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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.
The ISO Post­Mission Archive
R.D.Saxton, C. Arviset, J. Dowson, R. Carr, C. Todd, M.F.Kessler, J­L.
Hernandez, R.N.Jenkins, P.Osuna and A. Plug
ESA, ISO Science Operations Centre, Villafranca del Castillo, Apartado
50727, 28080 Madrid, Spain, Email: rsaxton@iso.vilspa.esa.es
Abstract.
ISO (the Infrared Space Observatory) was launched in November
1995 and is now expected to have an operational lifetime of 2.5 years, as
compared to the design requirement of 18 months. It is performing astro­
nomical observations at wavelengths from 2.4­240 microns with four in­
struments; a camera (2.5­18 microns), a photometer (2.5­240 microns), a
short­wavelength spectrometer (2.4­45.2 microns) and a long­wavelength
spectrometer (43­197 microns). By the end of the mission it will have
made in excess of 25,000 high quality Infrared observations which will
leave an important astronomical archive.
The ISO post­mission archive (PMA) is being designed to fully ex­
ploit this legacy by providing access to the data across the Internet. It
will provide an on­line service to the data, supporting documentation and
software through a WWW interface which has the goals of being friendly
for the novice user, flexible for the expert and rapid for everybody.
1. Introduction
ISO will make its final measurement on April 10 1998 (±2.5 weeks) when the
liquid Helium coolant is expected to run out. All of the data will then be bulk
reprocessed with the latest version of the ISO processing pipeline to produce an
INTERIM archive; which will be stored on CD in a set of jukeboxes to give easy
near­line access to the entire dataset.
The ISO PMA 1 will be hosted at the ESA site, VILSPA, in Villafranca del
Castillo, Spain and will become available to the public three months after the
end of the mission (i.e., it is expected to go live in July 1998).
The processing pipeline will continue to be regularly updated in the post­
mission phase as instrument knowledge and techniques improve. An On­The­
Fly­Reprocessing (OFRP) option will be made available to archive users to allow
them to retrieve observations processed by the latest software and using the
latest calibrations.
Three and a half years after Helium­loss the pipeline will be frozen and all
observations reprocessed to form a LEGACY archive. Data will become public
1 See http://isowww.estec.esa.nl/science/pub/isopma/isopma.html
438

The ISO Post­Mission Archive 439
Figure 1. Hardware configuration
one year after they have been shipped to the observer in fully­calibrated form,
which means that all data are likely to be public by April 1999. Until this point
is reached proprietary data rights will be respected.
2. High­Level Design
The INTERIM product archive will be stored in a near­line system on # 700
CDs spread between three jukeboxes. Each jukebox will contain four readers
and the retrieval software will optimise the performance by scheduling CDs to
be read in parallel.
The archive and associated Sybase database will be hosted on a Sun Sparc­
station connected by a 2Mb/s line to REDIRIS, which has a fast link to Europe
through the Ten 34 capital city network and is linked to the USA by 2 further
2Mb/s lines.
The user interface will be HTML and Java based and will issue SQL queries
to the database via JCONNECT. The basic interface will allow observations to
be selected based on astronomical considerations such as coordinates, source cat­
egory, exposure time, wavelength etc. An `expert' interface will also be provided
to allow calibration scientists to query the database using engineering, trend and
housekeeping parameters.
OFRP will be performed on a cluster of Alpha machines running Open­
VMS. The raw data will be stored locally on an array of 9 Gbyte disks and the
processing load will be shared between the machines and between disks so that
a configurable number of observations (initially 10) can be processed simultane­
ously.
Files will be returned in FITS format, optionally compressed, into a transfer
directory. For large datasets, or when requested, data will be sent on CD to a

440 Saxton et al.
REDIRIS
ESOC
ESTEC
VILSPA
64 Kb / s
64 Kb / s
2 Mb / s
10 x 34 Mb / s
TEN 34
2 x 2 Mb / s 34 Mb s
NLnet
US / NASA
2 Mb / s
2 Mb s
US
SPAIN
Academic Net
Figure 2. Network access
mail address. In this case data will be copied into a CD holding area and a batch
of CDs written once a week. To improve throughput a cache area of 30Gbytes
(# 10% of the archive) will be maintained on magnetic disk to avoid retrieving
from CD, or reprocessing, popular observations many times.
3. User Interface
This will be a suite of HTML pages and Java applets providing on­line ac­
cess to the archive. The observation catalogue searching and product request
functionality will be controlled by a single applet, working in a modulable load
configuration whereby parts of the applet are downloaded only when necessary.
3.1. Browse form
. allows the user to select observations based upon a wide range of astro­
nomical and engineering parameters
. a Java applet will run on the client machine to translate the submitted
request into SQL and send it to the database via JCONNECT
. the observation list will be displayed in a Results form which will include
a link to a viewable postage stamp product
. each observation may be moved into a SHOPPING BASKET
3.2. Shopping basket form
For each observation the user specifies:
. Archived product or OFRP

The ISO Post­Mission Archive 441
BROWSE
FORM
RESULTS
FORM
SHOPPING
BASKET
USER
REGISTRATION
RETRIEVAL
FORM
Figure 3. Schematic search/retrieve transition diagram
. Level of products required (Raw data, basic science data etc)
When the shopping basket is complete the data may be retrieved
3.3. Retrieval form
. summarises request and displays estimated retrieval time
. asks for transfer medium (FTP or CD)
Before the data is retrieved the user is asked to register
3.4. Registration form
First time users are asked to provide a Username,Password,E­mail address, Mail
address and Preferred transfer medium. Observers who own observations will
be sent a username and password by E­mail at the start of the archive phase.