JEM-EUSO with a large and wide-angle telescope mounted on the International Space Station (ISS) has been planned as a space mission to explore extremes of the universe through the investigation of extreme energy cosmic rays by detecting photons which accompany air showers developed in the earth's atmosphere. JEM-EUSO will be launched by Japanese H-II Transfer Vehicle (HTV) and mounted at the Exposed Facility of Japanese Experiment Module (JEM/EF) of the ISS in the second phase of utilization plan. The telescope consists of high transmittance optical Fresnel lenses with a diameter of 2.5m, 200k channels of multi anode-photomultiplier tubes, focal surface front-end, readout, trigger and system electronics. An infrared camera and a LIDAR system will be also used to monitor the earth's atmosphere

Arai, Y.

Ebisuzaki, T.

Ebizuka, N.

Inoue, N.

Kajino, F.

Kawai, K.

Kawasaki, Y.

Kurihara, Y.

Miyazaki, Y.

Nomoto, K.

Ohmori, H.

Sakaki, N.

Sakata, M.

Sato, H.

Sato, M.

Shibata, T.

Shimizu, H.M.

Takahashi, Yu.

Takeda, M.

Takizawa, Y.

Uchihori, Y.

Uehara, Y.

Wasa, T.

Yamamoto, T.

Yamamoto, Y.

NASA Technical Reports Server

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PsT___c - 3L-3
30TH INTERNATIONAL COSMIC RAY CONFERENCE
ICRCR
Merida,Mexico
Instrument Overview of the JEM-EUSO Mission
F. KAJINO, T.YAMAMOTO, M. SAKATA, Y. YAMAMOTO, H. SATO, N. EBIZUKA (KONAN UNIV.); T.EBISUZAKI,
Y. UEHARA, H. OHMORI, Y. KAWASAKI, M. SATO, Y. TAKIzAwA, T. WASA, K. KAwAi (RIKEN); Y. MIYA-
ZAKI (FUKUI INST. TECHNOLOGY); T. SHIBATA, N. SAKAKI (AOYAMA GAKUIN UNIV.); N:"INOUE (SAITAMA
UNIV.); Y. UCHIHORI (NIRS); K. NOMOTO (UNIV. TOKYO); Yu. TAKAHASHI (YOHOKU UNIV.); M.-TAKEDA
(ICRR); H.M. SHIMIZU, Y. ARAI, Y. KURIHARA, H. FUJIMOTO (KEK); S. YOSHIDA (CHIBA UNIV.); Y.Ml-
ZUMOTO, J. WATANABE S. INOUE, K. ASANO (NAOJ); H. IKEDA, M. SUZUKI, H. YANO (ISAS/JAXA); T.
MURAKAMJ, D. YONETOKU (KANAZAWA UNIV.); N. SUGIYAMA (NAGOYA UNIV.); Y. ITO (STE LAB, NA-
GOYA UNIV.); S. NAGATAKI (YUKAWA INSTITUTE, KYOTO UNIV.): T. SAITO (KYOTO UNIV.); S. ABE, M.
NAGATA (KOBE UNIV.); T. TAJIMA (ADVANCED QUANTUM OPTICS INSTITUTE, JAERI),	 I
J. H. ADAMS, S. MITCHELL, M.J. CHRISTL, J. WATTS JR., A.ENGLISH (NASA/MSFC) , Y. TAKAHASHI, D.
GREGORY, M. BONAMENTE, P. READON, V. CONNAUGHTON, K. PITALO, J.HADAwAY, J. GEARY,R. LUND-
QUIST, P. READoN (UNIV. ALABAMA), H. CRAWFORD, C. PENNYPACKER (LBL, UNIV. CALIFORNIA, BERKE-
LEY), K. ARISAKA, D. CLINE (UCLA), T. WEILER, S. CZORNA (VANDERBILT UNIV.),
J-N. CAPDEVIELLE, P. GORODETZKY, P. SALIN, D. SEMIKOZ, G. SIGL (CNRS), J. DOLBEAU (COLL. DE
FRANCE), E. PARIZOT, T. PATZAK, F. VANUCCI (UNIV. PARIS 7), J. WEISBA4D (IN2P3),
M. TESHIMA (MAX PLANCK MUNICH), A. SANTANGELO (TUEBINGEN), P. BIERMANN (MPI BONN), K.
MANNHEIM (WUERZBURG),
S. BOTTAL P. SPILLANTINI, A. ZUCCARo (FIRENZE), V. GRACCo, A. PETROLINI (GENOVA), A. G AMROSI,
ANZALONE, O. CATALANO, G D'ALI SAITI, M.C. MACCARONE, P. SCARSI, B. SACCO (PALERMO), B. ALP-AT,
R. BATTISTON, B. BERTUTTi, E. FIANDRINI, P. ZUCCON (PERUGIA), M. CASOLINO, M.P. DE PASCALE, A.
MORSELLI, P. PICOZZA, R. SPARVOLI (ROMA 2), M. BERTAINA, A. CAPPA_ , M. DATTOLI, P. GALEOTTI, P.
VALLANIA, C. VIGORITO, (TORINO), A. GREGORIO (TRIESTE),
G. MEDINA-TANCo (MEXICO UNAM), H. SALAZAR (PUEBLA),
S. NAM, I. H. PARK (EwHA W. UNiv.),
GARiPov G.K., KHRENov B.A., KLwov P.A. PANASYUK M.I., YASHIN I.V. (SINP MSU), NAuMov, D.,
TKACHEV. L (DUBNA JINR),
A. MAURISSEN, V. MITEV (NEUCHATEL)
JEM-EUSO Collaboration
kajino@konan-u.ac.jp
Abstract: JEM-EUSO with a large and wide-angle telescope mounted on the International Space Sta-
tion (ISS) has been planned as a space mission to explore extremes of the universe through the inves-
tigation of extreme energy cosmic rays by detecting photons which accompany air showers developed
in the earth's atmosphere. JEM-EUSO will be launched by Japanese H-II Transfer Vehicle (HTV) and
mounted at the Exposed Facility of Japanese Experiment Module (JEM/EF) of the ISS in the second
phase of utilization plan. The telescope consists of high transmittance optical Fresnel lenses with a di-
ameter of 2.5m, 200k channels of multi anode-photomultiplier tubes, focal surface front-end, readout,
trigger and system electronics. An infrared camera and a LIDAR system will be also used to monitor
the earth's atmosphere.
1. Overview of the Instruments of the
JEM-EUSO mission
Extreme energy cosmic rays (EECR) coming to
the earth's atmosphere collides with nucleus and
https://ntrs.nasa.gov/search.jsp?R=20090028650 2019-08-30T07:34:15+00:00Z
Fig
SHORT TITLE
produces many secondary particles to form an
extensive air shower. The number of the particles
reaches roughly 10 11 for 1O2oeV primary particles.
This number is proportional to the energy of the
primary particles. The charged particles in EAS
excite the nitrogen molecules to emit near UV
photons. They also produce Cherenkov light in
the cone of about 1.3 degree. JEM-EUSO mission
observes such near UV fluorescent and Cher-
enkov photons from the ISS orbit at an altitude of
about 400 km. JEM-EUSO observes such light
spot moving in nearly light velocity. When it
meets the ground or cloud, the Cherenkov light
reflected at them is observed as strong Cherenkov
mark. [1],[2]
JEM-EUSO instrument is divided into four parts;
optics, focal surface detector, electronics, and
structure. Optics focuses the UV light (330nm-
400nm) incident to the front lens onto the focal
surface with an angular resolution of 0.1 degree.
Focal Surface detector converts the incident pho-
tons to photoelectrons and to an electric pulse.
The electronics counts the number of photons in
the period of 25 microseconds and records as a
brightness of a pixel. When it finds a signal pat-
tern came from EAS, it issues trigger signal. It
starts a sequence to send the all the brightness
data close to the triggered pixels stored in the
memory and send to the ground operation center.
Structure encloses all the parts of the instruments
and keeps them out from the outer harmful envi-
ronment in the space. It also keeps the lenses and
focal surface to the preset place.
JEM-EUSO plans to reduce the threshold energy
of EAS down to as low as 10 19eV and increase
the exposure. The reduction of threshold energy
may realize 1) new material and improved optics
design, 2) higher quantum efficiency detector, and
3) improved trigger algorisms. The increase in
exposure is realized by inclining the telescope
from nadir (tilted mode). In this tilted mode, the
threshold energy gets higher since the mean dis-
tance to EAS and atmospheric absorption both
increase. First half of the mission lifetime is de-
voted to lower energy in the nadir mode and sec-
ond half of the mission to high energy by the
tilted mode.
Overview of the instruments is mentioned in the
following sections.
2. Optics
A double Fresnel lens module with 2.5m external
diameter is the baseline optics for the JEM-EUSO
Telescope, which observes the 330nm - 400nm
optical bandwidth. Fresnel lenses can provide a
large-aperture, wide Field of View (FoV) system
with reduced mass and low absorption. Its tele-
scope has a full angle FoV of 60° and a 6 arcmin
(=0.1') angular resolution. This resolution corre-
sponds approximately to (0.75 - 0.87) km on the
earth, depending on the location inside the FoV.
JEM-EUSO (min) optics design is described as
follows.
1) Material of the lens is UV transmitting fluo-
ropolymer (CYTOP, ASAHI GLASS CO., LTD.
JAPAN), which has high UV transparency of 99%
(15mm thickness) in the wavelength from 330nm
to 400nm.
2) Mass of the optics is 480kg. The density of
CYTOP is about twice as much as the VV-
PMMA.
3) CYTOP has —50% smaller dispersion than the
commercial UV-PMMA. Furthermore, we use the
diffractive optics technology to suppress the color
aberration. A diffractive plane is arranged be-
tween the iris and the rear lens. This arrangement
copes with an easy construction of the telescope
as well as its performance.
Overall light-collecting power of JEM-EUSO is
about 1.5 times better than ESA-EUSO (min).
Details of the optics are shown elsewhere [3].
30TH INTERNATIONAL COSMIC RAY CONFERENCE 2007
Fig. 2 Fresnel lenses of the JEM-EUSO consist-
ing of a central lens and peripheral petal segments
3. Focal Surface Detector
The focal surface of JEM-EUSO has a curved
surface of about 2.5m in diameter, and it is cov-
ered with about 6,000 multi-anode photomulti-
plier tubes (Hamamatsu R8900-M36: MAPMT).
The focal surface detector consists of Photo-
Detector Modules (PDMs), each of which con-
sists of 9 Elementary Cells (ECs). The EC con-
tains 4 units of the MAPMTs. Therefore, about
150 PDMs are arranged on the whole of the focal
surface (Fig. 3).
A high voltage power supply for the MAPMT is
set one unit on each PDM. A photoelectron is
multiplied to about 3x105 electrons in the
MAPMT. The output pulse signals of the
MAPMT are fed into ASICs (Application Spe-
cific Integrated Circuit) which are included in the
front-end electronic circuits.
Fundamental design of the JEM-EUSO focal
surface succeeds the design of ESA-EUSO. Ow-
ing to the recent technological progress, the quan-
tum efficiency of the MAPMT will be improved
to about 30-40%.
We are developing a high-voltage divider includ-
ing a protection circuit. It protects the MAPMT
from an instantaneous large amount of light like
the lightning. We can operate it safely by inter-
cepting the photoelectron multiplication at the
initial stage of the dynodes using a Photo-MOS
relay.
Details of the focal surface detector are shown
elsewhere [4].
4. Electronics
The electronics system of JEM-EUSO consists of
focal-surface electronics subsystem and monitor-
ing/control subsystem of the detector instruments.
The focal-surface electronics subsystem records
the signals of UV photons generated by EECRs at
the focal surface successively in time. The system
is required to keep high trigger efficiency with a
flexible trigger algorithm as well as a reasonable
linearity over 10 19-1021 eV range. The require-
ments of a power consumption within 2-3mV/ch
must be fulfilled to manage 200k signal channels
in an available power budget. Available volume
for the instruments is limited and radiation toler-
ance of the electronic circuits in the space envi-
ronment during a scheduled operation period is
also required.
The focal-surface electronics is configured in
three levels corresponding to the hierarchy of the
focal-surface detector system : front-end electron-
ics at an EC level, nine of which are consolidated
to a'PDM level. An FS level electronics controls
about 150 PDM level electronics.
Photoelectrons in the MAPMT are multiplied and
output signals are fed into a front-end ASIC. The
ASIC provides pulses with a width proportional
to the input charge.
Fig. 4 Layout of the front-end ASIC based on a
new method using a submicron CMOS process
SHORT TITLE
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Output signals are discriminated by a comparator
and the pulse widths are digitized. In order to
compensate for channel-to-channel gain var ation
the threshold voltage of the comparator is adjust-
able for each pixel, which covers from a fraction
of a single-photon-level to several-photon level.
The digitized signals of the comparator in a 2.5µs
interval (GTU) count up with a 10-bit scalar. The
scalar counts are recorded in a ring memory for
each GTU to wait for a trigger assertion, then, the
data are readout and are sent to a readout-and-
control (ROC) board. The depth of the ring mem-
ory is designed to compensate for the trigger
latency, which is tentatively 128.
The dynode signal is utilized to supplement the
anode signal; the dynode signal is integrated and
recorded in an analog memory. Once the trigger
condition is met, the signals stored in the analog
memory are digitized by an analog-to-digital
converter, then, transmitted to the ROC board of
the photo-detector module via a serial transmis-
sion line.
1,476 EC	 164 Boards
	
21 Boards	 2- 5 Boards
Fig. 5 Outline of the data processing system
JEM-EUSO uses "Truck trigger method", which
searches the light point moving with the light
speed at 400km ahead. This method reduces the
threshold energy. [5]
We are designing three trigger modes:
A) Normal mode with a GTU of 2.5µs for routine
data taking of EAS.
B) Slow mode with a programmable GTU up to a
few ms, for the study of meteorites and other
atmospheric luminous phenomena.
C) Detector calibration mode with a GTU value
suitable for the calibration runs. [6]
Calibration of JEM-EUSO instrument will be
performed by many methods.[6]
5. Atmospheric Monitoring
Atmospheric monitoring system of JEM-EUSO
observes the earth's atmosphere continuously
inside the FOV of the JEM-EUSO telescope. This
observation provides key parameters for the en-
ergy estimation of an extreme energy particle,
since the intensity and the atmospheric
transmittance of the fluorescence and Cherenkov
emissions strongly depend on the atmospheric
conditions, especially on the cloud amount and
cloud-top altitude. The atmospheric monitoring
onboard the JEM-EUSO telescope would permit
to correct the JEM-EUSO acceptance due to
cloud interference and to introduce correcting
factors in the observed EAS parameters. Thus, the
present concept for the atmospheric monitoring of
JEM-EUSO is based on the use of a complex of
sensors in synergy with each other, which have a
small impact on the overall budget: (A) Infrared
camera, (B) Lidar, and (C) JEM-EUSO slow-
data. [7]
6. Conclusions
JEM-EUSO had inherited ESA-EUSO and devel-
oped many new items to improve the observation
feasibility of EECR. As a result collection effi-
ciency of photons from EECR has been remarka-
bly increased and the observable energy threshold
decreased. One year long phase A study under
JAXA will be carried out this year.
7. Acknowledgements
This work is supported by RIKEN, JAXA and the
Hirao Taro Foundation of the Konan University
Association for Academic Research.
References
[1] T.Ebisuzaki et al., this conference
[2] Y.Takahashi, this conference
[3] J.H.Adams,Jr., et al., this conference
[4] Y.Kawasaki et al., this conference
[5] M.Bertaina et al., this conference
[6] N.Sakaki et al., this. conference
[7] M.Valentin et al., this conference


Instrument Overview of the JEM-EUSO Mission

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