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Astronomical Data Analysis Software and Systems VII
ASP Conference Series, Vol. 145, 1998
R. Albrecht, R. N. Hook and H. A. Bushouse, e
Ö Copyright 1998 Astronomical Society of the Pacific. All rights reserved.
ds.
Browsing the HST Archive with Java­enriched Database
Access
M. Dolensky, A. Micol and B. Pirenne
Space Telescope ­ European Coordinating Facility,
Karl­Schwarzschild­Str. 2, D­85748 Garching, Germany
Abstract. Our Web interface to the HST archive (WDB) was substan­
tially augmented during the past few months: A seamless integration of
Java applets and CGI interfaces to the database now allows basic manip­
ulation and visualization of data.
WDB can now delegate subtasks to Java applets. We use this abil­
ity to visualize quick­look (Preview) data with two applets: JIPA and
Spectral for direct FITS images and spectra visualization respectively.
They both allow basic data manipulation such as contrast enhancement,
zooming or X/Y plots.
Another utility, the Skymap applet, can display the location of HST
observations on a sky projection.
These applets only require a common Web browser and o#er very
helpful features to facilitate archive data selection.
1. Browsing the HST Archive
There are already a number of ESO and ECF archive services 1 and projects that
make use of the new Java technology. We will briefly discuss some applets used
for the following purposes:
Jplot Plot Contents of HST Observation Log Files
Spectral Plot Spectra ­ Preview of HST Observations
JIPA Display FITS Images of HST Observations
Skymap Present Maps of Parallel HST Observations
1.1. JPlot
ECF's HST archive uses WDB to implement query forms for its Web interface. A
few months ago the only way to retrieve data was to invoke a CGI script. Now we
also use WDB to fire up applets. In this way it is possible to replace component
by component on demand, without changing the whole archive system at once.
Jplot is an example of this strategy. It allows visualization of ASCII tables and
the production of basic X/Y plots (Figure 1). The same is true for the Spectrali
applet.
1 http://archive.eso.org/
412

Browsing the HST Archive with Java­enriched Database Access 413
Figure 1. Requesting and Displaying Pointing Information using Jplot
1.2. Spectral
This applet is a previewer for HST spectra. It is quite similar to Jplot and is
integrated into the WDB Web interface (Figure 3). The user has various options
for inspecting plots with the mouse and by means of hotkeys. As the screenshots
in this paper show, a standard Web browser supporting either JDK 1.0 or JDK
1.1 is su#cient to run this applet. No special software is required, in particular
no appletviewer or plug­ins for the Web browser have to be installed on the
client side. Micol et al. (1996) discussed this issue in more detail.
1.3. Java Image Preview Application (JIPA)
While Spectral presents plots of spectra, JIPA's task is to visualize images of
HST and to allow basic image processing. The input data format is compressed
FITS which makes JIPA the ideal previewer for the HST archive. There are sev­
eral options for contrast enhancement, zooming and displaying header keywords
(Figure 2). Another feature is the conversion of the mouse position from pixel
space into the World Coordinate System (WCS). JIPA is written in pure Java
like the other applets presented here and hence is platform independent.
1.4. Skymap
Figure 3 shows the Skymap applet. It graphically displays locations on the sky,
where observations took place. It is possible to select observations taken with
one or more specific instruments and to transform the mouse position into right
ascension and declination.

414 Dolensky, Micol and Pirenne
Figure 2. Inspecting FITS Image with the Java Applet JIPA
Figure 3. Applets Spectral (left) and Skymap (right)
2. Outlook
In the future more and more components of the archive user interface will be
replaced by Java applets. In this way not only data, but also programs are

Browsing the HST Archive with Java­enriched Database Access 415
provided to the user. It also means that the CPU on the client side will become
more and more busy manipulating data instead of running idle while waiting for
the response from some archive server.
References
Micol, A., Albrecht, R., & Pirenne, B. 1997, in ASP Conf. Ser., Vol. 125, As­
tronomical Data Analysis Software and Systems VI, ed. Gareth Hunt &
H. E. Payne (San Francisco: ASP), 104