************************************************************************ IERS Message No. 423 February 24, 2021 ************************************************************************ New release of the IAU SOFA software library The 17th Release of the SOFA (Standards of Fundamental Astronomy) Software Library was made available on 2021 January 25th at 14:00 UTC. This was a major release which implemented extra defensive precautions when computing refraction at low altitudes and the application of polar motion handling was changed to rigorous. Documentation was expanded, including a new cookbook for the SOFA Vector Matrix Library, and typographical and other minor corrections were applied. Changes were also made to the test programs for both distributions. A minor release (17a) for both the Fortran and ANSI C versions of Release 17 of the SOFA software library was made on 2021 February 24 at 12:00 UTC. The change relates to the handling of leap seconds during the period 1960 and 1971. Between the introduction of UTC at the start of 1960 and the first leap second at the end of 1971, there were a series of small offsets and rate changes with respect to TAI. The SOFA routine D2DTF takes these into account, but a shortcoming in the algorithm meant that under certain conditions a leap second could be flagged even though none had occurred. Such cases are extremely rare, and moreover, depended to some extent on compiler behaviour, affecting rounding. See the SOFA website at http://www.iausofa.org for the latest downloads and details of all changes. SOFA operates under the auspices of the International Astronomical Union (IAU) to provide algorithms and software for use in astronomical computing. The initiative is managed by an international panel, the SOFA Board, appointed through IAU Division A. The Board obtains the latest IAU-approved models and theories from the fundamental-astronomy community, implements them as computer code and checks them for accuracy. SOFA works closely with all the Commissions of the Division and with the International Earth Rotation and Reference Systems Service (IERS). ************************************************************************ IERS Messages are edited and distributed by the IERS Central Bureau. If not stated otherwise, the IERS is only the distributor of the message and is not responsible for its content. To submit texts for distribution, please write to . To subscribe or unsubscribe, please create an IERS account or modify it: https://www.iers.org/Login/Login/EN/login_node.html or write to . Archives: http://www.iers.org/Messages ************************************************************************