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             |              CCC  XX   XX    OOO           |
Chandra      |             CC     XX XX    OO OO          | CXC
Electronic   |            CC       XXX    OO   OO         | Number 19
Bulletin     |             CC     XX XX    OO OO          | November
             |              CCC  XX   XX    OOO           | 2002
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Welcome to the Chandra X-ray Center's Electronic News Bulletin Number 19.

CXC Web site: cxc.harvard.edu

If you would like to unsubscribe from this alias, simply reply to this message
to let us know.  

Please use this website to update your address or email: 
          http://cxc.harvard.edu/cdo/udb/userdat.html

Contents:

1. New in Cycle 5: Very Large Observing Proposals

2. Release of Updated Guide Star Catalog for Chandra

3. CIAO 2.3

4. Chandra Calibration Workshop 2002

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Item 1. New in Cycle 5: Very Large Observing Proposals
======================================================

Very Large Observing Projects are defined as requiring
1 Msec of observing time or more, regardless of whether they include
long-duration observations of single targets or shorter duration
observations of many targets.  This category is open to all science
topics and must be designated as such by the PI. Up to 3 Msec of time
will be available for projects in this category, subject to the
submission of proposals of high scientific merit.

Observations approved as part of a Very Large Project will have no 
proprietary time associated with them and the data will be made
public immediately. Note that approved Large Projects do have a one year
proprietary time period and that there is no upper
limit on the amount of observing time that may be requested in any
proposal category.

Very Large Projects which plan to deliver products, such as source catalogs, 
high fidelity data products, or software to the community are encouraged to
outline these plans in the proposal. A modest additional funding
allocation may be requested in the Stage 2 Cost proposal to
facilitate the delivery of such products.


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Item 2. Release of Updated Guide Star Catalog for Chandra
=========================================================
	
The AXAF (Chandra) Guide and Acquisition Star Catalog (AGASC) is used
for the selection of acquisition and guide stars for the Chandra
Observatory.  The guide stars are also used after the data reaches the
ground for aspect reconstruction - to assemble the dithered X-ray
events into a final high spatial resolution image with excellent
( < 1") relative and absolute astrometry.

The AGASC was originally based on the Hubble Space Telescope Guide
Star Catalog v1.1, containing 19 million stars.  In 2002 the Chandra
X-ray Center (CXC) completed a major upgrade of AGASC.  We merged data
from three catalogs---Tycho-2, GSC-ACT, and 2MASS. The Tycho-2 data
substantially improve the photometric and astrometric measurements of
stars as faint as V = 12 mag.  The GSC-ACT data merge decreases by about
half the systematic astrometric errors down to the catalog limit of
about V=14.5 mag. The 2MASS data identify galaxies down to
J=12.5 mag. These new catalog data enhance the value of AGASC for
scientific as well as operational purposes.

Specifically for Chandra's operational use of AGASC, we also recalibrated 
the estimated ACA magnitudes based on Chandra on-orbit measurements, and 
implemented a more sophisticated calculation of the effect of nearby stars 
on the best-fit centroid of a guide star.

AGASC 1.5 currently represents the only available catalog that 
combines  high quality astrometry on the ICRS system down to 14.5 mag
with detailed color and proper motion information down to about 12th.
In addition, the "spoiler codes" that indicate the degree to which
any stellar centroid might be disturbed by nearby objects is a unique 
feature. These properties make AGASC 1.5 a potentially important catalog for
guide star selection for other space- and ground-based telescopes
(e.g., for telescope guiding or Adaptive Optics).  AGASC 1.5 
should also prove useful for a variety of scientific purposes.

More information about the catalog, its constituents and construction
are available on the web.   A search and retrieval of AGASC star data
is also now accessible on the web at
	http://cxc.harvard.edu/agasc/


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Item 3. CIAO 2.3
================

The Chandra X-Ray Center is pleased to introduce the CIAO patch version
2.3 released in tandem with the CALDB version 2.18 on 12 November 2002.
All downloadable from
http://cxc.harvard.edu/ciao/download_ciao_reg.html

CIAO 2.3 Improvements include

     * The acis_process_events tool can now be used to apply the CTI 
(charge transfer inefficiency) adjustment procedure. This correction 
restores some of the resolution lost due to radiation damage to the ACIS 
detectors early in the mission. The ACIS CTI "why?" topic provides 
further details of this correction:          
see http://cxc.harvard.edu/ciao/why/cti.html                 

     * Enhancements and bug fixes to some of the tools, including 
asphist, acis_process_events, hrc_process_events, psf_project_ray and more.

For more information, please see the complete Release Notes for CIAO 2.3 
at http://cxc.harvard.edu/ciao/releasenotes/

CIAO 2.3 Thread Updates

The majority of the threads (~ 80%) have been updated for CIAO 2.3; the 
remaining threads did not require any changes for this release. The 
edits include revised parameter file listings, new explanatory text, and 
small syntax changes.

New (or with major updates) threads inlude:

*  Apply the ACIS CTI Correction
http://cxc.harvard.edu/ciao/threads/acisapplycti/ 
*  Extracting Extended Source Spectra and Responses
http://cxc.harvard.edu/ciao/threads/acisspec_extract/
*  HRC AMP_SF Correction and Reducing Tap-Ringing Distortions
http://cxc.harvard.edu/ciao/threads/hrc_ampsf/
*Coadding Spectra and Weighted Responses
http://cxc.harvard.edu/ciao/threads/acisspec_coadd/
* Fitting Spectral Data: Using A Pileup Model
http://cxc.harvard.edu/ciao/threads/sherpa_pileup/

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Item 4 Chandra Calibration Workshop 2002
========================================

    We the organizers would first like to thank all the
participants in the Chandra Calibration Workshop. We were very pleased with
the large turnout (final head count: 84!) as well as the participation
from the diverse interested parties, especially the users.

    We hope to make this a regular event and to that end we would like
to solicit any suggestions that anyone might have with regard to format,
length, and content of the event. We are especially interested in ways
of increasing the participation of the larger community, both as
active presenters and as attendees. [Please respond directly to Hank  
Donnelly at  rdonnelly@cfa.harvard.edu.]

    Finally, we are attempting to make the proceeding of the workshop
available online. To that end if you presented (either orally or
posterly(?)) if you could send us a copy of your presentation we will
make it available via our website. What we have so far can be found at 

http://cxc.harvard.edu/ccw_02/

To those of you who have already sent us your work, thanks (we have 21
of 49 so far).  As we receive presentations we will make them
available with all due speed. We, however, will *not* continue to
notify you that the website has been updated.  We can accept
presentations in postscript, pdf or powerpoint formats.

Keep an eye out for another workshop next year.  

Hank Donnelly, Dan Dewey and the rest of the Calibration Team


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