Chandra Calibration Status
Summary
1.
The gratings and mirrors are very well calibrated at this time and there are no
time-dependent effects as far as we can tell.
2.
Most activities in the calibration group are centered on improving the calibration
of the detectors and monitoring the time-dependence response of the detectors.
3.
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.
4.
The spectral response of both ACIS detectors and both HRC detectors is also
treated in a time-independent manner.
5.
The ACIS gains are calibrated every 3 months and the HRC gains are calibrated
once per year.
6.
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
ACIS
1.
Gain correction files for epochs 25 and 26 (Nov 2005-May 2006) were
released in CALDB 3.2.4 on Nov. 7, 2006.
2.
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.
3.
A revised version of the ACIS QE with corrections near the SI-K edge was
released in CALDB 3.3
4.
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
6.
Updates to the standard set of ACIS background images will be
released in CALDB 3.4.
HRC
1.
A set of gain correction files (one for each year) was released in
CALDB 3.3
2.
A rmf for the HRC-S was released in CALDB 3.3. This is
required to make energy invariant hardness ratio images.
3.
Further refinements to the set of HRC-I gain correction files will
be released in CLDB 3.4.
HRMA
1.
A verified Linux version (phase 1.0) of the SAOSAC software
was delivered to Data Systems in Feb. for integration into Level
III processing.
2.
A more portable version (phase 2.0) of the SAOsac raytrace
software will be available to the public in May.
3.
A memo was posted on the calibration web pages describing
the drift of the optical axis since launch.
LETG
1.
An updated HRC-S QE with correction near the O-K edge is
scheduled for release in CALDB 3.4.
HETG
1.
Updated OSIP files (required for cti-corrected data for the BI
chips) were released in CALDB 3.3
Current Calibration Activities
ACIS
1.
Improve graded mode calibration which cannot be cti-corrected
in the same way as faint mode data.
2.
Improve CC mode calibration. This primarily relates to gratings
data.
3.
Improve calibration at T=-110 C.
4.
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.
5.
Possible temperature-dependent cti-corrections.
6.
Possible revisions to the contamination model.
ACIS Flight Grades
Graded Mode Calibration
Line width vs. time at Al-Ka
Line width vs. time at Mn-Ka
HRC
1.
Update the HRC-I de-gap map using the AO8 raster scan of
Capella.
2.
Update the low energy HRC-I QE based on the recent
LETG/HRC-I observations of HZ43.
3.
Update the HRC-I QE map using the off-axis observations of
RXJ1856.
LETG
1.
Generate a set of finer grid time-dependent gain correction files (one per
year).
2.
Improve the HRC-S QE below the C-K edge.
3.
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).
4.
Derive an improved pulse-height-based background rejection filter using
the fine resolution time-dependent gain corrections.
5.
Further improve the HRC-S de-gap coefficients tables to include empirical
corrections from emission line and continuum sources.
6.
Incorporate the non-linearity in the LETG/HRC-S dispersion relation into
the line response function.
LETG/HRC-S Observations of HZ43
HETG
1.
Use HETG/ACIS-S data taken in CC mode to improve CC mode
calibration.
2.
Improve higher order efficiencies.
HRMA
1.
Finish analysis of ACIS piled-up observations and post a memo on
the calibration web pages.
2.
Continue development of the Linux version of the raytrace software
3.
Release the enclosed count fraction (ECFs) from elliptical rather
than circular apertures.