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What's New in the Chandra Data Archive
2008-01-30 and 2008-05-01
The old 2000 and the new 2007 data from the Chandra Deep Field South have been custom
processed to register all 21 individual observations astrometrically.
For more information, see the
README file.
On 2008-05-01 we have added a new set of merged products, for the 2007
data only, where event files were carefully de-streaked.
For more information, see the
updated README file.
We offer these types of products for download:
- Merged tar file containing the merged event file, exposure map,
and image
- By-ObsId tar file containing the event list and aspect solution
for each of the individual ObsIds
- Full resolution linear three-color image of merged datasets
- Full resolution enhanced three-color image of merged datasets
- Smoothed enhanced three-color image of merged datasets
Download:
2007-12-20
The new 2007 data from the Chandra Deep Field South have been custom
processed to register all 12 individual observations astrometrically.
For more information, see the
README file.
Images of the merged data:
At this time we offer the following packages for download:
-
Merged tar file: containing the merged event file, exposure map,
and image.
-
By ObsId tar file: containing the event list and aspect solution
for each of the 12 ObsIds.
The CDFS observations from 2000 will be processed in a similar manner
to make them compatible with the new set. We expect those tar files
to become available in January 2008.
Provisional Retrieval Interface Decommissioned
2006-12-15
The Provisional Retrieval Interface has been decommissioned and
is no longer available to access Chandra data.
Provisional Retrieval Interface Replaced by RetrievER
2006-11-28
The Provisional Retrieval Interface, which had been far beyond
its prime, has been replaced by
,
a simple interface that allows access to Engineering Request (ER)
data.
Support for the PRI will be discontinued on 2006-12-15.
WebChaSeR Access through the Mirror Site at LEDAS
2006-07-28
The WebChaser and PRI mirrors at LEDAS have been taken down. The
archive mirror at LEDAS is being converted to an ftp archive mirror
and will be integrated in WebChaser's retrieval network.
Archive Mirror in India
2005-10-14
Users in India are currently being redirected to the
SOUTHERN_ASIAN_SERVER at UICAA in Pune for data retrievals. Even
though they connect to WebChaser at CfA, when it comes to retrievals
of public Chandra data, their data will be packaged at, and available
from, the mirror in Pune. This should improve data transmission
speeds for users all over India. The same mechanism is being used for
Quick image.
Popular Search Interface
2004-12-08
A new Popular Interface
has been released that allows our users, and especially our visitors
who are not professional astronomers, quick and easy access to the
exciting images and photon event files that are available from the
Chandra Data Archive.
It may be used in two modes, depending on the user's needs and preferences:
- Quick image
This returns a Jpeg image from the (imaging) observation that
scored highest in the search for observations of a particular
object or at a particular position.
- Advanced search
This mode allows the user to specify additional search criteria,
select spectroscopic observations, and ask for all qualifying
observations to be returned.
The search results provides the user with a choice of
qualifying observations as well as different data products: Jpeg
as well as FITS images, event files, bibliographic references,
and other details on the observations.
New Data Distribution Procedures
2004-12-02
As of 1 December 2004, CXC Operations are running DS Release 7.4.
This release includes a large number of changes in the way data are
being handled, with two changes that will be very visible to the
users.
1. The software that creates the V&V reports has been completely
replaced. Consequently, they will look different and they will be in
PDF format. The primary package will contain a V&V report that is
similar in length to what you are used to. The secondary package
will, in addition, contain a V&V reference document (also PDF) that is
considerably longer and contains much more detail.
2. The on-line data distribution will no longer work through
pre-packaged tar files that are put in an ftp staging area. Users
(PIs and Observers) will still be notified that new data have become
available, but they will be directed to retrieve the data through
WebChaSeR using its login feature (either the proposal or PI
account) as long as the data are proprietary; the e-mail message will
contain a reminder of relevant information.
Please note that anybody can retrieve the non-proprietary data
products for a proprietary observation. But one needs to be logged in
to the authorized PI or proposal account in order to have the
proprietary products (in particular, the event files and the images)
included in the retrieval package.
Special Request Form
2004-12-02
There are a number of services provided by CXC-DS Operational groups
that are not currently available through a web interface, but have
required incidental e-mail.
Requesting these services has now been consolidated though a single
Request Form.
It covers requests for old data versions, for special processing, for data on
physical medium, for custom database queries, as well as anything not covered
by these categories (or anywhere else). In addition, it allows us to track
such requests.
Dataset Ids
2004-11-15
Starting in January 2005, the AAS journals will allow authors to
insert Dataset Ids into their manuscripts that will faciltate direct
linking between articles and the datasets that they used. We have
published the first version of a Dataset Id
Guide for our users, to help inserting them correctly.
2004-05-07
All ObsIds that are part of the 1 Ms exposure on Cas A have
become publicly available. However, because of the large size of the
event files it may be more efficient to download the data from the
anonymous ftp archive directly, rather than through ChaSeR. You will
find the links in the following table. Note that the long
observations have been split, to keep the event file size
(uncompressed) under 2 GB. Be warned, though, analyzing
the event files from these observations will require substantial
resources, in time, storage, and compute power. When everything is
complete, the L2 event files will amount to almost 20 GB.
| ObsId | Exposure (ks) | Date of
Observation | Release Date |
|---|
| 5196 |
50 | 2004-02-09 | 2004-02-12 |
| 5319 |
40 | 2004-04-19 | 2004-04-21 |
| 4638 |
170 | 2004-04-16 | 2004-05-03 |
| 4636 |
150 | 2004-04-21 | 2004-05-03 |
| 4637 |
170 | 2004-04-24 | 2004-05-10 |
| 4639 |
80 | 2004-04-25 | 2004-05-10 |
| 4634 |
148 | 2004-04-29 | 2004-05-12 |
| 4635 |
138 | 2004-05-02 | 2004-05-17 |
| 5320 |
54 | 2004-05-06 | 2004-05-10 |
New Interface to the Chandra Bibliography Database
2004-01-16
We have released a new and powerful interface to the
CDA Bibliography Database. It allows users to execute sophisticated
searches for Chandra-related papers in the literature.
WebChaSeR Access through the Mirror Site at LEDAS
Superseded
2003-07-03
WebChaSeR may now be accessed through
LEDAS, providing better
performance for our European users who are only interested in
downloading public data or just in browsing the Observation Catalog.
There is no access to proprietary data.
Chandra Group in ADS
2003-07-03
The
ADS main search page now also has a Chandra group, allowing its
users to filter publication searches on Chandra-related articles.
The AGASC (AXAF Guide and Acquisition Star Catalog) is available through ftp
2003-04-09
The full 2.6 Gigabyte AGASC1.5 catalog is available for
download
from the archive. No portable catalog reading software
is available, but the 9537 individual FITS files can be accessed
with e.g., FTOOLS.
The proper ASGASC interface is here.
Public DDT Observations of GRB021004
2002-10-11
The recent Chandra observations of Gamma Ray Burst GRB021004 (ObsId 4381) are
available from the archive through ChaSeR, WebChaSeR, the
Provisional Retrieval Interface, or directly (primary data products
only) from the
anonymous ftp archive. These data are public; there is no proprietary period.
Release of anonymous ftp version of the CDA
2002-09-19
The primary (only!) products of all public Chandra observations are now
accessible on an anonymous ftp site,
cdaftp.
This archive is being kept up-to-date in real time. That means that
observations that are released to the public are available from this
ftp archive almost immediately and that old data versions are replaced
by new, reprocessed ones as soon as they are released.
Note that, although it provides access to these data products by
ObsId, there are no search and query facilities. For search engines
and more sophisticated retrieve options we strongly recommend the use
of ChaSeR or
WebChaSeR.
See the README file
for details.
Public DDT Observations of GRB020813
2002-08-16
The recent Chandra observations of Gamma Ray Burst GRB020813 (ObsId 4381) are
available from the archive through ChaSeR, WebChaSeR, the
Provisional Retrieval Interface, or directly (primary data products
only) from the
anonymous ftp archive. These data are public; there is no proprietary period.
New Composition of Primary and Secondary packages
2002-05-14
We have improved the composition of the primary and secondary data
products packages. The "primary" package is leaner but more complete:
The primary package contains all that is needed to analyze the
Level-2 data files (in particular, the event list). The
secondary package contains all that is needed to regenerate the
L2 data products.
New release of ChaSeR and WebChaSeR
2002-04-09
New versions of our archive search and retrieval tools have been
released, with enhancements for WebChaSeR. The most notable
changes are the addition of SIMBAD and/or NED name resolvers, more
selection options, and the option to be notified by E-mail as soon as
the retrieval package is ready for download.
New release of ChaSeR and WebChaSeR
2002-02-13
New versions of our archive search and retrieval tools have been
released, with mainly bug fixes for ChaSeR and enhancements for
WebChaSeR.
ChaSeR:
- In Detail display data and label were misalligned following OCAT
modifications for NRA4; this has been fixed.
- Reset button on query form now clears all entries and restores the
default query constraints.
- ChaSeR will return with an error when the connection to the server fails.
- Prevent server error on search with all checkboxes unchecked.
- Add row number to observation search results table.
- Parse/validate format of entered value for radius and prevent server
error on wrong input.
- Disallow login with blank username and password.
- Fixed problem with public release date not displayed.
WebChaSeR:
- Support password change.
- Added Name Resolver option using SIMBAD.
- Added choice of coordinate system and format for input and output
coordinates.
- Limited to 50 the number of obsids selected for browse/retrieve data
(still coming: information message to user).
- Hide ftp path of retrieved data while the tar files is being created.
- Added numbers to displayed obsid rows.
- Added row number to Browse results table.
- Added choice of ascending/descending sort order for displayed obsids.
- Fixed problem with public release date not displayed.
- Added support for change password.
- Disallow login with blank username and password.
- Generate a validation error on Browse/retrieve with both Primary and
seconday unselected.
- Dynamically configure WebChaseR for installation at any server.
- No crashes on Search if everything is unselected.
- Parse/validate format of entered value for radius and prevent server
error on wrong input.
- Error in one input field does not clear form anymore.
Two caveats are being added:
- Selecting a range in galactic coordinates works reasonably well for
small rectangles, as long as one stays away from the poles. Large
ranges and ranges covering the polses may give surprising results.
- For certain ObsIds retrieval of secondary and/or supporting products
(e.g., aspect solutions) may not return all products that are required.
ChaSeR - Web version
2001-12-10
A Web version of ChaSeR,
the CDA Search and Retrieval tool is now available, with basic functionality.
The restriction are:
- No SIMBAD name resolution
- Position search only for J2000 RA and Dec, only cone search
- No selection by proposal number, exposure, time range, or category
- No file input or output
- Retrieval: only complete primary and/or secondary data products packages
- No preview images or observation details
On the other hand, specification of multiple ObsIds has been made
easier and log in for obtaining proprietary data has been improved.
This release is aimed at the majority of users who just want to
retrieve the primary and secondary data products for specific
observations; it offers, for instance, and alternative to PIs and CoIs
for obtaining their new observations. This interface works best with
Netscape 6.1 and higher, but Netscape 4.76 and Microsoft Explorer do
not present any problems; avoid Netscape 6.0x.
Over the next months we will be working on a much more flexible and
sophisticated vversion of the Web ChaSeR. In the meantime,
ChaSeR will allow users the full
spectrum of search and retrieval options.
New Processing Status Tool
2001-11-15
The old CXCDS Processing Status Tool has been replaced by a new one.
The new Processing Status Tool
is a vast improvement and provides more accurate and more complete
information, especially on different processing versions of our observations.
2001-11-09
The five observations totalling 500 ks on the isolated neutron star
RXJ1856.5-3754 have been released. Data products have been
collected into five separate tar files, one for each ObsId; included
are all primary and secondary data products except for the Level 1 and
Level 1.5 Event files. Additional products may be retrieved through
the CDA Provisional Retrieval Interface
or through ChaSeR. In addition, we
provide files containing the combined spectra and the exposure
weighted ARF files for the four most recent observations, as well as
all five observations.
More information on the processing and analysis of these data may be
found at the official release page.
These are the pre-packaged files available for download:
| File | Size (MB) | Contents | Exposure (ks) |
|---|
| 113.tar |
149 | Data products for ObsId 113 | 55.5 |
| 3380.tar |
526 | Data products for ObsId 3380 | 167.5 |
| 3381.tar |
561 | Data products for ObsId 3381 | 171.1 |
| 3382.tar |
370 | Data products for ObsId 3382 | 102.0 |
| 3399.tar |
293 | Data products for ObsId 3399 | 9.3 |
| ns4pha.fits.gz |
0.2 | Spectrum for ObsIds 3380, 3381, 3382, 3399 | 449.9 |
| ns4arf.fits.gz |
0.2 | ARF for ObsIds 3380, 3381, 3382, 3399 |
| ns5pha.fits.gz |
0.2 | Spectrum for ObsIds 113, 3380, 3381, 3382, 3399 | 505.4 |
| ns5arf.fits.gz |
0.2 | ARF for ObsIds 113, 3380, 3381, 3382, 3399 |
2001-09-18
It was discovered that the Level-1 event files distributed for the
Chandra Deep Field South were not properly corrected for aspect as
advertized. A new Primary Level-1 tar file has been created for
CDFS. Note that this only affects the Level-1 event files.
ChaSeR
ChaSeR, the new CDA Search and
Retrieval tool is now available as beta release. It is implemented as
a platform-independent Java application. Download and installation is
made easy and the application will notify users when updates are
available. The only caveat concerns older window managers such as
twm and tvtwm which are not fully X11-compliant and not
supported anymore.
ChaSeR allows users to browse the observation catalog with a
variety of search criteria, to display preview images, and to stage for
download any combination of public data products. In addition, it
allows authorized download of proprietary data products. In due
course it will replace the current procedure for proprietary data
distribution via the ftp site.
Links to ADS Abstract Service
Superseded
We have an experimental page that
links a list of ObsIds, provided by the user, to abstracts in the ADS.
Aspect
For the accuracy of relative and absolute aspect and for correcting
aspect, see the Aspect web page.
Chandra Deep Fields
The merged Deep Field datasets below are now fully corrected for all
aspect defects; they are perfectly aligned and the absolute
coordinates are correct.
The data from the Chandra/Hubble Deep Field North are public as of 20 April
2001. Click for
PostScript image.
For convenient download, we have pre-packaged the data products in the
following three tar files and a Verification & Validation directory.
Note: The 12 ObsIds have been merged into single event and image
files, after careful alignment and reprojection to a common coordinate
system. Hence, these products differ from what one would get by
downloading the individual ObsIds' products.
Note that these files are free from any alignment errors and that the
absolute coordinates are believed to be correct.
[In order not to exceed a 2GB file size, the Level 1 event files are
packaged into two files.]
We have also pre-packaged the data products in
single tarfiles by ObsId.
The CDFN comprises the following observations (click on the ObsId to
retrieve the data, on the SeqNum to see the image):
The data from the Chandra Deep Field South are public as of 13 March
2001. Click for
PostScript image.
For convenient download, we have pre-packaged the data products in the
following three tar files and a Verification & Validation directory.
Note: The 11 ObsIds have been merged into single event and image
files, after careful alignment and reprojection to a common coordinate
system. Hence, these
products differ from what one would get by downloading the individual
ObsIds' products.
Note that these files are free from any alignment errors and that the
absolute coordinates are believed to be correct.
[In order not to exceed a 2GB file size, the Level 1 event files are
packaged into three files: two for the "Faint" observations and one
for the "Very Faint" observations.]
The CDFS comprises the following observations (click on the ObsId to
go to the retrieval interface, on the SeqNum to see the image):
Caldb
The Chandra Caldb
is now available for download from the CDA ftp site.
Data Distribution to Designated Observers
The data distribution policy has been slightly modified. Notification
of the data products' being available from the web/ftp used to be sent
to the PI only. Effective 2000-12-01 this notification will also be
sent to the Designated Observer, if such a person has been selected.
Note that Designated Observers are appointed by proposal, not
individual observations. The physical medium is still sent only to
the PI.
Browse and retrieval of public observations is now possible through
the UK mirror at
LEDAS.
Reprocessing
We have started reprocessing all observations made before 14 August
2000. This will be done in two parts. First, the period 18 September
1999 till 14 August 2000 will be reprocessed, then the period prior to
18 September 1999. All observations made after 18 August 2000 are
processed with the same software version as is being used for
reprocessing.
As reprocessed observations are approved by V&V, the proprietary ones
are being redistributed to the GOs while for the public observations
the reprocessing products automatically replace the earlier ones. As
a general rule, all products bearing a timestamp after 20 August 2000
may be considered reprocessed.
Public Data Superseded
Certain non-CAL observations are already publicly available, either
because the PI waived proprietary rights or because the proprietary
period was less than one year. A listing may be found
here. The data may be obtained through the
Provisional Data Retrieval Interface.
Changed Sequence Numbers
In the past, when observations needed to be split (for instance, a
partially completed observation had to be continued with different
ACIS chips), a new ObsId with a new Sequence Number was created.
We have changed that policy and currently a new ObsId with the old
Sequence Number is created. In order to facilitate uniform
bookkeeping, we are now changing the Sequence Numbers of past
observations for these split cases so that the current policy will
appear uniformly applied since the beginning of the mission. This
way, different pieces of the same observation can always be tied
together by their common Sequence Number.
We have posted lists of ObsIds that had their Sequence Number changed,
accompanied by their parent ObsIds, separately for
GTO and
GO observations.
This page is maintained by the Chandra Data Archive Operations
group
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