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Chandra Electronic Announcement #87
CHANDRA ELECTRONIC ANNOUNCEMENT NUMBER 87

CXC Web site: cxc.harvard.edu

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Contents:

1. CIAO Workshop 22 - 24 April 2013
2. Additional reprocessing of certain HRC observations


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Item 1: CIAO Workshop 22 - 24 April 2013 
======================================================================

The 9th Chandra/CIAO workshop will be held 22 - 24 April 2013 at the
Chandra X-ray Center in Cambridge, MA, USA.  The workshop will feature
talks on introductory and advanced X-ray data analysis, statistics,
and topics in calibration.  Attendees will spend the afternoon
hands-on sessions doing their own analysis with members of the CIAO
team ready to assist. 

Registration is now open and is limited to 30 participants.

For more details and to register go to

http://cxc.harvard.edu/ciao/workshop/



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Item 2:  Additional reprocessing of certain HRC observations
======================================================================

This notice is intended to alert Chandra users that additional
reprocessing of certain HRC observations has taken place and to inform
them of the calibration status of these observations.

As all will be aware, we started in February of this year to reprocess
all Chandra observations made from 2000 through 2011. However, since
the beginning of that campaign, new HRC degap and gain calibrations
have become available. In the interest of uniformity, we decided to put
the Chandra Data Archive in a state where the default data products of
all HRC observations since 2000 will have been processed with these
new calibrations.

The main impact is on HRC-S observations.

Whether or not these changes have significance for your data analysis
is something only you can judge. What we can do is provide you with a
status update and descriptions of the changes and impacts which, we
trust, will aid in making an informed decision.

Regarding degap changes, please consult:
  http://cxc.cfa.harvard.edu/cal/Hrc/detailed_info.html#degap
  http://cxc.harvard.edu/caldb/downloads/Release_notes/CALDB_v4.5.0.html#TD_GAPLOOKUP
  http://cxc.cfa.harvard.edu/ciao/releasenotes/ciao_4.4.1_release.html#HowCALDB4.5.0AffectsYourAnalysis

For the gain changes, see:
  http://cxc.cfa.harvard.edu/cal/Letg/newHRCShv/
  http://cxc.cfa.harvard.edu/caldb4/downloads/Release_notes/CALDB_v4.5.1.html#TD_HRCS_TGMAP_N0002
  http://cxc.cfa.harvard.edu/ciao/releasenotes/ciao_4.4.1_release.html#HowCALDB4.5.1AffectsYourAnalysis


The status and plans for the various time ranges are:


January 2000 - Mid-November 2005
--------------------------------
We have started to reprocess these observations, but it will probably
take till the end of the year before this is completed.
When done, they will all be up-to-date in their calibrations.
However, there are no changes in the gains and the degap corrections
will be fairly small, especially for HRC-I observations.

Mid-November 2005 - 2011
------------------------
These observations have all been reprocessed already.
There are no changes in the gains and the degap corrections will be
fairly small for most of this period, especially for HRC-I
observations. However, the degap corrections will be
more significant since 2010 due to the shift in aimpoint, especially
for HRC-S observations and particularly grating observations.

2012
----
These observations were  originally not included in the reprocessing,
since their processing was consistent with the Repro IV reprocessing.
However, we did reprocess all HRC observations made from January
through July:
- For January through March there will be small corrections to the
  gains.
- Since April the gain corrections will be significant, since the
  high voltage setting on HRC-S was changed as of 29 March 2012.
  In addition, the degap corrections will be improved, especially for
  HRC-S observations and particularly grating observations.
As of 25 July 2012 the new calibration files are being used for our
Standard Data Processing and all data products created since that date
will be consistent with the new calibrations.


  - CXC Data Systems

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Last modified: 09/26/12

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