SOFA (Astronomy)
Encyclopedia
The SOFA software libraries are a collection of subroutines that implement official IAU
algorithms for astronomical
computations.
As of February 2009 they are available in both Fortran
and C
source code
format.
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
algorithms for astronomical
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
computations.
As of February 2009 they are available in both Fortran
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
and C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
source code
Source code
In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
format.
Capabilities
The subroutines in the libraries cover the following areas:- Calendars
- Time scalesTime standardA time standard is a specification for measuring time: either the rate at which time passes; or points in time; or both. In modern times, several time specifications have been officially recognized as standards, where formerly they were matters of custom and practice. An example of a kind of time...
- Earth's rotation and sidereal timeSidereal timeSidereal time is a time-keeping system astronomers use to keep track of the direction to point their telescopes to view a given star in the night sky...
- Ephemerides (limited precision)
- Precession, nutationNutationNutation is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behavior of a mechanism...
, polar motionPolar motionPolar motion of the earth is the movement of Earth's rotational axis across its surface. This is measured with respect to a reference frame in which the solid Earth is fixed... - Proper motionProper motionThe proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
- Star catalog conversions