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Chandra Calibration Status. Summary The gratings and mirrors are very well calibrated at this time and there are no time-dependent effects as far as we can tell.

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chandra calibration status

Chandra Calibration Status


The gratings and mirrors are very well calibrated at this time and there are no time-dependent effects as far as we can tell.

Most activities in the calibration group are centered on improving the calibration of the detectors and monitoring the time-dependence response of the detectors.

At present we have a single time-independent QE for each ACIS chip and HRC MCP, however, the transmission of the contaminate on ACIS is time-dependent.

The spectral response of both ACIS detectors and both HRC detectors is also treated in a time-independent manner.

The ACIS gains are calibrated every 3 months and the HRC gains are calibrated once per year.

There are two sets of trap maps for each ACIS FI chip (one set for the first 4 years and one set for the second 4 years) and only one set of trap maps for the ACIS BI chips.


Calibration Updates Since the Last CUC Meeting


Gain correction files for epochs 25 and 26 (Nov 2005-May 2006) were released in CALDB 3.2.4 on Nov. 7, 2006.

A set of cti-corrected (serial and parallel) calibration products for the BI chips at T=-120 C was released in CALDB 3.3 on Dec. 18, 2006. These products include: trap maps, QE maps, response files, and OSIP files.

A revised version of the ACIS QE with corrections near the SI-K edge was released in CALDB 3.3

Gain correction files for epoch 27 (May 2006-Nov 2006) were released in CALDB 3.3

5. Gain correction files for epoch 28 (Dec. 2006-Feb. 2007 will be released in CALDB 3.4
  • Updates to the standard set of ACIS background images will be released in CALDB 3.4.


  • A set of gain correction files (one for each year) was released in CALDB 3.3
  • A rmf for the HRC-S was released in CALDB 3.3. This is required to make energy invariant hardness ratio images.
  • Further refinements to the set of HRC-I gain correction files will be released in CLDB 3.4.
  • A verified Linux version (phase 1.0) of the SAOSAC software was delivered to Data Systems in Feb. for integration into Level III processing.
  • A more portable version (phase 2.0) of the SAOsac raytrace software will be available to the public in May.
  • A memo was posted on the calibration web pages describing the drift of the optical axis since launch.
  • An updated HRC-S QE with correction near the O-K edge is scheduled for release in CALDB 3.4.


  • Updated OSIP files (required for cti-corrected data for the BI chips) were released in CALDB 3.3
current calibration activities acis
Current Calibration ActivitiesACIS
  • Improve graded mode calibration which cannot be cti-corrected in the same way as faint mode data.
  • Improve CC mode calibration. This primarily relates to gratings data.
  • Improve calibration at T=-110 C.
  • Fitting the ECS data over the course of the mission shows that there has been an increase in the width of the lines by 15-35 eV (sigma). A metric is being devised to signal when a new set of trap maps will be necessary.
  • Possible temperature-dependent cti-corrections.
  • Possible revisions to the contamination model.
  • Update the HRC-I de-gap map using the AO8 raster scan of Capella.
  • Update the low energy HRC-I QE based on the recent LETG/HRC-I observations of HZ43.
  • Update the HRC-I QE map using the off-axis observations of RXJ1856.
  • Generate a set of finer grid time-dependent gain correction files (one per year).
  • Improve the HRC-S QE below the C-K edge.
  • Investigate the cause of the 5% drop in count rate in the LETG/HRC-S observations of HZ43 at low energies (i.e., on the outer MPCs).
  • Derive an improved pulse-height-based background rejection filter using the fine resolution time-dependent gain corrections.
  • Further improve the HRC-S de-gap coefficients tables to include empirical corrections from emission line and continuum sources.
  • Incorporate the non-linearity in the LETG/HRC-S dispersion relation into the line response function.
  • Use HETG/ACIS-S data taken in CC mode to improve CC mode calibration.
  • Improve higher order efficiencies.


  • Finish analysis of ACIS piled-up observations and post a memo on the calibration web pages.
  • Continue development of the Linux version of the raytrace software
  • Release the enclosed count fraction (ECFs) from elliptical rather than circular apertures.