Chandra X-Ray Observatory
	(CXC)
Skip to the navigation links
Last modified: 23 June 2017

URL: http://cxc.harvard.edu/ciao/bugs/skyfov.html

Bugs: skyfov


Table of Contents

Bugs


Bugs

Incorrect results when running with reprojected datasets without supplying the aspect solution file.

If running skyfov on datasets that have been reprojected using reproject_aspect, reproject_events, or wcs_update users must supply the aspect solution file, aspect.

If the aspect file is omitted, the original tangent point is used with will result in a shift of the field-of-view region file with respect to the data.

Incorrect results with marxasp generated aspect solution files.

skyfov uses the min() and max() values from the RA, DEC, and ROLL columns in the input aspect solution file. The marxasp simulated aspect solution files have a constant value for the ROLL column. This results in a degenerate set of data points (min(ROLL)==max(ROLL)). This degeneracy then results in incorrect FOV calculations.

Workaround:

One possible work around it to introduce a tiny amount of random jitter to the marxasp asol file

unix% dmtcalc asol.fits asol_jitter.fits exp="roll=(roll+((#trand-0.5)*0.0001))" 

Last modified: 23 June 2017
Smithsonian Institute Smithsonian Institute

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email:   cxchelp@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2017. All rights reserved.