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The International Astronomical Union's SOFA service has the task of establishing and maintaining an accessible and authoritative set of algorithms and procedures that implement standard models used in fundamental astronomy. The service is managed by an international panel, the SOFA Board, appointed through IAU Division I. SOFA also works closely with the International Earth Rotation and Reference Systems Service (IERS) and its reporting commission, IAU Commission 19 — "Rotation of the Earth".

IAU SOFA Center IAU SOFA Center

This web site provides access to the SOFA Software Collection which is currently available for both Fortran 77 and ANSI C. Information on how to obtain it and instructions for its use are available by following the link to Current Software.

Using SOFA software is free of charge under the terms and conditions of the SOFA licence.

Registration is encouraged as it helps to demonstrate the use being made of the SOFA Libraries and also provides users with e-mail notification of bugs and updates.

Quick Start  Quick start ...

Download Latest Release  Download the latest release ...

  • Latest Fortran 77 release is available ...
    [Released 2012-03-01]
  • Latest ANSI C release is available ...
    [Released 2012-03-01]
  • A summary of changes for the new release is available ...
  • A summary of SOFA documentation corrections for the latest release is available ...

News  News ...

News Item  2012 March 08 / Issue 2010-12-01 — Correction to documentation

It has been pointed out that there is an error in the comments in plan94.c. The dimensions of the PV-vector are the wrong way round. For "pv double[3][2] planet p,v (heliocentric, J2000.0, AU,AU/d)", read "pv double[2][3] planet p,v (heliocentric, J2000.0, AU,AU/d)".

News Item  2012 March 01 / Delay in release of Issue 2010-12-01

Due to a server configuration problem, the new release of the SOFA Fortran 77 and ANSI C libraries (2012-03-01) was delayed until 15:10:00 UTC. Our apologies for any inconvenience caused.

News Item  2012 March 01 / Release of Issue 2010-12-01

A new release (Issue 2012-03-01) of the SOFA Fortran 77 and ANSI C libraries will be made on 2012 March 1st at 12:00:00 UTC.

This release includes an update to reflect the leap second that will be applied on 2012 June 30th. The release also includes several updates to some declarations in the ANSI C code to minimize possible compiler warnings. A small number of errata in the documentation of the ANSI C routines as well as some cosmetic changes to the documentation have been included. A bug in the function Dsign (A,B) in sofam.h has also been fixed.

Please note that the numbering of this SOFA release has been kept in step with the Fortran release number while the ANSI C release number has been re-aligned with that of the Fortran release.

News Item  2011 December 07 / Revised list of documentation corrections

A revised list of documentation corrections has been made available for the latest Fortran and ANSI C releases. These corrections to p06e.for and p06e.c do not affect the operation of the code.

News Item  2011 May 24 / Revised list of documentation corrections

A revised list of documentation corrections has been made available for the latest Fortran and ANSI C releases. These corrections do not affect the operation of the code.

News Item  2011 April 19 / Correction to comments for tf2a.c and ut1tt.for / ut1tt.c

A small correction to the comment in the routine tf2a.c should be noted. In the "Returned:" section replace the variable "days" by the variable "rad". Small corrections have also been noted in the routines ut1tt.for and ut1tt.c. In both routines in the "Returned:" section, in the description replace "TAI as a 2-part Julian Date", by "TT as a 2-part Julian Date".

News Item  2011 April 11 / Correction to comments for dtf2d.for / dtf2d.c

Small corrections to a comment and a note in the routines dtf2d.for and dtf2d.c are brought to the attention of users of the SOFA software. In the comments for Fortran code the "Returned:" items JD1,JD2 should be D1,D2. Similarly, in the 2nd line of Note 7, JD1+JD2 should read D1+D2. The same issues exist in the C code except the variables are lower case.

News Item  2011 April 05 / Correction to comments for nut06a.for / nut06a.c

A correction to the wording of Note 3 in the routines nut06a.for and nut06a.c is brought to the attention of users of SOFA software. It is necessary to replace the words "dynamical flattening" by "dynamical form factor J2", so that the last line reads "...secular variation in the Earth's dynamical form factor J2."

News Item  2011 January 12 / Scholarpedia article

Catherine Hohenkerk has written an article for Scholarpedia on SOFA. It provides an overview of SOFA, its history, the SOFA Center and the libraries and test software it provides, as well as the relevant documentation and references.

News Item  2011 January 04 / Issue 2010-12-01

Two small typographical errors have been reported in issue 2010-12-01, neither of which affect the serviceability of the issue. In the files changes.pdf and changes.lis within the ANSI C release, the issue date in the first line of the files is given as 2012-12-01. The correct issue date is 2010-12-01. In the SOFA Time Scale and Calendar Tools documents sofa_ts_c.pdf and sofa_ts_f.pdf, a function called DTF is listed in Section 1.3 on page 1. The correct name of the function is D2TF.

News Item  2010 December 01 / Issue 2010-12-01

A new release of SOFA Fortran 77 and ANSI C libraries was made available. This includes eighteen new routines in the Time Scales section of the Astronomy Library and three new routines in the Operations on Angles section of the Vector Matrix Library for both the Fortran 77 and ANSI C releases. A new cookbook on Time Scale and Calendar Tools was also released. A bug in jdcalf.c has been corrected, enhancements have been made to the makefiles, header files and test programs and cosmetic changes have also been made to some of the routines.

News Item  2010 November 26 / Issue 2010-12-01

A new release (Issue 2010-12-01) of the SOFA Fortran 77 and ANSI C libraries will be made on 2010 December 1st at 12:00:00 UTC.

News Item  2010 September 28 / Anne-Marie Gontier

It is with great sadness that the SOFA board was informed of the passing of Anne-Marie Gontier on September 24th 2010. Anne-Marie had been a member of the board almost from the beginning, which provided a strong link with the Observatoire de Paris that has been to SOFA's great benefit. Our condolences go to her family, colleagues and friends at this difficult time.

News Item  PLEASE NOTE 2010 July 20 / SOFA web sites

The old SOFA web sites http://www.iau-sofa.rl.ac.uk and http://iau-sofa.hmnao.com are now automatically forwarding requests to our new site http://www.iausofa.org introduced in January 2010. It is our intention to shut down the old sites at the time of the next SOFA release. Consequently, users who have bookmarks pointing to specific material on the old sites should now update them to point to the new site.

News Item  2010 June 22 / New member of the SOFA Board

George Hobbs, representing Commission 31 (Time), from the Australia Telescope National Facility has been co-opted onto the SOFA Board to assist in the provision of authoritative time transformation software.

News Item  2010 March 20 / New Chair of the SOFA Board

Patrick Wallace steps down as Chair after 14 years; he is welcomed as a member of the Board. The new SOFA Board Chair is Catherine Hohenkerk who may be contacted at Catherine.Hohenkerk@ukho.gov.uk.

News Item  2010 March 20 / www.iausofa.org

Please note that the e-mail link at the foot of each web page now points to the new SOFA mailbox at sofa@ukho.gov.uk. This replaces the old address, sofa@rl.ac.uk, at the Rutherford Appleton Laboratory. This new contact address will be updated in the source code and documentation at the next release of the SOFA libraries.

News Item  2010 January 27 / Issue 2009-12-31

Downloads of Issue 2009-12-31 have been resumed. Updates to the validation software have been implemented.

News Item  2010 January 26 / Issue 2009-12-31

Downloads of Issue 2009-12-31 have been temporarily suspended pending checks on the validation software.

News Item  2010 January 25 / www.iausofa.org

The new SOFA web site www.iausofa.org has now gone live. Requests to the old site addresses iau-sofa.hmnao.com and www.iau-sofa.rl.ac.uk will be automatically forwarded to the new site. Please change any bookmarks you might have to the new address.

News Item  2010 January 25 / Issue 2009-12-31

An additional reference ellipsoid, WGS72, has been included in EFORM. A code change to GD2GC and GD2GC using ZP to zeroize a vector has been made. Corrections to comments in GC2GD and GC2GD have been made concerning routine names for inverse transformations. Comments involving references have been made to BP00, BPN2XY, C2I00A, C2I00B, C2IBPN, PN00A, PN00B, PN00, S00A, S00B, S00 and S06A. Validation software has been updated.

News Item  2010 January 19 / www.iausofa.org released for comments by SOFA Board

A new web site for the SOFA initiative has been registered called www.iausofa.org. The material on the site has been revised and updated to improve access to the software releases and their associated explanatory material.

News Item  2009 December 31 / Issue 2009-12-31

A new release of SOFA Fortran 77 and ANSI C libraries was generated. This includes five new Astronomy routines for performing geographic/geodetic transformations as well as a number of small cosmetic changes and code improvements. The five new routines are EFORM, GC2GD, GC2GDE, GD2GC and GD2GCE.

News Item  2009 April 02 / Issue 2009-02-01

An error in the description of the coordinates of the Celestial Intermediate Pole with respect to the International Terrestrial Reference System in the routines C2T00A, C2T00B, C2T06A, C2TPE, C2TXY and POM00 has been corrected in both the Fortran and ANSI C libraries. These revisions have no effect on the results produced by these routines.

News Item  2009 March 16 / Issue 2009-02-01
  1. A bug affecting the routines FK52H and H2FK5 (both Fortran and ANSI C) has been corrected. This caused erroneous proper motions (and also radial velocity) to be returned.
  2. The testbeds t_sofa_f.for and t_sofa_c.c have been updated to reflect the changes to FK52H and H2FK5.
  3. In the C header file sofa.h, an unused reference has been removed.
  4. In the C functions iauFk5hip, iauGmst00, iauObl80 and iauObl06, use of the ANSI C language feature "unary plus" has been eliminated, to avoid difficulties with older compilers.
News Item  2009 March 13 / Issue 2009-02-01

The routines FK52H and H2FK5 (both Fortran and ANSI C) have been found to return incorrect proper motions. The fault is being rectified.

News Item  2009 March 03 / Issue 2009-02-01

The ANSI C version of the DAT routine, iauDat, released on 2009-02-01 contained a bug that caused erroneous answers (platform dependent) for certain dates in 1972. The problem was corrected in the 2009-03-03 update. The Fortran version, iau_DAT, was not affected.

News Item  2009 February 01 / Issue 2009-02-01

A new release of SOFA Fortran 77 and ANSI C libraries was generated. This includes the initial release of the ANSI C library. Cosmetic changes were made to a number of Fortran routines and a test program has been added.

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