MINI-EUSO
(Version française disponible)
1 INTRODUCTION
MINI-EUSO (Extreme Universe Space Observatory) is a precursor of a space telescope dedicated to probe the UV light in the
atmosphere within his field of view, continuously during the night, with an unprecedented spatial and time resolution.
Monitoring earth UV emission remains largely unexplored and suggests a huge potential for new measurements and
discoveries in earth related sciences.
The context of this project is the large international project JEM-EUSO, which involves the participation of 13 countries in 3
continents. The objective of JEM-EUSO is to install a large space telescope fluorescence light on the International Space
Station (ISS) to perform the UV 3-D imaging of the atmosphere with a high spatial and time resolution. The primary objective
of this project is the detection of large air showers induced by cosmic rays of very high energies (above 10 20 eV), whose
original sources are still unknown despite the generations of ground-based observatories that have succeeded over the past
five decades. However, the study of UV emission into the atmosphere is very interesting not only for the astrophysics of the
nearby universe but also applies to earth and atmospheric sciences.
An exceptional opportunity comes to install at negligible costs (without any launch and maintenance costs), a compact minitelescope of JEM-EUSO type, on board of the ISS, behind a UV transparent window pointing towards the earth, under the
control of astronauts. This project would start by the end of the year 2015, for a minimum duration of 1.5 to 2 years. The
MINI-EUSO project comes after the completion of two pioneering projects EUSO-TA (project of JEM-EUSO collaboration) on
the site of the Telescope Array Observatory (TA) in Utah and the EUSO-BALLOON (also from JEM-EUSO collaboration and
partially funded by CNES), which implement in a similar manner and a reduced scaled version of the JEM-EUSO concept, on
the basis of classical industrial technology in terrestrial and the stratospheric environments. These two pioneering projects
are currently under assembly and integration for later operation campaigns starting in 2014. However, it is also important to
demonstrate that the technological designs developed for both EUSO-TA and EUSO-BALLOON projects are also valid in the
context of a space project on the ISS.
To facilitate the approval of the JEM-EUSO telescope by international space agencies, it seems essential to go through the
stage where the most critical elements of optics and electronics are tested in the appropriate space environment.
Particular attention should be considered to expose the sensitive elements of the instrument to the lower atmosphere, such
as the PMMA lenses, the multi-anode photomultipliers (MAPMT) and high voltage power supplies, the ASICs (Application
Specific Integrated Circuit) performing the analog to digital conversion of signals and the FPGAs (Field Programmable Gate
Array) that implements the hierarchical trigger system that controls the dataflow recorded by the data acquisition system.
Despite the small size of MINI-EUSO making unlikely the observation of air showers, the detailed mapping of the UV emission
of earth and the atmosphere becomes conceivable and could lead to significant scientific advances in these areas.
2 SCIENTIFIC AND TECHNOLOGICAL OBJECTIVES
The objectives of MINI-EUSO are divided into two categories. Firstly, the scientific objectives are related to the outstanding
technical performances of the instrument, which are of particular interest in earth and atmospheric sciences. Secondly, the
technological objectives are directly related to detection instrumentation issues for future space telescope like JEM-EUSO.
The aim is to study the behaviour of the materials and components of JEM-EUSO in terms of resistance, aging, when exposed
to an appropriate environment of the ISS. This stage is necessary to establish the compliance of the technological readiness
level of the various elements with the requirements for spatialization.
2.1 INSTRUMENT MINI- EUSO
MINI-EUSO provides an imaging system with a high spatial and time resolution for night observations of the surface of the
earth in the UV band for the first time with unprecedented performances. Data previously acquired by the Russian TATIANA
satellite, equipped with a single photomultiplier, provided a rough map of the UV background radiation with a resolution of
the order of 100 km. These data were supplemented by measurements from the Italian balloon born BABY experiment with a
resolution scale of ten kilometres over a limited area of Sicily.
MINI-EUSO proposes to carry out a precise mapping of almost the entire world, with a resolution of 6 km or less on
timescales as short as microseconds (JEM- EUSO will have a resolution of 0.5 km). Smoothing data over longer time periods
can expand the timescale.
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MINI-EUSO has a ground breaking optical system that can focus UV light rays on a focal surface instrumented with a UV
camera with an exceptional accuracy achieved in space. In particular, the camera is very fast, and its image surface is finely
segmented into pixels. Each electronic channel is highly sensitive with a detection threshold below the single photon level. It
operates exclusively at nights. This instrument has the possibility of being calibrated in absolute way and therefore has the
ability to measure accurately very low photon flux with a few percent accuracy.
This instrument will be placed on the ISS for a period of several years, under the direct control of astronauts. It will be
installed in the pressurized module Russian service or in the airlock WORF of the U.S. lab, behind a window transparent to UV.
It may also be directly exposed to the outside on the external platform of the Japanese module (called JEM or Kibo).
The orbit of the ISS is particularly well suited for monitoring our planet, covering a wide range of latitudes. So this MINI-EUSO
project is particularly appropriate to achieve a broad scientific program of earth and atmosphere sciences.
2.2 SCIENTIFIC OBJECTIVES
This instrument is particularly suitable for producing the UV emission studies described below. For JEM-EUSO, these UV
emissions are background, which must be measured primarily by MINI-EUSO to prepare the detection of air showers. For
earth sciences, these measurements are used directly for physical interpretations in the various disciplines:
a) Study of the Earth's UV emission for environmental sciences
• A comparative study of the UV emissivity according the different types of soil (mountains, desert, snow, lakes, cities,..)
allowing to estimate accurately the anthropogenic contribution around 400 nm,
• Detection of the time variations in the emissivity possibly in correlation with the seasonal dependences, with the activities
of human nature, with trends induced by climate changes.
b ) Study of atmospheric phenomena
• The observation of the atmosphere in the ultraviolet band has never been watched from space with a spatial and time
resolution that fine. MINI-EUSO observations offer the ability of conducting surveys on the concentration of gases such as
ozone, water vapour and aerosols, as well as monitoring their evolution in time.
• The spatial and time resolution is particularly suited to the study of light and transient electromagnetic phenomena such
storm in the upper atmosphere such as lightning, sprites, elves and jets...). The MINI-EUSO imaging advantageously
complement in the field of short timescales and the UV band, the measurements provided by other specific instruments on
satellites or the ISS such as TARANIS (satellite to be launched in 2015), SMILES (ISS instrument below in the millimetre
wavelength) and ASIM (ISS instrument to be installed in 2015). These measurements should lead to a better understanding
of the mechanisms of formation of filamentous structures in the plasma.
c) Bioluminescence of plant and animal organisms
MINI-EUSO allows the detection and the monitoring of the evolution of the bioluminescence phenomenon produced by living
organisms. In particular, the observation of UV emissions over the seas and oceans, caused by algae or plankton, provide
information on marine pollution. Similar studies over land provide information on the status of terrestrial vegetation.
d) Monitoring of meteorites
MINI-EUSO, covering a projected surface on ground of about 300 x 300 km area, plays an irreplaceable role as a precursor
for the optimization of future instruments for detecting meteors from space. Indeed, it will be able to detect micrometeorites
with a lower limit in apparent magnitude between 0 and 1 in the ultraviolet. These events correspond to very common
meteorites with have masses in ranges of grams. The time dependence of the light intensity will be determined for each event.
The frequency-intensity distribution, of these events allows making an inventory of the population of near-Earth objects in a
range of sizes and masses inaccessible by ground-based observations. When meteors are observed in coincidence with
ground-based telescopes, it is possible to determine their actual path. Light curves thus obtained, to be compared with
similar data obtained by ground-based observations will provide useful data for the development of models for meteoric
ablation.
MINI-EUSO would also be a precursor of future space meteorite detectors. Research on meteors is compulsory to prepare the
JEM-EUSO mission for adjusting the algorithms of the trigger system according to the selected run operation mode of the
trigger (air showers or meteors selection).
2.3 TECHNOLOGICAL OBJECTIVES
A major technological objective of MINI-EUSO is preparing the space mission of JEM-EUSO. In particular, the MINI-EUSO
instrument includes a large number of technical innovations that have never been tested in space. The ISS provides an ideal
environment where are combined the following effects: the various types of radiation, no pressure variations associated with
high and rapid succession of day and night temperatures. The combination of these effects is not easily reproducible on the
ground with limited resources.
a) First use of Fresnel lenses in space.
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Fresnel lenses are particularly suitable for use in space due to their low weight and good performance UV such as their good
optical transparency, their excellent focusing power and their ability to reduce the chromatic aberrations. However, it worth
monitoring the resistance, strength or degradation of their material to the environment of space vacuum, temperature
variations and radiations, in the short and medium term.
b ) Photo-detection system
The photodetection system consists of a new type of multi-anode photomultiplier (MAPMT) with a very high spatial
resolution and its high-voltage supply has very low power consumption and an innovative control mechanism for automatic
MAPMT gain adjustment. This allows high voltage supply to adjust dynamically and automatically the amplification gain for
measuring an incident photon flux in a large relative range of 1-106. In case of excessive flux, it is important to turn off the
high voltage on the photocathode under the risk of the sensor destruction. This logic is entirely controlled by a FPGA in less
than 5 microseconds. The revolutionary concept of this system, as well as the potential risks of breakdown should be
absolutely tested in space.
c) Front-End Electronics
Electronics Front-End is a matrix highly modular system consisting of a camera block of 2304 pixels comprising various
essentials such as the Elementary Cell, High voltage power supply electronics and analog and digital readout electronics. This
camera has the function of representing the instrumented focal surface. The need for compacity, light weight, and the absence
of dead space detection zones, requires extreme compactness of this electronic potentially prone to potential problems of
heat dissipation in the absence of air convection. This point needs to be verified in situ, over the medium term and actual
operating conditions.
d) ASICs
The family of ASICs called SPACIROC was developed by our French teams, for a space applications which need
photomultipliers readout, that is to say, for the measuring electronics signal according two complementary methods, one by
counting photons of the other by measuring the charge during a time gate of 2.5 microseconds. For their first implementation
in space, these ASICs must be absolutely space qualified.
e ) Digital Electronics and Embedded Computer
The instrument is controlled by a complex digital electronics and embedded CPU, representative of the final Data Acquisition
System of JEM-EUSO. It manages on the one hand a fast dataflow of events, filtered by a two levels trigger system, then stored
on a disk or a SD card. On the other hand, a slow dataflow of monitoring data is recorded. One of the crucial issues is the
development of algorithms and trigger filtering in FPGAs, to conform the data acquisition rate to the local processing capacity
and storage system.
3 RELEVANCE AND STRATEGY
3.1 SCIENTIFIC PROGRAMME AND FRAMEWORK
The MINI-EUSO project to install a mini-telescope on the ISS in preparation for the future JEM-EUSO mission is part of the
development of a series of high-energy cosmic rays observatories since half a century. The evolution of those observatories
was driven by on-going research to ever probe a greater atmospheric surface as one searches for the highest energies thus
unusual events, especially in the region of the strong suppression of the spectrum called GZK cut-off atmosphere (at 6x1019
eV). Today, ground observatories reach their maximum practicable size. The continuation of this research can only be
conducted in space with telescopes installed on the space station or on board satellites.
The main scientific motivation for these space observatories is to promote the emergence of a new discipline: " astronomy
with particles", with particles which trajectory is only marginally bent by the extra-galactic magnetic fields. This
interdisciplinary subject includes additional topics such as fundamental physics, high-energy physics and astrophysics. The
main subject is supplemented by secondary motivations related to possible significant progresses in the earth sciences and
the atmosphere.
Currently, the cosmic rays scientific community of adopted two complementary strategies: most ground-based observatories
carry out improvements in detector performance to better unravel the mystery of the nature of cosmic rays (protons or
heavy nuclei). They are focusing more on the energy range of 10 17-1019 eV, in the heart of the transition from galacticextragalactic radiation and well below the GZK cut-off. The evidence about the rise of the anisotropy in the arrival directions
is far being sketched. It requires the implementation of larger observatories in space, probing the atmosphere with larger
exposition and better quasi-uniform sky coverage, for studying the events beyond the GZK cut with sufficient statistics. These
space observatories should allow identification of point sources in the universe.
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The funding instrument-type to consider in this MINI-EUSO proposal can only be carried out in the framework of an
international project like for EUSO-BALLOON or JEM-EUSO, due to the diversity and specific scientific and technical
skills required.
The multiple scientific interests about JEM- EUSO is recognized by ESA within the ELIPS program, and also partly by the CNES
which selected JEM-EUSO in 2009 among future mission opportunities, and since 2011. CNES balloon division has selected
and funded a large part of EUSO-BALLOON. In anticipation of an upcoming quadripartite agreement of international space
agencies on JEM- EUSO, MINI-EUSO is a rightful project after the first demonstrators EUSO-BALLOON and EUSO-TA.
The contribution of ANR 2014 would perfectly fit in time its participation in a 3-years program, with a phase of development
and production of 12 months (starting in the third or fourth quarter of 2014), followed by a phase of testing and qualification
within 6 months, followed by a scientific observation period of 1.5 years to 2 years (beginning in late 2015 to early 2016).
3.2 INTEREST TECHNOLOGY
Achieving MINI-EUSO will increase the technology readiness level (TRL) of the most critical elements of JEM-EUSO such as
lenses, photomultipliers, high voltages, ASICs and FPGAs. Most of the components would pass from a current TRL level of 4 or
5 to a level of 7. This step MINI-EUSO helps to accelerate the development phases of the JEM-EUSO project, once it will be
validated by the international space agencies.
3.3 STRATEGY FOR THE FRENCH TEAM
The French teams in JEM-EUSO are grouped in four CNRS laboratories: the APC , IRAP , LAL and OMEGA . These teams
participated very actively in the design of JEM- EUSO and the R & D on key elements and their practical implementation in
EUSO-BALLOON and EUSO-TA. OMEGA team is specialized in the development of ASICs dedicated for reading
photomultipliers in space. APC has a key role in the implementation of photomultipliers, their high-voltage power supplies
and their control including the calibrating method of the whole measurement. LAL has the speciality to develop numerous
electronic boards, the design and testing of photodetection elements, ASICs and implementation of all electronic front-end of
the camera. IRAP is specialized in the realization of the mechanics of the instrument and the optical tests of the lenses. JEMEUSO collaboration sincerely hopes that our teams, which are so deeply technically involved in EUSO BALLOON and EUSO-TA,
could continue their work in MINI-EUSO. Our teams also want to continue their activities in perspective of the JEM-EUSO
project, which they have joined in participation since 2009.
4 PRESENTATION OF THE CONSORTIUM
MINI-EUSO is a consortium of four main contributing countries, France, Italy, Japan and Russia, which are all members of the
international JEM-EUSO collaboration. Three partners are very active and essential in EUSO-BALLOON and TA-EUSO. Each
contributor of this consortium has partnership on technical and technological aspects with other members of the JEM-EUSO
Collaboration, involved in the implementation EUSO-BALLOON and EUSO–TA.
• Japan, with laboratory Riken is the worldwide specialist in the design, implementation and testing of Fresnel lenses in
PMMA (polymethylmethacrylate) of all sizes (from tens of centimetres to more than two meters), with a machining accuracy
as low as 10 nm, which is essential for the correction of chromatic aberrations. It is associated with JAXA (Japanese Space
Agency) for the preparation of the JEM- EUSO mission.
• France, through its CNRS laboratories, APC, IRAP, LAL, and OMEGA contributes to the front-end electronics of the UV
camera, in partnership with the Polish National Centre for Nuclear Research (NCBJ) from Cosmic Ray Physics Division in Lodz.
• Italy, through the laboratories of INFN (Rome, Naples, Bari, Turin and Frascati) makes the mechanics, power supply system
and monitoring system of the equipment. It works in collaboration with German laboratories Karlsruhe Institute of
Technology (KIT) and the Institut für Astronomie und Astrophysik Tübingen (IAAT). The Italian team has been heavily
involved in the Russian- Italian experiment PAMELA on satellite.
• Russia, through the laboratory of the Lomonosov Moscow State University (MSU) and the space agency Roscosmos
contributes in installing MINI-EUSO in the Russian compartment of the ISS, the application of the instrument and its control
by Russian cosmonauts. The Russian group has a long experience in the measurement of the UV emission of airglow on
satellite with TATIANA and soon TUS.
The Italian groups in relationship with the major support of their national space agency ASI carry out the leadership of the
MINI-EUSO mission.
INFN granted for all activities JEM-EUSO an envelope of 150k€ in the year 2014, of which 100k€ are dedicated to MINI-EUSO
funding. INFN is awaiting confirmation of the commitment of the international partners to expand its participation.
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ASI has recognized the large interest of MINI-EUSO and his committee welcomed this opportunity to test a smaller version of
JEM- EUSO aboard the ISS. ASI expects the commitment of the French and Japanese partners to contribute financially.
Lenses and some photo-multipliers will be funded by the laboratory Riken and JAXA.
Given the importance of the participation of French laboratories in the projects EUSO-BALLOON and EUSO-TA, France's
contribution is essential to the achievement of MINI-EUSO. His commitment will lead inevitably all its partners to pursue
their own investments.
The table below gives the precise coordinates of the main scientists responsible MINI- EUSO project and their affiliation
mail
dagoret@lal.in2p3.fr
Institute
LAL
Italy
Responsible person MINI-EUSO
Dr Sylvie DAGORETCAMPAGNE (coordinator)
Dr Marco CASOLINO
marco.casolino@roma2.infn.it
INFN
Japan
Russia
Dr Yoshiyuki TAKIZAWA
Prof Mikael PANASYUK
takky@riken.jp
panasyuk@srd.sinp.msu.ru
RIKEN
MSU
Country
France
Name affiliation
Laboratoire de l’accélérateur
linéaire
Istituto Nazionale di Fisica
Nucleare
RIKEN Advanced Science Institute
Lomonosov Moscow State
University
The references to recent work are:
Reference/ publication
“An evaluation of the exposure in nadir observation of the
JEM-EUSO mission”, JEM-EUSO collaboration, Astroparticle
Physics, Volume 44, April 2013, Pages 76–90
JEM-EUSO Publications at ICRC2013 conference on EUSOBALLON
Set of EUSO-BALLOON documents presented at CNES project
reviews (available on demand)
PRR (Phase A review, February 2012)
CDR (Phase B review, December 2012)
link
http://arxiv.org/abs/1305.2478
http://arxiv.org/abs/1307.7071
http://euso-balloon.lal.in2p3.fr/
http://groups.lal.in2p3.fr/jem-euso/ (new web site)
http://euso-balloon.lal.in2p3.fr/spip.php?article108
http://euso-balloon.lal.in2p3.fr/spip.php?article112
http://euso-balloon.lal.in2p3.fr/spip.php?article281
http://euso-balloon.lal.in2p3.fr/spip.php?article280
5 CONCLUSIONS
MINI-EUSO project is reduced scaled version of a future space telescope to be installed aboard the ISS to prepare the future
mission of JEM-EUSO. It continues in line with the precursors but with an exposition to a spatial environment.
The objectives are to both technical and scientific, on the one hand to increase the technology readiness level to establish the
spatial compliance of various elements of JEM-EUSO and on the other hand to measure before operation, the irreducible
background noise background sky and prepare algorithms trigger systems. The reduced MINI-EUSO size does not allow the
study of air showers. However its unique performances allow for accurate mapping of the Earth’s and atmosphere in UV
emission and suggest that dramatic advances in the various themes of Earth and atmosphere Sciences may arise.
The data accumulated by the current ground-based observatories cosmic rays lead to two puzzles to solve. While groundbased observatories focus on the study of the nature of cosmic rays, the search for anisotropies and sources discovery not be
considered without space telescopes. So MINI-EUSO is the essential step to prepare the development of astronomy with
cosmic rays within the next decade.
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