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TOP > Report & Column > The Forefront of Space Science > 2010 > Development and Publication of the data-access service “AKARI Catalog Archive Server”

The Forefront of Space Science

Development and Publication of the data-access service “AKARI Catalog Archive Server”
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What is the catalog data-access service?

Astronomical catalogs contain a variety of observational information in columns, including coordinates, magnitude of objects, etc. Generally, catalogs are published as tables with lines of numerous objects (e.g., stars, galaxies). The catalog set of AKARI All-Sky Survey has two catalogs (tables): far-infrared (FIS) catalog with about 430,000 lines; and mid-infrared (IRC) catalog with about 870,000 lines. In more large-scale survey projects, catalogs with up to several hundred million lines are sometimes produced.

Some researches need to use the entire content of large-scale catalogs for analysis. In many cases, however, researchers pick up objects from catalogs according to certain conditions meeting their research purpose and analyze them. Therefore, the main function needed for service is "search," for which high-speed operation and flexibility are required.

Since computers today are very high-performance, even with the AKARI IRC Catalogue (about 870,000 objects), a search can be completed within about one second if you check a single object from top to bottom of the catalog according to a certain condition. In astronomy, there are also many cases where a search is required for 10,000 to 100,000 objects according to the coordinates (longitude/latitude) in the celestial sphere plane. In these cases, when a search of each item requires one second, we have to spend several hours or even more than one day.

If we use AKARI-CAS for such a search, we can complete one search within several thousandths of a second to several tens of thousandths of a second. One frequently used search is "Match-up between FIS and IRC Catalogues." For this search, AKARI-CAS's high-speed search performance is very effective. "Match-up" means a search to check up objects in IRC Catalogue corresponding to all of approx. 430,000 objects in FIS Catalogue. Even for this search, AKARI-CAS does not require more than 30 sec. High-speed search capability is a chance to show off our expertise as data processing professionals (please note that the high-speed capability is not due to high-performance of the AKARI-CAS computer).

In order to meet more advanced search needs other than search by coordinates, AKARI-CAS supports direct input of database language (SQL). This function is relatively rare. Its good reputation for flexibility is attracting an increasing number of mainly young users. Further, there may be cases where researchers want to see images of the searched objects or to investigate such objects on data services provided by other countries. For such requests, AKARI-CAS provides links to images of the objects searched and other data services.

As discussed above, an astronomical catalog's data-access service should be developed so as to meet a wide range of research themes with various added functions other than search by coordinates, which is a basic service in catalog data-access even in other countries. In addition, each service offers original features. As anyone can download the AKARI Catalogues, it is registered in other countries' data-access services. As a result, AKARI-CAS competes with them. To beat other services, AKARI-CAS needs to offer excellent usability in basic function and, simultaneously, to have its own original, high value-added functions.

Figure 1
Figure 1. AKARI Catalogue Archive Server
This server is equipped with powerful search and image-browsing tools, and documentation of the same level as that offered by foreign countries, in order to support a variety of research using the AKARI Catalogues.

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