CalDB PUBLIC Release Notes
Effective Date:
(UTC) 2008-03-24T16:00:00
Public Release Date: 31 March
2008
Version:
3.4.3
Release Type:
SDP + PUBLIC
I. Introduction
CalDB 3.4.3 includes two T_GAIN upgrades. The first is for the
usual current epoch update to Epoch 32 (Nov 07 through Jan 08), and the
second part is the -110C upgrade to include a single T_gain file for 16
Sep 1999 effective through 28 Jan 2000. This latter includes TGAIN
corrections ONLY for ACIS-S1 and -S3, and requires an upgrade to the S1
and S3 GAIN file as well. There is a particular advantage here for
these two chips, because users may now reprocess their own -110C ACIS
data, and use mkacisrmf for S3 and S1 RMFs. Also, for gratings
observations, they get the new improved S1 GAIN function we
introduced for the -120C data with CalDB 3.3.0.
II. Summary of Changes
A. ACIS -120C T_GAIN Epoch 32
LOCATION: $CALDB/data/chandra/acis/bcf/t_gain/
FILENAMES: acisD2007-08-01t_gainN0005.fits (A-P-E "apply_cti=no")
acisD2007-08-01t_gainN0006.fits
(A-P-E "apply_cti=yes")
acisD2007-11-01t_gainN0002.fits
(flat, A-P-E "apply_cti=no")
acisD2007-11-01t_gain_biN0002.fits
(flat, A-P-E "apply_cti=yes")
Epoch 32 includes the 01 Nov 2007-31 Jan 2008 period. The T_GAIN
interpolation files effective for 2007-08-01 include both Epochs 31 and
32. The new files effective on 2007-11-01 are non-interpolating or
"flat" files including only Epoch 32. 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"
(ACIS data at FP_TEMP=-120C, DATE_OBS=2007-08-01T00:00:00 or later)
Threads affected:
"Reprocessing Data to Create a New Level=2 Event File"
http://cxc.cfa.harvard.edu/ciao/threads/createL2/
See also the CIAO 4.0 release notes at:
http://cxc.cfa.harvard.edu/ciao/releasenotes/ciao_4.0_release.html#HowCALDB3.4.3AffectsYourAnalysis
B. ACIS T_GAIN -110C (16 Sep 1999 through 28 Jan 2000 *PLUS* Summer
2000 -110C CAL ObsIDs) and associated GAIN file
LOCATION: $CALDB/data/chandra/acis/bcf/t_gain/
FILENAME: acisD1999-09-16t_gainN0005.fits
LOCATION: $CALDB/data/chandra/acis/bcf/gain/
FILENAME: acisD1999-09-16gainN0006.fits
Pipes/Tools affected:
SDP/CIAO ACIS L1 processing tool "acis_process_events"
(ACIS data at FP_TEMP=-110C, DATE_OBS=1999-09-16T00:00:00 through
2000-01-29T20:00:00;
Also, Calibration Observations taken on 2000-07-03, 2000-07-05, and
2000-08-11 with FP_TEMP at -110C)
Threads affected:
"Reprocessing Data to Create a New Level=2 Event File"
http://cxc.cfa.harvard.edu/ciao/threads/createL2/
See also the CIAO 4.0 release notes at:
http://cxc.cfa.harvard.edu/ciao/releasenotes/ciao_4.0_release.html#HowCALDB3.4.3AffectsYourAnalysis
III. Technical Details
A. ACIS Epoch 32 T_GAIN files
The new -120C T_GAIN data were derived from ACIS External Calibration
Source (ECS) data taken during radiation zone passes during Nov 2007-
Jan 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).
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.
Figure 3: 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.
Hence the new Epoch 32 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.
B. ACIS Epoch 0 (-110C, Sep 1999-Jan 2000) T_GAIN and GAIN
files
Below is an illustration of the time-dependent correction to be
applied to all -110C data taken between TT=1999-09-16T00:00:00 and
2000-01-29T20:00:00 at the aimpoint of ACIS-S3 (a BI chip). See figure
4. In fact, we will apply the same correction for all of these data,
because it is meaningless to interpolate them with -120C data. The
sense of the correction is the opposite for the -120C T_GAINs
illustrated.
Figure 4: The T_GAIN corrections for
-110C ACIS-S3 data at the aimpoint, compared with Epochs 1-4 -120C
data. Note that the fix is in the opposite sense, i.e., that the
correction in the energies is NEGATIVE for the -110C cases.
We also illustrate the effect for the midpoint of
Chip S1 (ACIS-5). A very similar effect is seen, though the degree of
change is somewhat larger for S1 than for S3 above.
Figure 5: The T_GAIN corrections for
-110C ACIS-S1 data at the MIDpoint, compared with Epochs 1-4 -120C
data. Here, too, the fix is in the opposite sense, i.e., that the
correction in the energies is NEGATIVE for the -110C cases.