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\title{The {\it INTEGRAL} Ground Segment}
\titlemark{{\it INTEGRAL} Operations}

\author{R.\ Walter, A.\ Aubord, P.\ Bartholdi, M.\
Beck, V.\ Beckmann, P.\ Binko, J.\ Borkowski, M.\ Chernyakova, T.\ Contessi, T.\
Courvoisier, P.\ Dubath, K.\ Ebisawa, P.\ Favre, M.\ Gaber, D.\ G{\"o}tz, T.\
Jaffe, D.\ Jennings, P.\ Kretschmar, D.\ Landriu, I.\ Lecoeur, L.\ Lerusse,T.\
Lock, M.\ Meharga, S.\ Mereghetti, N.\ Morisset, N.\ Mowlavi, S.\ Paltani, J.\
Peachey, K.\ Pottschmidt, B.\ O'Neel, N.\ Produit, R.\ Rohlfs, A.\ Sauvageon,
S.\ Shaw, M.\ T\"urler}

\affil{{\it INTEGRAL} Science Data Center, Chemin d'Ecogia 16, CH-1291 Versoix, Switzerland, \texttt{\rm http://isdc.unige.ch/}}

\author{R.\ Diehl$^1$, A.\ Domingo$^2$, A.\ Goldwurm$^3$, L.\ Hansson$^4$, M.\ Schmidt$^5$, N.-J.\ Westergaard$^6$, C.\ Winkler$^4$}

\affil{
$^1$Max Planck Inst. f\"ur extraterr. Physik, Postfach 1312, D--85741 Garching bei M\"unchen, Germany;
$^2$Laboratorio de Astrof\`{\i}sica Espacial y F\'{\i}sica Fundamental, POB 50727, E--28080 Madrid, Spain;
$^3$Service d'Astrophysique, Centre d'Etude de Saclay, F--911190 Gif-sur-Yvette Cedex, France;
$^4$European Space Technology Center, P.O. Box 299, NL--2200 AG Nordwijk, The Netherland;
$^5$European Space Operation Center, Robert Bosch Str. 5, D--64293 Darmstadt, Germany;
$^6$Danish Space Research Institute, Juliane Maries Vej 30, DK--2100 Copenhagen}

\contact{Roland Walter}
\email{Roland.Walter@obs.unige.ch}

\paindex{Walter, R.}
\aindex{Aubord, A.}
\aindex{Bartholdi, P.}
\aindex{Beck, M.}
\aindex{Beckmann, V.}
\aindex{Binko, P.}
\aindex{Borkowski, J.}
\aindex{Chernyakova, M.}
\aindex{Contessi, T.}
\aindex{Courvoisier, T. J.-L.}
\aindex{Dubath, P.}
\aindex{Ebisawa, K.}
\aindex{Favre, P.}
\aindex{Gaber, M.}
\aindex{Gotz@G{\"o}tz, D.}
\aindex{Jaffe, T.}
\aindex{Jennings, D.}
\aindex{Kretschmar, P.}
\aindex{Landriu, D.}
\aindex{Lecoeur, I.}
\aindex{Lerusse, L.}
\aindex{Lock, T.}
\aindex{Meharga, M.}
\aindex{Mereghetti, S.}
\aindex{Morisset, N.}
\aindex{Mowlavi, N.}
\aindex{Paltani, S.}
\aindex{Peachey, J.}
\aindex{Pottschmidt, K.}
\aindex{ONeel@O'Neel, B.}
\aindex{Produit, N.}
\aindex{Rohlfs, R.}
\aindex{Sauvageon, A.}
\aindex{Shaw, S.}
\aindex{Turler@T\"urler, M.}
\aindex{Diehl, R.}
\aindex{Domingo, A.}
\aindex{Goldwurm, A.}
\aindex{Hansson, L.}
\aindex{Schmidt, M.}
\aindex{Westergaard, N.-J.}
\aindex{Winkler, C.}

\authormark{Walter, R. et al.}

\keywords{astronomy: globular clusters, bosons, bozos}

\begin{abstract} 
The INTernational Gamma-Ray Astrophysics Laboratory ({\it INTEGRAL}), an
observatory mission of the European Space Agency, was launched on October 17,
2002. Since then, nominal operations have been conducted successfully and
scientific alerts and products are made available to the science community with
a short delay. Here we briefly describe the 3 centres responsible for the {\it
INTEGRAL} operations, with emphasis on the system built at the {\it INTEGRAL}
Science Data Centre and conclude on the performance of the ground segment.
\end{abstract}
%\parskip=0.2cm
%\vspace{-0.5cm}

\section{Introduction}

{\it INTEGRAL} was successfully launched  by a PROTON rocket from Baikonour on October 17, 2002.
During the Launch \& Early Orbit Phase (LEOP) the final orbit of 72 hours was
reached and most of the spacecraft platform functions were commissioned. The
scientific payload was then switched on, commissioned, tuned, and partially
calibrated within the allocated time so that routine science operations could
start, as planned, in the last days of 2002.

The status and performance of the satellite (platform and payload) is good. All
prime equipment is still used. The on-board resources are efficiently used
providing the option to extend the mission for many years beyond the nominal
mission phase of 2 years. The mission has now been extended to December 2008.

Observation proposals, sent in reply to the first {\it INTEGRAL} announcement of
opportunity, requested 19 times more exposure time than available. The ground
segment is in charge to use {\it INTEGRAL} efficiently and to optimize the
scientific return of the mission.

The operations of the {\it INTEGRAL} mission are split between 3 centres. The
{\it INTEGRAL} Science Operation Centre (ISOC, located in ESTEC, Noordwijk, The
Netherlands) derives the sequence of observations to be executed from the
accepted proposals. Those sequences are converted to operational timelines by
the flight control team at the Mission Operation Center (MOC, located in ESOC,
Darmstadt, Germany) and are used to control the satellite. The MOC also monitors
the satellite safety and health. TM and appropriate auxiliary data are forwarded
to the INTEGRAL Science Data Centre (ISDC, located in Versoix, Switzerland). The
ISDC analyzes the TM on different time scales and produces and distributes
science alerts and data products to the scientific community.

%\vspace{-0.3cm}

\section{The {\it INTEGRAL} Science Operation Centre}

The main role of the {\it INTEGRAL} Science Operations Centre, is to put
together an observation program based on accepted proposals. For each
revolution, ISOC provides to the MOC a timeline of what targets are to be
observed with which instrument settings. To put together a schedule is a complex
task. Besides the proposals themselves, the planning process takes into account,
e.g., proposal priority, target visibility and spacecraft constraints,
efficiency, i.e., minimizing the time spent in slewing.

The ISOC systems supporting proposal capture, handling and scheduling are
centered around an ORACLE data base. All ISOC software is written in JAVA. The
ISOC proposal generation and submission is unique. All proposers generate their
proposals using a downloaded JAVA application. All proposals are prepared
locally and when ready they can be submitted using the same
application. The sending of a proposal only takes seconds of load on the ISOC
system which fully supports heavy peak loads and avoids the usual
bottle necks, that occur before a proposal submission deadline.

%\vspace{-0.3cm}

\section{The {\it INTEGRAL} Mission Operation Centre}

The {\it INTEGRAL} flight operations are conducted from the Mission Operations
Centre (MOC). The two prime ground stations that ensure real time contact with
the satellite 68 hours out of the 72 hours orbit are the ESA station in Redu,
Belgium, and the NASA station at Goldstone, California.

The science operations are very demanding. For example, due to the design of the
payload, the spacecraft attitude is to be changed every 30 minutes, which
requires a highly automated control system. The telemetry (TM) that is received
continuously from the satellite and the auxiliary data are processed in real
time and have to be distributed within the various centers of the ground
segment.

The MOC uses generic infrastructure that is provided by the European Space
Operation Centre (ESOC). The routine operations are highly automated. In order
to operate the satellite in the most efficient way new software tools have been
applied for the first time: the S2K infrastructure for the monitoring and
control system and the new Space Link Extension (SLE) protocol for the interface
to the NASA ground stations at Goldstone.

%\vspace{-0.8cm}

\section{The {\it INTEGRAL} Science Data Centre}

The {\it INTEGRAL} Science Data Center receives the telemetry, broadcasts
gamma-ray burst alerts in real-time, monitors the status of the scientific
instruments, searches for new and transient sources within few hours of the
observation, performs a standard analysis of the data, archives 2 TB of
compressed data per year and distributes them to the scientific community with
analysis software.

The ISDC is provided to the mission by the scientific community through a
consortium led by the Geneva Observatory. The ISDC staff increased from 2 in
1995 to about 40 people at launch. The software and hardware systems were built
and integrated locally following the ESA quality standards. A large fraction of
the analysis software was developed by the teams providing the scientific
instruments.

Several key design decisions were made early in the ISDC project: 
\begin{rwitemize}
\item Use only FITS as data format (most data files are compressed); 
\item Keep all data on-line on hard disks; 
\item Control all interfaces using IRAF parameter files and the data format of every FITS extension
          through CFITSIO template files.
\item Build each analysis step with a standalone executable (FTOOL concept); 
\item Customize a public domain and modern environment  (CERN's ROOT) to develop analysis scripts 
          and applications (Rohlfs et al, this volume); 
\item Use OPUS developed at the STSCI to control the processing flow (Beck et al, this volume); 
\item Use a single operating system for operations (SUN/Solaris) but port the analysis software on 
          Linux as well; 
\item Use HEASARC's W3Browse as archive interface and distribute all data  through the internet
          (Meharga et al, this volume)
\end{rwitemize}

The {\it INTEGRAL} data model and implementation has been developed to allow
scientific analysis with thousands of different datasets without the need for a
Database Management System. As {\it INTEGRAL} spends a considerable fraction of
the time dithering around the target that is being observed, about a hundred
pointings or slews are performed every day and a new dataset is created for each
of them. Those datasets can be grouped in an arbitrary way for scientific
analysis. The FITS grouping convention has been extensively used (O'Neel et al,
this volume) to build observation datasets and various indexing tables.

Several key applications have been developed:
\begin{rwitemize}
\item A library of tools to receive and broadcast CCSDS telemetry and to wrap it to FITS format.
\item A real-time multi-threaded system made of several concurrent and communicating processes 
          to extract the relevant information from the telemetry, searches for gamma-ray bursts using  
          various algorithms in the data of the different instruments, filter the triggers and broadcasts
          gamma-ray burst alerts over the internet.
\item An application to decommute the telemetry and store the complete information in
         FITS format. The decommutation is driven by the S2K database for the decoding of 
         the housekeeping  telemetry and by specific code for each of the scientific telemetry
         packet (Morisset et al, this volume).
\item Several processing pipelines have been written to handle data sets derived from the 
          telemetry as well as auxiliary files.
\item A set of portable graphical user interfaces to browse, display and perform simple analysis of the 
         data and of the results of the scientific quick-look analysis (Lerusse et al, this volume).
\item A set of analysis scripts (with user interfaces, Beck et al, this volume) calling the scientific software
         modules written in part by the teams building the instruments. Those scripts are used with standard parameters for     
         automated analysis and are also distributed to the scientific community for offline analysis.
\item An archive, indexing and distribution system used to ingest, store and distribute on line all 
         {\it INTEGRAL} data (Meharga et al, this volume).
\end{rwitemize}

The software was built as much as possible mission independent and a part is
currently being reused for the Planck mission (T\"urler et al, this volume).
Tools have also been developed to manage software deliveries, configuration and
automatic testing (Beck et al, this volume).

%\vspace{-0.3cm}

\section{Conclusions}

From the user's perspective, the {\it INTEGRAL} operations are very successful:
\begin{rwitemize}
\item  The planning overhead has been minimized such that more than 96\% of the available time is 
            used for scientific observations. 

\item Science operations during the first nominal year of the mission will be completed as planned.
         Target of opportunity observations have been scheduled in less than one revolution. 
           
\item The accuracy of the mission auxiliary data necessary for science analysis mission exceeds the     
          performance requirements.

\item Gamma-ray burst alerts are broadcast on the internet within 30 seconds. 13  new gamma-ray 
          sources have been detected in the Galaxy and announced often within one day, which generated 
          about 60 IAU circulars or astronomical telegrams.

\item Real time data have been made available to observers within 3 hours. First public data have been
          made available in the archive 2 months after the end of the performance-verification (PV) phase. 
          First data resulting from the standard analysis together with analysis software were distributed to 
          observers 3 months after the end of the PV phase. 
\end{rwitemize}
The performance of the  {\it INTEGRAL} ground segment meet the requirements defined prior to launch and are essential for the scientific return of the mission.
}
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