[Last Change: 09 Oct 2020 (rev 8) — Page History]

SAOTrace Release Notes


There should be no user-visible changes in this release.

Build Fixes

  • SAOTrace now runs on current versions of GNU/Linux and MacOS.
  • A C++ 11 compiler is now required


Bug Fixes

  • trace-nest didn't recognize variants of the FITS output format, so setting output_fmt=fits-axaf failed.


There should be no user-visible changes in this release.


  • The surface scattering module is now significantly faster.

Known Bugs

  • If a source is specified in mirror spherical coordinates (e.g. θ, φ) with a roll, the roll is doubled. As most sources are specified as RA & Dec (required in order to pass simulations on to Marx), this is rarely an issue. The next release of SAOTrace will fix this bug, but will change how telescope roll is specified, and is thus will break existing source description scripts.



  • SAOTrace can now read MARX generated aspect solution files

Bug Fixes

  • specifying limits as densities sometimes caused the ray generator to infinitely loop.
  • some Chandra dither files were rejected because timestamp validation tolerances were too high
  • Chandra and MARX dither files are now assumed to be FITS formatted (previously the filename extensions were used to determine this).


  • SAOTrace now compiles on Red Hat Enterprise Linux 6

Upgrade Instructions

When upgrading from a previous version using the standard upgrade instructions, after following all of those instructions, rerun the build-saotrace command adding the following arguments to the command line:

-m -force -m -only -m scatter

For example,

$SRCDIR/build-saotrace -s $SRCDIR -d $INSTALLDIR -m -force -m -only -m scatter


This release addresses inconsistencies in how SAOTrace interacts with Chandra aspect solution files when generating dithered observations.


  • raygen, trace-shell and trace-nest now take a tstart parameter indicating the start time of the simulation.
  • raygen: simulation start and durations are no longer obtained from the dither file.

API Changes

  • The Chandra dither_asol() function no longer returns the pointing information from the Chandra asol file, as that information has been reported to be incorrect. The user should use the _PNT header keywords from the event file.

Build Fixes

  • Builds should now succeed on Mac OS X case-insensitive file systems
  • Builds should now work on platforms which symlink gfortran as f77
  • Slackware 13.37.0 64bit is now supported

Known Build Issues

  • On some platforms gmp and gsl will fail some of their tests. It's not always apparent that these failures are significant. In some cases the versions available from the OS vendor fail identically, but it's not known if the OS vendor evaluated the failures.
This page is maintained by the CXC Optics Group
CXC logo

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email: cxcweb@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2013. All rights reserved.