Updates for SOFA Release 13 : 2017 April 20
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Summary of Changes
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The changes fall into the following categories:

1. Implementation of the IAU 2012 definition of the astronomical 
   unit (au).  Not only has this constant been updated, but also 
   (a) all derived quantities are evaluated via the appropriate 
       formulas, and
   (b) all documentation now uses the appropriate symbols for the 
       unit, for example, 1 au and 2.3 au/day.

2. Update to PVSTAR to make it consistent with the version of STARPV 
   that was updated in the previous release.
   
3. Other minor typographical corrections to various routines.

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FORTRAN Library
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1. iau_APCS      The IAU 2012 value of the astronomical unit (au) is 
   iau_LDN       now implemented in these six routines.
   iau_PMPX
   iau_PVSTAR
   iau_STARPM
   iau_STARPV

2. iau_PVSTAR    An expression (sqrt(1-x)-1), where x is usually tiny,
                 has been replaced with (-x/(sqrt(1-x)+1) to improve
                 numerical precision. 

3. t_sofa_f      Check values in this validation program updated due 
                 to the change in the astronomical unit.

4. sofa_ast_f    The SOFA Astrometry Tools cookbook.  
                 (a) In the table on page 22 there is a change of 
                     +1 x 10^-7 seconds in RA for three results when 
                     compared to using the previous value for the au.  
                     These cases are repeated on the next 2 pages.
                 (b) The listing of the relativistic version of the
                     routine iau_PMPX in the Appendix has been updated 
                     on page 77 with the required changes for the au. 

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ANSI C Library
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1. sofam.h       The astronomical unit (au) has been updated in this  
                 include file and all constants that are derived from  
                 the au have been replaced by the appropriate formulas.

2. iauPvstar     An expression (sqrt(1-x)-1), where x is usually tiny,
                 has been replaced with (-x/(sqrt(1-x)+1) to improve
                 numerical precision.  

3. t_sofa_c      Check values in this validation program updated due 
                 to the change in the astronomical unit.

4. sofa_ast_c    The SOFA Astrometry Tools cookbook.  In the table on 
                 page 20 there is a change of +1 x 10^-7 seconds in RA 
                 for three results when compared to using the previous 
                 value for the au.  These cases are repeated on the  
                 next three pages. 

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End of Updates
2017 March 22
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