Proceedings of 10th Asian-Paciﬁc Regional IAU Meeting 2008, 1–?? (2008)

Printed 1 November 2008

(APRIM LATEX style ﬁle v1.0)

Design and Implementation of the Japanese Virtual
Observatory (JVO) system
Y. Shirasaki1 , M. Tanaka1 , M. Ohishi1 , Y. Mizumoto1 , S. Kawanomoto1 , S. Honda2 ,N. Yasuda3 , Y. Masunaga4 , Y. Ishihara5 , Y. Machida5 , H. Nakamoto,6 and M. Sakamoto6
1 National Astronomical Observatory of Japan, Mitaka City, Tokyo, Japan,
2 Gunma Astronomical Observatory, Takayama Village, Gunma, Japan,
3 University of Tokyo, Kashiwa City, Chiba, Japan
4 Aoyama Gakuin Univerisity, Sagamihara City, Kanagawa, Japan
5 Fujitsu Ltd., Mihama District, Chiba, Japan
6 Systems Engineering Consultants Co. Ltd., Shibuya District, Tokyo, Japan

ABSTRACTThe Japanese Virtual Observatory (JVO) is a web portal to various kinds ofastronomical resources distributed all over the world. We have started oﬃcial operationof the JVO portal since March 2008. The JVO provides seamless access to the VO
compliant data service, and also access to the reduced Subaru data and on-line data
reduction system for Suprime-Cam instrument of the Subaru telescope. The system
implements standards of the International Virtual Observatory Alliance (IVOA) to
communicate with the VO components in the world. As of October 24 of 2008, over
2,400 astronomical data resources are registered to the JVO portal.
Key words: Virtual Observatory, JVO

1INTRODUCTION

The Japanese Virtual Observatory (JVO) is a web portal
to astronomical data, and it provides seamless access to the
distributed databases, and quick overview of the data, andalso provides astronomical data analysis services. The mostof the functionality of the JVO portal is open to everyone,and some limited functionality is restricted to a registereduser. The access URL is http://jvo.nao.ac.jp/portal.
There are a lot of astronomical data archives accessible thorough the Internet, which enables astronomical
researcher to conduct their research based on the public
databases very easily. As an increase of the number of thedatabases, visibility of of each database become lowered andit become diﬃcult to ﬁnd a database which is suitable for
an individual research. Therefore, a general way to publish
the data resource need to be deﬁned. International Virtual
Observatory Alliance (IVOA) was formed to deﬁne the standard way to publish the data resource and make it searchable
in a standard method.
There are many activity to make an environment which
provides better usability of the data resources distributedin the world by adapting the VO standards. There are two
major approaches. One is to make a stand-alone application,and the other is to make a server side web application. The
advantage of the former approach is that it can provide afancy interface and better interactivity. The advantage of thec 2008 APRIM°

latter is that user does not need to install any software otherthan a web browser, and most of the processes are done on
the server side so it does not require high performance PC
even when the large amount of data is used. Considering thatthe former approach are made by many other VO projects
and we have enough computing and storage resources at the
NAOJ, we selected the latter approach.
We also aim to increase the usability of the Subaru databy distributing the data thorough the JVO system. Especially the data of Suprime-Cam have a remarkable featurethat it provides a wide ﬁeld and deep image of the universe
and it contains a lot of information unexplored by the primary investigator of the data. The raw data is distributed
thorough the astronomy data center of NAOJ, however there
are diﬃculties on downloading the large amount of data, andreducing the data is not an easy task. So we reduced all theSuprime-Cam data and they are distributed thorough theVO interface and on a dedicated web interface. We also provide a access to an on-demand data reduction pipeline bywhich user can reduce the data by their own data selection
criteria.

2

JVO PORTALThe JVO system consists of several independent components
as shown in Figure 1. The component shown at the center of

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Y. Shirasaki et al.

Figure 1. Overview of the JVO system
Figure 2. Top page of the JVO portal

the ﬁgure (portal) is a web application which authenticatesa user, accepts a query and job submission request from auser, creates and executes a workﬂow to achieve the request (Tanaka et al. 2006 ), and manages the user storage where
search result and uploaded ﬁles are saved. So the portal isa core component of the JVO system, and plays a role of akind of broker so that a user can seamlessly utilize a lot of
VO components both of the JVO and the other VO project.
The data service component shown at the right middle
and bottom of the ﬁgure is a collection of VO compliant
data services under the JVO and external VO system, respectively. All the VO services of the JVO are searchable
with the SkyNode interface, and some of the image dataarchives are searchable with the simple image access (SIA)
interface too. JVO skynode toolkit( Shirasaki et al. 2006 )is developed for setting up the VO compliant service, and isfreely available ? .
The registry service component shown at the left bottom of the ﬁgure is a metadata database of VO services.
The publishing registry is used to expose metadata of the
JVO data services. The searchable registry periodically collects metadata from the publishing registries which are registered in the IVOA’s registry of registry † . As of October 24
of 2008, ∼2400 resources are registered in the JVO searchable registry. It is used to ﬁnd astronomical resources witha given search condition among the thousands of registeredresources, and also used to resolve the service endpoint URL
in executing a query requested by a user. The grid system
shown at the left top of the ﬁgure is used to execute astronomical data analysis, such as data reduction of Subaru
Suprime-Cam, source extraction from an image data, andphotometric redshift calculation for a given multi-band catalog. More details is described by Shirasaki et al.( 2008 ;2007 ; 2006 ).
Figure 2 shows a snapshot of JVO portal top page.
There are links to various user interfaces each of which
are dedicated interface to some speciﬁc functionality of the
JVO. Those links are categorized according to their functionality. At the “Data Search” section, there are links to
ﬁve kinds of query interfaces. We provides three easy-to-use
interfaces for a novice user, and two interfaces for an advanced user to directly specify an SQL. At the quick search? http://jvo.nao.ac.jp/download/skynode-toolkit† http://rofr.ivoa.net

page (Figure 3), one can access to the “Digital Universe”,
which is a database containing only coordinates and brightness of objects from various published catalogs, such as Subaru deep survey, TWOMASS, SDSS DR6, UKIDSS DR2,ROSAT bright catalog, and so on. Since the database areconstructed under the JVO system and a quick coordinate
search algorithm is employed ( Tanaka et al. 2008 ), query
response is fast; It just takes 0.8 s to search thousands of objects from three billions objects. At the parallel search page,
one can submit region queries to all the VO data services
at once (Figure 4). Over 1,000 resources are queried in 10
minutes. At the single service search page, individual dataservice can be queried with more detailed search condition.
Those interfaces are complement each other. If you want to
get only the coordinates and brightness of objects in a speciﬁc region, “Quick Search” page is recommended for theﬁrst use. If you cannot ﬁnd data by the “Quick Search”, try
to use the “Parallel Search” page. If you have a speciﬁc service which you want to search on, you may use the “Single
Service Search” page.
Search result described in a VOTable format, which isa VO standard format to exchange tabular data, can beviewed by using a VOTable viewer, which run on the serverside and translate the VOTable to an HTML, so it can beviewed on an web browser. The VOTable viewer can be invoked by clicking the “Result” button that appears after thequery is completed, or by clicking the ﬁlename on the JVO
space viewer. The JVO space is a data storage for a JVO
user, where one can save the search result. The tabular data
can be plotted using the JVO plot, which currently support
XY scatter plot, histogram plot, and line plot. Image andspectrum data in FITS format can be viewed by using the
JVO image and spectrum viewer, which convert the FITS
data to a graphical format that can be displayed on a web
browser. Those JVO viewers are running on the server side,
so the user does not need to install any software on the local
machine. One can also use applets developed by VO India(VOPlot), CDS (Aladin), and ESAC (VOSpec) to plot thetabular data, view the image and spectrum data, respectively. To use them, you need to install Java on the local
machine.
We also provide the reduced data taken by the Subaru
telescope through the SkyNode and SIA interface, or at a
dedicated query page on the JVO portal. The raw data takenby the Suprime-Cam instrument are calibrated, then thec 2008 APRIM, 1–??
°

Design and Implementation of the JVO

3Figure 3. Query interface for the Digital Universe.

data set that have the same object name are stacked tomake a single mosaic frame. Diﬀerent demands on image
quality are expected depending on the science target of eachresearch. So we applied seeing selection when stacking the
ccd frame data, and created mosaic frames of four diﬀerent
quality levels. It is also possible to submit a data reduction
job and create a mosaic frame with ones own criteria. The 1D
spectrum extracted from data taken by the HDS instrument
are also available although they have not been corrected byﬂat ﬁelds.
Figure 5 shows the usage statistic of the JVO system.
There are more than 40 thousands of page requests for all
the JVO system every month, however, 36 thousands are automated periodic accesses from JVO system itself and theexternal VO system. So the net value is about 4 to 30 thousands for actual usage. The data download size is dominatedby Subaru data retrievals; the ratio exceeds 90% of the total
download since March 2008. The contribution of automatedperiodic accesses is just a few hundreds MB/month.

3

SUMMARY

We have started the oﬃcial operation of the JVO systemsince March 1st of 2008. Improvement of the capability andusability should be continued by taking account of use cases
which many of the users want to do. Currently we are making improvements on enabling the users to do a multiple region search, to make their own multi-band catalog from thediﬀerent catalogs very easily. We are also trying to improving the content of the “Digital Universe” by collecting thedata from VO services in a automated way. Another issue
we should tackle is to increase the fraction of VO compliant
data services. There are still many data resources which are
not accessible through the VO interface. The success of theVO primarily depends on how quickly we can have a large
fraction of the data resource accessible through the VO application.

ACKNOWLEDGMENT
This work was supported by the JSPS Core-to-Core Program and Grant-in-aid for Information Science (15017289,
16016292, 18049074 and 19024070) carried out by the Ministry of Education, Culture, Sports, Science and Technology
c 2008 APRIM, 1–??
°Figure 4. Result of the parallel query.

Figure 5. The histogram shows the history of number of requested pages per month (left axis) for all the JVO system (portal + skynode + registry). The Solid circles connected with lines
represents download size in kB per month for the JVO system.
The pie chart shows the usage ratio (based on the number ofrequested pages) for each resource of the portal system.

(MEXT) of Japan. YS is grateful for support under Grantin-aid for Young Scientists (B) (17700085) carried out by
the MEXT of Japan.

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