CXC Support


My CXC support work is primarily on the specification and test of the software tools for processing high-resolution X-rays spectra obtained with the Chandra High Energy Transmission Grating Spectrograph (HETGS) or the Low Energy Transmission Grating Spectrograph (LETGS).

CIAO Tools

Some specific CIAO tools for which I have been responsible are:
  • tg_detect: zero-order source detection and centroid;
  • tg_create_mask: spatial mask for event filtering;
  • tg_resolve_events: compute grating wavelengths, orders;
  • tg_extract: bin events into a high-resolution spectrum;
  • asphist: compute the aspect histogram
  • fullgarf: compute effective area files.

Work in Progress

Enhancements are under way (as of September 2005) to generalize and improve the region filtering in tg_resolve_events and tg_extract to provide larger and asymmetric background regions, and variable source and/or background region widths. This entails polygonal sky regions for the filter input to tg_resolve_events, and polygonal region files in diffraction coordinates for binning with tgextract.

The figure shows an example of asymmetric regions (to avoid HEG-MEG background-region overlap) with non-constant-width.

An example

Calibration Database Files for Analysis

In addition, I have defined and constructed calibration database (CALDB) files required for the data processing and for effective area computation. Some of these are:
  • Mirror effective area and vignetting;
  • ACIS QE, QE-uniformity;
  • HRC QE, QE-uniformity;
  • HETG and LETG efficiency;
  • ACIS contamination;
  • ACIS/Grating order-sorting table;

This page was last updated Nov 16, 2017 by David P. Huenemoerder. To comment on it or the material presented here, send email to
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