CalDB
Release Notes
Effective Date: 09
August 2006
Version: 3.2.3
Release Type:
SDP + PUBLIC
I.
INTRODUCTION
CalDB
3.2.3 is a patch upgrade to version 3.2.2, which includes two new files
affecting only the HRC-I configuration, and both of which are used only
by the pipeline/CIAO tool "hrc_process_events". One is an upgrade to
the "degap" correction data table (GAPLOOKUP), and the other is a
correction to the HRC-I gain map (GMAP) applicable to observations
taken before UTC=1999-10-04T12:00:00, i.e. applicable only to the first
two months of the Chandra mission.
CalDB 3.2.3
will be installed in Standard Data Processing, and released to the
public as a cumulative upgrade to any and all preceding versions back
to CalDB 3.0.0 (released in December 2004).
II.
SUMMARY OF CHANGES
A. HRC-I
GAPLOOKUP Table version N0002
Location:
$CALDB/data/chandra/hrc/bcf/gaplookup/
Filename:
hrciD1999-07-22gaplookupN0002.fits
This new
GAPLOOKUP table will improve the encircled energy fraction modestly but
significantly for any on-(optical-)axis point sources. As such it
represents the latest and best degap correction data available for the
Chandra HRC-I. The data were derived from numerous Capella imaging
observations taken throughout the mission, and verified against point
sources such as AR Lac, 3C273, and Cen A.
An illustration
of the improvement in the encircled energy fraction versus radius from
the source position is given in Fig. 1 below:
Fig.
1: Illustration
of the encircled energy (COUNTS) fraction versus radius for the N0001
(black curve) versus the new N0002 (red curve) HRC-I GAPLOOKUP tables.
Pipes/Threads
affected:
SDP HRC L1/CIAO
tool hrc_process_events
Create a New
Level=2 Event File
http://asc.harvard.edu/ciao/threads/createL2/
HRC-I Degap
Correction
http://asc.harvard.edu/ciao/threads/hrci_degap/
B. HRC-I
1998-10-30 gain map (GMAP) version N0002 (correction)
Location:
$CALDB/data/chandra/hrc/bcf/gain/
Filename:
hrciD1998-10-30gainN0002.fits
The HRC team
has informed us that the early mission gain map for HRC-I, released
with CalDB 3.2.0 in November 2005, is in error. The image in the file
hrciD1998-10-30gainN0001.fits is shifted in the horizontal (U) axis,
and will generate errors in the calculated PI's in hrc_process_events.
The HRC team has provided an correction to this file for immediate
testing, inspection and release. The CalDB manager has complied,
releasing the N0002 version of the same CalDB file type.
NOTE: This gain map is applicable only to HRC-I observations taken
within the first two months of the mission, specifically before UTC
1999-10-04T12:00:00. Only the PI values are adversely affected by the
errant GMAP file. If you have reprocessed observations within this
period since November 2005, in order to use the PI information
included for quantile color-color mapping, you will need to repeat that reprocessing
with the corrected GMAP in CalDB 3.2.3.
Pipes/Threads
affected:
SDP HRC L1/CIAO
tool hrc_process_events
Create a New
Level=2 Event File
http://asc.harvard.edu/ciao/threads/createL2/
III.
TECHNICAL DETAILS
A. HRC-I
GAPLOOKUP Table version N0002
The derivation
of the new GAPLOOKUP table is presented in the memorandum "HRC-I Degap
Lookup from Capella Data" http://hea-www.harvard.edu/~juda/memos/hrci_degap_lookup/capella/degap/degap_lookup.html. It was developed
using twenty Capella observations taken during the Chandra Cycle 7
observation period. The method that was to be used was presented in an
earlier memorandum, "HRC-I Degap Lookup Table"
at http://hea-www.harvard.edu/~juda/memos/hrci_degap_lookup/index.html. Fig. 1 above
illustrates the improvement made using version N0002 versus version
N0001 of the GAPLOOKUP table for HRC-I.
B. HRC-I
1998-10-30 gain map (GMAP) version N0002
We have been
alerted of an errant HRC-I Gain Map (GMAP) installed and released in
CalDB 3.2.0 in November 2005 has an errant shift in it which will
adversely affect PI's calculated from it. That GMAP (filename:
hrciD1998-10-30gainN0001.fits) contains the following image:
Fig.
2: The
shifted GMAP image in the horizontal (U) axis direction contained in
the N0001 GMAP file, which is being replaced. The dark maroon vertical
stripe on the right side of the image is a region of zero image values,
which would corrupt the calculated PI values generated therefrom. The
scale is linear, with minimum image value of "0" and maximum of "4.5748"
The new map,
minus the shift, is shown in Fig. 3 below:
Fig.
3: The
image from the corrected GMAP version N0002. The image minimum value is
now "0.8508" and the max is the same as the above, "4.5748".
The image value
is used pixel-for-pixel to convert PHA values in the level 1 events
file EVENTS table into the PI (pulse-invariant) values, via the formula
PI = PHA * GMAP. Hence having zero values in the GMAP, as in Fig. 2
above, would produce PI's of "0" over a portion of the data, which
would sabotage the use of the quantile color-color mapping recommended
for the derivation of hardness ratio estimates for those events.
