CIAO 3.4 ONLY:
CalDB PUBLIC Release Notes
Effective Date:
(UTC) 2008-12-05T18:15:00
SDP Installation Date: (UTC) 2008-12-05T18:15:00
Public Release Date: 09 January 2009
Version:
3.5.1
Release Type:
SDP + PUBLIC
I. Introduction
CalDB 3.5.1 is only for use with CIAO 3.4;
If you are using CIAO 4.1, you require the new
CalDB, version 4.1.0, or later versions, as available on the CALDB4 web page.
CalDB 3.5.1 includes one ACIS upgrade, and an header/index
correction for a particular gain file:
- ACIS -120C T_GAIN Epoch 35
updates.
- One ACIS -120C DET_GAIN file header/index boundary
correction.
For user documentation, or How
CalDB 3.5.1 affects your analysis, see "CalDB 3.5.1 Tech
Details" below.
http://cxc.harvard.edu/caldb3/downloads/Release_notes/CALDB_v3.5.1.html#TechDetails
II. Summary of Changes
A. ACIS -120C T_GAIN Epoch 35
LOCATION: $CALDB/data/chandra/acis/bcf/t_gain/
FILENAMES: acisD2008-05-01t_gainN0005.fits
acisD2008-05-01t_gainN0006.fits
acisD2008-08-01t_gainN0002.fits
acisD2008-08-01t_gain_biN0002.fits
Epoch 35 covers the 01 August through 31 Oct 2008 period. The T_GAIN
interpolation files effective for 2008-05-01 include both Epochs 34 and
35. The new files effective on 2008-08-01 are non-interpolating or
"flat" files including only Epoch 35. The four datasets follow the
current convention for T_GAIN
upgrades, in that the first and third files include data for S1 and S3
(the BI chips) that are NOT CTI corrected. The second and fourth files
have CTI-corrected BI chip data. For the FI data, the CTI correction is
always applied, as no
calibration for T_GAIN exists for the FI non-CTI case.
Pipes/Tools affected:
SDP/CIAO ACIS L1 processing tool "acis_process_events"
Threads affected:
"Reprocessing Data to Create a New Level=2 Event File"
http://cxc.harvard.edu/ciao3.4/threads/createL2/
Why Topic: "ACIS Time-dependent Gain Correction (T_GAIN)"
http://cxc.harvard.edu/ciao3.4/why/acistgain.html
B. Correction to ACIS gain file header/index
listing
LOCATION: $CALDB/data/chandra/acis/bcf/gain/
FILENAMES: acisD2000-01-29gain_ctiN0006.fits
There has been an error in the boundary conditions listed in the ACIS
branch CalDB index file for the file acisD2000-01-29gain_ctiN0006.fits,
for several releases since CalDB 3.3.0. The error would have been
completely ineffectual in current processing, and would only affect
reprocessing of certain calibration observations with FP_TEMP=-110C,
taken in the summer of 2000. With the existing SDP and CIAO 3.4
dispositions of acis_process_events, selecting the required -110C
DET_GAIN file requires psets of acis_process_events in any case, for
these observations. However the minor fix below eliminates the
requirement to pset the "gainfile" keyword.
In CalDB versions 3.3.0-3.5.0, the file in question listed the boundary
conditions as
dagny-147: dmlist
caldb.indx"[cal_file=acisD2000-01-29gain_ctiN0006.fits][cols
cal_cnam,cal_file,cal_cbd]" data,array,clean
| CAL_CNAM |
CAL_FILE |
CAL_CBD[9] |
| DET_GAIN |
acisD2000-01-29gain_ctiN0006.fits |
CTI_APP(PPPPPBPBPP) |
|
|
CTI_CORR(DEPRECATED) |
|
|
CCD_ID(0-9) |
|
|
CTI_CORR(YES) |
|
|
CTI_CCD(0-4,6-6,8-9)
|
|
|
NONE
|
|
|
NONE
|
|
|
NONE
|
|
|
NONE
|
Note that the CTI_CORR parameter is listed twice, with different
specifications. The FP_TEMP parameter should be there, but is missing.
The CTI_CCD parameter is not necessary, and had been discarded in all
other DET_GAIN listings. The above is due to a miswritten header in the
file.
This header and index listing has been adjusted to the following:
dagny-150: dmlist
caldb.indx"[cal_file=acisD2000-01-29gain_ctiN0006.fits][cols
cal_cnam,cal_file,cal_cbd]" data,array,clean
| CAL_CNAM |
CAL_FILE |
CAL_CBD[9] |
| DET_GAIN |
acisD2000-01-29gain_ctiN0006.fits |
CTI_APP(PPPPPBPBPP) |
|
|
CTI_CORR(DEPRECATED) |
|
|
CCD_ID(0-9) |
|
|
FP_TEMP(148.23-158.23)K |
|
|
NONE
|
|
|
NONE
|
|
|
NONE
|
|
|
NONE
|
|
|
NONE
|
Above, the second CTI_CORR has been removed, as has the CTI_CCD,
and the FP_TEMP value range has been included.
Pipes/Tools affected: SDP/CIAO 3.4 acis_process_events,
only when reprocessing -110C ACIS data taken during July and August of
2000.
Note however that a pset of a-p-e to turn off the CTI correction is
still required for these 25 datasets.
Threads affected: NONE
III. Technical Details
A. ACIS Epoch 35 T_GAIN files
The new -120C T_GAIN data were derived from ACIS External
Calibration
Source (ECS) data taken during radiation zone passes during Aug - Oct
2008. Here are the plotted corrections, showing the changes from
the previous files and the new ones, for the aimpoint of ACIS-I3
(Figure 1). At 5 keV, the new correction is about 5-10 eV and at 10keV
the correction is 9-18 eV (0.09-0.18%), depending on the interpolation
point (DATE-OBS).
Figure 1: A comparison of old and new
T_GAIN
corrections for the CTI-corrected FI chip I3 at the aimpoint. There is
not much of change with the new files.
Likewise, below is the comparison between old and new T_GAIN
data
for the aimpoint of ACIS-S3, with the BI chip CTI correctors
applied.
Figure 2: A comparison of old and new
T_GAIN
corrections for the CTI-corrected BI chip ACIS-S3 at the
aimpoint. The changes here are minor as well, though a bit larger than
the other two illustrated cases.
Now consider the non-CTI corrected case for ACIS-S3, applied to
data
for which the CTI correction is unavailable or has not been applied to
the BI chips.
Figure 3: A comparison of old and new
T_GAIN
corrections for the non-CTI-corrected BI chip ACIS-S3 at the
aimpoint. The changes here are minor as well.
Hence the new Epoch 34 T_GAIN corrections are basically
necessary for optimal application of the time-dependent gains for the
most recent Chandra ACIS data. Hence the continued need for our period
upgrades to these data.
