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ChaSeR and WebChaSeR


Access to the Chandra Data Archive (CDA) has been improved in 2001. Two important tools were released: ChaSeR (Chandra Search & Retrieval) and its web-based cousin, WebChaSeR. Both will continue to be further developed in the future.

WebChaSeR is targeted at the average user: it is easy to use, does not require any setup, but it does not have the full flexibility of ChaSeR.

ChaSeR is a Java-based application that needs to be installed on your host. It has more sophisticated capabilities, both in searching and retrieving. The installation is a simple download-and-install process that is no more complicated than the average application installation on a PC or Mac, particularly if you take the bundled Java installation.

Both are accessible from the CDA home page:


WebChaSeR simply works through your web browser. It allows searching the Chandra observation catalog by:

$\bullet$ ObsId: single, list, range, list of ranges

$\bullet$ Sequence Number: as for ObsId

$\bullet$ Target name: the given string will be matched as a substring in target names; blanks are not significant; optional use of name resolver

$\bullet$ Coordinates: cone search in equatorial, ecliptic, or galactic coordinates

$\bullet$ Type: CAL, GO, GTO, TOO, or DDT observations

$\bullet$ Status: unobserved, scheduled, partially observed, observed, archived, canceled, discarded

$\bullet$ Instrument

$\bullet$ Grating

$\bullet$PI name: substring

The user has some control over the format of the search results: sort order and coordinate system and format. Individual observations may be selected from the search list for data product retrieval and the user has the choice between the primary and/or secondary packages of data products. The user may also log in to a PI or proposal account, in which case WebChaSeR allows retrieval of proprietary data for which the account is authorized. The selected products may be browsed before retrieval. Retrieval of the data products is effected by WebChaSeR's transferring the products to a tar file that is deposited on an ftp staging disk and the user being informed of the exact path/URL; note that this is important: the cryptic path serves as your security to protect proprietary data.


The ``regular" ChaSeR allows at this time approximately the same observation search constraints, but these will be expanded in the future to allow for more sophisticated searches and satisfy the more specialized needs of CXC staff. At this point, the most siginficant difference is that ChaSeR allows searches in rectangular coordinate regions and, by implication, greater-than and less-than constraints. More significant are the difference in the handling of search results and retrieval capabilities.

$\bullet$ The user can change the order of the search results table interactively (click-and-drag).

$\bullet$ ChaSeR provides access to preview images and detailed observation information.

$\bullet$ The user has the ability of customizing the retrieval package down to specific filetypes by ObsId, by filling a ``shopping cart".

$\bullet$ Retrieval may be via the ftp staging area or through a direct connection.

ChaSeR has been succesfully installed and used on Solaris, Linux, Dec Alpha, Windows, and Mac (OS X) platforms.

Future Development

During 2002 there will be further enhancements in ChaSeR and WebChaSeR functionality, with two areas of main focus: a more flexible search menu and more extensive linking. The latter includes links to preview images, associated observations from other observatories, the literature, V&V reports, the Processing Issues database, etc. Some of this linkage is currently available in other places, in particular the Processing Status Tool and the ADS linking.

Processing Status Tool

Another major effort during 2001 was to redesign and backfill the Processing Status Database. This was completed in September and with it came a new web-based interface. This tool can provide the user with a complete processing history and overview of all processing versions of the major data products for a single observation or a selected subset of observations. This tool, also accessible from the CDA homepage, provides links to V&V reports (for public observations) and to the Processing Issues database. It is a most useful tool to find out quickly what has happened to an observation or a group of observations; note though, that it only contains observations for which processing has started.

ADS links

We have been building a database of published papers associated with individual observations. Eventually, these links will appear in ChaSeR. However, for the present, there is a special page that allows users to search for papers by ObsId. Follow the ADS link under ``Links" on the CDA homepage. Only papers in refereed journals and in conference proceedings are included and the database lags publication by about two to three months.

Conversely, the ADS links to the CDA: when ADS users browse through the articles, those that are associated with specific Chandra observations will have a link that goes directly to the WebChaSeR retrieval page for those observations.

Needless to say, the maintenance of this database is very labor intensive. It would help us greatly if you could inform us of any papers that are about to be published (or that have been published but are missing from the database), with all ObsIds that were used in these papers. Please send E-mail to Thank you.


All this would not have been possible without the dedication and hard work of the following people.

The other members of the Archive Operations team: Stephane Paltani, Ed DeLuca, Sherry Winkelman, Padmanabhan Ramadurai, Michael Preciado, and Emily Blecksmith

The database development team: Panagoula Zografou, Peter Harbo, John Moran, Alesha Estes, David Van Stone, and Alex Patz

Processing Status Tool interface: Diane Hall

- Arnold Rots

next up previous contents
Next: CIAO:Focus on Threads Up: Chandra News Previous: Shelter from the Storm: