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Table of Contents -
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Author Index -
PS reprint -
Rohlfs, R. & O'Neel, B. 2000, in ASP Conf. Ser., Vol. 216, Astronomical Data
Analysis Software and Systems IX, eds. N. Manset, C. Veillet, D. Crabtree (San Francisco: ASP), 687
The ROOT Object Oriented Framework to Analyze INTEGRAL Data
R. Rohlfs, B. O'Neel
INTEGRAL Science Data Centre, 16 ch. d'Ecogia, CH-1290
Versoix, Switzerland
Abstract:
The Integral Science Data Centre (ISDC), located near
Geneva, Switzerland, is building a software system to receive,
analyze and visualize the data from the INTEGRAL satellite
which launches in 2001. The ISDC decided to use the ROOT
package developed at CERN for data display. ROOT consists of a
C++ interpreter, a huge scientific C++ library and a file
structure to archive objects. The C++ interpreter of ROOT will
be used at ISDC as a scripting language to call other programs,
for example FTOOLS, to start analysis scripts and to display
the results with the built-in graphical classes. The classes in
the ROOT C++ library are used to build on- and off-line
applications with graphical user interfaces and graphics. The
scientific and housekeeping data of the INTEGRAL satellite
will be displayed using a wide range of different types of
graphs. The GUIs of ROOT are used to select the data to be
displayed by time, by data type and by their meta data.
ISDC
is responsible for the analysis and processing of the data
from the INTEGRAL satellite to make it directly usable by
scientists. Furthermore, ISDC has to closely monitor the
instruments and will solve eventual problems during the
mission. OPUS pipelines are planned to process the data in an
automatic way from raw data to first scientific results. The
output of these pipelines can be displayed interactively to
investigate any problems.
ISDC will use ROOT (Brun & Rademakers 1997) as a graphical
tool to display the housekeeping data and the science data of
the INTEGRAL satellite. All displays are freely configurable
and the configured graphs can be saved in a ROOT - file and
reused in an other session.
ROOT
is a C++ framework developed since 1994 at CERN. The experience
in developing PAW, PIAF and GEANT was used to design a new
object oriented package including a C++ interpreter. Both the
change from FORTRAN to C++ and the huge amount of data of the
new experiments at CERN (up to 10 TB or raw data per
run) were the drivers of this new development.
The ROOT system consists of a huge C++ library with all the
functionality needed to handle and analyze large amounts of
data in a very efficient way. New methods are used to save
objects in ROOT - files and to get direct access to attributes
of selected objects, without reading the the bulk of data.
Included in the ROOT system are histograming methods in 1, 2
and 3 dimensions, curve fitting, function evaluation,
graphics and visualization classes.
Thanks to the built-in CINT C++ interpreter, the command
language, the scripting, or macro, language and the programming
language are all C++. The interpreter allows for fast
prototyping of the macros since it removes the time consuming
compile/link cycle. It also provides a good environment to
learn C++. If more performance is needed, the interactively
developed macros can be compiled using a C++ compiler.
The Interactive Operation Status Monitoring at ISDC consists of
several display tools build with the ROOT C++ library of
graphic classes and GUI - classes.
The housekeeping (HK) display tool (Figure 1) is used to
monitor several of the more than 7000 HK - parameters of the
instruments and the satellite. The ROOT - classes allow the
interactive modification of the graphs. The size of graphs,
lines and text, the colors of background, graphs and axis and
the style of the graphs can be changed with some mouse clicks.
The selection of the HK - parameters to be displayed and the
time range of interest can be defined through a graphical user
interface.
Figure 1:
Display of INTEGRAL Housekeeping Data.
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During operation the modes of the instruments and the sub-assemblies
of the instruments will change. A graphical display
can show the modes of more than 25 sub systems. With a
graphical user interface the subsystems of interest can be
selected. Each mode is coded in a specific color. The time
range of the display can be defined from some minutes up to
several months.
There will be instrument specific display tools for each of the
four instruments of the INTEGRAL satellite to monitor the
detectors. They will show the count rates of a detector
element, energy spectra and light curves.
Every display tool is freely configurable with some mouse
clicks and through a GUI. The configuration of one tool as well as a
set of tools displaying data on the same screen can be saved in
a ROOT file and read again in another session to restore
exactly the same setup of the screen. Every user modification
of the standard display is saved in the ROOT file. The
ROOT feature of writing C++ classes into a file is used to save
the configurations of the graphic tools.
A standard analysis will be performed at ISDC in an automatic
pipeline process. First scientific results will be produced
during this automatic process. The scientists at ISDC as well
as at their home institutes can use off-line the ROOT C++
interpreter to analyze their data in more detail. C / C++ -
scripts, called macros, define the interactive process. A
typical script will read the data, will call analysis tools like
FTOOLS, can calculate new result, using the C / C++ language
of the script and will display the result.
The functionality of the C++ interpreter can be enlarged.
Functions in a shared library or a dll - library can be read by
the interpreter environment to make these functions available
in an interactive session. ISDC has already written a shared
library to read and write FITS files with the DAL (data access
layer) library (O'Neel et al. 2000) developed at ISDC. All
INTEGRAL data in the ISDC archive are stored in FITS files and
can be read with the DAL functions into the interpreter
environment for further calculations and displays.
ROOT was not developed for astronomical purpose. It has
therefore no astronomical specific displays. But the common
graphics to display 1, 2 and 3 dimensional histograms can be
used to display astronomical sky maps. ROOT does not have
built-in astronomical sky coordinates. But with the object
oriented methods display classes can be inherited to add any
coordinate system to the displays. ISDC has already developed a
class to read the coordinate system from FITS headers and to
display a sky map in l/b and RA/DEC coordinate systems. The
standard ROOT classes to display any two dimensional graph will
be used to display INTEGRAL light curves and spectra. No
additional development is necessary.
ISDC will use ROOT as a display development tool and the ROOT
interpreter as a scripting language for interactive analysis
and displays. The advantages are the freely configurable graphs
and displays. It is not necessary to define the data to be
displayed or the style of the graphs in advance. They can be
defined when a problem has to be investigated. Furthermore, any
modified graph can be saved and printed without any additional
work of development. Thanks to the object oriented ROOT missing
features can be added easily. The ROOT development team at CERN
is happy to add new features to the standard delivery of ROOT
from any side and to maintain it.
References
Brun, R., & Rademakers, F. 1997,
Nucl. Inst. & Meth. in Phys. Res., A 389, 81-86
O'Neel, B., Jennings, D., Rohlfs, R.,
& Paltani, S. 2000, this volume, 187
© Copyright 2000 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
Next: CDS Services; recent Developments
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Previous: Real Time Linux -- The RTOS for Astronomy?
Table of Contents -
Subject Index -
Author Index -
PS reprint -
adass@cfht.hawaii.edu