** ** where [CRS] is a vector in the Geocentric Celestial Reference ** System and [TRS] is a vector in the International Terrestrial ** Reference System (see IERS Conventions 2003), RBPN is the ** bias-precession-nutation matrix, GST is the Greenwich (apparent) ** Sidereal Time and RPOM is the polar motion matrix. ** ** 5) Although its name does not include "00", This function is in fact ** specific to the IAU 2000 models. ** ** Called: ** eraPn00 bias/precession/nutation results, IAU 2000 ** eraGmst00 Greenwich mean sidereal time, IAU 2000 ** eraSp00 the TIO locator s', IERS 2000 ** eraEe00 equation of the equinoxes, IAU 2000 ** eraPom00 polar motion matrix ** eraC2teqx form equinox-based celestial-to-terrestrial matrix ** ** Reference: ** ** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), ** IERS Technical Note No. 32, BKG (2004) ** ** Copyright (C) 2013-2015, NumFOCUS Foundation. ** Derived, with permission, from the SOFA library. See notes at end of file. */ { double epsa, rb[3][3], rp[3][3], rbp[3][3], rn[3][3], rbpn[3][3], gmst, ee, sp, rpom[3][3]; /* Form the celestial-to-true matrix for this TT. */ eraPn00(tta, ttb, dpsi, deps, &epsa, rb, rp, rbp, rn, rbpn); /* Predict the Greenwich Mean Sidereal Time for this UT1 and TT. */ gmst = eraGmst00(uta, utb, tta, ttb); /* Predict the equation of the equinoxes given TT and nutation. */ ee = eraEe00(tta, ttb, epsa, dpsi); /* Estimate s'. */ sp = eraSp00(tta, ttb); /* Form the polar motion matrix. */ eraPom00(xp, yp, sp, rpom); /* Combine to form the celestial-to-terrestrial matrix. */ eraC2teqx(rbpn, gmst + ee, rpom, rc2t); return; }