Chandra Transmission Grating Data Catalog & Processing Software



TGCat is an archive of Chandra transmission grating spectra, and a suite of software for processing such data.

Data processing for the catalog was done with a suite of ISIS/S-Lang scripts. The software is available for download. These ISIS scripts wrap and call CIAO tools for reprocessing from "Level 1" (acis_process_events or hrc_process_events) through "Level 2" (binned spectra, via tg_resolve_events and tgextract), compute responses (grating "RMFs" and "ARFs", via mkgrmf and mkgarf), and make summary plots.

Documentation for the reprocessing scripts is in this PDF file, which also describes the required software (ISIS, S-Lang modules, CIAO).


October 2017:

Compute new bad pixel maps and afterglow; revised order of destreak and bad pixel filtering. Perform 2-passes on CC-mode data, to improve CTI correction and order-sorting. (Both as per standard CIAO processing, since CIAO 4.8).

Migrate to more recent "" (which is not back-compatible with the prior version.) Deprecated "", and use the ISIS built-in group() function.

Small changes to download, setup scripts to change to new Chandra ftp site, and to set up bias file names.

December 2010:

Handle parameter changes introduced by CIAO 4.3 in acis_process_events (subpixel algorithm will be on by default). Modified download scripts to create mtl1 file symlink required by CIAO 4.3. (Changes are back-compatible with CIAO 4.2.)

Added a top-level control for tg_resolve_events "osort" parameters (mostly useful for CC-mode and poor gain corrections).

August 2010:

Miscellaneous improvements, bug fixes:

Updated aglc (acis light curves); better definition of exposure for bright souces with many dropped frames;

findzo improved to handle multi-OBI data (uses ROLL_PNT, not ROLL_NOM).

Summary field plotting fixed to handle multiple OBI (uses ROLL_PNT to de-aspect sky field images).

Summary flux plot bug fix for the "Sco X-1 problem" (zeroth order off-array, zero-valued ARFs causing infinities in flux).

December 2009:

Enhancment: Automatically support HRC-S time-dependent gain application in CIAO 4.2. This reduces LETG/HRC-S backgrounds by about a factor of 2.

Enhancement: Produce Type I PHA files (single spectrum) by default. The Type II ("pha2") still present. Type I files can be more convenient for use with Xspec.

Miscellaneous bug-fixes, mostly for special cases (zeroth order off array and handling missing arfs).

August 2009:

Problem: Archive download (via download_obsid) would hang. The chandra-get script was modified slightly to support CXC OS upgrades and new ftp defaults.

Problem: S-Lang 2.2 improved error-checking uncovered a bug in (in code not used in tgcat) which prevented the file from loading. Version 1.3.9 fixed this problem.

Enhancements: High-level control of extraction regions added to scripts, particularly for extended source support. See documentation for set_tg_create_mask_info, set_tgextract_info, and run_cfg. Added use of "qualifiers" to run_cfg to handle processing configuration variables.

(Previous version of software and manual.)

Processing Quick Example

See the manual for examples. The top-level, do-it-all case looks like this... (which runs the pipeline using the instrumental configuration as read from the event file's header):
    > download_obsid 16
    > isis
    isis> require( "tgcat" );
    isis> run_cfg( "obs_16" );
    isis> exit ;
    > display obs_16/summary*.ps &
...and you get a pha file (spectrum), responses (grating ARFs and RMFs), light curves, and quick-look summary plots (like THESE).

Thanks to...

Thanks to Mike Nowak, Dan Dewey, and Arik Mitschang for extensive testing and use of the scripts, and again to Arik Mitschang for the great web interface. Thanks to a number of people for their active interest and participation in the catalog definition and development, especially John Davis, Dan Dewey, John Houck, Herman Marshall, Arik Mitschang, Joy Nichols, Mike Noble, Mike Nowak, and Norbert Schulz. And for behind the scenes work: Craig Anderson, Jen Lauer, Doug Morgan, Beth Sundheim.

Thanks to Claude Canizares for the initial encouragement to work on a catalog and archive.


We want your suggestions, on the interface, on features you would like to see, and on the software. Please email me: (David Huenemoerder).

This page was last updated Oct 9, 2020 by David P. Huenemoerder. To comment on it or the material presented here, send email to
Valid HTML 4.01! Made with JED. Viewable With Any Browser.
MIT Accessibility