Acquisition and Data Logging for the ANTARES Project
J.F. Gournay, R. Azoulay, N. de Botton, P. Lamare, J. Poinsignon
CEA, DSM/DAPNIA, Saclay, FranceAbstract
The goal of the ANTARES R&D project (Astronomywith a Neutrino Telescope and Abyss environmental
RESearch) is to study the feasibility of the deployment andoperation of a very large deep sea high energy cosmic
neutrino detector. This program has begun in 1996 in theMediterranean sea along the French coast at depth down to2500 m. Several lines have been deployed repeatedly forsite parameter measurements such as optical background,bacteria and sediment fouling, undersea currents.
These lines include a small autonomous intelligent controller which performs the acquisition and the storage ofenvironment parameters, the interfacing with photomultiplier tubes and the control of some specific devices(acoustic modem, current meter, compass, motor).
This paper presents these tests and the different configurations of the controller used to drive them. The controller
has to work autonomously with limited resources and withhigh reliability. The technical options chosen to meet thesestringent requirements are described.
The next step of the program is presented. It will consist
in the deployment of a complex mooring line including 8
photo-multiplier tubes and several instrumentation subsystems. This line will be connected to the shore by a 40
km electro-optical cable which will bring the power andallow data acquisition and supervision. The same controller
as above will be used for slow control data concentration
in a WorldFIP fieldbus architecture.
1 Introduction
The detection of high energy neutrinos offers unique
opportunities for astrophysical investigations. A neutrino
detector detects the neutrino by its interaction products.
High energy neutrinos coming from astrophysical point
sources will occasionally interact with matter and create amuon. At energies above 1TeV the angle between theinteracting neutrino and the produced muon is very small.
Therefore, the direction of the parent neutrino is welldetermined. In the water, the muon emits Cerenkov lightwhich can be detected by photomultipliers tubes (PMTs).
The principle of the detector is based on an arrangementof PMTs in a 3-dimensional array. As the expected events
rate is low, a volume of 1 km3 is needed. The PMT and its
electronics is enclosed in a pressure resistant glass sphere :the Optical Module (OM). The OMs are attached to amechanical structure made of flexible and rigid elements
which ensure their relative position in the water.
2 R & D Program of ANTARESOne goal of the ANTARES program [1] is to measureseveral crucial site parameters such as optical background(natural 40K radioactivity and bioluminescence emitted by awide range of sea animal species), bio-fouling (sedimentsdeposit), water transparency and sea currents.
These measurements were begun in spring 1996 along
the French Mediterranean coast at the depth of 2500 m.
The site was chosen about 30 km off-shore from La Seynesur-Mer where we can profit from a good infrastructure.
Several types of mooring lines have been launched inorder to carry out these measurements. They all include,from top to bottom : an ARGOS beacon, several buoys, themeasurement instrumentation, a remote controlled releaseand a ballast. The instrumentation set-up is the following :• 1 or 3 OMs for optical background measurement,• several captors on the inside surface of an OM facing
an LED for bio-fouling measurement,• an OM facing an LED mobile along a rigid structure
for water transparency measurement.
The usual length of a line is 200 to 300 m. The line
descent or ascent takes 20 to 30 minutes at a depth of2500m. During the first year of tests (from June 96 to July97), a total number of 20 missions, either for deployment or
recovery, have been made.
The acquisition system which has to be used must work
autonomously without any connection to the shore or to aboat. Furthermore, the containers able to sustain highpressure from -2500 to -4000 m have a price which
increases rapidly with their volume. So the stringent
requirements the system has to meet are : high reliability,
low power consumption and compactness.
3 The MBX micro-controller system for ANTARES
3.1 Hardware overview
The points listed above are well fulfilled by the off-theshelf micro-controller system MBX from the firm MII. It isbased on the MC68306 micro-controller, a CMOS deviceof the 68000 family. The system is composed of several
boards connected together by a simple bus. The main board
contains the micro-controller, 512 KB of EPROM and 1 to2 MB of battery back-up RAM. The micro-controller
supports 2 serial lines and timers, a dedicated chip isprovided for real-time clock and calendar. An I /O board
comes with the CPU board and has 8 analog inputs, 4analog outputs, 16 digital inputs/outputs. An extension
board may double the number of input/output channels. For
specific purposes, a custom board is available. The overall
power consumption of the system is 6 W (250 mA / 24Volts). The space occupied by the 3 superimposed boards is
22 cm x 12 cm x 10 cm. The system is powered by externallithium batteries.
Another strong point for using the MBX is the extensive
experience we acquired with it during the development ofthe CABTF program (Low Temperature Acquisition

System with a FIP connection). For this application, theMBX includes a standard WorldFIP fieldbus interface from
MII and a custom board for cryogenic temperatureacquisition. WorldFIP is used to interconnect the acquisition satellites to PLCs and supervision PCs [2]. An
important decision was to use the vxWorks real-time
operation system from Wind River System on this platform.
For this purpose, a porting of the standard 68306 vxWorks
support package was done. The FIP library, alreadyavailable on the MBX but in a different OS environment,
was adapted for vxWorks. This system is now used on
several cryogenics installations at Saclay and CERN.

system and recovery of stored data. Typical transmission
rates are 600 Baud from the bottom to the surface and 16
Baud from the surface to the bottom.
3.2.3 Water quality measurement
The MBX is interfaced to a PMT and, via standard I/Ochannels, to a motor. The goal is to move a trolley in a 35m
long rigid structure. This trolley is equipped with a LED
controlled by a DAC. A PMT and the MBX are located on
top of the structure (see Fig. 1). The trolley is stopped on
predefined locations and measurements of the transmitted
light between the LED and the PMT are made.

3.2 Hardware configurations
For all the configurations, the MBX is interfaced to acommon set of signals (temperature, battery voltages...)which are periodically logged. A binary input is used which
notifies the system of an imminent power failure. Then, thesoftware can smoothly stopped the activity of the system.
The specific features for each underwater type of sitemeasurement are described in the following paragraphs.
3.2.1 Optical background measurement
The MBX is equipped with a Saclay designed board forinterfacing PMTs. This board consists of :• a front end logic building fast coincidences (510-9 sec
resolution) and the pulse shaping of the incoming
signals.
• Four 50 MHz 24 bits counters.
• The interface with the MBX extension bus.
To have some qualitative information on bio-luminescence, a first serie of tests was done with a single PMT. To
study coincidences and then to make a good discrimination
between the different origins of light, 3 PMTs are now
interfaced to the system. A current meter is linked to theMBX via one serial line and gives information aboutvelocity and direction of current, pressure etc... The system
is powered 1 or 2 times each day for a duration of 1 or 2hours. During this period, a predefined sequence ofmeasurements is carried out. A typical deployment lasts
from 2 weeks to 1 month.
3.2.2 Bio-fouling measurement
The MBX is equipped with a standard extension I/Oboard. An upper glass sphere includes a LED and its
electronics. The lower glass sphere includes the batteries,
the MBX and 9 photo-diodes used to measure the lightreceived on different spots of the sphere. The system ispowered twice a day for a duration of a measurement
which is about 2 minutes. The line has to stay deployed forseveral months to appreciate the slow degradation of thelight signals due to bio-fouling. The phenomenon isstrongly correlated to the strength of the currents. Thus, acurrent meter is interfaced to the MBX to record
simultaneously variation in bio-fouling and sea current. To
be able to check periodically the system on site, an acoustic
modem is also connected to the MBX. With this system, it
is possible from the surface, to power the MBX and toestablish a communication with it, for checking of theFig. 1. Diagram of the Mooring Line for Water Quality
Measurements
The time used to make a return trip along the complete
length of the structure and to make 25 measurements is 90
minutes. The system is powered on the boat and themeasurement procedure occurs automatically 2 hours later.
An acoustic modem is also available, providing interaction
with the system either to read data or, if required, at the endof the automatic procedure, to make <<manual>> trolley
displacements and light transmission measurements.
3.3 Software overview
The software (RTOS + Application) is stored on the512K PROMS of the MBX. The particular conditions inwhich this system is used have also strong implications on
the software. The container of the MBX is usually closed
several days before the deployment for high pressure tests.
From this moment until the recovery of the system, thesystem must work without human intervention. The firstrule was to build a software as simple as possible with allnecessary run-time checks made and with possibilities ofdegraded operation. All the return parameters of the system
calls are tested, all the important events and the errors arelogged for analysis. Despite the concern to make thesoftware as simple as possible, the battery back-up RAM ishandled as a RAMdisk with a DOS compatible file system.
The evolution of the different tests have proved the validityof this choice, as more and more data of different type isstored in several files. To insure the highest level of data
security but with a penalty on the performance, a special<<auto-sync>> mode is used. With this mode the data isimmediately written on the <<disk>> without waiting a
flush of the buffer. For the long duration bioluminescencemeasurements several hundreds of files are created, each ofthem identified by the time of creation and the type ofmeasurement (calibration, coincidence, selected PMTs...).
The format for the data files is SDDS compliant [3] and thedata are usually stored in binary format. The storage
resources of the MBX are scarce, so a compression
algorithm is planned to be used, enabling a compression
factor of 2 or 3. For the future, a development for anadditional 20 to 80 MB flash EPROM board is under study.
For development and debugging purpose, one serial portof the MBX is connected to a SUN workstation and is usedwith SLIP (Serial Line Internet Protocol). This link is also
used after a deployment to retrieve the data with ftp.
The reliability is a key feature for this system. To date,
we have only 2 partial failures to deplore : one was caused
by a risky on-site transmission rate reconfiguration of
theacoustic modem. Although the system was still working,the dialog from the surface became very difficult andeventually impossible. The second one was a saturation of
the file system which occurred after the creation ofroughly 110 files. This problem caused the loss of 2 weeks
of data over a total of 4 weeks. The tests done in thelaboratory have been limited to a few tens of files and then,were not able to indicate the possible problem.
4 Use of the MBX for the prototype detector
Besides the deployments of autonomous mooring lines

for site quality measurements, a first element of a neutrino
detector will be deployed in 1998. This line will beequipped with 30 OMs containing only 8 PMTs but with all
the cables and containers needed for normal operation. Theline will be connected to the shore by a 40 km electrooptical cable. This cable will bring the power to the lineand will transmit the information from the 8 PMTs and theslow control data and commands.
The main constraints for the slow control system are :reliability, possibility of extensions (addition of newsensors) and distributed architecture (several satellites far
from each other). To fulfill these requirements, anarchitecture based on the WorldFIP fieldbus technology
was chosen [4]. The redundancy (physical medium and bus
arbitration), the good data transfer rate (1 Mb/s over a 1 kmlong twisted pair), the on-line reconfigurability are some ofthe vital features of this fieldbus for its use in this context.
The MBX controller equipped with its WorldFIP interface
will act as data concentrators.
5 Conclusion
The ANTARES collaboration is involved in an ambitious
program. A successful deep-sea deployment is the combination of many complicated processes. The microcontroller has obviously an important role in the success or
failure of a deployment. The use of the MBX, anindustrial product, enabled the fast development of a very
reliable solution for deep-sea autonomous acquisition anddata logging and is retained for future remotely controlledoperation.
References[1] ANTARES Proposal, http://ccsrv04.in2p3.fr/antares[2] C. Walter, Proceedings of Workshop on Fieldbuses,
CERN, Sept 16-18, 1997
[3] M. Borland, L. Emery, <<The Self-Describing DataSets
File Protocol and Program Toolkit>>, Proceedings of
ICALEPCS’95, Oct 29-Nov 3, 1995
[4] A. Le Van Suu, <<The Slow Control System of theAntares Project>>, Proceedings of RT97, Sept 22-26, 1997