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SuperNOVAS v1.5
The NOVAS C library, made better
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Enumerations | |
enum | novas_dynamical_type { NOVAS_DYNAMICAL_MOD = 0 , NOVAS_DYNAMICAL_TOD , NOVAS_DYNAMICAL_CIRS } |
Constants that determine the type of dynamical system. More... | |
enum | novas_frametie_direction { J2000_TO_ICRS = -1 , ICRS_TO_J2000 } |
Direction constant to use for frame_tie(), to determine the direction of transformation between J2000 and ICRS coordinates. More... | |
enum | novas_reference_system { NOVAS_GCRS = 0 , NOVAS_TOD , NOVAS_CIRS , NOVAS_ICRS , NOVAS_J2000 , NOVAS_MOD , NOVAS_TIRS , NOVAS_ITRS } |
The basic types of positional coordinate reference systems supported by NOVAS. More... | |
Functions | |
double | app_to_cirs_ra (double jd_tt, enum novas_accuracy accuracy, double ra) |
Converts an apparent right ascension coordinate (measured from the true equinox of date) to a CIRS R.A., measured from the CIO. | |
short | cio_ra (double jd_tt, enum novas_accuracy accuracy, double *restrict ra_cio) |
Computes the true right ascension of the celestial intermediate origin (CIO) vs the equinox of date on the true equator of date for a given TT Julian date. | |
double | cirs_to_app_ra (double jd_tt, enum novas_accuracy accuracy, double ra) |
Converts a CIRS right ascension coordinate (measured from the CIO) to an apparent R.A. | |
int | cirs_to_gcrs (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from the Celestial Intermediate Reference System (CIRS) frame at the given epoch to the ICRS / GCRS. | |
int | cirs_to_itrs (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) |
Rotates a position vector from the dynamical CIRS frame of date to the Earth-fixed ITRS frame (IAU 2000 standard method). | |
int | cirs_to_tod (double jd_tt, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from the Celestial Intermediate Reference System (CIRS) at the given epoch to the True of Date (TOD) reference system. | |
int | frame_tie (const double *in, enum novas_frametie_direction direction, double *out) |
Transforms a vector from the dynamical reference system to the International Celestial Reference System (ICRS), or vice versa. | |
short | gcrs2equ (double jd_tt, enum novas_dynamical_type sys, enum novas_accuracy accuracy, double rag, double decg, double *restrict ra, double *restrict dec) |
Converts GCRS right ascension and declination to coordinates with respect to the equator of date (mean or true). | |
int | gcrs_to_cirs (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from the ICRS / GCRS to the Celestial Intermediate Reference System (CIRS) frame at the given epoch. | |
int | gcrs_to_j2000 (const double *in, double *out) |
Changes ICRS / GCRS coordinates to J2000 coordinates. | |
int | gcrs_to_mod (double jd_tdb, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from the ICRS / GCRS to the Mean of Date (MOD) reference frame at the given epoch. | |
int | gcrs_to_tod (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from the ICRS / GCRS to the True of Date (TOD) reference frame at the given epoch. | |
double | ira_equinox (double jd_tdb, enum novas_equinox_type equinox, enum novas_accuracy accuracy) |
Compute the intermediate right ascension of the equinox at the input Julian date, using an analytical expression for the accumulated precession in right ascension. | |
int | itrs_to_cirs (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) |
Rotates a position vector from the Earth-fixed ITRS frame to the dynamical CIRS frame of date (IAU 2000 standard method). | |
int | itrs_to_tod (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) |
Rotates a position vector from the Earth-fixed ITRS frame to the dynamical True of Date (TOD) frame of date (pre IAU 2000 method). | |
int | j2000_to_gcrs (const double *in, double *out) |
Change J2000 coordinates to ICRS / GCRS coordinates. | |
int | j2000_to_tod (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from J2000 coordinates to the True of Date (TOD) reference frame at the given epoch. | |
int | mod_to_gcrs (double jd_tdb, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from Mean of Date (MOD) reference frame at the given epoch to the ICRS / GCRS. | |
int | tod_to_cirs (double jd_tt, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from the True of Date (TOD) reference system to the Celestial Intermediate Reference System (CIRS) at the given epoch to the . | |
int | tod_to_gcrs (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from True of Date (TOD) reference frame at the given epoch to the ICRS / GCRS. | |
int | tod_to_itrs (double jd_tt_high, double jd_tt_low, double ut1_to_tt, enum novas_accuracy accuracy, double xp, double yp, const double *in, double *out) |
Rotates a position vector from the dynamical True of Date (TOD) frame of date the Earth-fixed ITRS frame (pre IAU 2000 method). | |
int | tod_to_j2000 (double jd_tdb, enum novas_accuracy accuracy, const double *in, double *out) |
Transforms a rectangular equatorial (x, y, z) vector from True of Date (TOD) reference frame at the given epoch to the J2000 coordinates. | |
enum novas_dynamical_type |
Constants that determine the type of dynamical system.
I.e., the 'current' equatorial coordinate system used for a given epoch of observation.
Direction constant to use for frame_tie(), to determine the direction of transformation between J2000 and ICRS coordinates.
Enumerator | |
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J2000_TO_ICRS | Change coordinates from ICRS to the J2000 (dynamical) frame. (You can also use any negative value for the same effect).
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ICRS_TO_J2000 | Change coordinates from J2000 (dynamical) frame to the ICRS. (You can use any value >=0 for the same effect).
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The basic types of positional coordinate reference systems supported by NOVAS.
These determine only how the celestial pole is to be located, but not how velocities are to be referenced. specific pos-vel coordinates are referenced to an 'astro_frame', which must specify one of the values defined here.
double app_to_cirs_ra | ( | double | jd_tt, |
enum novas_accuracy | accuracy, | ||
double | ra ) |
Converts an apparent right ascension coordinate (measured from the true equinox of date) to a CIRS R.A., measured from the CIO.
jd_tt | [day] Terrestrial Time (TT) based Julian date |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) |
ra | [h] the apparent R.A. coordinate measured from the true equinox of date. |
References cio_ra().
short cio_ra | ( | double | jd_tt, |
enum novas_accuracy | accuracy, | ||
double *restrict | ra_cio ) |
Computes the true right ascension of the celestial intermediate origin (CIO) vs the equinox of date on the true equator of date for a given TT Julian date.
This is simply the negated return value ofira_equinox() for the true equator of date.
REFERENCES:
jd_tt | [day] Terrestrial Time (TT) based Julian date | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
[out] | ra_cio | [h] Right ascension of the CIO, with respect to the true equinox of date (+ or -), or NAN when returning with an error code. |
References ira_equinox(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, and NOVAS_TRUE_EQUINOX.
double cirs_to_app_ra | ( | double | jd_tt, |
enum novas_accuracy | accuracy, | ||
double | ra ) |
Converts a CIRS right ascension coordinate (measured from the CIO) to an apparent R.A.
measured from the true equinox of date.
jd_tt | [day] Terrestrial Time (TT) based Julian date |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) |
ra | [h] The CIRS right ascension coordinate, measured from the CIO. |
References cio_ra().
int cirs_to_gcrs | ( | double | jd_tdb, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from the Celestial Intermediate Reference System (CIRS) frame at the given epoch to the ICRS / GCRS.
(We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
This function uses Method 2 of the IERS Conventions 2010 (Chapter 5, Section 5.9), converting CIRS to TOD first via a rotation by the equation of origins, then using the IAU 2006 precession-nutation model (P03; Capitaine et al. 2003) to convert to J2000, and finally correcting for the frame bias to arrive at GCRS.
REFERENCES:
jd_tdb | [day] Barycentric Dynamical Time (TDB) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | CIRS Input (x, y, z) position or velocity vector | |
[out] | out | Output position or velocity 3-vector in the ICRS / GCRS coordinate frame. It can be the same vector as the input. |
References cirs_to_tod(), and tod_to_gcrs().
int cirs_to_itrs | ( | double | jd_tt_high, |
double | jd_tt_low, | ||
double | ut1_to_tt, | ||
enum novas_accuracy | accuracy, | ||
double | xp, | ||
double | yp, | ||
const double * | in, | ||
double * | out ) |
Rotates a position vector from the dynamical CIRS frame of date to the Earth-fixed ITRS frame (IAU 2000 standard method).
If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.
If extreme (sub-microarcsecond) accuracy is not required, you can use UT1-based Julian date instead of the TT-based Julian date and set the 'ut1_to_tt' argument to 0.0. and you can use UTC-based Julian date the same way.for arcsec-level precision also.
REFERENCES:
jd_tt_high | [day] High-order part of Terrestrial Time (TT) based Julian date. | |
jd_tt_low | [day] Low-order part of Terrestrial Time (TT) based Julian date. | |
ut1_to_tt | [s] TT - UT1 Time difference in seconds | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
xp | [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
yp | [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
in | Position vector, geocentric equatorial rectangular coordinates, referred to CIRS axes (celestial system). | |
[out] | out | Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system). |
References cel2ter(), EROT_ERA, and NOVAS_DYNAMICAL_CLASS.
int cirs_to_tod | ( | double | jd_tt, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from the Celestial Intermediate Reference System (CIRS) at the given epoch to the True of Date (TOD) reference system.
jd_tt | [day] Terrestrial Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | CIRS Input (x, y, z) position or velocity vector | |
[out] | out | Output position or velocity 3-vector in the True of Date (TOD) frame. It can be the same vector as the input. |
References ira_equinox(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NOVAS_TRUE_EQUINOX, and spin().
int frame_tie | ( | const double * | in, |
enum novas_frametie_direction | direction, | ||
double * | out ) |
Transforms a vector from the dynamical reference system to the International Celestial Reference System (ICRS), or vice versa.
The dynamical reference system is based on the dynamical mean equator and equinox of J2000.0. The ICRS is based on the space-fixed ICRS axes defined by the radio catalog positions of several hundred extragalactic objects.
For geocentric coordinates, the same transformation is used between the dynamical reference system and the GCRS.
NOTES:
REFERENCES:
in | Position vector, equatorial rectangular coordinates. | |
direction | <0 for for dynamical to ICRS transformation, or else >=0 for ICRS to dynamical transformation. Alternatively you may use the constants J2000_TO_ICRS (-1; or negative) or ICRS_TO_J2000 (0; or positive). | |
[out] | out | Position vector, equatorial rectangular coordinates. It can be the same vector as the input. |
short gcrs2equ | ( | double | jd_tt, |
enum novas_dynamical_type | sys, | ||
enum novas_accuracy | accuracy, | ||
double | rag, | ||
double | decg, | ||
double *restrict | ra, | ||
double *restrict | dec ) |
Converts GCRS right ascension and declination to coordinates with respect to the equator of date (mean or true).
For coordinates with respect to the true equator of date, the origin of right ascension can be either the true equinox or the celestial intermediate origin (CIO). This function only supports the CIO-based method.
jd_tt | [day] Terrestrial Time (TT) based Julian date. (Unused if 'coord_sys' is NOVAS_ICRS_EQUATOR) | |
sys | Dynamical equatorial system type | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) (unused if 'coord_sys' is not NOVAS_ICRS [3]) | |
rag | [h] GCRS right ascension in hours. | |
decg | [deg] GCRS declination in degrees. | |
[out] | ra | [h] Right ascension in hours, referred to specified equator and right ascension origin of date. |
[out] | dec | [deg] Declination in degrees, referred to specified equator of date. |
References gcrs_to_cirs(), gcrs_to_mod(), gcrs_to_tod(), NOVAS_DYNAMICAL_CIRS, NOVAS_DYNAMICAL_MOD, NOVAS_DYNAMICAL_TOD, radec2vector(), and vector2radec().
int gcrs_to_cirs | ( | double | jd_tdb, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from the ICRS / GCRS to the Celestial Intermediate Reference System (CIRS) frame at the given epoch.
(We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
This function uses Method 2 of the IERS Conventions 2010 (Chapter 5, Section 5.9), first applying the frame bias to convert GCRS to J2000, then using the IAU 2006 precession-nutation model (P03; Capitaine et al. 2003) to convert to TOD, and finally to CIRS via a rotation by the equation of origins.
REFERENCES:
jd_tdb | [day] Barycentric Dynamical Time (TDB) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | ICRS / GCRS Input (x, y, z) position or velocity vector | |
[out] | out | Output position or velocity 3-vector in the True equinox of Date coordinate frame. It can be the same vector as the input. |
References gcrs_to_tod(), and tod_to_cirs().
int gcrs_to_j2000 | ( | const double * | in, |
double * | out ) |
Changes ICRS / GCRS coordinates to J2000 coordinates.
Same as frame_tie() called with ICRS_TO_J2000. (We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
in | ICRS / GCRS input 3-vector | |
[out] | out | J2000 output 3-vector |
References frame_tie(), and ICRS_TO_J2000.
int gcrs_to_mod | ( | double | jd_tdb, |
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from the ICRS / GCRS to the Mean of Date (MOD) reference frame at the given epoch.
(We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
jd_tdb | [day] Barycentric Dynamical Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
in | ICRS / GCRS Input (x, y, z) position or velocity vector | |
[out] | out | Output position or velocity 3-vector in the Mean wquinox of Date coordinate frame. It can be the same vector as the input. |
References frame_tie(), ICRS_TO_J2000, NOVAS_JD_J2000, and precession().
int gcrs_to_tod | ( | double | jd_tdb, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from the ICRS / GCRS to the True of Date (TOD) reference frame at the given epoch.
(We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
jd_tdb | [day] Barycentric Dynamical Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | ICRS / GCRS Input (x, y, z) position or velocity vector | |
[out] | out | Output position or velocity 3-vector in the True equinox of Date coordinate frame. It can be the same vector as the input. |
References frame_tie(), ICRS_TO_J2000, and j2000_to_tod().
double ira_equinox | ( | double | jd_tdb, |
enum novas_equinox_type | equinox, | ||
enum novas_accuracy | accuracy ) |
Compute the intermediate right ascension of the equinox at the input Julian date, using an analytical expression for the accumulated precession in right ascension.
For the true equinox, the result is the equation of the origins.
NOTES:
REFERENCES:
jd_tdb | [day] Barycentric Dynamic Time (TDB) based Julian date |
equinox | NOVAS_MEAN_EQUINOX (0) or NOVAS_TRUE_EQUINOX (1, or non-zero) |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1, or non-zero) |
References e_tilt(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, and NOVAS_TRUE_EQUINOX.
int itrs_to_cirs | ( | double | jd_tt_high, |
double | jd_tt_low, | ||
double | ut1_to_tt, | ||
enum novas_accuracy | accuracy, | ||
double | xp, | ||
double | yp, | ||
const double * | in, | ||
double * | out ) |
Rotates a position vector from the Earth-fixed ITRS frame to the dynamical CIRS frame of date (IAU 2000 standard method).
If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.
If extreme (sub-microarcsecond) accuracy is not required, you can use UT1-based Julian date instead of the TT-based Julian date and set the 'ut1_to_tt' argument to 0.0. and you can use UTC-based Julian date the same way.for arcsec-level precision also.
REFERENCES:
jd_tt_high | [day] High-order part of Terrestrial Time (TT) based Julian date. | |
jd_tt_low | [day] Low-order part of Terrestrial Time (TT) based Julian date. | |
ut1_to_tt | [s] TT - UT1 Time difference in seconds | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
xp | [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
yp | [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
in | Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system) | |
[out] | out | Position vector, geocentric equatorial rectangular coordinates, referred to CIRS axes (celestial system). |
References EROT_ERA, NOVAS_DYNAMICAL_CLASS, and ter2cel().
int itrs_to_tod | ( | double | jd_tt_high, |
double | jd_tt_low, | ||
double | ut1_to_tt, | ||
enum novas_accuracy | accuracy, | ||
double | xp, | ||
double | yp, | ||
const double * | in, | ||
double * | out ) |
Rotates a position vector from the Earth-fixed ITRS frame to the dynamical True of Date (TOD) frame of date (pre IAU 2000 method).
If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.
If extreme (sub-microarcsecond) accuracy is not required, you can use UT1-based Julian date instead of the TT-based Julian date and set the 'ut1_to_tt' argument to 0.0. and you can use UTC-based Julian date the same way.for arcsec-level precision also.
REFERENCES:
jd_tt_high | [day] High-order part of Terrestrial Time (TT) based Julian date. | |
jd_tt_low | [day] Low-order part of Terrestrial Time (TT) based Julian date. | |
ut1_to_tt | [s] TT - UT1 Time difference in seconds | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
xp | [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
yp | [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
in | Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system) | |
[out] | out | Position vector, geocentric equatorial rectangular coordinates, referred to True of Date (TOD) axes (celestial system) |
References EROT_GST, NOVAS_DYNAMICAL_CLASS, and ter2cel().
int j2000_to_gcrs | ( | const double * | in, |
double * | out ) |
Change J2000 coordinates to ICRS / GCRS coordinates.
Same as frame_tie() called with J2000_TO_ICRS. (We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
in | J2000 input 3-vector | |
[out] | out | ICRS / GCRS output 3-vector |
References frame_tie(), and J2000_TO_ICRS.
int j2000_to_tod | ( | double | jd_tdb, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from J2000 coordinates to the True of Date (TOD) reference frame at the given epoch.
jd_tdb | [day] Barycentric Dynamical Time (TDB) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | Input (x, y, z) position or velocity vector in rectangular equatorial coordinates at J2000 | |
[out] | out | Output position or velocity 3-vector in the True equinox of Date coordinate frame. It can be the same vector as the input. |
References NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NUTATE_MEAN_TO_TRUE, nutation(), and precession().
int mod_to_gcrs | ( | double | jd_tdb, |
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from Mean of Date (MOD) reference frame at the given epoch to the ICRS / GCRS.
(We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
jd_tdb | [day] Barycentric Dynamical Time (TDB) based Julian date that defines the input epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
in | Input (x, y, z) position or velocity 3-vector in the Mean equinox of Date coordinate frame. | |
[out] | out | Output ICRS / GCRS position or velocity vector. It can be the same vector as the input. |
References frame_tie(), J2000_TO_ICRS, NOVAS_JD_J2000, and precession().
int tod_to_cirs | ( | double | jd_tt, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from the True of Date (TOD) reference system to the Celestial Intermediate Reference System (CIRS) at the given epoch to the .
jd_tt | [day] Terrestrial Time (TT) based Julian date that defines the output epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | CIRS Input (x, y, z) position or velocity vector | |
[out] | out | Output position or velocity 3-vector in the True of Date (TOD) frame. It can be the same vector as the input. |
References ira_equinox(), NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NOVAS_TRUE_EQUINOX, and spin().
int tod_to_gcrs | ( | double | jd_tdb, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from True of Date (TOD) reference frame at the given epoch to the ICRS / GCRS.
(We treat ICRS and GCRS the same, since they only define the orientation of the equator, and not the origin. The origin is defined by the observer location separately.)
jd_tdb | [day] Barycentric Dynamical Time (TDB) based Julian date that defines the input epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | Input (x, y, z) position or velocity 3-vector in the True equinox of Date coordinate frame. | |
[out] | out | Output ICRS / GCRS position or velocity vector. It can be the same vector as the input. |
References frame_tie(), J2000_TO_ICRS, and tod_to_j2000().
int tod_to_itrs | ( | double | jd_tt_high, |
double | jd_tt_low, | ||
double | ut1_to_tt, | ||
enum novas_accuracy | accuracy, | ||
double | xp, | ||
double | yp, | ||
const double * | in, | ||
double * | out ) |
Rotates a position vector from the dynamical True of Date (TOD) frame of date the Earth-fixed ITRS frame (pre IAU 2000 method).
If both 'xp' and 'yp' are set to 0 no polar motion is included in the transformation.
If extreme (sub-microarcsecond) accuracy is not required, you can use UT1-based Julian date instead of the TT-based Julian date and set the 'ut1_to_tt' argument to 0.0. and you can use UTC-based Julian date the same way.for arcsec-level precision also.
REFERENCES:
jd_tt_high | [day] High-order part of Terrestrial Time (TT) based Julian date. | |
jd_tt_low | [day] Low-order part of Terrestrial Time (TT) based Julian date. | |
ut1_to_tt | [s] TT - UT1 Time difference in seconds. | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
xp | [arcsec] Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
yp | [arcsec] Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds. | |
in | Position vector, geocentric equatorial rectangular coordinates, referred to True of Date (TOD) axes (celestial system). | |
[out] | out | Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system). |
References cel2ter(), EROT_GST, and NOVAS_DYNAMICAL_CLASS.
int tod_to_j2000 | ( | double | jd_tdb, |
enum novas_accuracy | accuracy, | ||
const double * | in, | ||
double * | out ) |
Transforms a rectangular equatorial (x, y, z) vector from True of Date (TOD) reference frame at the given epoch to the J2000 coordinates.
jd_tdb | [day] Barycentric Dynamical Time (TDB) based Julian date that defines the input epoch. Typically it does not require much precision, and Julian dates in other time measures will be unlikely to affect the result | |
accuracy | NOVAS_FULL_ACCURACY (0) or NOVAS_REDUCED_ACCURACY (1) | |
in | Input (x, y, z) position or velocity 3-vector in the True equinox of Date coordinate frame. | |
[out] | out | Output position or velocity vector in rectangular equatorial coordinates at J2000. It can be the same vector as the input. |
References NOVAS_FULL_ACCURACY, NOVAS_REDUCED_ACCURACY, NUTATE_TRUE_TO_MEAN, nutation(), and precession().