Feature release, with critical bug fixes.
Fixed#188: Critical bug in novas_make_transform() since inception in v1.1. Compound transforms were calculated using matrix products in the wrong commutation order (successive transforms were multiplied from the right instead of from the left). Very embarrasing indeed, and somehow it went unnoticed with the testing suite also (even more embarrassing...).
#183: IERS Earth orientation corrections set via cel_pole() were not taken into account for true obliquity and the equation of equinoxes in e_tilt(). This was a bug since v1.0. The bug only affected the old (pre IAU 2006) ways of incorporating polar offsets into TOD coordinates, at the sub-arcsec level. Note, than even with the old method, it is now preferrable to apply such offsets with wobble() for the PEF / TIRS to ITRS (and reverse) conversions instead.
#184: The frame based approach introduced in v1.1 has ommitted applying polar wobble corrections for transforming between the TIRS / PEF and ITRS, and vice versa. This resulted in an error at the sub-arcsec level for celestial to ITRS / horizontal (or reverse) calculations, when IERS Earth orientation parameters were explicitly set.
#187: The NOVAS C 3.1 implementation of cel2ter() / ter2cel() was such that if both xp and yp parameters were zero, then no wobble correction was applied, not even for the TIO location (s') when converting between CIRS and ITRS. The error from this omission is very small, at just a few μas (micro-acrseconds) within a couple of centuries of J2000.
#190: Reverse wobble() (ITRS to TIRS/PEF) had wrong 2nd order corrections, resulting in negligible errors below 0.1 μas (micro-arcseconds) typically.
#193: C++ namespace conflict in novas_frame declaration. Fixed by declaring and using named structure types instead of the conflicting typedef aliases.
#172: Added novas_time_gst() and novas_time_lst() convenience functions to calculate the Greenwich (apparent) Sidereal Time (GST / GaST) and Local (apparent) Sidereal Time (LST / LaST) for a given astrometric time (and observer location) more easily.
#173: Added our own implementation of the wavelength-dependent IAU refraction model as novas_wave_refraction(), which is based on the SOFA iauRefco() function. The wavelength for which the refraction is calculated can be set by novas_refract_wavelength(). By default 550 nm (0.55 μm) is assumed.
#176: novas_make_planet_orbit() to generate Keplerian orbital elements for the major planets (sans Earth), and the Earth-Moon Barycenter (EMB), based on Standish & Williams 1992. In most cases such orbitals can provide arcmin-level precisions, especially for current dates.
#176:novas_make_moon_orbit() to generate geocentric Keplerian orbital elements for the Moon using the Chapront et al. 2002 model.
#176: novas_approx_heliocentric() and novas_approx_sky_pos() to calculate approximate heliocentric ICRS and observable apparent positions, respectively, for the major planets (including Earth), and Moon and the Earth-Moon Barycenter, using the orbital models mentioned above.
#176: novas_moon_phase() and novas_next_moon_phase() to calculate the Moon's apparent phase or the date/time when it reaches a specific phase, respectively, using the Keplerian orbitals for the E-M Barycenter by Standish & Williams 1992, and the geocentric orbitals of the Moon by Chapront et al. 2002.
#176: novas_orbital_native_posvel() to calculate orbital positions in the native system, in which the orbital is defined (e.g. ecliptic coordinates for planetary orbits).
#177: Added novas_day_of_week() and novas_day_of_year() functions to convert JD dates to a 1-based day of week index, or to a day of the year in the calendar of choice.
#185: Added NOVAS_TIRS and NOVAS_ITRS to enum novas_reference_systems. All frame-based functions now support these. Legacy place() and its variants support TIRS but not ITRS (because of the lack of information available to the legacy calls), while Keplerian orbitals may not be be defined in either TIRS or ITRS since these Earth co-rotating systems are not inertial systems.
#186: Added NOVAS_RADIO_REFRACTION and NOVAS_WAVE_REFRACTION to enum novas_refraction_model, for referencing the Berman & Rockwell 1976 radio-wave model, or the IAU / SOFA wavelength-dependent model, respectively.
#191: Added tt2tdb_hp() (high-precision) and tt2tdb_fp() (flexible-precision) functions for calculating the TDB-TT time difference (in seconds), with up to 0.1 μs accuracy based on Fairhead & Bretagnon 1990.
#194: Added documentation under resources/ for a side-by-side example comparison with astropy.
#173: Added parameter range checking to refract() function and novas_radio_refraction() model. If called with weather parameters or an elevation angle outside of reasonable values, NaN will be returned and errno will be set to EINVAL.
#181: Changed nutation_angles() to apply P03 model rescaling to IAU2000 nutation angles to provide 'IAU2006' values (see Capitaine et al. 2005). The same rescaling has been adopted by SOFA also.
#186: Tweaked error handling in atmospheric refraction functions (in refract.c).
NOVAS_RMASS_INIT (in novas.h) and LG (in timescale.c) values updated with DE440 data (Park et al. 2021).
Moved some functions around between source files.
cel_pole() function and EPS_COR / PSI_COR global variables, which provided support for the old (now disfavored) way of incorporating Earth orientation parameters as corrections into the true equator and equinox of date. The preferred way to incorpotate Earth orientation corrections is to use dx,dy offsets relative to the IAU2006 precession-nutation model only when transforming between the Terrestrial Intermediate Reference System (TIRS) or Pseudo Earth-Fixed (PEF) system and the International Terrestrial Reference System (ITRS), and vice versa.Bug fix release with minor enhancements.
Fixed#167: Fixes for Debian i386 cross builds.
#174: accum_prec() had linear and quadratic time evolution coefficients swapped since v1.0. The bug affected
the IAU2000 precession-nutation calculations, and the calculation of the complementary terms in the equation of
equinoxes in ee_ct() / e_tilt(). The effect however is small, typically just a few micro-arcseconds (μas),
for dates within a century of J2000.
#166: Improved detection of invalid seconds in parse_degrees().
#169: novas_parse_degrees() to support parsing values in exponential notation also, e.g. 1.23E2, 1.23E2W etc.
#170: make_on_surface() to validate temperature and pressure values, and return -1 (with errno set to EINVAL)
if the supplied values are outside of the sensible range.
#171: Cache nutation_angles() instead of e_tilt() to improve performance in more usage scenarios. (See updated
benchmarks).
#171: Moved precession(), nutation(), and nutation_angles() to equinox.c.
#178: novas_jd_to_date() to check if input calendar is valid and return -1 with errno set to EINVAL if it is
not.
#179: novas_jd_from_date() to check if input calendar is valid and return NaN with errno set to EINVAL if it
is not.
Corrected benchmarks for individual frames.
Corrections and edits to API documentation.
Deprecated ee_ct() and ira_equinox() functions. Both are meant for internal use only, and need not be exposed to
users in general.
Deprecated solarsystem(), solarsystem_hp(), and readeph() functions. These were prototypes for user-defined
implementations that had to be linked together with NOVAS. In SuperNOVAS, the same functionality can be (should be)
set dynamically, during runtime. Thus, these functions are provided to support building legacy NOVAS applications
only, and should be avoided in new application code going forward.
Feature release with many new convenience functions, such as for handling times and angles as strings; calculating rise, set, transit times; and other common astrometric calculations. In addition, the release brings various changes to improve performance.
Fixed#116: transform_cat() to update parallax to the recalculated value when precessing or changing epochs. This was a SuperNOVAS bug since v.1.0.
#128: transform_cat() had insufficient string length checking of out_id parameter. Prior to the fix it checked for the longer object name size instead of the catalog name size. However, even if longer than expected input names were left uncaught, only the appropriatre number of characters were used -- hence it broke nothing, only failed to remind the caller (with an error) when the supplied name was too long.
#139: Legacy linking of external solarsystem() / solarsystem_hp() provider modules was blocked by solsys-ephem.c inadvertently definining these functions when BUILTIN_SOLSYS_EPHEM was set to 1 (default) during the build, even though it was not supposed to.
#156: obs_posvel() called geo_posvel() with TDB instead of TT. It less than a 2 ms difference, so not typically signifficant, unless <10-m level poitioning is required for Earth-orbiting satellites.
#113: New novas_frame_lst() convenience function to readily return the Local (apparent) Sidereal Time for a given Earth-based observing frame.
#113: New novas_hms_hours() and novas_dms_degrees() convenience functions to make it easier to parse HMS or DMS based time or angle values, returning the result in units of hours or degrees, appropriately for use in SuperNOVAS.
#113: New novas_rises_above() and novas_sets_below() functions to return the date/time a source rises above or sets below a specific elevation on a given date, and novas_transit_time() to calculate the time a source transits over the local meridian. (For Earth-based observers only). #140, #146: Further fixes to these calculations after the v1.3.0-rc5 release candidate [thanks to @valeriy-sokoloff].
#113: New novas_helio_dist() function to calculate the heliocentric distance of a Solar-system body on a given date. The novas_solar_power() function can be used to estimate the incident Solar power on a Solar-system body, while novas_solar_illum() can be used to calculate the fraction of a spherical body that is illuminated by the Sun seen from the observer location.
#113: New novas_hpa() and novas_epa() functions to calculate the parallactic angle (a.k.a. vertical position angle) for a given location on sky, using the local horizontal coordinates, or else the equatorial position, respectively. The parallactic angle (PA) can be useful to convert local Cartesian offsets (e.g. from a flat image or detector array) between the local horizontal and equatorial orientations, e.g. via the newly added novas_h2e_offset() or novas_e2h_offset() functions. The conversion between offsets and absolute coordinates usually requires a WCS projections, such as described in Calabretta & Greisen 2002.
#113: New novas_sep(), novas_equ_sep(), and novas_object_sep() functions can be used to calculate the precise apparent distance between to spherical or equatorial locations, or between two sources, respectively. novas_sun_angle() and novas_moon_angle() can be used to calculate the apparent angular distance of sources from the Sun and Moon, respectively.
#113: New novas_observable and novas_track data structures to provide second order Taylor series expansion of the apparent horizontal or equatorial positions, distances, and redshifts for sources. They can be calculated with the newly added novas_hor_track() or novas_equ_track() functions. Such tracking values, including rates and accelerations, can be directly useful for controlling telescope drives in horizontal or equatorial mounts to track sources (hence the name). You can also obtain instantaneous projected (extrapolated) positions from the tracking parameters via novas_track_pos() at low computational cost.
#113: New novas_los_to_xyz() and novas_xyz_to_los() functions to convert between line-of-sight (δφ, δθ, δr) vectors and rectangular equatorial (δx, δy, δz) vectors.
#113: New novas_xyz_to_uvw() and novas_uvw_to_xzy() functions to convert between ITRS Earth locations (absolute or differential) to equatorial projections along a line of sight in the direction of a source. Such projections are oft used in interferometry.
#114: New novas_lsr_to_ssb_vel() can be used to convert velocity vectors referenced to the LSR to Solar-System Barycentric velocities. And, novas_ssb_to_lsr_vel() to provide the inverse conversion.
#117: Added benchmarks under the benchmark/ folder, for SuperNOVAS as well as equivalent benchmarks for astropy. To run the SuperNOVAS benchmarks, simply make benchmark in the distribution directory.
#118: New novas_parse_date() / novas_parse_date_format() to parse date/time specifications, novas_parse_dms() and novas_parse_hms() to return hours and degrees for HMS and DMS specifications, as well as the updated parse position.
#118: New novas_timescale_for_string() to match timescale constants to string representations, such as "UTC", or "TAI", and novas_print_timescale() to convert to string representation.
#118: New novas_iso_timestamp() to print UTC timestamps in ISO date format with millisecond precision, and novas_timestamp() to print timestamps in specific timescales. #151: Various fixes to new timestamping after rc7. [thanks to @valeriy-sokoloff]
#122: New novas_jd_to_date(), and novas_jd_from_date() which convert between JD day and calendar dates using the specific type of calendar: Gregorian, Roman/Julian, or the conventional calendar of date.
#131: New novas_date() and novas_date_scale() for the simplest conversion of string times to Julian days, and in case of the latter also to a corresponding timescale (without returning a parse position).
#133: New novas_parse_timescale() to parse a timescale from a string specification, and return the updated parse position after also.
#134: New novas_parse_hours() and novas_parse_degrees() to convert strings in decimal or HMS/DMS formats to floating point values for SuperNOVAS, and return the parse position after the time/angle specification.
#135: New novas_str_hours() and novas_str_degrees() for the simplest conversion of strings in decimal or HMS/DMS formats to floating point values for SuperNOVAS (without retruning a parse position).
#137: New novas_epoch() to convert string coordinate system specifications to the Julian date of the corresponding epoch, and new make_cat_object_sys() and make_redshifted_object_sys() to make it simpler to define ICRS catalog sources in the coordinate system of choice.
#143: Added FORTIFY build configuration setting to enable gcc source code fortification checking by setting the _FORTIFY_SOURCE macro to the specified value. It is now used with a value of 3 in the build and test CIs.
#150: Further initializers for SuperNOVAS structures that can be used to empty initialize data.
#154: Added novas_print_hms() and novas_print_dms() functions to convert time / angles to their HMS/DMS string representations, with the chosen separators, and the desired decimal places on the seconds.
#155: Added novas_parse_iso_date() for pasing ISO 8601 timestamps, including those expressed in the proleptic Gregorian calendar prior to the Gregorian calendar reform of 1582, for which the ISO 8601 timestamp differs from the astronomical calendar date assumed by novas_parse_timestamp().
Added example-time.c and example-rise-set.c under examples/, for demonstrating date/time handling functions and rise, set, and transit time calculations.
#130 Use C99 restrict keyword to prevent pointer argument aliasing. Modern compilers will warn if restricted pointer arguments are aliased. At the least, it is a hint to users that pointer arguments marked as such should be distinct from (not overlapping with) the other pointer arguments.
#139 Reorganized code into more manageably sized modules. It also makes the API documentation by source file more logically organized.
#139: Legacy source code moved to legacy/ folder.
#150: Use standard C initializers instead of the non-standard empty backets {}. While the empty brackets have been OK with gcc for quite a while, they only became standard in C23. Other compilers might barf at their use.
#152: For C++ compatibility do not use class as a parameter name. [thanks to @valeriy-sokoloff]
#156: Omit TDB-TT time difference, a maximum of 2 ms, in Earth tilt calculations, where it really does not make any difference. As a result some calculations are now faster than before.
#156: Higher precision time match requirement for re-using cached ephemeris calculations.
#156: tt2tdb() now caches last calculation also.
#156: Eliminate redundant caching of calculations. (Also in #158).
#156: Tighten precession() time checking.
#157: Switch to iau2000b() as the low-precision nutation series. It is good to about 1 arcsec, which is the promised precision in reduced accuracy, but a lot faster than the nu2000k() series, which in turn is barely faster than the full iau2000a() nutation series.
#157: fund_args() to always calculate full polynomial expansion. There is little performance to gain from the truncation we used in the vicinity of J2000. No real change in the results.
#159: Add caching to ee_ct(). Just in case someone wants to call...
Feature release. New easy to use adapter modules for CALCEPH or the NAIF CSPICE Toolkit to provide precise positions for Solar-system sources. Also, added support for Keplerian orbitals, such as the ones published by the IAU Minor Planet Center (MPC) for asteroids, comets, and Near-Earth-Objects (NEOs). And, many more fixes and improvements.
This is a replacement for the somewhat botched release from the day before, which contained an unfortunate build oops. The replacement does not change the source code or the API, so the version stays at 1.2.0.
FixedFixes to GCC version checking for macros.
Fixed dummy readeph() implementation in readeph0.c, and the use of DEFAULT_READEPH in config.mk. readeph0.c is not linked by default, and was not linked in prior releases either.
Cure LLVM clang compiler warnings, in tests and examples also.
#57: New generic redshift-handling functions novas_v2z(), novas_z2v().
#57, #102: New make_redshifted_cat_entry() and make_redshifted_object() to simplify the creation of distant catalog sources that are characterized with a redshift measure rather than a radial velocity value.
#58: New functions to calculate and apply additional gravitational redshift corrections for light that originates near massive gravitating bodies (other than major planets, or Sun or Moon), or for observers located near massive gravitating bodies (other than the Sun and Earth). The added functions are grav_redshift(), redhift_vrad(), unredshift_vrad(), novas_z_add(), and novas_z_inv().
#83: CALCEPH integration: novas_use_calceph() and/or novas_use_calceph_planets() to specify and use ephemeris data via CALCEPH for Solar-system sources in general, and for major planets specifically; and novas_calceph_use_ids() to specify whether object.number in NOVAS_EPHEM_OBJECT type objects is a NAIF ID (default) or else a CALCEPH ID number of the Solar-system body. These functions are provided by the libsolsys-calceph.so[.1] and/or .a plugin libraries, which are built contingent on the CALCEPH_SUPPORT variable being set to 1 prior to the build. The build of the plugin module requires an accessible installation of the CALCEPH development files (C headers and unversioned static or shared libraries depending on the needs of the build).
#86: NAIF CSPICE integration: novas_use_cspice(), novas_use_cspice_planets(), novas_use_cspice_ephem() to use the NAIF CSPICE library for all Solar-system sources, major planets only, or for other bodies only. NOVAS_EPHEM_OBJECTS should use NAIF IDs with CSPICE (or else -1 for name-based lookup). Also provides cspice_add_kernel() and cspice_remove_kernel() functions for convenience to manage the set of active kernels (#89). These functions are provided by the libsolsys-cspice.so[.1] and/or .a plugin libraries, which are built contingent on the CSPICE_SUPPORT variable being set to 1 prior to the build. The build of the plugin module requires an accessible installation of the CSPICE development files (C headers and unversioned static or shared libraries depending on the needs of the build).
#87: Added novas_planet_for_name() function to return the NOVAS planet ID for a given (case insensitive) name.
NOVAS-NAIF conversions for major planets (and Sun, Moon, SSB): novas_to_naif_planet() (planet centers), novas_to_dexxx_planet() (mixed planet center/barycenter for DExxx ephemeris files), and the inverse naif_to_novas_planet().
Added get_planet_provider() and get_planet_provider_hp() functions for convenience to return the solarsystem() / solarsystem_hp() type custom planet ephemeris provider functions currently configured, so they may be used directly, outside of ephemeris() calls.
#93: Now supporting make install with prefix and DESTDIR support (e.g. make prefix="/opt" install to install under /opt, and/or make DESTDIR="/tmp/stage" install to stage install under /tmp/stage). You can also set other standard directory variables, as prescribed by the GNU standard to further customize the install locations.
#95, #98: Added support for using orbital elements. object.type can now be set to NOVAS_ORBITAL_OBJECT, whose orbit can be defined by the set of novas_orbital, relative to a novas_orbital_system. You can initialize an object with a set of orbital elements using make_orbital_object(), and for planetary satellite orbits you might use novas_set_orbsys_pole(). For orbital objects, ephemeris() will call on the new novas_orbit_posvel() to calculate positions. While orbital elements do not always yield precise positions, they can for shorter periods, provided that the orbital elements are up-to-date. For example, the Minor Planer Center (MPC) publishes accurate orbital elements for all known asteroids and comets regularly. For newly discovered objects, this may be the only and/or most accurate information available anywhere.
#97: Added NOVAS_EMB (Earth-Moon Barycenter) and NOVAS_PLUTO_BARYCENTER to enum novas_planets to distinguish from the planet center in calculations.
#98: Added gcrs_to_tod() / tod_to_gcrs() and gcrs_to_mod() / mod_to_gcrs() vector conversion functions for convenience.
#106: New example files under examples/ demonstrating the recommended approach for using SuperNOVAS to calculate positions for various types of object.
Added various object initializer macros in novas.h for the major planets, Sun, Moon, and barycenters, e.g. NOVAS_EARTH_INIT or NOVAS_SSB_INIT. These wrap the parametric NOVAS_PLANET_INIT(num, name) macro, and can be used to simplify the initialization of NOVAS objects.
Added more physical unit constants to novas.h and a corresponding section in the README on how these may be used to convert to/from NOVAS conventional quantities.
SuperNOVAS headers now include each other as system-headers, not local headers. This is unlikely to affect anything really but it is more proper for an installation of the library, and works with our own Makefile too.
Added 'Coordinate Systems and Conversions' flowchart to README.
Added a GNU standard documentation targets to Makefile.
Added infer make target for running Facebook's infer static analysis tool.
Added missing error tracing in nutation().
Added README.md Figure 1, to clarify relation of coordinate systems and (Super)NOVAS function to convert vectors among them.
#96: Changed object structure to include novas_orbital for NOVAS_ORBITAL_OBJECT types. To keep ABI compatibility to earlier SuperNOVAS releases, make_object() will not initialize the new .orbit field unless type is set to NOVAS_ORBITAL_OBJECT (which was not available before).
#97: Updated NOVAS_PLANETS, NOVAS_PLANET_NAMES_INIT, and NOVAS_RMASS_INIT macros to include the added planet constants.
#106: The old (legacy) NOVAS C example has been removed. Instead a new set of examples are provided, which are better suited for SuperNOVAS.
make check now runs both static analysis by cppcheck (new analysis target) and regression tests (test target), in closer conformance to GNU Makefile standards.
Added -g to default CFLAGS as a matter of GNU best practice.
Static library is now named ibsupernovas.a, which is symlinked to libnovas.a for back compatibility.
readeph0.c moved to examples/. It's a dummy legacy NOVAS C implementation that is not really needed in SuperNOVAS.
Various small tweaks to Makefiles.
Updated README.md and API documentation.
Bug fix release. Nothing too scary, mainly just a collection of smaller fixes and improvements. The re-release addresses the excessive precision in tests, which caused testing failure on some platforms for the original #82 release. Otherwise, the library itself is identical to the earlier v1.1.1 release.
Fixed#55: Relativistic corrections to radial velocity were still not applied correctly. The revised calculation now uses the actual relativistic velocity differential between the source and observer to apply the appropriate time dilation factor, and applies gravitational corrections for Sun and Earth consistently at source and observer alike.
#64: NOVAS_TAI_TO_TT definition had wrong decimal in last place, thus was 3 ms off from what it should have been. (thanks to @kiranshila)
#68: readeph_dummy() dummy implementation in readeph0.c called non existing error handler function.
#59: For observing major planets (and Sun and Moon) rad_vel(), rad_vel2(), place(), and novas_sky_pos() will include gravitational corrections to radial velocity for light originating at the surface, and observed near Earth or else at a large distance away. These corrections, along with those for the Solar potential at the source, may be skipped for rad_vel() / rad_vel2() by setting d_src_sun negative.
#55: Use relativistic formulae to add/difference velocities (i.e. change velocity reference frame).
#60: Moved SuperNOVAS-only functions to a separate super.c module to alleviate the bloating of novas.c, which can still be used as a self-contained, standalone, NOVAS C replacement for legacy applications if need be.
#62: Improve debug mode error tracing when NAN values are returned, so the trace indicates NAN rather than a bogus integer return value before.
#66: Various tweaks for C/C++ best practices (by @kiranshila)
#67: Use accuracy argument in tod_to_cirs(). (thanks to @kiranshila)
#68: Various improvements to debug error tracing.
#73: Initializer macros (primarily for internal use), forced 'use' of unused variables after declarations, and no order-only-dependencies in Makefiles -- in order to cure warnings and to conform with older compilers and make.
Slight tweaks to Makefile, and .mk snippets, with added make configurability.
Feature release. Introducing a more efficient and elegant approach to position and velocity calculations using observer frames; versatile handling of astronomical timescales; and support for further observer locations, coordinate reference systems, and atmospheric refraction models. The release also fixes a number of bugs, of varying severity, which affected prior SuperNOVAS (and NOVAS C) releases.
Fixed#29: Fix portability to non-Intel platforms. Previously, SuperNOVAS used char for storing small integer coefficients, assuming char was signed. However, on some platforms like ARM and PowerPC char is unsigned, which broke calculations badly. As of now, we use the explicit platform independent signed int8_t storage type for these coefficients.
#38: gcrs_to_j2000() transformed in the wrong direction in v1.0.
#39: tod_to_itrs() used wrong Earth rotation measure (NOVAS_ERA instead of NOVAS_GST) in v1.0.
#45: cel2ter() invalid output in v1.0 with CIRS input coordinates (erot = EROT_ERA and class = NOVAS_DYNAMICAL_CLASS) if output vector was distinct from input vector. Affects cirs_to_itrs() also.
#36: tt2tdb() Had a wrong scaling in sinusoidal period in v1.0, resulting in an error of up to +/- 1.7 ms.
#37: gcrs_to_cirs() did not handle well if input and output vectors were the same in v1.0.
#28: Division by zero bug in d_light() (since NOVAS C 3.1) if the first position argument is the ephemeris reference position (e.g. the Sun for solsys3.c). The bug affects for example grav_def(), where it effectively results in the gravitational deflection due to the Sun being skipped. See Issue #28.
#41: grav_def() gravitating body position antedated somewhat incorrectly (in v1.0) when observed source is a Solar-system object between the observer and the gravitating body. The resulting positional error is typically small at below 10 uas.
#50: The NOVAS C 3.1 implementation of rad_vel() applied relativistic corrections for a moving observer conditional on applying relativistic gravitational corrections (for Sun and/or Earth potential) for the observer. However, it seems more reasonable that the corrections for a moving observer should be applied always and independently of the (optional) gravitational corrections.
#34: place() radial velocities were not quite correct in prior SuperNOVAS releases. The radial velocity calculation now precedes aberration, since the radial velocity that is observed is in the geometric direction towards the source (unaffected by aberration). As for gravitational deflection, the geometric direction is the correct direction in which light was emitted from the source for sidereal objects. For Solar system sources we now reverse trace the deflected light to calculate the direction in which it was emitted from the source. As such, the radial velocities calculated should now be precise under all conditions. The typical errors of the old calculations were up to tens of m/s because of aberration, and a few m/s due to the wrong gravitational deflection calculation.
#24: Bungled definition of SUPERNOVAS_VERSION_STRING in novas.h in v1.0.
Bungled definition of NOVAS_OBSERVER_PLACES in novas.h in v1.0.
#33: New observing-frame based approach for calculations (frames.c). A novas_frame object uniquely defines both the place and time of observation, with a set of pre-calculated transformations and constants. Once the frame is defined it can be used very efficiently to calculate positions for multiple celestial objects with minimum additional computational cost. The frames API is also more elegant and more versatile than the low-level NOVAS C approach for performing the same kind of calculations. And, frames are inherently thread-safe since post-creation their internal state is never modified during the calculations. The following new functions were added: novas_make_frame(), novas_change_observer(), novas_geom_posvel(), novas_geom_to_app(), novas_sky_pos(), novas_app_to_hor(), novas_app_to_geom(), novas_hor_to_app(), novas_make_transform(), novas_invert_transform(), novas_transform_vector(), and novas_transform_sky_pos().
#33: New novas_timespec structure for the self-contained definition of precise astronomical time (timescale.c). You can set the time via novas_set_time() or novas_set_split_time() to a JD date in the timescale of choice (UTC, UT1, GPS, TAI, TT, TCG, TDB, or TCB), or to a UNIX time with novas_set_unix_time(). Once set, you can obtain an expression of that time in any timescale of choice via novas_get_time(), novas_get_split_time() or novas_get_unix_time(). And, you can create a new time specification by incrementing an existing one, using novas_increment_time(), or measure time differences via novas_diff_time(), novas_diff_tcg(), or novas_diff_tcb().
Added novas_planet_bundle structure to handle planet positions and velocities more elegantly (e.g. for gravitational deflection calculations).
#32: Added grav_undef() to undo gravitational bending of the observed light to obtain geometric positions from observed ones.
Added obs_posvel() to calculate the observer position and velocity relative to the Solar System Barycenter (SSB).
Added obs_planets() to calculate apparent planet positions (relative to observer) and velocities (w.r.t. SSB).
Added new observer locations NOVAS_AIRBORNE_OBSERVER for an observer moving relative to the surface of Earth e.g. in an aircraft or balloon based telescope platform, and NOVAS_SOLAR_SYSTEM_OBSERVER for spacecraft orbiting the Sun. Both of these use the observer.near_earth strcture to define (positions and) velocities as appropriate. Hence the 'near_earth name is a bit misleading, but sticks for back compatibility.
Added coordinate reference systems NOVAS_MOD (Mean of Date) which includes precession by not nutation and NOVAS_J2000 for the J2000 dynamical reference system.
New observer locations NOVAS_AIRBORNE_OBSERVER and NOVAS_SOLAR_SYSTEM_OBSERVER, and corresponding make_airborne_observer() and make_solar_system_observer() functions. Airborne observers have an Earth-fixed momentary location, defined by longitude, latitude, and altitude, the same way as for a stationary observer on Earth, but are moving relative to the surface, such as in an aircraft or balloon based observatory. Solar-system observers are similar to observers in Earth-orbit but their momentary position and velocity is defined relative to the Solar System Barycenter (SSB), instead of the geocenter.
Added humidity field to on_surface structure, e.g. for refraction calculations at radio wavelengths. The make_on_surface() function will set humidity to 0.0, but the user can set the field appropriately afterwards.
New set of built-in refraction models to use with the frame-based novas_app_to_hor() / novas_hor_to_app() functions. The models novas_standard_refraction() and novas_optical_refraction() implement the same refraction model as refract() in NOVAS C 3.1, with NOVAS_STANDARD_ATMOSPHERE and NOVAS_WEATHER_AT_LOCATION respectively, including the reversed direction provided by refract_astro(). The user may supply their own custom refraction also, and may make use of the generic reversal function novas_inv_refract() to calculate refraction in the reverse direction (observer vs astrometric elevations) as needed.
Added radio refraction model novas_radio_refraction() based on the formulae by Berman & Rockwell 1976.
Added cirs_to_tod() and tod_to_cirs() functions for efficient tranformation between True of Date (TOD) and Celestial Intermediate Reference System (CIRS), and vice versa.
Added make_cat_object() function to create a NOVAS celestial object structure from existing cat_entry data.
Added rad_vel2() to calculate radial velocities precisely in the presense of gravitational deflection i.e., when the direction in which light was emitted is different from the direction it is detected by the observer. This new function is now used by both place() and novas_sky_pos().
make help to provide a brief list and explanation of the available build targets. (Thanks to @teuben for suggesting this.)
Added GitHub CI regression testing for non-x86 platforms: armv7, aarch64, riscv64, ppc64le. Thus, we should avoid misphaps, like the platform specific bug Issue #29, in the future.
#42: cio_array() can now parse the original ASCII CIO locator data file (data/CIO_RA.TXT) efficiently also, thus no longer requiring a platform-specific binary translation via the cio_file tool.
#51: The NOVAS C implementation of rad_vel() has ignored this redshifting when the Sun was being observed. From now on, we shall gravitationally reference radial velocities when observing the Sun to its photosphere.
cio_file tool parses interval from header rather than the less precise differencing of the first two record timestamps. This leads to cio_array() being more accurately centered on matching date entries, e.g. J2000.
grav_def() estimation of light time to where light passes nearest to gravitating body is improved by starting with the body position already antedated for light-time for the gravitating mass. The change typically improves the grativational deflection calculations at the few uas level.
grav_def() is simplified. It no longer uses the location type argument. Instead it will skip deflections due to any body, if the observer is within ~1500 km of its center.
place() now returns an error 3 if and only if the observer is at (or very close, to within ~1.5m) of the observed Solar-system object.
Improved precision of some calculations, like era(), `...
This release is affected by many of the same issues as the original 1.0 release, except what is explicitly listed below as fixed for this version.
Fixedcirs_to_itrs(), itrs_to_cirs(), tod_to_itrs(), and itrs_to_tod() all had a unit conversion bug in using the ut1_to_tt argument [s] when converting TT-based Julian date to UT1-based JD [day] internally. (thanks to @hannorein)examples.ccirs_to_app_ra() and app_to_cirs_ra() for convenience to convert between right ascensions measured from the CIO (for CIRS) vs measured from the true equinox of date, on the same true equator of date.NOVAS_AU to the IAU definition of exactly 149597870.7 km (a <10 m change from the previously defined value, which has been renamed to DE405_AU). (thanks to @hannorein)This is the initial release of the SuperNOVAS library. Changes are indicated w.r.t. the upstream NOVAS C 3.1 library
from which SuperNOVAS is forked from.
cirs_to_itrs(), itrs_to_cirs(), tod_to_itrs(), and itrs_to_tod() all have a unit conversion bug in using the ut1_to_tt argument [s] when converting TT-based Julian date to UT1-based JD [day] internally. A fix for this bug is included in the main branch and the v1.0.1 bug fix release.d_light() divide by zero if called with pos argument is a zero vector (e.g. Sun or SSB, depending on the solar-system calculator type). Fix available on the main branch and will be included in the v1.0.2 bug fix release.ee_ct() yield invalid results on non-Intel x86 platforms, such as ARMv7 or PowerPC, due to a different signedness of the char integer type on these platforms. Fix available on the main branch and will be included in the v1.0.2 bug fix release.tt2tdb() had the wrong scaling in the period, resulting in an error up to ~3.4 ms. A fix will be included in the v1.1.0 release and is available on the main branch.gcrs_to_j2000() applied transformation in the wrong direction, resulting in an error up to 44 mas when place() was called with NOVAS_TOD as the desired output system (1). A fix will be included in the v1.1.0 release and is available on the main branch.tod_to_itrs() used the wrong Earth rotation measure (NOVAS_ERA instead of NOVAS_GST). A fix will be included in the v1.1.0 release and is available on the main branch.grav_def() gravitating body position antedated somewhat incorrectly (in v1.0) when observed source is a Solar-system object between the observer and the gravitating body. The resulting positional error is typically small at below 10 uas. A fix will be included in the v1.1.0 release and is available on the main branch.cel2ter() invalid output with CIRS input coordinates (erot = EROT_ERA and class = NOVAS_DYNAMICAL_CLASS) if output vector was distinct from input vector. Affects prior SuperNOVAS releases. A fix will be included in the v1.1.0 release and is available on the main branch.Fixes the sidereal_time bug, whereby the sidereal_time() function had
an incorrect unit cast. This is a known issue of NOVAS C 3.1.
Some remainder calculations in NOVAS C 3.1 used the result from fmod() unchecked, which led to the wrong results
when the numerator was negative. This affected the calculation of the mean anomaly in solsys3.c (line 261) and
the fundamental arguments calculated in fund_args() and ee_ct() for dates prior to J2000. Less critically, it
also was the reason cal_date() did not work for negative JD values.
Fixes antedating velocities and distances for light travel time in ephemeris(). When getting positions and
velocities for Solar-system sources, it is important to use the values from the time light originated from the
observed body rather than at the time that light arrives to the observer. This correction was done properly for
positions, but not for velocities or distances, resulting in incorrect observed radial velocities or apparent
distances being reported for spectroscopic observations or for angular-physical size conversions.
Fixes bug in ira_equinox() which may return the result for the wrong type of equinox (mean vs. true) if the theequinox argument was changing from 1 to 0, and back to 1 again with the date being held the same. This affected
routines downstream also, such as sidereal_time().
Fixes accuracy switching bug in cio_basis(), cio_location(), ecl2equ(), equ2ecl_vec(), ecl2equ_vec(),geo_posvel(), place(), and sidereal_time(). All these functions returned a cached value for the other
accuracy if the other input parameters are the same as a prior call, except the accuracy.
Fixes multiple bugs related to using cached values in cio_basis() with alternating CIO location reference
systems.
Fixes bug in equ2ecl_vec() and ecl2equ_vec() whereby a query with coord_sys = 2 (GCRS) has overwritten the
cached mean obliquity value for coord_sys = 0 (mean equinox of date). As a result, a subsequent call withcoord_sys = 0 and the same date as before would return the results GCRS coordinates instead of the requested mean
equinox of date coordinates.
Fixes aberration() returning NaN vectors if the ve argument is 0. It now returns the unmodified input vector
appropriately instead.
Fixes unpopulated az output value in equ2hor() at zenith. While any azimuth is acceptable really, it results in
unpredictable behavior. Hence, we set az to 0.0 for zenith to be consistent.
Fixes potential string overflows and eliminates associated compiler warnings.
Fixes the ephem_close bug, whereby ephem_close() ineph_manager.c did not reset the EPHFILE pointer to NULL. This is a known issue of NOVAS C 3.1.
Supports calculations in parallel threads by making cached results thread-local.
New debug mode and error traces. Simply call novas_debug(NOVAS_DEBUG_ON) or novas_debug(NOVAS_DEBUG_EXTRA)
to enable. When enabled, any error conditions (such as NULL pointer arguments, or invalid input values etc.) will
be reported to the standard error, complete with call tracing within the SuperNOVAS library, s.t. users can have
a better idea of what exactly did not go to plan (and where). The debug messages can be disabled by passingNOVAS_DEBUF_OFF (0) as the argument to the same call.
Added Doxygen markup of source code and header.
Added Makefile for GNU make.
Added continuous integration on GitHub, including regression testing, static analysis, and doxygen validation.
Added an number of precompiler constants and enums in novas.h to promote consistent usage and easier to read
code.
New runtime configurability:
The planet position calculator function used by ephemeris() can be set at runtime via set_planet_provider(),
and set_planet_provider_hp() (for high precision calculations). Similarly, if planet_ephem_provider() orplanet_ephem_provider_hp() (defined in solsys-ephem.c) are set as the planet calculator functions, thenset_ephem_provider() can set the user-specified function to use with these to actually read ephemeris data
(e.g. from a JPL ephemeris file).
If CIO locations vs GSRS are important to the user, the user may call set_cio_locator_file() at runtime to
specify the location of the binary CIO interpolation table (e.g. cio_ra.bin) to use, even if the library was
compiled with the different default CIO locator path.
The default low-precision nutation calculator nu2000k() can be replaced by another suitable IAU 2006 nutation
approximation via set_nutation_lp_provider(). For example, the user may want to use the iau2000b() model
instead or some custom algorithm instead.
New intutitive XYZ coordinate conversion functions:
gcrs_to_cirs(), cirs_to_itrs(), and itrs_to_cirs(),cirs_to_gcrs().gcrs_to_j2000(), j2000_to_tod(), tod_to_itrs(), anditrs_to_tod(), tod_to_j2000(), j2000_to_gcrs().New itrs_to_hor() and hor_to_itrs() functions to convert Earth-fixed ITRS coordinates to astrometric azimuth
and elevation or back. Whereas tod_to_itrs() followed by itrs_to_hor() is effectively a just a more explicit
2-step version of the existing equ2hor() for converting from TOD to to local horizontal (old methodology), thecirs_to_itrs() followed by itrs_to_hor() does the same from CIRS (new IAU standard methodology), and had no
prior equivalent in NOVAS C 3.1.
New ecl2equ() for converting ecliptic coordinates to equatorial, complementing existing equ2ecl().
New gal2equ() for converting galactic coordinates to ICRS equatorial, complementing existing equ2gal().
New refract_astro() complements the existing refract() but takes an unrefracted (astrometric) zenith angle as
its argument.
New convenience functions to wrap place() for simpler specific use: place_star(), place_icrs(),place_gcrs(), place_cirs(), and place_tod().
New radec_star() and radec_planet() as the common point for existing functions such as astro_star()local_star(), virtual_planet(), topo_planet() etc.
New time conversion utilities tt2tdb(), get_utc_to_tt(), and get_ut1_to_tt() make it simpler to convert
between UTC, UT1, TT, and TDB time scales, and to supply ut1_to_tt arguments to place() or topocentric
calculations.
Co-existing solarsystem() variants. It is possible to use the different solarsystem() implementations
provided by solsys1.c, solsys2.c, solsys3.c and/or solsys-ephem.c side-by-side, as they define their
functionalities with distinct, non-conflicting names, e.g. earth_sun_calc() vs planet_jplint() vsplanet_eph_manager vs planet_ephem_provider(). See the section on
Building and installation further above on including a selection of these in your library
build.)
New novas_case_sensitive(int) to enable (or disable) case-sensitive processing of object names. (By default NOVASobject names were converted t...
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