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                         RELEASE NOTES FOR HEASOFT 6.21
                                 April 5, 2017
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HEASoft 6.21 is a patch-level release containing updates to the core
FITS file I/O library (CFITSIO) to handle the recent transition to
HTTPS server connections at the HEASARC.  Users who do not typically
access the HEASARC CALDB remotely (or perform other HEASARC virtual
file operations) may largely be unaffected by this transition, but
those who do should download HEASoft 6.21 and start setting their
$CALDB environment variable to

  ftp://heasarc.gsfc.nasa.gov/caldb

Note that CFITSIO FTP access to the HEASARC servers was broken in
versions of HEASOFT prior to v6.21, so users should only try the ftp
setting for CALDB once they begin using the new release.  For more
information about remote access to the CALDB, please see

  https://heasarc.gsfc.nasa.gov/docs/heasarc/caldb/caldb_remote_access.html


As before, configuration-related changes thoughout the package mean that
users who already have HEASoft v6.x.x installed will need to completely
replace their software installation; there is no clean way to simply
overlay this new release or to update an existing installation.

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                                    CFITSIO
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Version 3.42:

- In ftp_open_network and in ftp_file_exist, added code to repeatedly
  attempt to make a ftp connection if the ftp server does not respond
  to the first request. (some ftp servers don't appear to be 100%
  reliable).

- In drvrnet.c added many calls to 'fclose' to close unneeded files,
  to avoid exceeding the maximum allowed number of files that can be
  open at once.
  
- Made substantial changes to the ftp_checkfile and http_checkfile
  routines to streamline the process of checking for the existence
  of a .gz or .Z compressed version of the file before opening the
  uncompressed file (when using http or ftp to open the file). 

- Modified the code in ftp_open_network to send "\r\n" as end-of-line
  characters instead of just "\n".  Some ftp servers (in particular,
  at heasarc.gsfc.nasa.gov) now require both characters, otherwise
  the network connection simply hangs.
  
- Modified the http_open_network routine to handle HTTP 301 or 302
  redirects to a FTP url.  This is needed to support the new
  configuration on the heasarc HTTP server which sometimes redirects
  http URLS to a ftp URL.

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                                      FV
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- Update to handle HTTPS.

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                                     SWIFT
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UVOT:

- uvotpict: WebQuery.pm updated to use wget to retrieve URLs.