Chandra Data Archive: New Procedures and New Services

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Chandra Data Archive: New Procedures and New Services

Over the past months several new features have been introduced for the Chandra Data Archive. Some of these were already announced in Chandra Bulletin 33, but it seemed helpful to repeat the information and put it all together for the Chandra Newsletter. The new webpages mentioned below are also linked from the CDA homepage at

In December 2004, a new format was introduced for the Verification and Validation (V&V) reports. They are now formatted as PDF files and included in the primary data products package. In addition, the secondary package contains a V&V reference document (also PDF) that is considerably longer and contains much more detail about the data.

The on-line data distribution no longer works through pre-packaged tar files that are put in an ftp staging area. Users (PIs and Observers) are still being notified that new data have become available, but they are 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 contains a reminder of relevant information required for downloading the data. 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 included in the retrieval package (in particular, the event files and the images). WebChaSeR, on its login dialog box, provides an option to send users a reminder of their passwords. Account names are proposal numbers, for proposal accounts. or (usually) first initial plus full last name (all lower case), for PI accounts.

Dataset Identifiers

The journals managed by the AAS now provide authors with a mechanism that allows them to establish links between their articles and the observational data that are presented in them. We would like to urge our users to take full advantage of this opportunity to incorporate a meaningful linkage in their future papers. The links will automatically be entered into the Chandra Bibliographic Database. An explanation of the system and the syntax of the identifiers is provided at:

Special Data Services Requests

The CXC-DS Operational groups provide various services through web interfaces, such as browsing the archive and the bibliographic database and retrieving data products. However, there are also a number of services that are not covered by web interfaces and require incidental e-mail messages instead. We have consolidated the requests for those services though a single webpage interface:
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). Custom database queries so far have included specialized searches of the observation catalog and the bibliography database that are not available through the standard interfaces. The system also allows us to track these requests in order to ensure that they do not get lost.

Chandra Fast Image

A new Chandra Data Archive Interface to public data:
Chandra Fast Image is a simplified interface that offers the general public, as well as professional astronomers, quick access to images and event files. It can operate in two modes: Quick Image (default) and Advanced.

In Quick Image mode it will search the archive for JPEG images based on a celestial position or an object name; if there is more than one image it will return the one that it thinks may be the most interesting for the user.

In Advanced mode there are a few more search options, the user may indicate whether (s)he wants all or just the best candidates returned, and the user will be given the choice of JPEG or FITS images or event files. It also provides access to directories containing the Primary and Secondary data products and to published articles for selected ObsIds.
This interface has been incorporated into DS9.

SPIE Papers on Chandra

We are in the process of expanding our collection of online Chandra-related SPIE papers and expect to have a significantly increased list by the time you read this:

SIAP Service

For the Virtual Observatory (VO) afficionados, the CDA now offers a Simple Image Access Protocol (NVO's SIAP) service. Proper access information is available from the NVO Registries.

Arnold Rots & Sherry Winkelman for the Archive Operations team

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